Neuronetics (STIM) 10-Q 3 Aug 21 2021 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2021	Jul. 28, 2021
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Trading Symbol	STIM
Entity Registrant Name	NEURONETICS, INC.
Entity Central Index Key	0001227636
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Common Stock, Shares Outstanding		26,318,346
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity File Number	001-38546
Entity Tax Identification Number	33-1051425
Entity Address, Address Line One	3222 Phoenixville Pike
Entity Address, City or Town	Malvern
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	19355
City Area Code	610
Local Phone Number	640-4202
Title of 12(b) Security	Common Stock ($0.01 par value)
Security Exchange Name	NASDAQ
Entity Incorporation, State or Country Code	DE
Entity Interactive Data Current	Yes
Document Quarterly Report	true
Document Transition Report	false

Balance Sheets

Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 115,783	$ 48,957
Accounts receivable, net	9,002	7,166
Inventory	5,393	3,720
Current portion of net investments in sales-type leases	2,034	1,887
Current portion of prepaid commission expense	1,219	1,096
Prepaid expenses and other current assets	1,447	2,186
Total current assets	134,878	65,012
Property and equipment, net	708	730
Operating lease right-of-use assets	3,228	3,418
Net investments in sales-type leases	1,854	2,331
Prepaid commission expense	5,454	5,300
Other assets	1,976	1,866
Total Assets	148,098	78,657
Current liabilities:
Accounts payable	2,425	3,749
Accrued expenses	6,604	7,319
Deferred revenue	1,937	2,020
Current portion of operating lease liabilities	612	594
Current portion of long-term debt, net
Total current liabilities	11,578	13,682
Long-term debt, net	34,944	34,620
Deferred revenue	1,488	1,741
Operating lease liabilities	2,922	3,121
Total Liabilities	50,932	53,164
Commitments and contingencies (Note 16)
Stockholders' Equity:
Preferred stock, $0.01 par value: 10,000 shares authorized; no shares issued or outstanding at June 30, 2021 and December 31, 2020
Common stock, $0.01 par value: 200,000 shares authorized; 26,167 and 19,114 shares issued and outstanding at June 30, 2021 and December 31, 2020, respectively	262	191
Additional paid-in capital	389,850	302,842
Accumulated deficit	(292,946)	(277,540)
Total Stockholders' Equity	97,166	25,493
Total Liabilities and Stockholders' Equity	$ 148,098	$ 78,657

Balance Sheets (Parenthetical)

Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	26,167,000	19,114,000
Common stock, shares outstanding	26,167,000	19,114,000

Statements of Operations

Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Statement [Abstract]
Revenues	$ 14,203	$ 9,741	$ 26,491	$ 21,217
Cost of revenues	2,750	2,323	4,971	5,134
Gross Profit	11,453	7,418	21,520	16,083
Operating expenses:
Sales and marketing	9,042	8,151	17,604	18,874
General and administrative	6,681	4,010	12,785	9,298
Research and development	2,294	2,116	4,604	5,137
Total operating expenses	18,017	14,277	34,993	33,309
Loss from Operations	(6,564)	(6,859)	(13,473)	(17,226)
Other (income) expense:
Interest expense	977	986	1,962	2,509
Loss on extinguishment of debt				924
Other income, net	(16)	(80)	(29)	(281)
Net Loss	$ (7,525)	$ (7,765)	$ (15,406)	$ (20,378)
Net loss per share of common stock outstanding, basic	$ (0.29)	$ (0.41)	$ (0.63)	$ (1.09)
Net loss per share of common stock outstanding, diluted	$ (0.29)	$ (0.41)	$ (0.63)	$ (1.09)
Weighted-average common shares outstanding, basic	25,903	18,747	24,608	18,714
Weighted-average common shares outstanding, diluted	25,903	18,747	24,608	18,714

Statement of Changes in Stockho

Statement of Changes in Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Total
Beginning balance at Dec. 31, 2019	$ 186	$ 297,753	$ (250,087)	$ 47,852
Beginning balance, shares at Dec. 31, 2019	18,645
Share-based awards and options exercises	$ 1	75		76
Share-based awards and options exercises, shares	81
Share-based compensation expense		1,196		1,196
Net loss			(12,613)	(12,613)
Ending balance at Mar. 31, 2020	$ 187	299,024	(262,700)	36,511
Ending balance, shares at Mar. 31, 2020	18,726
Beginning balance at Dec. 31, 2019	$ 186	297,753	(250,087)	47,852
Beginning balance, shares at Dec. 31, 2019	18,645
Net loss				(20,378)
Ending balance at Jun. 30, 2020	$ 188	299,717	(270,465)	29,440
Ending balance, shares at Jun. 30, 2020	18,809
Beginning balance at Mar. 31, 2020	$ 187	299,024	(262,700)	36,511
Beginning balance, shares at Mar. 31, 2020	18,726
Share-based awards and options exercises	$ 1	47		48
Share-based awards and options exercises, shares	83
Share-based compensation expense		646		646
Net loss			(7,765)	(7,765)
Ending balance at Jun. 30, 2020	$ 188	299,717	(270,465)	29,440
Ending balance, shares at Jun. 30, 2020	18,809
Beginning balance at Dec. 31, 2020	$ 191	302,842	(277,540)	25,493
Beginning balance, shares at Dec. 31, 2020	19,114
Share-based awards and options exercises	$ 11	1,581		1,592
Share-based awards and options exercises, shares	1,076
Issuance of common stock, net of issuance costs of $401	$ 56	80,515		80,571
Issuance of common stock, net of issuance costs of $401 (in shares)	5,566
Share-based compensation expense		2,196		2,196
Net loss			(7,881)	(7,881)
Ending balance at Mar. 31, 2021	$ 258	387,134	(285,421)	101,971
Ending balance, shares at Mar. 31, 2021	25,756
Beginning balance at Dec. 31, 2020	$ 191	302,842	(277,540)	25,493
Beginning balance, shares at Dec. 31, 2020	19,114
Net loss				(15,406)
Ending balance at Jun. 30, 2021	$ 262	389,850	(292,946)	97,166
Ending balance, shares at Jun. 30, 2021	26,167
Beginning balance at Mar. 31, 2021	$ 258	387,134	(285,421)	101,971
Beginning balance, shares at Mar. 31, 2021	25,756
Share-based awards and options exercises	$ 4	707		711
Share-based awards and options exercises, shares	411
Share-based compensation expense		2,009		2,009
Net loss			(7,525)	(7,525)
Ending balance at Jun. 30, 2021	$ 262	$ 389,850	$ (292,946)	$ 97,166
Ending balance, shares at Jun. 30, 2021	26,167

Statement of Changes in Stock_2

Statement of Changes in Stockholders' Equity (Parenthetical) $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)
Statement Of Stockholders Equity [Abstract]
Issuance of common stock, issuance costs	$ 401

Statements of Cash Flows

Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Cash Flows from Operating Activities:
Net loss	$ (15,406)	$ (20,378)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	552	534
Share-based compensation	4,205	1,842
Non-cash interest expense	324	944
Cost of rental units purchased by customers	137	122
Loss on extinguishment of debt		622
Changes in certain assets and liabilities:
Accounts receivable, net	(1,835)	(66)
Inventory	(1,673)	(557)
Net investments in sales-type leases	330	(777)
Leasehold reimbursement		836
Prepaid commission expense	(278)	(723)
Prepaid expenses and other assets	1,120	356
Accounts payable	(1,365)	(2,408)
Accrued expenses	(715)	(3,492)
Deferred revenue	(336)	14
Net Cash Used in Operating Activities	(14,940)	(23,131)	$ (28,400)
Cash Flows from Investing Activities:
Purchases of property and equipment and capitalized software	(1,108)	(484)
Net Cash Used in Investing Activities	(1,108)	(484)
Cash Flows from Financing Activities:
Proceeds from issuance of long-term debt		41,360
Repayment of long-term debt		(38,860)
Payments of debt issuance costs		(721)
Proceeds from exercises of stock options	2,303	124
Proceeds from the issuance of common stock	80,972
Payments of common stock offering issuance costs	(401)
Net Cash Provided by Financing Activities	82,874	1,903
Net Increase (Decrease) in Cash and Cash Equivalents	66,826	(21,711)
Cash and Cash Equivalents, Beginning of Period	48,957	75,708	75,708
Cash and Cash Equivalents, End of Period	115,783	53,997	$ 48,957
Supplemental disclosure of cash flow information:
Cash paid for interest	1,638	2,227
Supplemental disclosure of non-cash investing and financing activities:
Purchases of property and equipment and capitalized software in accounts payable and accrued expenses	$ 41	$ 80

Description of Business

Description of Business	6 Months Ended
	Jun. 30, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Description of Business	1. DESCRIPTION OF BUSINESS Neuronetics, Inc., or the Company, is a commercial stage medical technology company focused on designing, developing and marketing products that improve the quality of life for patients who suffer from psychiatric disorders. The Company’s first commercial product, the NeuroStar Advanced Therapy System, is a non-invasive and non-systemic office-based treatment that uses transcranial magnetic stimulation, or TMS, to create a pulsed, MRI-strength magnetic field that induces electrical currents designed to stimulate specific areas of the brain associated with mood. The system was cleared in 2008 by the United States Food and Drug Administration, or the FDA, to treat adult patients with major depressive disorder, or MDD, who have failed to achieve satisfactory improvement from prior antidepressant medication in the current episode. NeuroStar Advanced Therapy is also available in other parts of the world, including Japan, where it is listed under Japan’s national health insurance. The Company intends to continue to pursue development of its NeuroStar Advanced Therapy System for additional indications. COVID-19 The Company is continuing to monitor the impact of the COVID-19 pandemic on all aspects of its business and geographies, including how it will continue to impact the Company’s customers, supply chain, employees and other business partners. While the Company began to experience significant disruptions in March 2020 through the end of June 30, 2021 from the COVID-19 pandemic, it is unable to predict the full impact that the pandemic may have on its financial condition, results of operations and cash flows due to numerous uncertainties. These uncertainties include the scope, severity and duration of the pandemic, the actions taken to contain the pandemic or mitigate its impact and the direct and indirect economic effects of the pandemic and containment measures, among others. The pandemic has significantly adversely impacted global economic activity and has contributed to significant volatility and negative pressure in financial markets, and may contribute to periods of economic uncertainty in the future. The Company applied for and received a $6.4 million loan in April 2020 under the Paycheck Protection Program (the “PPP”) established by the Coronavirus Aid, Relief, and Economic Security Act (“CARES Act”) on March 27, 2020. Due to questions concerning the eligibility of public companies similarly situated to the Company, on May 7, 2020, the Company repaid the loan in full, including interest accrued to date. Liquidity As of June 30, 2021, the Company had cash and cash equivalents of $115.8 million and an accumulated deficit of $292.9 million. The Company incurred negative cash flows from operating activities of $14.9 million for the six months ended June 30, 2021 and $28.4 million for the year ended December 31, 2020. The Company has incurred operating losses since its inception, and management anticipates that its operating losses will continue in the near term as the Company continues to invest in sales, marketing and product development activities. The Company’s primary sources of capital to date have been proceeds from its IPO, private placements of its convertible preferred securities, borrowings under its credit facilities, proceeds from its secondary public offering of common stock, revenues from sales of its products and other public offerings of the Company’s common stock. As of June 30, 2021, the Company had $35.0 million of borrowings outstanding under its credit facility, which has a final maturity in February 2025

Basis of Presentation

Basis of Presentation	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation	2. BASIS OF PRESENTATION The accompanying financial statements have been prepared in accordance with United States generally accepted accounting principles, or GAAP. Any reference in these notes to applicable guidance is meant to refer to GAAP as found in the Accounting Standards Codification, or ASC, and Accounting Standards Updates, or ASUs, promulgated by the Financial Accounting Standards Board, or FASB. Interim Financial Statements The accompanying unaudited interim financial statements have been prepared from the books and records of the Company in accordance with GAAP for interim financial information and Rule 10-01 of Regulation S-X promulgated by the United States Securities and Exchange Commission, or SEC, which permit reduced disclosures for interim periods. All adjustments, consisting only of normal recurring adjustments, necessary for a fair presentation of the accompanying balance sheets and statements of operations and stockholders’ deficit and cash flows have been made. Although these interim financial statements do not include all of the information and footnotes required for complete annual financial statements, management believes the disclosures are adequate to make the information presented not misleading. Unaudited interim results of operations and cash flows for the three and six months ended June 30, 2021 are not necessarily indicative of the results that may be expected for the full year. Unaudited interim financial statements and footnotes should be read in conjunction with the audited financial statements and footnotes included in the Company’s Form 10-K filed with the SEC on March 2, 2021, wherein a more complete discussion of significant accounting policies and certain other information can be found. Use of Estimates The preparation of financial statements in accordance with GAAP and the rules and regulations of the SEC requires the use of estimates and assumptions, based on judgments considered reasonable, which affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. The Company bases its estimates and assumptions on historical experience, known trends and events and various other factors that management believes to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying value of assets and liabilities that are not readily apparent from other sources. Although management believes its estimates and assumptions are reasonable when made, they are based upon information available at the time they are made. Management evaluates the estimates and assumptions on an ongoing basis and, if necessary, makes adjustments. Due to the risks and uncertainties involved in the Company’s business and evolving market conditions, including those related to the COVID-19 pandemic, and given the subjective element of the estimates and assumptions made, actual results may differ materially from estimated results.

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	3. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES The Company’s complete summary of significant accounting policies can be found in “Note 3. Summary of Significant Accounting Policies” in the audited financial statements included in the Company’s Form 10-K filed with the SEC on March 2, 2021.

Recent Accounting Pronouncement

Recent Accounting Pronouncements	6 Months Ended
	Jun. 30, 2021
New Accounting Pronouncements And Changes In Accounting Principles [Abstract]
Recent Accounting Pronouncements	4. RECENT ACCOUNTING PRONOUNCEMENTS New Accounting Standards Not Yet Adopted by the Company In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments “Topic 326” ASU 2019-04, ASU 2019-05, Financial Instruments - Credit Losses (Topic 326) Targeted Transition Relief the fair value option under ASC 825-10, Financial Instruments - Overall , applied on an instrument-by-instrument basis for eligible instruments ASU 2019-10, Topic 326, Topic 815, and Topic 842 amends the mandatory effective date for Topic 326. These ASUs are effective for fiscal years beginning after December 15, 2022 for entities that are eligible to be defined by the SEC as a smaller reporting company. The Company is a smaller reporting company. Although the impact upon adoption will depend on the financial instruments held by the Company at that time, the Company does not anticipate a significant impact on its financial statements based on the instruments currently held and its historical trend of bad debt expense relating to trade accounts receivable. ​ Other than the items noted above, there have been no new accounting pronouncements not yet effective or adopted in the current year that we believe have a significant impact, or potential significant impact, to our unaudited interim financial statements.

Fair Value Measurement and Fina

Fair Value Measurement and Financial Instruments	6 Months Ended
	Jun. 30, 2021
Fair Value Disclosures [Abstract]
Fair Value Measurement and Financial Instruments	5. FAIR VALUE MEASUREMENT AND FINANCIAL INSTRUMENTS The carrying values of cash equivalents, accounts receivable, prepaids and other current assets, and accounts payable on the Company’s balance sheets approximated their fair values as of June 30, 2021 and December 31, 2020 due to their short-term nature. The carrying values of the Company’s credit facility approximated its fair value as of June 30, 2021 and December 31, 2020 due to its variable interest rate. Certain of the Company’s financial instruments are measured at fair value using a three-level hierarchy that prioritizes the inputs used to measure fair value. This hierarchy maximizes the use of observable inputs and minimizes the use of unobservable inputs. The three levels of inputs used to measure fair value are as follows: Level 1 Inputs are quoted prices for identical instruments in active markets. Level 2 Inputs are quoted prices for similar instruments in active markets; quoted prices for identical or similar instruments in markets that are not active; or model-derived valuations whose inputs are observable or whose significant value drivers are observable. Level 3 Inputs are unobservable and reflect the Company’s own assumptions, based on the best information available, including the Company’s own data . The following tables set forth the carrying amounts and fair values of the Company’s financial instruments as of June 30, 2021 and December 31, 2020 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2021 ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurement Based on ​ ​ ​ ​ ​ ​ ​ ​ Quoted ​ Significant ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Prices In ​ other ​ Significant ​ ​ ​ ​ ​ ​ ​ ​ Active ​ Observable ​ Unobservable ​ ​ Carrying ​ ​ ​ ​ Markets ​ Inputs ​ Inputs ​ Amount Fair Value (Level 1) (Level 2) (Level 3) Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds (cash equivalents) ​ $ 114,626 ​ $ 114,626 ​ $ 114,626 ​ $ — ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurement Based on ​ ​ ​ ​ ​ ​ ​ ​ Quoted ​ Significant ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Prices In ​ other ​ Significant ​ ​ ​ ​ ​ ​ ​ ​ Active ​ Observable ​ Unobservable ​ ​ Carrying ​ ​ ​ ​ Markets ​ Inputs ​ Inputs ​ ​ Amount ​ Fair Value ​ (Level 1) ​ (Level 2) ​ (Level 3) Assets ​ ​ ​ ​ ​ Money market funds (cash equivalents) ​ $ 47,117 ​ $ 47,117 ​ $ 47,117 ​ $ — ​ $ — ​

Accounts Receivable

Accounts Receivable	6 Months Ended
	Jun. 30, 2021
Receivables [Abstract]
Accounts Receivable	6. ACCOUNTS RECEIVABLE The following table presents the composition of accounts receivable, net as of June 30, 2021 and December 31, 2020 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ ​ 2021 2020 ​ Gross accounts receivable - trade ​ $ 9,926 ​ $ 8,178 ​ Less: Allowances for doubtful accounts ​ (924) ​ (1,012) ​ Accounts receivable, net ​ $ 9,002 ​ $ 7,166 ​ ​

Property and Equipment and Capi

Property and Equipment and Capitalized Software	6 Months Ended
	Jun. 30, 2021
Property Plant And Equipment [Abstract]
Property and Equipment and Capitalized Software	7. PROPERTY AND EQUIPMENT AND CAPITALIZED SOFTWARE The following table presents the composition of property and equipment, net as of June 30, 2021 and December 31, 2020 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ ​ 2021 2020 ​ Laboratory equipment ​ $ 184 ​ $ 150 ​ Office equipment ​ 497 ​ 487 ​ Computer equipment and software ​ 1,541 ​ 1,360 ​ Manufacturing equipment ​ 327 ​ 273 ​ Leasehold improvements ​ 459 ​ 459 ​ Rental equipment ​ 131 ​ 405 ​ Property and equipment, gross ​ 3,139 ​ 3,134 ​ Less: Accumulated depreciation ​ (2,431) ​ (2,404) ​ Property and equipment, net ​ $ 708 ​ $ 730 ​ ​ As of June 30, 2021 and December 31, 2020, the Company had capitalized software costs, net of $1.6 million and $1.2 million, respectively, which are included in “Prepaid expenses and other current assets” and “Other assets” on the balance sheet. Depreciation and amortization expense was $0.3 million and $0.2 million for the three months ended June 30, 2021 and 2020, respectively, and $0.6 million and $0.5 million for the six months ended June 30, 2021 and 2020, respectively.

Leases

Leases	6 Months Ended
	Jun. 30, 2021
Leases [Abstract]
Leases	8. LEASES Lessee: The Company has operating leases for its corporate headquarters and office equipment, including copiers. The Company leases an approximately 32,000 square foot facility in Malvern, Pennsylvania for its corporate headquarters, which includes office and warehouse space. The Company does not currently have any finance leases or executed leases that have not yet commenced. Operating lease rent expense was $0.1 million and $0.2 million for the three months ended June 30, 2021 and 2020, respectively, and $0.3 million for the six months ended June 30, 2021 and 2020, respectively. As of June 30, 2021, the weighted-average remaining lease term of operating leases was 6.6 years and the weighted-average discount rate was 6.5%. In the first quarter of 2020, the Company received a reimbursement of $0.8 million for leasehold expenses previously incurred in connection with the lease agreement for its Malvern facility. The reimbursement was recorded as an offset to the non-current lease liability that was established when the lease agreement was executed. The following table presents the supplemental cash flow information as a lessee related to leases (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six Months Ended ​ ​ ​ June 30, 2021 June 30, 2020 ​ Cash paid for amounts included in the measurement of lease liabilities: ​ ​ ​ Operating cash flows from operating leases ​ $ 392 ​ $ 394 ​ ​ The following table sets forth by year the required future payments of operating lease liabilities (in thousands): ​ ​ ​ ​ ​ ​ ​ June 30, 2021 Remainder of 2021 ​ $ 313 2022 ​ ​ 639 2023 ​ 636 2024 ​ 646 2025 ​ 660 Thereafter ​ 1,487 Total lease payments ​ 4,381 Less imputed interest ​ (847) Present value of operating lease liabilities ​ $ 3,534 ​ Lessor sales-type leases: Certain customers have purchased NeuroStar Advanced Therapy Systems on a rent-to-own basis. The lease term is three The following table sets forth the profit recognized on sales-type leases (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended June 30, ​ Six Months Ended June 30, ​ 2021 2020 2021 2020 Profit recognized at commencement, net ​ $ 148 ​ $ 474 ​ $ 281 ​ $ 726 Interest income ​ — ​ — ​ — ​ — Total sales-type lease income ​ $ 148 ​ $ 474 ​ $ 281 ​ $ 726 ​ The following table sets forth a maturity analysis of the undiscounted lease receivables related to sales-type leases (in thousands): ​ ​ ​ ​ ​ ​ June 30, ​ ​ 2021 Remainder of 2021 ​ $ 1,176 2022 ​ ​ 1,804 2023 ​ 729 2024 ​ 140 2025 ​ ​ 39 Total sales-type lease receivables ​ $ 3,888 ​ As of June 30, 2021, the carrying amount of the lease receivables is $3.9 million. The Company does not Lessor operating leases: NeuroStar Advanced Therapy Systems sold on a rent-to-own basis prior to January 1, 2019 are accounted for as operating leases. For the three months ended June 30, 2021 and 2020, the Company recognized operating lease income of $0.1 million and $0.1 million, respectively. For the six months ended June 30, 2021 and 2020, the Company recognized operating lease income of $0.2 million and $0.2 million, respectively. The following table sets forth a maturity analysis of its undiscounted lease receivables related to operating leases as of June 30, 2021 (in thousands): ​ ​ ​ ​ ​ ​ June 30, ​ ​ 2021 Remainder of 2021 ​ $ 18 Total lease receivables ​ $ 18 ​ The Company maintained Rental Equipment, net of $0.1 million and $0.2 million as of June 30, 2021 and December 31, 2020, respectively, which are included in “Property and equipment, net” on the balance sheet. Rental equipment depreciation expense was $0.01 million and $0.02 million for the three months ended June 30, 2021 and 2020, respectively, and $0.02 million and $0.05 million for the six months ended June 30, 2021 and 2020.

Prepaid Commission Expense

Prepaid Commission Expense	6 Months Ended
	Jun. 30, 2021
Amortization Of Deferred Charges [Abstract]
Prepaid Commission Expense	9. PREPAID COMMISSION EXPENSE The Company pays a commission on both NeuroStar Advanced System sales and Treatment Session sales. Since the commission paid for System sales is not commensurate with the commission paid for Treatment Sessions, the Company capitalizes commission expense associated with NeuroStar Advanced Therapy System sales commissions paid that is incremental to specifically anticipated future Treatment Session orders. In developing this estimate, the Company considered its historical Treatment Session sales and customer retention rates, as well as technology development life cycles and other industry factors. These costs are periodically reviewed for impairment. NeuroStar Advanced Therapy System commissions are deferred and amortized on a straight-line basis over a seven year period equal to the average customer term, which the Company deems to be the expected period of benefit for these costs. On the Company’s balance sheets, the current portion of capitalized contract costs is represented by the current portion of prepaid commission expense, while the long-term portion is included in prepaid commission expense. Amortization expense was $0.3 million and $0.2 million for the three months ended June 30, 2021 and 2020, respectively, and $0.6 million and $0.4 million for the six months ended June 30, 2021 and 2020, respectively.

Accrued Expenses

Accrued Expenses	6 Months Ended
	Jun. 30, 2021
Payables And Accruals [Abstract]
Accrued Expenses	10. ACCRUED EXPENSES The following table presents the composition of accrued expenses as of June 30, 2021 and December 31, 2020 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, December 31, ​ ​ 2021 ​ 2020 Compensation and related benefits ​ $ 3,707 ​ $ 5,023 Consulting and professional fees ​ 525 ​ 292 Research and development expenses ​ 539 ​ 138 Sales and marketing expenses ​ ​ 344 ​ ​ 73 Warranty ​ 381 ​ 536 Sales and other taxes payable ​ 680 ​ 726 Other ​ 428 ​ 531 Accrued expenses ​ $ 6,604 ​ $ 7,319 ​

Deferred Revenue

Deferred Revenue	6 Months Ended
	Jun. 30, 2021
Deferred Revenue [Abstract]
Deferred Revenue	11. DEFERRED REVENUE Payment terms typically require payment upon shipment or installation of the System and additional payments as access codes for Treatment Sessions are delivered, which can span several years after the System is first delivered and installed. The timing of revenue recognition compared to billings and cash collections typically results in accounts receivable. However, sometimes customer advances and deposits might be required for certain customers and are recorded as deferred revenue. For multi-year agreements, the Company generally invoices customers annually at the beginning of each annual coverage period and recognizes revenue over the term of the coverage period. As of June 30, 2021, the Company expects to recognize approximately the following percentages of deferred revenue by year: ​ ​ ​ ​ ​ ​ Revenue Year: ​ Recognition Remainder of 2021 ​ 38 % 2022 23 % 2023 17 % 2024 17 % 2025 5 % Thereafter — % Total 100 % ​ Customers For the three months ended June 30, 2021 and 2020, one customer accounted for more than 10% of the Company’s revenues, respectively. For the six months ended June 30, 2021 and 2020, one customer accounted for more than 10% of the Company’s revenues, respectively.

Debt

Debt	6 Months Ended
	Jun. 30, 2021
Debt Disclosure [Abstract]
Debt	12. DEBT The following table presents the composition of debt as of June 30, 2021 and December 31, 2020 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ ​ 2021 2020 ​ Outstanding principal ​ $ 35,000 ​ $ 35,000 ​ Accrued final payment fees ​ 1,925 ​ 1,925 ​ Less debt discounts ​ (1,981) ​ (2,305) ​ Total debt, net ​ 34,944 ​ 34,620 ​ Less current portion ​ — ​ — ​ Long-term debt, net ​ $ 34,944 ​ $ 34,620 ​ ​ For the three months ended June 30, 2021, the Company recognized interest expense of $1.0 million, of which $0.8 million was cash and $0.2 million was non-cash interest expense related to the amortization of deferred debt issuance costs and accrual of final payment fees. For the three months ended June 30, 2020, the Company recognized interest expense of $1.0 million, of which $0.8 million was cash paid for interest during the period and $0.2 million was non-cash interest expense related to the amortization of deferred debt issuance costs and accrual of final payment fees. For the six months ended June 30, 2021, the Company recognized interest expense of $2.0 million, of which $1.7 million was cash and $0.3 million was non-cash interest expense related to the amortization of deferred debt issuance costs and accrual of final payment fees. For the six months ended June 30, 2020, the Company recognized interest expense of $2.5 million, of which $2.2 million was cash paid for interest during the period and $0.3 million was non-cash interest expense related to the amortization of deferred debt issuance costs and accrual of final payment fees. Solar Credit Facility On March 2, 2020, the “Company entered into a loan and security agreement with Solar Capital Ltd., or Solar, as collateral agent, and other lenders defined in the agreement, for a credit facility, or the Solar Facility, that replaced the Company’s previous $35.0 million credit facility with Oxford Finance LLC, or Oxford, and such facility, the Oxford Facility. The Solar Facility permits the Company to borrow up to an aggregate amount of $50.0 million in two tranches of term loans, a “Term A Loan” and “Term B Loan.” On March 2, 2020, the Company borrowed an aggregate amount of $35.0 million, which was the aggregate amount available under the Term A Loan portion of the Solar Facility. The Term A Loan portion of the Solar Facility matures, and all amounts borrowed thereunder are due, on February 28, 2025. Under the Term B Loan portion of the Solar Facility, the Company is permitted to borrow, at its election, up to an aggregate amount of $15.0 million, (i) upon the Company achieving a specified amount of trailing twelve Each of the Term A Loan and Term B Loan accrue interest from the date of borrowing through the date of repayment at a floating per annum rate of interest, which resets monthly and is equal to 7.65% plus the greater of (a) 1.66% or (b) the rate per annum rate published by the Intercontinental Exchange Benchmark Administration Ltd. The Term A Loan and the Term B Loan both include an interest-only period through March February 2023 In addition to the principal and interest payments due under the Solar Facility, the Company is required to pay a final payment fee to Solar due upon the earlier of prepayment, acceleration or the maturity date of the Term A Loan or Term B Loan portion of the Solar Facility equal to 5.50% of the principal amount of the term loans actually funded. The Company is accruing the final payment fees using the effective interest rate, with a charge to non-cash interest expense, over the term of borrowing. If the Company prepays either the of the Term A Loan or Term B Loan prior to their respective scheduled maturities, the Company will also be required to pay prepayment fees to Solar equal to 3% of the principal amount of such term loan then-prepaid if prepaid on or before the first anniversary of funding, 2% of the principal amount of such term loan then-prepaid if prepaid after the first anniversary and on or before the second anniversary of funding, or 1% of the principal amount of such term loan then-prepaid if prepaid after the second anniversary of funding of the principal amounts borrowed. The Company is also required to pay Solar an exit fee upon the occurrence, prior to March 2, 2030, of (a) any liquidation, dissolution or winding up of the Company, (b) transaction that results in a person obtaining control over the Company, (c) the Company achieving $100 million in trailing twelve month net product revenue or (d) the Company achieving $125 million in trailing twelve month net product revenue. The exit fee for liquidation, dissolution, winding up or change of control of the Company is equal to 4.50% of the principal amount of the term loans actually funded. The exit fee for achieving either $100 million or $125 million in trailing twelve-month net product revenue is equal to 2.25% of the principal amount of the term loans actually funded or, if both net product revenue milestones are achieved, 4.50% of the principal amount of the term loans actually funded. The exit fee is capped at 4.50% of the principal amount of the term loans actually funded. On December 8, 2020, the Company, Solar Capital Ltd., and our other lenders defined in the Solar Facility, executed an amendment to the Solar Facility (the “Solar Amendment”). The Solar Amendment divides the aggregate Term B Loan borrowing amount of $15.0 million allowable upon our achievement of specific trailing twelve-month net product revenue targets into three separate $5.0 million tranches (“Amended Term B Loan”, “Term C Loan” and “Term D Loan”). The three tranches are available through June 20, 2021, December 20, 2021, and June 20, 2022, respectively, based on the achievement of agreed upon trailing twelve-month net product revenue targets for each tranche. The Solar Amendment also reduces the trailing twelve-month net product revenue requirement for the Amended Term B Loan portion of the facility. Subject to certain conditions, the Company has the ability to extend the interest-only period on the initial Term A Loan to 36 months from 24 months upon achieving the revenue targets associated with the Amended Term B Loan. As of June 30, 2021, the Company is in compliance with the required minimum net product revenue covenant and anticipates electing to extend the interest-only period through March 1, 2023 for the Term A Loan, subject to continuing to meet the required conditions through and as of March 1, 2022. The Company is projected to be in compliance with the required covenant. The Company was required to pay an amendment fee of $0.1 million to Solar, which has been recognized as a deferred debt issuance cost as of December 31, 2020 that will be amortized to interest expense using the effective interest method. The Company’s obligations under the Solar Facility are secured by a first priority security interest in substantially all of its assets, including its intellectual property. The loan and security agreement requires the Company to comply with certain financial covenants as well as customary affirmative and negative covenants. The Solar Facility contains events of default, including, without limitation, events of default upon: (i) failure to make payment pursuant to the terms of the agreement; (ii) violation of covenants; (iii) material adverse changes to the Company’s business; (iv) attachment or levy on the Company’s assets or judicial restraint on its business; (v) insolvency; (vi) material cross-defaults; (vii) significant judgments, orders or decrees for payments by the Company not covered by insurance; (viii) incorrectness of representations and warranties; (ix) incurrence of subordinated debt; (x) a termination or breach of a guaranty; (xi) revocation of governmental approvals necessary for the Company to conduct its business; and (xii) failure by the Company to maintain a valid and perfected lien on the collateral securing the borrowing. The Solar Facility includes subjective acceleration clauses which permit the lenders to accelerate the maturity date under certain circumstances, including, but not limited to, material adverse effects on a Company’s financial status or otherwise. The Solar Facility includes a financial covenant requiring the attainment of a minimum trailing net revenue amount beginning on December 31, 2020. The Company and lenders executed the Solar Amendment in December 2020 that reduced the minimum trailing net revenue covenant requirement amounts beginning on December 31, 2020 to allow the Company to maintain compliance with the covenant as of December 31, 2020. As of June 30, 2021, the Company is in compliance with the financial covenant and is projected to be in compliance with the reduced minimum revenue covenant amounts going forward. As of June 30, 2021, the Company is in compliance with all covenants in the Solar Facility. Oxford Credit Facility Prior to March 2020, the Company had a $35.0 million credit facility in place with Oxford, which it entered into in March 2017 and that allowed it to borrow up to $35.0 million in three tranches of term loans: a Term A Loan in the amount of $25 million, which was drawn immediately upon closing in March 2017, a Term B Loan in the amount of $5.0 million, which was drawn down in December 2017, and a Term C Loan in the amount of $5.0 million which was never drawn down. Each term loan accrued interest from the date of borrowing through the date of repayment at a floating per annum rate of interest, which reset monthly and was equal to the greater of (a) 8.15% or (b) the 30 day U.S. LIBOR on the last business day of the month plus 7.38%. This facility featured an interest-only period on all tranches through March 2019. In addition to principal and interest payments due under the $35.0 million Oxford credit facility, the Company was required to make final payment fees to Oxford upon the earlier of prepayment or maturity and equal to 8.5% and 7.5% of the principal amounts of the Term A and Term B Loans, respectively. The Company accrued final payment fees using the effective interest rate, with a charge to non-cash interest expense, over the term of borrowing and until its entry into the Solar credit facility in March 2020, at which time the Company paid Oxford $2.5 million in satisfaction of all final payment fee liabilities due under the Oxford credit facility. The Company evaluated whether the Solar Facility entered into in March 2020 represented a debt modification or extinguishment in accordance with ASC 470-50, Debt—Modifications and Extinguishments and determined that the existing debt was extinguished as a result of the full repayment of the existing facility and concurrent issuance of a new credit facility with a new lender. The unamortized balance of the Company’s combined debt discount and deferred issuance costs of $0.6 million related to the Oxford facility were accounted for as a loss on extinguishment of debt in March 2020.

Common Stock

Common Stock	6 Months Ended
	Jun. 30, 2021
Equity [Abstract]
Common Stock	13. COMMON STOCK Common Stock Offering On February 2, 2021, we closed on our public offering and sale (the “Offering) of our common stock in which we issued and sold 5,566,000 shares of our common stock, which included shares pursuant to an option granted to underwriters to purchase additional shares, at a public offering price of $15.50 per share. We received net proceeds of $80.6 million after deducting underwriting discounts, commissions and offering expenses. Common Stock The following table summarizes the total number of shares of the Company’s common stock issued and reserved for issuance as of June 30, 2021 and December 31, 2020 (in thousands): ​ ​ ​ ​ ​ ​ ​ June 30, 2021 December 31, 2020 Shares of common stock issued 26,167 19,114 Shares of common stock reserved for issuance for: Common stock warrants outstanding 75 105 Stock options outstanding 1,607 2,365 Restricted stock units outstanding 2,139 1,860 Shares available for grant under stock incentive plan 2,153 1,530 Shares available for sale under employee stock purchase plan 799 608 Total shares of common stock issued and reserved for issuance 32,940 25,582 ​ Common Stock Warrants The following tables summarize the Company’s outstanding common stock warrants as of June 30, 2021, and December 31, 2020: ​ ​ ​ ​ ​ ​ ​ June 30, 2021 ​ Warrants ​ Outstanding ​ ​ ​ ​ ​ (in thousands) ​ Exercise Price ​ Expiration Date 14 ​ $ 19.55 Dec-2022 20 ​ $ 9.73 Aug-2023 20 ​ $ 9.73 Mar-2024 21 ​ $ 9.73 Dec-2024 75 ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ Warrants ​ Outstanding ​ ​ ​ ​ ​ (in thousands) ​ Exercise Price ​ Expiration Date 14 ​ $ 19.55 Dec-2022 30 ​ $ 9.73 Feb-2021 20 ​ $ 9.73 Aug-2023 20 ​ $ 9.73 Mar-2024 21 ​ $ 9.73 Dec-2024 105 ​ ​

Loss Per Share

Loss Per Share	6 Months Ended
	Jun. 30, 2021
Earnings Per Share [Abstract]
Loss Per Share	14. LOSS PER SHARE The Company’s basic loss per common share is computed by dividing the net loss by the weighted-average number of shares of common stock outstanding during the period. The Company’s restricted stock awards (non-vested shares) are issued and outstanding at the time of grant but are excluded from the Company’s computation of weighted-average shares outstanding in the determination of basic loss per share until vesting occurs. A net loss cannot be diluted, so when the Company is in a net loss position, basic and diluted loss per common share are the same. If in the future the Company achieves profitability, the denominator of a diluted earnings per common share calculation will include both the weighted-average number of shares outstanding and the number of common stock equivalents, if the inclusion of such common stock equivalents would be dilutive. Dilutive common stock equivalents potentially include warrants, stock options, non-vested restricted stock units and non-vested performance restricted stock units using the treasury stock method, along with the effect, if any, from the potential conversion of outstanding securities, such as convertible preferred stock. The following potentially dilutive securities outstanding as of June 30, 2021 and 2020 have been excluded from the denominator of the diluted loss per share of common stock outstanding calculation (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ ​ 2021 2020 ​ Stock options ​ 1,607 ​ 1,865 ​ Non-vested performance restricted stock units 395 — ​ Non-vested restricted stock units 1,744 1,289 ​ Common stock warrants 75 105 ​ ​

Share-Based Compensation

Share-Based Compensation	6 Months Ended
	Jun. 30, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Share-Based Compensation	15. SHARE-BASED COMPENSATION The amount of share-based compensation expense recognized by the Company by location in its statements of operations for the three and six months ended June 30, 2021 and 2020 is as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended June 30, ​ Six Months Ended June 30, ​ ​ ​ 2021 2020 2021 2020 ​ Cost of revenues ​ $ 13 ​ $ 15 ​ $ 33 ​ $ 31 ​ Sales and marketing ​ 518 ​ 236 ​ 1,093 ​ 666 ​ General and administrative ​ 1,482 ​ 261 ​ 3,000 ​ 868 ​ Research and development ​ (4) ​ 134 ​ 79 ​ 277 ​ Total ​ $ 2,009 ​ $ 646 ​ $ 4,205 ​ $ 1,842 ​ ​ 2018 Equity Incentive Plan In June 2018, the Company adopted the 2018 Equity Incentive Plan, or 2018 Plan, which authorized the issuance of up to 1.4 million shares, subject to an annual 4% increase based on the number of shares of common stock outstanding, in the form of restricted stock, stock appreciation rights and stock options to the Company’s directors, employees and consultants. The amount and terms of grants are determined by the Company’s board of directors. All stock options granted to date have had exercise prices equal to the fair value, as determined by the closing price as reported by the Nasdaq Global Market, of the underlying common stock on the date of grant. The contractual term of stock options is up to 10 years, and stock options are exercisable in cash or as otherwise determined by the board of directors. Generally, stock options vest 25% upon the first anniversary of the date of grant and the remainder ratably monthly thereafter for 36 months. Restricted stock units generally vest ratably in three equal installments on the first, second and third anniversaries of the grant date. Performance restricted stock units (“PRSUs”) generally vest based on appreciation of the Company’s common stock to a certain price as determined by the Company’s board of directors measured using a trailing 30-day volume weighted average price of a share of the Company’s common stock. The fair value of the PRSU awards are determined using a risk neutral Monte Carlo simulation valuation model. As of June 30, 2021, there were 2.1 million shares available for future issuance under the 2018 Plan. 2020 Inducement Incentive Plan In December 2020, the Company adopted the 2020 Inducement Incentive Plan, which authorized the issuance of up to 0.4 million shares in the form of stock options, stock appreciation rights, restricted stock awards, restricted stock unit awards, performance stock awards and other stock awards to eligible employees who satisfy the standards for inducement grants under Nasdaq global market rules. An individual who previously served as an employee or director of the Company is not eligible to receive awards under this plan. The amount and terms of grants are determined by the Company’s board of directors. As of June 30, 2021, there were 0.1 million shares available for future issuance under the 2020 Inducement Incentive Plan. Stock Options The following table summarizes the Company’s stock option activity for the six months ended June 30, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Aggregate ​ ​ Number of ​ Weighted- ​ Weighted- ​ average ​ ​ Shares under ​ average ​ Remaining ​ Intrinsic ​ ​ Option ​ Exercise Price ​ Contractual ​ Value ​ ​ (in thousands) ​ per Option ​ Life (in years) ​ (in thousands) Outstanding at December 31, 2020 2,365 ​ $ 4.62 ​ ​ ​ Granted — ​ $ — ​ Exercised (655) ​ $ 3.94 ​ Forfeited (103) ​ $ 14.84 ​ Outstanding at June 30, 2021 1,607 ​ $ 4.39 7.8 $ 18,763 Exercisable at June 30, 2021 451 ​ $ 7.44 5.0 $ 3,925 Vested and expected to vest at June 30, 2021 1,607 ​ $ 4.39 7.8 $ 18,763 ​ The Company recognized share-based compensation expense related to stock options of $0.2 million and $0.3 million for the three months ended June 30, 2021 and 2020, respectively, and $0.4 million and $0.8 million for the six months ended June 30, 2021 and 2020, respectively. As of June 30, 2021, there was $1.7 million of total unrecognized compensation cost related to non-vested stock options which the Company expects to recognize over a weighted-average period of 2.5 years. The total intrinsic value of stock options exercised during the six months ended June 30, 2021 was $8.0 million. Restricted Stock Units and Performance Restricted Stock Units The following table summarizes the Company’s restricted stock unit and performance restricted stock unit activity for June 30, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Non-vested ​ Weighted- Non-vested ​ Weighted- ​ ​ Restricted ​ ​ average ​ Performance Restricted ​ ​ average ​ ​ Stock Units ​ ​ Grant-date ​ Stock Units ​ ​ Grant-date ​ ​ (in thousands) ​ ​ Fair Value ​ (in thousands) ​ ​ Fair Value Non-vested at December 31, 2020 ​ 1,860 ​ $ 3.58 500 ​ $ 1.71 Granted 721 ​ $ 13.58 145 ​ $ 15.59 Vested (586) ​ $ 3.65 (250) ​ $ 1.77 Forfeited (250) ​ $ 6.88 — ​ $ — Non-vested at June 30, 2021 1,744 ​ $ 7.21 395 ​ $ 6.77 ​ The Company recognized $1.8 million and $0.4 million in share-based compensation expense related to the restricted stock units and performance restricted stock units for the three months ended June 30, 2021 and 2020, respectively, and $3.8 and $1.0 million for the six months ended June 30, 2021 and 2020, respectively. As of June 30, 2021, there was $11.9 million of unrecognized compensation cost related to non-vested restricted stock units and performance restricted stock units, which the Company expects to recognize over a weighted-average period of 2.3 years. The total fair value at the vesting date of restricted stock units and performance restricted stock units vested during the six months ended June 30, 2021, was $11.8 million. For the period ended June 30, 2021 and December 31, 2020, the grant-date fair value of the performance restricted stock units was estimated at the time of grant using the following inputs and assumptions in the Monte Carlo simulation valuation model: ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2021 ​ ​ December 31, 2020 Closing price of common stock ​ $ 15.92 ​ $ 1.98 ​ Risk-free interest rate ​ 1.15 % ​ 0.63 % Expected volatility ​ 99.7 % ​ 87.4 % ​

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2021
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	16. COMMITMENTS AND CONTINGENCIES Legal Matters The Company is subject from time to time to various claims and legal actions arising during the ordinary course of its business. Management believes that there are currently no claims or legal actions that would reasonably be expected to have a material adverse effect on the Company’s results of operations, financial condition, or cash flows.

Geographical Segment Informatio

Geographical Segment Information	6 Months Ended
	Jun. 30, 2021
Segments Geographical Areas [Abstract]
Geographical Segment Information	17. GEOGRAPHICAL SEGMENT INFORMATION Operating segments are defined as components of an enterprise about which separate discrete information is available for evaluation by the chief operating decision maker, or decision-making group, in deciding how to allocate resources and in assessing performance. The Company currently operates in one business segment as it is managed and operated as one business. A single management team that reports to the chief operating decision maker comprehensively manages the entire business. The Company does not operate any material separate lines of business or separate business entities with respect to its products or product development. The following geographic data includes revenue generated from the Company’s third-party distributors. The Company’s revenue was generated in the following geographic regions and by product line for the periods indicated (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Revenues by Geography ​ ​ Three Months Ended June 30, ​ ​ 2021 ​ 2020 ​ ​ ​ ​ ​ % of ​ ​ ​ ​ % of ​ ​ Amount ​ Revenues ​ Amount ​ Revenues ​ ​ (in thousands, except percentages) ​ United States $ 13,809 97 % $ 9,267 95 % International ​ 394 3 % 474 5 % Total revenues ​ $ 14,203 100 % $ 9,741 100 % ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Revenues by Product Category ​ ​ Three Months Ended June 30, ​ ​ 2021 ​ 2020 ​ ​ ​ ​ ​ % of ​ ​ ​ % of ​ Amount Revenues Amount Revenues ​ (in thousands, except percentages) ​ NeuroStar Advanced Therapy System ​ $ 2,577 ​ 19 % $ 2,338 ​ 25 % Treatment sessions ​ 10,801 78 % 6,547 71 % Other ​ 431 3 % 382 4 % Total U.S. revenues ​ $ 13,809 100 % $ 9,267 100 % ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ International Revenues by Product Category ​ ​ Three Months Ended June 30, ​ ​ 2021 ​ 2020 ​ ​ ​ ​ ​ % of ​ ​ ​ ​ % of ​ Amount Revenues Amount Revenues ​ (in thousands, except percentages) ​ NeuroStar Advanced Therapy System ​ $ 284 72 % $ 310 66 % Treatment sessions ​ 14 4 % 115 24 % Other ​ 96 24 % 49 10 % Total International revenues ​ $ 394 100 % $ 474 100 % ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Revenues by Geography ​ ​ ​ Six Months Ended June 30, ​ ​ ​ 2021 ​ 2020 ​ ​ ​ ​ ​ ​ % of ​ ​ ​ ​ % of ​ ​ ​ Amount ​ Revenues ​ Amount ​ Revenues ​ ​ ​ (in thousands, except percentages) ​ ​ United States $ 25,611 97 % $ 20,444 96 % ​ International ​ 880 3 % 773 4 % ​ Total revenues ​ $ 26,491 100 % $ 21,217 100 % ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Revenues by Product Category ​ ​ ​ Six Months Ended June 30, ​ ​ ​ 2021 ​ 2020 ​ ​ ​ ​ ​ ​ % of ​ ​ ​ % of ​ ​ Amount Revenues Amount Revenues ​ ​ (in thousands, except percentages) ​ ​ NeuroStar Advanced Therapy System ​ $ 4,333 ​ 17 % $ 4,932 ​ 24 % ​ Treatment sessions ​ 20,429 80 % 14,740 72 % ​ Other ​ 849 3 % 772 4 % ​ Total U.S. revenues ​ $ 25,611 100 % $ 20,444 100 % ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ International Revenues by Product Category ​ ​ ​ Six Months Ended June 30, ​ ​ ​ 2021 ​ 2020 ​ ​ ​ ​ ​ ​ % of ​ ​ ​ ​ % of ​ ​ Amount Revenues Amount Revenues ​ ​ (in thousands, except percentages) ​ ​ NeuroStar Advanced Therapy System ​ $ 491 56 % $ 410 53 % ​ Treatment sessions ​ 145 16 % 192 25 % ​ Other ​ 244 28 % 171 22 % ​ Total International revenues ​ $ 880 100 % $ 773 100 % ​ ​

Severance

Severance	6 Months Ended
	Jun. 30, 2021
Restructuring And Related Activities [Abstract]
Severance	18. SEVERANCE On April 8, 2020, the Company took action to reduce expenses through a reduction in force (“RIF”). As part of this action the Company terminated 95 employees who received separation benefits upon their termination. During the second quarter of 2020, the Company recorded a separation-related charge for the RIF equal to the fair value of the terminated employees benefits as of the communication date in the amount of $2.1 million. This amount was paid out during the quarter with the final payoff occurring on June 15, 2020. The Company entered into transition agreements outlining the separation with its former chief executive officer in March 2020, the vice president of medical operations in September 2020, the chief commercial officer and director of medical operations in December 2020, the VP of sales and five business development managers in January 2021, the director of strategic clinical development in February 2021, and other employees during the three months ended June 30, 2021. In connection with these agreements, the Company recorded $0.1 million and $1.1 million of charges in salary, payroll tax and bonus expenses for the three months ended June 30, 2021 and 2020, respectively, and $0.2 million and $1.1 million for the six months ended June 30, 2021 and 2020, respectively. For the six months ended June 30, 2021 and 2020, $0.8 million and $0.3 million of termination benefits were paid associated with the termination of the employees and charged against this liability. As of June 30, 2021 and December 31, 2020, $0.4 million and $1.0 million, respectively, remain in accrued liabilities for the unpaid portion of the separation benefits.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Interim Financial Statements	Interim Financial Statements The accompanying unaudited interim financial statements have been prepared from the books and records of the Company in accordance with GAAP for interim financial information and Rule 10-01 of Regulation S-X promulgated by the United States Securities and Exchange Commission, or SEC, which permit reduced disclosures for interim periods. All adjustments, consisting only of normal recurring adjustments, necessary for a fair presentation of the accompanying balance sheets and statements of operations and stockholders’ deficit and cash flows have been made. Although these interim financial statements do not include all of the information and footnotes required for complete annual financial statements, management believes the disclosures are adequate to make the information presented not misleading. Unaudited interim results of operations and cash flows for the three and six months ended June 30, 2021 are not necessarily indicative of the results that may be expected for the full year. Unaudited interim financial statements and footnotes should be read in conjunction with the audited financial statements and footnotes included in the Company’s Form 10-K filed with the SEC on March 2, 2021, wherein a more complete discussion of significant accounting policies and certain other information can be found.
Use of Estimates	Use of Estimates The preparation of financial statements in accordance with GAAP and the rules and regulations of the SEC requires the use of estimates and assumptions, based on judgments considered reasonable, which affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. The Company bases its estimates and assumptions on historical experience, known trends and events and various other factors that management believes to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying value of assets and liabilities that are not readily apparent from other sources. Although management believes its estimates and assumptions are reasonable when made, they are based upon information available at the time they are made. Management evaluates the estimates and assumptions on an ongoing basis and, if necessary, makes adjustments. Due to the risks and uncertainties involved in the Company’s business and evolving market conditions, including those related to the COVID-19 pandemic, and given the subjective element of the estimates and assumptions made, actual results may differ materially from estimated results.

Fair Value Measurement and Fi_2

Fair Value Measurement and Financial Instruments (Tables)	6 Months Ended
	Jun. 30, 2021
Fair Value Disclosures [Abstract]
Schedule of Carrying Amounts and Fair Values of Financial Instruments	The following tables set forth the carrying amounts and fair values of the Company’s financial instruments as of June 30, 2021 and December 31, 2020 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2021 ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurement Based on ​ ​ ​ ​ ​ ​ ​ ​ Quoted ​ Significant ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Prices In ​ other ​ Significant ​ ​ ​ ​ ​ ​ ​ ​ Active ​ Observable ​ Unobservable ​ ​ Carrying ​ ​ ​ ​ Markets ​ Inputs ​ Inputs ​ Amount Fair Value (Level 1) (Level 2) (Level 3) Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds (cash equivalents) ​ $ 114,626 ​ $ 114,626 ​ $ 114,626 ​ $ — ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurement Based on ​ ​ ​ ​ ​ ​ ​ ​ Quoted ​ Significant ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Prices In ​ other ​ Significant ​ ​ ​ ​ ​ ​ ​ ​ Active ​ Observable ​ Unobservable ​ ​ Carrying ​ ​ ​ ​ Markets ​ Inputs ​ Inputs ​ ​ Amount ​ Fair Value ​ (Level 1) ​ (Level 2) ​ (Level 3) Assets ​ ​ ​ ​ ​ Money market funds (cash equivalents) ​ $ 47,117 ​ $ 47,117 ​ $ 47,117 ​ $ — ​ $ —

Accounts Receivable (Tables)

Accounts Receivable (Tables)	6 Months Ended
	Jun. 30, 2021
Receivables [Abstract]
Composition of Accounts Receivable, Net	The following table presents the composition of accounts receivable, net as of June 30, 2021 and December 31, 2020 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ ​ 2021 2020 ​ Gross accounts receivable - trade ​ $ 9,926 ​ $ 8,178 ​ Less: Allowances for doubtful accounts ​ (924) ​ (1,012) ​ Accounts receivable, net ​ $ 9,002 ​ $ 7,166 ​

Property and Equipment and Ca_2

Property and Equipment and Capitalized Software (Tables)	6 Months Ended
	Jun. 30, 2021
Property Plant And Equipment [Abstract]
Summary of Composition of Property and Equipment, Net	The following table presents the composition of property and equipment, net as of June 30, 2021 and December 31, 2020 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ ​ 2021 2020 ​ Laboratory equipment ​ $ 184 ​ $ 150 ​ Office equipment ​ 497 ​ 487 ​ Computer equipment and software ​ 1,541 ​ 1,360 ​ Manufacturing equipment ​ 327 ​ 273 ​ Leasehold improvements ​ 459 ​ 459 ​ Rental equipment ​ 131 ​ 405 ​ Property and equipment, gross ​ 3,139 ​ 3,134 ​ Less: Accumulated depreciation ​ (2,431) ​ (2,404) ​ Property and equipment, net ​ $ 708 ​ $ 730 ​

Leases (Tables)

Leases (Tables)	6 Months Ended
	Jun. 30, 2021
Leases [Abstract]
Schedule of Supplemental Cash Flow Information as Lessee Related to Leases	The following table presents the supplemental cash flow information as a lessee related to leases (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six Months Ended ​ ​ ​ June 30, 2021 June 30, 2020 ​ Cash paid for amounts included in the measurement of lease liabilities: ​ ​ ​ Operating cash flows from operating leases ​ $ 392 ​ $ 394 ​
Schedule of Future Payments of Operating Lease Liabilities	The following table sets forth by year the required future payments of operating lease liabilities (in thousands): ​ ​ ​ ​ ​ ​ ​ June 30, 2021 Remainder of 2021 ​ $ 313 2022 ​ ​ 639 2023 ​ 636 2024 ​ 646 2025 ​ 660 Thereafter ​ 1,487 Total lease payments ​ 4,381 Less imputed interest ​ (847) Present value of operating lease liabilities ​ $ 3,534
Schedule of Profit Recognized on Sales-type Leases	The following table sets forth the profit recognized on sales-type leases (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended June 30, ​ Six Months Ended June 30, ​ 2021 2020 2021 2020 Profit recognized at commencement, net ​ $ 148 ​ $ 474 ​ $ 281 ​ $ 726 Interest income ​ — ​ — ​ — ​ — Total sales-type lease income ​ $ 148 ​ $ 474 ​ $ 281 ​ $ 726
Schedule of Maturity Analysis of Undiscounted Lease Receivables Related to Sales-type Leases	The following table sets forth a maturity analysis of the undiscounted lease receivables related to sales-type leases (in thousands): ​ ​ ​ ​ ​ ​ June 30, ​ ​ 2021 Remainder of 2021 ​ $ 1,176 2022 ​ ​ 1,804 2023 ​ 729 2024 ​ 140 2025 ​ ​ 39 Total sales-type lease receivables ​ $ 3,888
Schedule of Maturity Analysis of Undiscounted Lease Receivable Related to Operating Leases	The following table sets forth a maturity analysis of its undiscounted lease receivables related to operating leases as of June 30, 2021 (in thousands): ​ ​ ​ ​ ​ ​ June 30, ​ ​ 2021 Remainder of 2021 ​ $ 18 Total lease receivables ​ $ 18

Accrued Expenses (Tables)

Accrued Expenses (Tables)	6 Months Ended
	Jun. 30, 2021
Payables And Accruals [Abstract]
Summary of Composition of Accrued Expenses	The following table presents the composition of accrued expenses as of June 30, 2021 and December 31, 2020 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, December 31, ​ ​ 2021 ​ 2020 Compensation and related benefits ​ $ 3,707 ​ $ 5,023 Consulting and professional fees ​ 525 ​ 292 Research and development expenses ​ 539 ​ 138 Sales and marketing expenses ​ ​ 344 ​ ​ 73 Warranty ​ 381 ​ 536 Sales and other taxes payable ​ 680 ​ 726 Other ​ 428 ​ 531 Accrued expenses ​ $ 6,604 ​ $ 7,319

Deferred Revenue (Tables)

Deferred Revenue (Tables)	6 Months Ended
	Jun. 30, 2021
Deferred Revenue [Abstract]
Summary of Percentages of Deferred Revenue by Year	As of June 30, 2021, the Company expects to recognize approximately the following percentages of deferred revenue by year: ​ ​ ​ ​ ​ ​ Revenue Year: ​ Recognition Remainder of 2021 ​ 38 % 2022 23 % 2023 17 % 2024 17 % 2025 5 % Thereafter — % Total 100 %

Debt (Tables)

Debt (Tables)	6 Months Ended
	Jun. 30, 2021
Debt Disclosure [Abstract]
Summary of Composition of Debt	The following table presents the composition of debt as of June 30, 2021 and December 31, 2020 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ ​ 2021 2020 ​ Outstanding principal ​ $ 35,000 ​ $ 35,000 ​ Accrued final payment fees ​ 1,925 ​ 1,925 ​ Less debt discounts ​ (1,981) ​ (2,305) ​ Total debt, net ​ 34,944 ​ 34,620 ​ Less current portion ​ — ​ — ​ Long-term debt, net ​ $ 34,944 ​ $ 34,620 ​

Common Stock (Tables)

Common Stock (Tables)	6 Months Ended
	Jun. 30, 2021
Equity [Abstract]
Summary of Common Stock Issued and Reserved for Issuance	The following table summarizes the total number of shares of the Company’s common stock issued and reserved for issuance as of June 30, 2021 and December 31, 2020 (in thousands): ​ ​ ​ ​ ​ ​ ​ June 30, 2021 December 31, 2020 Shares of common stock issued 26,167 19,114 Shares of common stock reserved for issuance for: Common stock warrants outstanding 75 105 Stock options outstanding 1,607 2,365 Restricted stock units outstanding 2,139 1,860 Shares available for grant under stock incentive plan 2,153 1,530 Shares available for sale under employee stock purchase plan 799 608 Total shares of common stock issued and reserved for issuance 32,940 25,582
Summary of Outstanding Warrants	The following tables summarize the Company’s outstanding common stock warrants as of June 30, 2021, and December 31, 2020: ​ ​ ​ ​ ​ ​ ​ June 30, 2021 ​ Warrants ​ Outstanding ​ ​ ​ ​ ​ (in thousands) ​ Exercise Price ​ Expiration Date 14 ​ $ 19.55 Dec-2022 20 ​ $ 9.73 Aug-2023 20 ​ $ 9.73 Mar-2024 21 ​ $ 9.73 Dec-2024 75 ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ Warrants ​ Outstanding ​ ​ ​ ​ ​ (in thousands) ​ Exercise Price ​ Expiration Date 14 ​ $ 19.55 Dec-2022 30 ​ $ 9.73 Feb-2021 20 ​ $ 9.73 Aug-2023 20 ​ $ 9.73 Mar-2024 21 ​ $ 9.73 Dec-2024 105 ​

Loss Per Share (Tables)

Loss Per Share (Tables)	6 Months Ended
	Jun. 30, 2021
Earnings Per Share [Abstract]
Schedule of Potentially Dilutive Securities Outstanding Excluded from Diluted Loss Per Share Calculation	The following potentially dilutive securities outstanding as of June 30, 2021 and 2020 have been excluded from the denominator of the diluted loss per share of common stock outstanding calculation (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ ​ 2021 2020 ​ Stock options ​ 1,607 ​ 1,865 ​ Non-vested performance restricted stock units 395 — ​ Non-vested restricted stock units 1,744 1,289 ​ Common stock warrants 75 105 ​

Share-Based Compensation (Table

Share-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Share-Based Compensation Expense	The amount of share-based compensation expense recognized by the Company by location in its statements of operations for the three and six months ended June 30, 2021 and 2020 is as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended June 30, ​ Six Months Ended June 30, ​ ​ ​ 2021 2020 2021 2020 ​ Cost of revenues ​ $ 13 ​ $ 15 ​ $ 33 ​ $ 31 ​ Sales and marketing ​ 518 ​ 236 ​ 1,093 ​ 666 ​ General and administrative ​ 1,482 ​ 261 ​ 3,000 ​ 868 ​ Research and development ​ (4) ​ 134 ​ 79 ​ 277 ​ Total ​ $ 2,009 ​ $ 646 ​ $ 4,205 ​ $ 1,842 ​
Summary of Stock Option Activity	The following table summarizes the Company’s stock option activity for the six months ended June 30, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Aggregate ​ ​ Number of ​ Weighted- ​ Weighted- ​ average ​ ​ Shares under ​ average ​ Remaining ​ Intrinsic ​ ​ Option ​ Exercise Price ​ Contractual ​ Value ​ ​ (in thousands) ​ per Option ​ Life (in years) ​ (in thousands) Outstanding at December 31, 2020 2,365 ​ $ 4.62 ​ ​ ​ Granted — ​ $ — ​ Exercised (655) ​ $ 3.94 ​ Forfeited (103) ​ $ 14.84 ​ Outstanding at June 30, 2021 1,607 ​ $ 4.39 7.8 $ 18,763 Exercisable at June 30, 2021 451 ​ $ 7.44 5.0 $ 3,925 Vested and expected to vest at June 30, 2021 1,607 ​ $ 4.39 7.8 $ 18,763
Summary of Restricted Stock Units and Performance Restricted Stock Units Activity	The following table summarizes the Company’s restricted stock unit and performance restricted stock unit activity for June 30, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Non-vested ​ Weighted- Non-vested ​ Weighted- ​ ​ Restricted ​ ​ average ​ Performance Restricted ​ ​ average ​ ​ Stock Units ​ ​ Grant-date ​ Stock Units ​ ​ Grant-date ​ ​ (in thousands) ​ ​ Fair Value ​ (in thousands) ​ ​ Fair Value Non-vested at December 31, 2020 ​ 1,860 ​ $ 3.58 500 ​ $ 1.71 Granted 721 ​ $ 13.58 145 ​ $ 15.59 Vested (586) ​ $ 3.65 (250) ​ $ 1.77 Forfeited (250) ​ $ 6.88 — ​ $ — Non-vested at June 30, 2021 1,744 ​ $ 7.21 395 ​ $ 6.77
Summary of Inputs and Assumptions used to Estimated Grant-date Fair Value of Performance Restricted Stock Units	For the period ended June 30, 2021 and December 31, 2020, the grant-date fair value of the performance restricted stock units was estimated at the time of grant using the following inputs and assumptions in the Monte Carlo simulation valuation model: ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2021 ​ ​ December 31, 2020 Closing price of common stock ​ $ 15.92 ​ $ 1.98 ​ Risk-free interest rate ​ 1.15 % ​ 0.63 % Expected volatility ​ 99.7 % ​ 87.4 %

Geographical Segment Informat_2

Geographical Segment Information (Tables)	6 Months Ended
	Jun. 30, 2021
Summary of Revenue Generated in Geographic Regions for Years Indicated	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Revenues by Geography ​ ​ Three Months Ended June 30, ​ ​ 2021 ​ 2020 ​ ​ ​ ​ ​ % of ​ ​ ​ ​ % of ​ ​ Amount ​ Revenues ​ Amount ​ Revenues ​ ​ (in thousands, except percentages) ​ United States $ 13,809 97 % $ 9,267 95 % International ​ 394 3 % 474 5 % Total revenues ​ $ 14,203 100 % $ 9,741 100 % ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Revenues by Geography ​ ​ ​ Six Months Ended June 30, ​ ​ ​ 2021 ​ 2020 ​ ​ ​ ​ ​ ​ % of ​ ​ ​ ​ % of ​ ​ ​ Amount ​ Revenues ​ Amount ​ Revenues ​ ​ ​ (in thousands, except percentages) ​ ​ United States $ 25,611 97 % $ 20,444 96 % ​ International ​ 880 3 % 773 4 % ​ Total revenues ​ $ 26,491 100 % $ 21,217 100 % ​
United States
Summary of Revenue Generated in Product Category for Years Indicated	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Revenues by Product Category ​ ​ Three Months Ended June 30, ​ ​ 2021 ​ 2020 ​ ​ ​ ​ ​ % of ​ ​ ​ % of ​ Amount Revenues Amount Revenues ​ (in thousands, except percentages) ​ NeuroStar Advanced Therapy System ​ $ 2,577 ​ 19 % $ 2,338 ​ 25 % Treatment sessions ​ 10,801 78 % 6,547 71 % Other ​ 431 3 % 382 4 % Total U.S. revenues ​ $ 13,809 100 % $ 9,267 100 % ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Revenues by Product Category ​ ​ ​ Six Months Ended June 30, ​ ​ ​ 2021 ​ 2020 ​ ​ ​ ​ ​ ​ % of ​ ​ ​ % of ​ ​ Amount Revenues Amount Revenues ​ ​ (in thousands, except percentages) ​ ​ NeuroStar Advanced Therapy System ​ $ 4,333 ​ 17 % $ 4,932 ​ 24 % ​ Treatment sessions ​ 20,429 80 % 14,740 72 % ​ Other ​ 849 3 % 772 4 % ​ Total U.S. revenues ​ $ 25,611 100 % $ 20,444 100 % ​
International
Summary of Revenue Generated in Product Category for Years Indicated	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ International Revenues by Product Category ​ ​ Three Months Ended June 30, ​ ​ 2021 ​ 2020 ​ ​ ​ ​ ​ % of ​ ​ ​ ​ % of ​ Amount Revenues Amount Revenues ​ (in thousands, except percentages) ​ NeuroStar Advanced Therapy System ​ $ 284 72 % $ 310 66 % Treatment sessions ​ 14 4 % 115 24 % Other ​ 96 24 % 49 10 % Total International revenues ​ $ 394 100 % $ 474 100 % ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ International Revenues by Product Category ​ ​ ​ Six Months Ended June 30, ​ ​ ​ 2021 ​ 2020 ​ ​ ​ ​ ​ ​ % of ​ ​ ​ ​ % of ​ ​ Amount Revenues Amount Revenues ​ ​ (in thousands, except percentages) ​ ​ NeuroStar Advanced Therapy System ​ $ 491 56 % $ 410 53 % ​ Treatment sessions ​ 145 16 % 192 25 % ​ Other ​ 244 28 % 171 22 % ​ Total International revenues ​ $ 880 100 % $ 773 100 % ​

Description of Business - Addit

Description of Business - Additional Information (Details) - USD ($) $ in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Apr. 30, 2020
Description Of Business [Line Items]
Cash and cash equivalents	$ 115,783		$ 48,957
Accumulated deficit	292,946		277,540
Cash flows from operating activities	14,940	$ 23,131	$ 28,400
Paycheck Protection Program (the "PPP") | Silicon Valley Bank
Description Of Business [Line Items]
Unsecured debt				$ 6,400
$35.0 Million Credit Facility | Oxford Finance LLC
Description Of Business [Line Items]
Borrowings outstanding under credit facility	$ 35,000
Credit facility maturity date	Feb. 1, 2025

Fair Value Measurement and Fi_3

Fair Value Measurement and Financial Instruments - Schedule of Carrying Amounts and Fair Values of Financial Instruments (Details) - Money market funds - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Carrying Amount
Assets
Total assets	$ 114,626	$ 47,117
Fair Value
Assets
Total assets	114,626	47,117
Quoted Prices In Active Markets (Level 1)
Assets
Total assets	$ 114,626	$ 47,117

Accounts Receivable - Compositi

Accounts Receivable - Composition of Accounts Receivable, Net (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Receivables [Abstract]
Gross accounts receivable - trade	$ 9,926	$ 8,178
Less: Allowances for doubtful accounts	(924)	(1,012)
Accounts receivable, net	$ 9,002	$ 7,166

Property and Equipment and Ca_3

Property and Equipment and Capitalized Software - Summary of Composition of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 3,139	$ 3,134
Less: Accumulated depreciation	(2,431)	(2,404)
Property and equipment, net	708	730
Laboratory Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	184	150
Office Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	497	487
Computer Equipment and Software
Property Plant And Equipment [Line Items]
Property and equipment, gross	1,541	1,360
Manufacturing Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	327	273
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross	459	459
Rental Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	131	405
Property and equipment, net	$ 100	$ 200

Property and Equipment and Ca_4

Property and Equipment and Capitalized Software - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Property Plant And Equipment [Line Items]
Depreciation and amortization expense	$ 0.3	$ 0.2	$ 0.6	$ 0.5
Prepaid Expenses and Other Current Assets [Member]
Property Plant And Equipment [Line Items]
Capitalized software cost, net	$ 1.6		$ 1.6
Other Assets [Member]
Property Plant And Equipment [Line Items]
Capitalized software cost, net					$ 1.2

Leases - Additional Information

Leases - Additional Information (Details) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2021USD ($)ft²	Jun. 30, 2020USD ($)	Mar. 31, 2020USD ($)	Jun. 30, 2021USD ($)ft²	Jun. 30, 2020USD ($)	Dec. 31, 2020USD ($)
Leases [Line Items]
Lessee, finance lease, lease not yet commenced, description				The Company does not currently have any finance leases or executed leases that have not yet commenced.
Operating lease, rent expense, net	$ 100	$ 200		$ 300	$ 300
Operating lease, weighted-average remaining lease term	6 years 7 months 6 days			6 years 7 months 6 days
Operating lease, weighted-average discount rate	6.50%			6.50%
Reimbursement of leasehold expenses			$ 800
Carrying amount of lease receivables	$ 3,900			$ 3,900
Unguaranteed residual assets	0			0
Operating lease income	100	100		200	200
Property and equipment, net	$ 708			$ 708		$ 730
NeuroStar Advanced Therapy Systems | Minimum
Leases [Line Items]
Lessor sales-type lease, Term	3 years			3 years
NeuroStar Advanced Therapy Systems | Maximum
Leases [Line Items]
Lessor sales-type lease, Term	4 years			4 years
Headquarters and Office Equipment, Including Copiers
Leases [Line Items]
Area of lease facility | ft²	32,000			32,000
Rental Equipment
Leases [Line Items]
Property and equipment, net	$ 100			$ 100		$ 200
Rental equipment depreciation expense	$ 10	$ 20		$ 20	$ 50

Leases - Schedule of Supplement

Leases - Schedule of Supplemental Cash Flow Information as Lessee Related to Leases (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$ 392	$ 394

Leases - Schedule of Future Pay

Leases - Schedule of Future Payments of Operating Lease Liabilities (Details) $ in Thousands	Jun. 30, 2021USD ($)
Operating Lease Liabilities Payments Due [Abstract]
Remainder of 2021	$ 313
2022	639
2023	636
2024	646
2025	660
Thereafter	1,487
Total lease payments	4,381
Less imputed interest	(847)
Present value of operating lease liabilities	$ 3,534

Leases - Schedule of Profit Rec

Leases - Schedule of Profit Recognized on Sales-type Leases (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Sales Type Lease Lease Income [Abstract]
Profit recognized at commencement, net	$ 148	$ 474	$ 281	$ 726
Total sales-type lease income	$ 148	$ 474	$ 281	$ 726

Leases - Schedule of Maturity A

Leases - Schedule of Maturity Analysis of Undiscounted Lease Receivables Related to Sales-type Leases (Details) $ in Thousands	Jun. 30, 2021USD ($)
Sales Type And Direct Financing Leases Lease Receivable Fiscal Year Maturity [Abstract]
Remainder of 2021	$ 1,176
2022	1,804
2023	729
2024	140
2025	39
Total sales-type lease receivables	$ 3,888

Leases - Schedule of Maturity_2

Leases - Schedule of Maturity Analysis of Undiscounted Lease Receivable Related to Operating Leases (Details) $ in Thousands	Jun. 30, 2021USD ($)
Lessor Operating Lease Payments Fiscal Year Maturity [Abstract]
Remainder of 2021	$ 18
Total lease receivables	$ 18

Prepaid Commission Expense - Ad

Prepaid Commission Expense - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Amortization Of Deferred Charges [Abstract]
Amortization period of deferred commissions			7 years
Amortization expense	$ 0.3	$ 0.2	$ 0.6	$ 0.4

Accrued Expenses - Summary of C

Accrued Expenses - Summary of Composition of Accrued Expenses (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Payables And Accruals [Abstract]
Compensation and related benefits	$ 3,707	$ 5,023
Consulting and professional fees	525	292
Research and development expenses	539	138
Sales and marketing expenses	344	73
Warranty	381	536
Sales and other taxes payable	680	726
Other	428	531
Accrued expenses	$ 6,604	$ 7,319

Deferred Revenue - Summary of P

Deferred Revenue - Summary of Percentages of Deferred Revenue by Year (Details)	Jun. 30, 2021
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Revenue, remaining performance obligation	100.00%
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction Start Date [Axis]: 2021-07-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Revenue, remaining performance obligation	38.00%
Revenue, remaining performance obligation, expected timing of satisfaction, period	1 year
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction Start Date [Axis]: 2022-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Revenue, remaining performance obligation	23.00%
Revenue, remaining performance obligation, expected timing of satisfaction, period	1 year
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction Start Date [Axis]: 2023-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Revenue, remaining performance obligation	17.00%
Revenue, remaining performance obligation, expected timing of satisfaction, period	1 year
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction Start Date [Axis]: 2024-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Revenue, remaining performance obligation	17.00%
Revenue, remaining performance obligation, expected timing of satisfaction, period	1 year
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction Start Date [Axis]: 2025-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Revenue, remaining performance obligation	5.00%
Revenue, remaining performance obligation, expected timing of satisfaction, period	1 year
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction Start Date [Axis]: 2026-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Revenue, remaining performance obligation, expected timing of satisfaction, period	1 year

Deferred Revenue - Additional I

Deferred Revenue - Additional Information (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021USD ($)customer	Jun. 30, 2020customer	Jun. 30, 2021USD ($)customer	Jun. 30, 2020customer
Deferred Revenue [Abstract]
Revenue recognized | $	$ 0.3		$ 1.5
Number of customer accounted for more than 10% of revenues | customer	1	1	1	1

Debt - Summary of Composition o

Debt - Summary of Composition of Debt (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Debt Disclosure [Abstract]
Outstanding principal	$ 35,000	$ 35,000
Accrued final payment fees	1,925	1,925
Less debt discounts	(1,981)	(2,305)
Total debt, net	34,944	34,620
Less current portion
Long-term debt, net	$ 34,944	$ 34,620

Debt - Additional Information (

Debt - Additional Information (Details)	Dec. 08, 2020USD ($)tranche	Mar. 02, 2020USD ($)trancheitem	Feb. 29, 2020USD ($)	Mar. 31, 2020USD ($)	Jun. 30, 2021USD ($)	Jun. 30, 2020USD ($)	Jun. 30, 2021USD ($)	Jun. 30, 2020USD ($)	Dec. 31, 2020USD ($)	Mar. 31, 2017USD ($)
Debt Instrument [Line Items]
Interest expense					$ 1,000,000	$ 1,000,000	$ 2,000,000	$ 2,500,000
Cash interest expense					800,000	800,000	1,700,000	2,200,000
Non-cash interest expense					200,000	$ 200,000	$ 300,000	$ 300,000
Solar Capital Ltd
Debt Instrument [Line Items]
Amendment fee payable									$ 100,000
Solar Capital Ltd | Term A Loan | Maximum
Debt Instrument [Line Items]
Extended period of interest only term loan	36 months
Solar Capital Ltd | Term A Loan | Minimum
Debt Instrument [Line Items]
Extended period of interest only term loan	24 months
Solar Capital Ltd | Term A Loan and Term B Loan
Debt Instrument [Line Items]
Basis spread on variable rate		1.66%
Interest rate		7.65%
Interest-only period		2022-03
Interest-only period upon achievement of revenues		2023-02
Number of default events | item		0
Line of credit facility, conversion to term loan, conditions							At the Company’s election, the interest only period may be extended through February 2023 if the Company satisfies a minimum net product revenue covenant through March 1, 2022 and no event of default shall have occurred
Solar Capital Ltd | $35.0 Million Credit Facility
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity										$ 35,000,000
Solar Capital Ltd | $35.0 Million Credit Facility | Term A Loan
Debt Instrument [Line Items]
Borrowings outstanding under credit facility		$ 35,000,000
Solar Capital Ltd | $50.0 Million Credit Facility
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity		$ 50,000,000
Term loans number of tranches | tranche		2
Increase in final payment fees percentage upon extension interest only periods		5.50%
Trailing twelve month net product revenue first threshold limit to pay exit fee		$ 100,000,000
Trailing twelve month net product revenue Second threshold limit to pay exit fee		$ 125,000,000
Percentage of exit fee for liquidation, dissolution, winding up or change of control of the Company		4.50%
Percentage of exit fee upon achievement of any trailing twelve month revenues		2.25%
Percentage of exit fee upon achievement of both trailing twelve month revenues		4.50%
Capped exit fee percentage on term loan principal amount		4.50%
Solar Capital Ltd | $50.0 Million Credit Facility | Prepaid on or Before First Anniversary of Funding
Debt Instrument [Line Items]
Prepayment fees percentage		3.00%
Solar Capital Ltd | $50.0 Million Credit Facility | Prepaid After First and on or Before Second Anniversary of Funding
Debt Instrument [Line Items]
Prepayment fees percentage		2.00%
Solar Capital Ltd | $50.0 Million Credit Facility | Prepaid After Second Anniversary of Funding
Debt Instrument [Line Items]
Prepayment fees percentage		1.00%
Solar Capital Ltd | $50.0 Million Credit Facility | Term A Loan
Debt Instrument [Line Items]
Credit facility maturity date		Feb. 28, 2025
Solar Capital Ltd | $15 Million Credit Facility
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 15,000,000
Solar Capital Ltd | $15 Million Credit Facility | Term B Loan
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity		$ 15,000,000
Line of credit facility, conversion to term loan, conditions							Under the Term B Loan portion of the Solar Facility, the Company is permitted to borrow, at its election, up to an aggregate amount of $15.0 million, (i) upon the Company achieving a specified amount of trailing twelve months net product revenue, and (ii) assuming there has been no event of default under the Solar Facility prior to such election. Once the net product revenue condition has been satisfied, the Company may only make an election to borrow under the Term B Loan portion of the Solar Facility until the earlier of (a) December 15, 2021, (b) 30 days following achievement of the net product revenue condition or (c) the occurrence of an event of default.
Solar Capital Ltd | $5.0 Million Credit Facility
Debt Instrument [Line Items]
Borrowings outstanding under credit facility	$ 5,000,000
Term loans number of tranches | tranche	3
Oxford Finance LLC
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity				$ 35,000,000
Debt instrument, final payment fee				2,500,000
Combined debt discount and deferred issuance costs				$ 600,000
Oxford Finance LLC | Term A Loan
Debt Instrument [Line Items]
Final payment fees percentage			8.50%
Oxford Finance LLC | Term B Loan
Debt Instrument [Line Items]
Final payment fees percentage			7.50%
Oxford Finance LLC | $35.0 Million Credit Facility
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity			$ 35,000,000
Borrowings outstanding under credit facility					$ 35,000,000		$ 35,000,000
Credit facility maturity date							Feb. 1, 2025
Debt instrument, interest rate					8.15%		8.15%
Oxford Finance LLC | $35.0 Million Credit Facility | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate							7.38%
Debt instrument, description of variable rate basis							30 day U.S. LIBOR
Oxford Finance LLC | $35.0 Million Credit Facility | Term A Loan
Debt Instrument [Line Items]
Borrowings outstanding under credit facility			25,000,000
Oxford Finance LLC | $35.0 Million Credit Facility | Term B Loan
Debt Instrument [Line Items]
Borrowings outstanding under credit facility			5,000,000
Oxford Finance LLC | $35.0 Million Credit Facility | Term C Loan
Debt Instrument [Line Items]
Line of credit facility, current borrowing capacity			$ 5,000,000

Common Stock - Additional Infor

Common Stock - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	Feb. 02, 2021	Jun. 30, 2021
Equity [Abstract]
Common stock shares issued and sold	5,566,000
Public offering price	$ 15.50
Net proceeds from initial public offering	$ 80,600	$ 80,972

Common Stock - Summary of Commo

Common Stock - Summary of Common Stock Issued and Reserved for Issuance (Details) - shares	Jun. 30, 2021	Dec. 31, 2020
Stockholders Deficit [Line Items]
Shares of common stock issued	26,167,000	19,114,000
Shares of common stock reserved for issuance for:
Total shares of common stock issued and reserved for issuance	32,940,000	25,582,000
Common Stock Warrants
Shares of common stock reserved for issuance for:
Shares of common stock reserved for issuance	75,000	105,000
Stock Options Outstanding
Shares of common stock reserved for issuance for:
Shares of common stock reserved for issuance	1,607,000	2,365,000
Restricted Stock Units Outstanding
Shares of common stock reserved for issuance for:
Shares of common stock reserved for issuance	2,139,000	1,860,000
Shares Available for Grant Under Stock Incentive Plan
Shares of common stock reserved for issuance for:
Shares of common stock reserved for issuance	2,153,000	1,530,000
Shares Available for Sales Under Employee Stock Purchase Plan
Shares of common stock reserved for issuance for:
Shares of common stock reserved for issuance	799,000	608,000

Common Stock - Summary of Outst

Common Stock - Summary of Outstanding Common Stock Warrants (Details) - $ / shares shares in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Class Of Warrant Or Right [Line Items]
Warrants Outstanding	75	105
Exercise Price $19.55
Class Of Warrant Or Right [Line Items]
Warrants Outstanding	14	14
Exercise Price	$ 19.55	$ 19.55
Expiration Date	2022-12	2022-12
Exercise Price $9.73.
Class Of Warrant Or Right [Line Items]
Warrants Outstanding		30
Exercise Price		$ 9.73
Expiration Date		2021-02
Exercise Price $9.73
Class Of Warrant Or Right [Line Items]
Warrants Outstanding	20	20
Exercise Price	$ 9.73	$ 9.73
Expiration Date	2023-08	2023-08
Exercise Price. $9.73
Class Of Warrant Or Right [Line Items]
Warrants Outstanding	20	20
Exercise Price	$ 9.73	$ 9.73
Expiration Date	2024-03	2024-03
Exercise Price. $9.73.
Class Of Warrant Or Right [Line Items]
Warrants Outstanding	21	21
Exercise Price	$ 9.73	$ 9.73
Expiration Date	2024-12	2024-12

Loss Per Share - Schedule of Po

Loss Per Share - Schedule of Potentially Dilutive Securities Outstanding Excluded from Diluted Loss Per Share Calculation (Details) - shares shares in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Stock Options Outstanding
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities outstanding excluded from diluted loss per share	1,607	1,865
Non-Vested Performance Restricted Stock Units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities outstanding excluded from diluted loss per share	395
Restricted Stock Units Outstanding
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities outstanding excluded from diluted loss per share	1,744	1,289
Common Stock Warrants
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities outstanding excluded from diluted loss per share	75	105

Share-Based Compensation - Summ

Share-Based Compensation - Summary of Share-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total	$ 2,009	$ 646	$ 4,205	$ 1,842
Cost of Revenues
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total	13	15	33	31
Sales and Marketing
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total	518	236	1,093	666
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total	1,482	261	3,000	868
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total	$ (4)	$ 134	$ 79	$ 277

Share-Based Compensation - Addi

Share-Based Compensation - Additional Information (Details) $ in Thousands, shares in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021USD ($)shares	Jun. 30, 2020USD ($)	Jun. 30, 2021USD ($)installmentshares	Jun. 30, 2020USD ($)	Dec. 31, 2020shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expenses	$ 2,009	$ 646	$ 4,205	$ 1,842
Intrinsic value of stock options exercised			8,000
Stock Options Outstanding
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expenses	200	300	400	800
Unrecognized compensation cost related to non-vested stock options	1,700		$ 1,700
Non-vested awards not yet recognized weighted-average period for recognition			2 years 6 months
Restricted Stock Units and Performance Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expenses	1,800	$ 400	$ 3,800	$ 1,000
Non-vested awards not yet recognized weighted-average period for recognition			2 years 3 months 18 days
Unrecognized compensation cost related to non-vested restricted stock	$ 11,900		$ 11,900
Fair value of restricted stock vested			$ 11,800
2018 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Annual percentage increase in number of shares authorized for issuance			4.00%
Vesting terms of stock options			stock options vest 25% upon the first anniversary of the date of grant and the remainder ratably monthly thereafter for 36 months. Restricted stock units generally vest ratably in three equal installments on the first, second and third anniversaries of the grant date.
Number of vesting installments | installment			3
Shares available for future issuance | shares	2.1		2.1
2018 Equity Incentive Plan | PRSUs | Common Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted average price, number of days trailing			30 days
2018 Equity Incentive Plan | First Anniversary of Date of Grant
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting percentage of stock options			25.00%
2018 Equity Incentive Plan | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized for issuance | shares	1.4		1.4
Maximum contractual term of stock options			10 years
2020 Inducement Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares available for future issuance | shares	0.1		0.1
2020 Inducement Incentive Plan | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized for issuance | shares					0.4

Share-Based Compensation - Su_2

Share-Based Compensation - Summary of Stock Option Activity (Details) - Stock Options Outstanding - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	6 Months Ended
	Jun. 30, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares under Option, Outstanding, Beginning balance	2,365
Number of Shares under Option, Exercised	(655)
Number of Shares under Option, Forfeited	(103)
Number of Shares under Option, Outstanding, Ending balance	1,607
Number of Shares under Option, Exercisable	451
Number of Shares under Option, Vested and expected to vest	1,607
Weighted-average Exercise Price per Option, Outstanding, Beginning balance	$ 4.62
Weighted-average Exercise Price per Option, Exercised	3.94
Weighted-average Exercise Price per Option, Forfeited	14.84
Weighted-average Exercise Price per Option, Outstanding, Ending balance	4.39
Weighted-average Exercise Price per Option, Exercisable	7.44
Weighted-average Exercise Price per Option, Vested and expected to vest	$ 4.39
Weighted-average Remaining Contractual Life, Outstanding	7 years 9 months 18 days
Weighted-average Remaining Contractual Life, Exercisable	5 years
Weighted-average Remaining Contractual Life, Vested and expected to vest	7 years 9 months 18 days
Aggregate Intrinsic Value, Outstanding	$ 18,763
Aggregate Intrinsic Value, Exercisable	3,925
Aggregate Intrinsic Value, Vested and expected to vest	$ 18,763

Share-Based Compensation - Su_3

Share-Based Compensation - Summary of Restricted Stock Units and Performance Restricted Stock Unit Activity (Details) shares in Thousands	6 Months Ended
	Jun. 30, 2021$ / sharesshares
Restricted Stock Units Outstanding
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Non-vested, Beginning balance | shares	1,860
Granted | shares	721
Vested | shares	(586)
Forfeited | shares	(250)
Non-vested, Ending balance | shares	1,744
Weighted-average Grant-date Fair Value, Non-vested, Beginning balance | $ / shares	$ 3.58
Weighted-average Grant-date Fair Value, Granted | $ / shares	13.58
Weighted-average Grant-date Fair Value, Vested | $ / shares	3.65
Weighted-average Grant-date Fair Value, Forfeited | $ / shares	6.88
Weighted-average Grant-date Fair Value, Non-vested, Ending balance | $ / shares	$ 7.21
Performance Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Non-vested, Beginning balance | shares	500
Granted | shares	145
Vested | shares	(250)
Non-vested, Ending balance | shares	395
Weighted-average Grant-date Fair Value, Non-vested, Beginning balance | $ / shares	$ 1.71
Weighted-average Grant-date Fair Value, Granted | $ / shares	15.59
Weighted-average Grant-date Fair Value, Vested | $ / shares	1.77
Weighted-average Grant-date Fair Value, Non-vested, Ending balance | $ / shares	$ 6.77

Share-Based Compensation - Su_4

Share-Based Compensation - Summary of Inputs and Assumptions used to Estimated Grant-date Fair Value of Performance Restricted Stock Unit (Details) - $ / shares	6 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020	Feb. 02, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Closing price of common stock			$ 15.50
Performance Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Closing price of common stock	$ 15.92	$ 1.98
Risk-free interest rate	1.15%	0.63%
Expected volatility	99.70%	87.40%

Geographical Segment Informat_3

Geographical Segment Information - Additional Information (Details)	6 Months Ended
	Jun. 30, 2021segment
Segments Geographical Areas [Abstract]
Number of operating business segment	1

Geographical Segment Informat_4

Geographical Segment Information - Summary of Revenue Generated in Geographic Regions for Years Indicated (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Revenues	$ 14,203	$ 9,741	$ 26,491	$ 21,217
Revenues | Geographic Concentration
Segment Reporting Information [Line Items]
Revenues	$ 14,203	$ 9,741	$ 26,491	$ 21,217
Percentage of Revenues	100.00%	100.00%	100.00%	100.00%
Revenues | United States | Geographic Concentration
Segment Reporting Information [Line Items]
Revenues	$ 13,809	$ 9,267	$ 25,611	$ 20,444
Percentage of Revenues	97.00%	95.00%	97.00%	96.00%
Revenues | International | Geographic Concentration
Segment Reporting Information [Line Items]
Revenues	$ 394	$ 474	$ 880	$ 773
Percentage of Revenues	3.00%	5.00%	3.00%	4.00%

Geographical Segment Informat_5

Geographical Segment Information - Summary of Revenue Generated in Product Category for Years Indicated (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Revenues	$ 14,203	$ 9,741	$ 26,491	$ 21,217
Product Category | United States | Revenues
Segment Reporting Information [Line Items]
Revenues	$ 13,809	$ 9,267	$ 25,611	$ 20,444
Percentage of Revenues	100.00%	100.00%	100.00%	100.00%
Product Category | United States | Revenues | NeuroStar Advanced Therapy System
Segment Reporting Information [Line Items]
Revenues	$ 2,577	$ 2,338	$ 4,333	$ 4,932
Percentage of Revenues	19.00%	25.00%	17.00%	24.00%
Product Category | United States | Revenues | Treatment Sessions
Segment Reporting Information [Line Items]
Revenues	$ 10,801	$ 6,547	$ 20,429	$ 14,740
Percentage of Revenues	78.00%	71.00%	80.00%	72.00%
Product Category | United States | Revenues | Other
Segment Reporting Information [Line Items]
Revenues	$ 431	$ 382	$ 849	$ 772
Percentage of Revenues	3.00%	4.00%	3.00%	4.00%
Product Category | International | Revenues
Segment Reporting Information [Line Items]
Revenues	$ 394	$ 474	$ 880	$ 773
Percentage of Revenues	100.00%	100.00%	100.00%	100.00%
Product Category | International | Revenues | NeuroStar Advanced Therapy System
Segment Reporting Information [Line Items]
Revenues	$ 284	$ 310	$ 491	$ 410
Percentage of Revenues	72.00%	66.00%	56.00%	53.00%
Product Category | International | Revenues | Treatment Sessions
Segment Reporting Information [Line Items]
Revenues	$ 14	$ 115	$ 145	$ 192
Percentage of Revenues	4.00%	24.00%	16.00%	25.00%
Product Category | International | Revenues | Other
Segment Reporting Information [Line Items]
Revenues	$ 96	$ 49	$ 244	$ 171
Percentage of Revenues	24.00%	10.00%	28.00%	22.00%

Severance - Additional Informat

Severance - Additional Information (Details) $ in Thousands	Apr. 08, 2020employee	Jun. 30, 2021USD ($)	Jun. 30, 2020USD ($)	Jun. 30, 2021USD ($)	Jun. 30, 2020USD ($)	Dec. 31, 2020USD ($)
Restructuring Cost And Reserve [Line Items]
Accrued liabilities		$ 6,604		$ 6,604		$ 7,319
Transition Separation Agreement
Restructuring Cost And Reserve [Line Items]
Restructuring charges		100	$ 1,100	200	$ 1,100
Accrued liabilities		$ 400		400		$ 1,000
Reduction in Force
Restructuring Cost And Reserve [Line Items]
Number of employees terminated | employee	95
Restructuring charges			$ 2,100
Termination Benefits | Transition Separation Agreement
Restructuring Cost And Reserve [Line Items]
Payments for restructuring				$ 800	$ 300