Summary of Significant Accounting Policies (Policies)	9 Months Ended
Sep. 30, 2023
Accounting Policies [Abstract]
Basis of Presentation and Unaudited Interim Financial Information	Basis of Presentation The unaudited interim condensed financial statements have been prepared in conformity with generally accepted accounting principles in the United States, or GAAP, as defined by the Financial Accounting Standards Board, or the FASB. Unaudited Interim Financial Information The condensed balance sheet as of December 31, 2022 was derived from the Company’s audited financial statements, but does not include all disclosures required by GAAP. The accompanying unaudited condensed financial statements as of September 30, 2023 and for the three and nine months ended September 30, 2023 and 2022, have been prepared by the Company, pursuant to the rules and regulations of the Securities and Exchange Commission, or the SEC, for interim financial statements. Certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. However, the Company believes that the disclosures are adequate to make the information presented not misleading. Accordingly, these financial statements should be read in conjunction with the audited financial statements as of and for the year ended December 31, 2022 and notes thereto, which are included in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2022 filed with the SEC on March 2, 2023. In the opinion of management, all adjustments, consisting only of normal recurring adjustments necessary for a fair statement of the Company’s condensed financial position as of September 30, 2023 and condensed results of operations for the three and nine months ended September 30, 2023 and 2022 and condensed cash flows for the nine months ended September 30, 2023 and 2022 have been made. The results of operations for the three and nine months ended September 30, 2023 are not necessarily indicative of the results of operations that may be expected for the year ending December 31, 2023.
Use of Estimates	Use of Estimates The preparation of unaudited interim condensed financial statements in conformity with GAAP requires the Company to make estimates and assumptions that affect the amounts and disclosures reported in the financial statements. The Company uses significant judgment when making estimates related to the valuation of deferred tax assets and related valuation allowances and provision for excess and obsolete inventories. The Company bases its estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Although these estimates are based on the Company’s knowledge of current events and actions it may undertake in the future, actual results may ultimately materially differ from these estimates and assumptions.
Fair Value of Financial Instruments and Fair Value Measurements	Fair Value of Financial Instruments Carrying amounts of certain of the Company’s financial instruments, including cash equivalents, accounts receivable, accounts payable and accrued liabilities, approximate fair value because of the short-term nature of these instruments. The Company has a short-term investment in a fixed income mutual fund, which is classified as equity security and carried at fair value based on quoted market prices. Changes in the fair value of the short-term investment are recorded in income or loss. The Company believes that its borrowings bear interest at the prevailing market rates for instruments with similar characteristics; accordingly, the carrying value of this instrument approximates its fair value. The Company determines the fair value of financial and non-financial assets and liabilities using the fair value hierarchy which establishes three levels of inputs that may be used to measure fair valueThe Company measures certain financial assets and liabilities at fair value on a recurring basis. Fair value is an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or a liability. A three-tier fair value hierarchy is established as a basis for considering such assumptions and for inputs used in the valuation methodologies in measuring fair value: Level 1Quoted prices in active markets for identical assets or liabilities. Level 2Observable inputs other than Level 1 prices such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. The Company utilizes the market approach to measure fair value for its financial assets and liabilities. The market approach uses prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities.
Concentration of Credit Risk, and Other Risks and Uncertainties	Concentration of Credit Risk, and Other Risks and Uncertainties Financial instruments that potentially subject the Company to credit risk consist of cash and cash equivalents, short-term investments and accounts receivable to the extent of the amounts recorded on the balance sheets. The Company’s cash is invested in major financial institutions in the United States. Deposits in these financial institutions may exceed federally insured limits, and the Company is exposed to credit risk on deposits in the event of default of the financial institutions to the extent account balances exceed the amount insured by the Federal Deposit Insurance Corporation. The Company’s cash equivalents are invested in money market funds. The Company’s accounts receivable are due from a variety of health care organizations in the United States. For the three and nine months ended September 30, 2023 and 2022, there were no customers that represented 10% or more of revenue. As of September 30, 2023 and December 31, 2022, no customer represented 10% or more of the Company’s accounts receivable. The Company is subject to certain risks, including that its devices may not be approved or cleared or continue to be approved or cleared for marketing by governmental authorities or be successfully marketed for expanded indications. There can be no assurance that the Company’s products will achieve widespread adoption in the marketplace, nor can there be any assurance that existing devices or any future devices can be developed or manufactured at an acceptable cost and speed and with appropriate performance characteristics. The Company is also subject to risks common to companies in the medical device industry, including, but not limited to, new technological innovations, dependence on healthcare providers to prescribe initial implants and replacements, dependence upon third-party payors to provide adequate coverage and reimbursement, dependence on key personnel, single-source suppliers and vendors in connection with the manufacture of its products, concentration of comprehensive epilepsy centers, or CECs, and epileptologists, obtaining, maintaining, protecting, enforcing, and defending intellectual property rights and proprietary technology, product liability claims, legal proceedings, and compliance with government regulations. The Company’s medical devices require approvals or clearances from the U.S. Food and Drug Administration, or the FDA, or international regulatory agencies. In addition, in order to continue the Company’s operations, compliance with various federal and state laws is required. If approvals or clearances were withdrawn by the FDA for the Company’s current products or if such approvals or clearances were denied or delayed for future products, product updates, or expanded indications for use, it would have a material adverse impact on the Company.
Accounts Receivable	Accounts Receivable Accounts receivable are recorded at the invoiced amount and do not bear interest. The Company makes estimates on the collectability of customer accounts based primarily on analysis of historical trends and experience, the age of the receivable and changes in customers’ financial condition. The Company uses its judgment, based on the best available facts and circumstances, and records an allowance against amounts due to reduce the receivable to the amount that is expected to be collected. The Company determined that no allowance was required as of September 30, 2023 and December 31, 2022. To date, the Company has not experienced any credit-related losses.
Government Programs	Government Programs In May 2021, the Company was awarded a grant by the National Institutes of Health, or NIH, to support research of thalamocortical responsive neurostimulation for the treatment of Lennox-Gastaut Syndrome, a type of epilepsy. The award was issued for a five-year period and has a total budget of over $9.3 million, which includes approximately $5.5 million in funding for subawards to third party academic epilepsy centers that are collaborating on the study and are subinvestigators on the study funded by NIH. The subawardees are determined by NIH. The Company’s responsibility for the subawards is to submit the funding requests on behalf of the subawardees. The funding of subawards does not have any impact on the Company’s condensed financial statements. Initially funding was approved for the first year beginning June 1, 2021 and provides for reimbursement of qualified direct and indirect expenses in the amount of $0.8 million, including $0.4 million for subawards. Approvals of funds for years two through five are subject to the completion of certain milestones. On July 30, 2022, the Company received funding approval for year two in the amount of $2.6 million, which includes $1.6 million for subawards. On May 25, 2023, the Company received funding approval for year three in the amount of $3.0 million, which includes $1.5 million for subawards. For funds received under the NIH funding agreement, the Company recognizes a reduction in research and development expenses in an amount equal to the qualifying expenses incurred in each period up to the amount awarded by the NIH. Qualifying expenses incurred by the Company in advance of funding by the NIH are recorded within prepaid expenses and other current assets on the balance sheets. Through September 30, 2023, $1.7 million of qualifying expenses have been incurred and funded by the NIH related to the first, second and third year funding. As of September 30, 2023, the Company recorded prepaid expenses and other current assets of $0.1 million related to the third year funding.
Net Loss per Share Attributable to Common Stockholders	Net Loss per Share Attributable to Common Stockholders Basic net loss per common share is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of shares of common stock outstanding during the period, without consideration of potentially dilutive securities. Diluted net loss per share is computed by dividing the net loss attributable to common stockholders by the weighted-average number of shares of common stock and potentially dilutive securities outstanding for the period. For purposes of the diluted net loss per share calculation, stock options, common stock subject to repurchase related to early exercise of stock options, and restricted stock units are considered to be potentially dilutive securities. Basic and diluted net loss attributable to common stockholders per share is presented in conformity with the two-class method required for participating securities. The Company considers the shares issued upon the early exercise of stock options subject to repurchase to be participating securities, because holders of such shares have non-forfeitable dividend rights in the event a dividend is paid on common stock. The holders of the shares issued upon early exercise of stock options subject to repurchase do not have a contractual obligation to share in the Company’s losses. As such, the net loss was attributed entirely to common stockholders. Because the Company has reported a net loss for all periods presented, diluted net loss per common share is the same as basic net loss per common share for those periods.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Recently Adopted Accounting Pronouncements In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, which amends existing guidance on the impairment of financial assets and adds an impairment model that is based on expected losses rather than incurred losses and requires an entity to recognize as an allowance its estimate of expected credit losses for its financial assets. An entity will apply this guidance through a cumulative-effect adjustment to retained earnings upon adoption (a modified-retrospective approach) while a prospective transition approach is required for debt securities for which an other-than-temporary impairment had been recognized before the effective date. For public business entities that meet the definition of an SEC filer, excluding entities eligible to be smaller reporting companies as defined by the SEC, adoption is effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. For SEC filers that are eligible to be smaller reporting companies and for all other entities, this ASU is effective for fiscal years beginning after December 15, 2022, and interim periods within those fiscal years. The Company adopted this ASU effective January 1, 2023. The adoption of this ASU did not have a material effect on the Company’s financial statements and related disclosures.

Summary of Significant Accounting Policies (Policies)

9 Months Ended

Sep. 30, 2023

Basis of Presentation and Unaudited Interim Financial Information

Basis of Presentation

The unaudited interim condensed financial statements have been prepared in conformity with generally accepted accounting principles in the United States, or GAAP, as defined by the Financial Accounting Standards Board, or the FASB.

Unaudited Interim Financial Information

The condensed balance sheet as of December 31, 2022 was derived from the Company’s audited financial statements, but does not include all disclosures required by GAAP. The accompanying unaudited condensed financial statements as of September 30, 2023 and for the three and nine months ended September 30, 2023 and 2022, have been prepared by the Company, pursuant to the rules and regulations of the Securities and Exchange Commission, or the SEC, for interim financial statements. Certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. However, the Company believes that the disclosures are adequate to make the information presented not misleading. Accordingly, these financial statements should be read in conjunction with the audited financial statements as of and for the year ended December 31, 2022 and notes thereto, which are included in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2022 filed with the SEC on March 2, 2023. In the opinion of management, all adjustments, consisting only of normal recurring adjustments necessary for a fair statement of the Company’s condensed financial position as of September 30, 2023 and condensed results of operations for the three and nine months ended September 30, 2023 and 2022 and condensed cash flows for the nine months ended September 30, 2023 and 2022 have been made. The results of operations for the three and nine months ended September 30, 2023 are not necessarily indicative of the results of operations that may be expected for the year ending December 31, 2023.

Use of Estimates

The preparation of unaudited interim condensed financial statements in conformity with GAAP requires the Company to make estimates and assumptions that affect the amounts and disclosures reported in the financial statements. The Company uses significant judgment when making estimates related to the valuation of deferred tax assets and related valuation allowances and provision for excess and obsolete inventories. The Company bases its estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Although these estimates are based on the Company’s knowledge of current events and actions it may undertake in the future, actual results may ultimately materially differ from these estimates and assumptions.

Fair Value of Financial Instruments and Fair Value Measurements

Fair Value of Financial Instruments

Carrying amounts of certain of the Company’s financial instruments, including cash equivalents, accounts receivable, accounts payable and accrued liabilities, approximate fair value because of the short-term nature of these instruments. The Company has a short-term investment in a fixed income mutual fund, which is classified as equity security and carried at fair value based on quoted market prices. Changes in the fair value of the short-term

investment are recorded in income or loss. The Company believes that its borrowings bear interest at the prevailing market rates for instruments with similar characteristics; accordingly, the carrying value of this instrument approximates its fair value. The Company determines the fair value of financial and non-financial assets and liabilities using the fair value hierarchy which establishes three levels of inputs that may be used to measure fair valueThe Company measures certain financial assets and liabilities at fair value on a recurring basis. Fair value is an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be

determined based on assumptions that market participants would use in pricing an asset or a liability. A three-tier fair value hierarchy is established as a basis for considering such assumptions and for inputs used in the valuation methodologies in measuring fair value:

Level 1Quoted prices in active markets for identical assets or liabilities.

Level 2Observable inputs other than Level 1 prices such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.

Level 3Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.

The Company utilizes the market approach to measure fair value for its financial assets and liabilities. The market approach uses prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities.

Concentration of Credit Risk, and Other Risks and Uncertainties

Financial instruments that potentially subject the Company to credit risk consist of cash and cash equivalents, short-term investments and accounts receivable to the extent of the amounts recorded on the balance sheets. The Company’s cash is invested in major financial institutions in the United States. Deposits in these financial institutions may exceed federally insured limits, and the Company is exposed to credit risk on deposits in the event of default of the financial institutions to the extent account balances exceed the amount insured by the Federal Deposit Insurance Corporation. The Company’s cash equivalents are invested in money market funds.

The Company’s accounts receivable are due from a variety of health care organizations in the United States. For the three and nine months ended September 30, 2023 and 2022, there were no customers that represented 10% or more of revenue. As of September 30, 2023 and December 31, 2022, no customer represented 10% or more of the Company’s accounts receivable.

The Company is subject to certain risks, including that its devices may not be approved or cleared or continue to be approved or cleared for marketing by governmental authorities or be successfully marketed for expanded indications. There can be no assurance that the Company’s products will achieve widespread adoption in the marketplace, nor can there be any assurance that existing devices or any future devices can be developed or manufactured at an acceptable cost and speed and with appropriate performance characteristics. The Company is also subject to risks common to companies in the medical device industry, including, but not limited to, new technological innovations, dependence on healthcare providers to prescribe initial implants and replacements, dependence upon third-party payors to provide adequate coverage and reimbursement, dependence on key personnel, single-source suppliers and vendors in connection with the manufacture of its products, concentration of comprehensive epilepsy centers, or CECs, and epileptologists, obtaining, maintaining, protecting, enforcing, and defending intellectual property rights and proprietary technology, product liability claims, legal proceedings, and compliance with government regulations.

The Company’s medical devices require approvals or clearances from the U.S. Food and Drug Administration, or the FDA, or international regulatory agencies. In addition, in order to continue the Company’s operations, compliance with various federal and state laws is required. If approvals or clearances were withdrawn by the FDA for the Company’s current products or if such approvals or clearances were denied or delayed for future products, product updates, or expanded indications for use, it would have a material adverse impact on the Company.

Accounts Receivable

Accounts receivable are recorded at the invoiced amount and do not bear interest. The Company makes estimates on the collectability of customer accounts based primarily on analysis of historical trends and experience, the age of the receivable and changes in customers’ financial condition. The Company uses its judgment, based on the best available facts and circumstances, and records an allowance against amounts due to reduce the receivable to the amount that is expected to be collected. The Company determined that no allowance was required as of September 30, 2023 and December 31, 2022. To date, the Company has not experienced any credit-related losses.

Government Programs

In May 2021, the Company was awarded a grant by the National Institutes of Health, or NIH, to support research of thalamocortical responsive neurostimulation for the treatment of Lennox-Gastaut Syndrome, a type of epilepsy. The award was issued for a five-year period and has a total budget of over $9.3 million, which includes approximately $5.5 million in funding for subawards to third party academic epilepsy centers that are collaborating on the study and are subinvestigators on the study funded by NIH. The subawardees are determined by NIH. The Company’s responsibility for the subawards is to submit the funding requests on behalf of the subawardees. The

funding of subawards does not have any impact on the Company’s condensed financial statements. Initially funding was approved for the first year beginning June 1, 2021 and provides for reimbursement of qualified direct and indirect expenses in the amount of $0.8 million, including $0.4 million for subawards. Approvals of funds for years two through five are subject to the completion of certain milestones. On July 30, 2022, the Company received funding approval for year two in the amount of $2.6 million, which includes $1.6 million for subawards. On May 25, 2023, the Company received funding approval for year three in the amount of $3.0 million, which includes $1.5 million for subawards.

For funds received under the NIH funding agreement, the Company recognizes a reduction in research and development expenses in an amount equal to the qualifying expenses incurred in each period up to the amount awarded by the NIH. Qualifying expenses incurred by the Company in advance of funding by the NIH are recorded within prepaid expenses and other current assets on the balance sheets. Through September 30, 2023, $1.7 million of qualifying expenses have been incurred and funded by the NIH related to the first, second and third year funding. As of September 30, 2023, the Company recorded prepaid expenses and other current assets of $0.1 million related to the third year funding.

Net Loss per Share Attributable to Common Stockholders

Basic net loss per common share is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of shares of common stock outstanding during the period, without consideration of potentially dilutive securities. Diluted net loss per share is computed by dividing the net loss attributable to common stockholders by the weighted-average number of shares of common stock and potentially dilutive securities outstanding for the period. For purposes of the diluted net loss per share calculation, stock options, common stock subject to repurchase related to early exercise of stock options, and restricted stock units are considered to be potentially dilutive securities. Basic and diluted net loss attributable to common stockholders per share is presented in conformity with the two-class method required for participating securities. The Company considers the shares issued upon the early exercise of stock options subject to repurchase to be participating securities, because holders of such shares have non-forfeitable dividend rights in the event a dividend is paid on common stock. The holders of the shares issued upon early exercise of stock options subject to repurchase do not have a contractual obligation to share in the Company’s losses. As such, the net loss was attributed entirely to common stockholders. Because the Company has reported a net loss for all periods presented, diluted net loss per common share is the same as basic net loss per common share for those periods.

Recent Accounting Pronouncements

Recently Adopted Accounting Pronouncements

In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, which amends existing guidance on the impairment of financial assets and adds an impairment model that is based on expected losses rather than incurred losses and requires an entity to recognize as an allowance its estimate of expected credit losses for its financial assets. An entity will apply this guidance through a cumulative-effect adjustment to retained earnings upon adoption (a modified-retrospective approach) while a prospective transition approach is required for debt securities for which an other-than-temporary impairment had been recognized before the effective date. For public business entities that meet the definition of an SEC filer, excluding entities eligible to be smaller reporting companies as defined by the SEC, adoption is effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. For SEC filers that are eligible to be smaller reporting companies and for all other entities, this ASU is effective for fiscal years beginning after December 15, 2022, and interim periods within those fiscal years. The Company adopted this ASU effective January 1, 2023. The adoption of this ASU did not have a material effect on the Company’s financial statements and related disclosures.