gammaCore Sapphire

K211856 · Electrocore, Inc. · PKR · Sep 10, 2021 · Neurology

Device Facts

• Record ID: K211856
• Device Name: gammaCore Sapphire
• Applicant: Electrocore, Inc.
• Product Code: PKR · Neurology
• Decision Date: Sep 10, 2021
• Decision: SESE
• Submission Type: Traditional
• Regulation: 21 CFR 882.5892
• Device Class: Class 2
• Attributes: Therapeutic

Indications for Use

The gammaCore Sapphire Non-invasive Vagus Nerve Stimulator is intended to provide non-invasive vagus nerve stimulation (nVNS) on the side of the neck. The gammaCore Sapphire device is indicated for: - The preventive treatment of migraine headache in adolescent (aged 12 and older) and adult patients - The acute treatment of pain associated with migraine headache in adolescents (aged 12 and older) and adult patients - Adjunctive use for the preventive treatment of cluster headache in adult patients - The acute treatment of pain associated with episodic cluster headache in adult patients - Treatment of hemicrania continua in adults - Treatment of paroxysmal hemicrania in adults

Device Story

Handheld, rechargeable, portable nVNS device; delivers mild electrical stimulation to vagus nerve via neck application. User controls signal amplitude (0-40) via slide switch. Device provides 120-second stimulation cycles; automatically shuts off. Features include LED/audible status feedback; daily dose limits; RFID-based prescription refill system (proprietary encryption). Bluetooth enabled for manufacturer-only diagnostics (usage/doses). Used by patients under physician prescription. Benefits include pain reduction and management of headache frequency/severity. No changes to design or functionality from predicate.

Clinical Evidence

Clinical data for hemicrania continua and paroxysmal hemicrania extrapolated from randomized controlled trials (DEN150048, K182369) and clinical audits/case series (n=19 hemicrania continua, n=14 paroxysmal hemicrania). 79% of hemicrania continua patients and 11/14 paroxysmal hemicrania patients experienced clinically meaningful benefits (reduced pain severity/frequency). No serious adverse events reported.

Technological Characteristics

Materials: SS, ABS-PC, SignaGel. Waveform: Sinusoidal, symmetrical biphasic, 5000-Hz pulses at 25 Hz. Max output: 30V peak, 60mA peak. Load impedance: 450-550 ohms. Power: 3V LiFePo4 battery. Connectivity: RFID for prescription loading, Bluetooth for manufacturer diagnostics. Electrical: UL 60601-1 Class III Type BF Applied Part.

Indications for Use

Indicated for preventive treatment of migraine (adolescents 12+ and adults), acute treatment of migraine pain (adolescents 12+ and adults), adjunctive preventive treatment of cluster headache (adults), acute treatment of episodic cluster headache pain (adults), treatment of hemicrania continua (adults), and treatment of paroxysmal hemicrania (adults).

Regulatory Classification

Identification

An external vagal nerve stimulator for headache is a prescription device used to apply an electrical current to a patient's vagus nerve through electrodes placed on the skin for the treatment of headache.

Special Controls

*Classification.* Class II (special controls). The special controls for this device are:(1) The technical parameters of the device, including waveform, output modes, maximum output voltage and current (with 500, 2,000, and 10,000 ohm loads), pulse duration, frequency, net charge (µC) per pulse, maximum phase charge at 500 ohms, maximum current density (mA/cm 2 , r.m.s.), maximum average current (mA), maximum average power density (W/cm2 ), and the type of impedance monitoring system shall be fully characterized through non-clinical performance testing.(2) Software verification, validation, and hazard analysis shall be performed. (3) Biocompatibility evaluation of the patient-contacting components of the device shall be performed. (4) The device shall be tested for electrical, thermal, and mechanical safety, and for electromagnetic compatibility (EMC). (5) The labeling must include: (i) Instructions for proper use of the device, including placement of the device on the patient; and (ii) Instructions on care and cleaning of the device.

Predicate Devices

• gammaCore Sapphire (K203546)

Reference Devices

• DEN150048
• K182369

Submission Summary (Full Text)

{0}------------------------------------------------

September 10, 2021

Image /page/0/Picture/1 description: The image shows the logo of the U.S. Food and Drug Administration (FDA). On the left is the Department of Health & Human Services logo. To the right of that is the FDA logo, which is a blue square with the letters "FDA" in white. To the right of the FDA logo is the text "U.S. FOOD & DRUG ADMINISTRATION" in blue.

Electrocore, Inc. Mike Romaniw VP, Quality Assurance & Regulatory Affairs 200 Forge Way, Suite 205 Rockaway, New Jersey 07866

Re: K211856

Trade/Device Name: gammaCore Sapphire Regulation Number: 21 CFR 882.5892 Regulation Name: External Vagal Nerve Stimulator For Headache Regulatory Class: Class II Product Code: PKR, QAK Dated: June 15, 2021 Received: June 16, 2021

Dear Mike Romaniw:

We have reviewed your Section 510(k) premarket notification of intent to market the device referenced above and have determined the device is substantially equivalent (for the indications for use stated in the enclosure) to legally marketed predicate devices marketed in interstate commerce prior to May 28, 1976, the enactment date of the Medical Device Amendments, or to devices that have been reclassified in accordance with the provisions of the Federal Food, Drug, and Cosmetic Act (Act) that do not require approval of a premarket approval application (PMA). You may, therefore, market the device, subject to the general controls provisions of the Act. Although this letter refers to your product as a device, please be aware that some cleared products may instead be combination products. The 510(k) Premarket Notification Database located at https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfpmn/pmn.cfm identifies combination product submissions. The general controls provisions of the Act include requirements for annual registration, listing of devices, good manufacturing practice, labeling, and prohibitions against misbranding and adulteration. Please note: CDRH does not evaluate information related to contract liability warranties. We remind you, however, that device labeling must be truthful and not misleading.

If your device is classified (see above) into either class II (Special Controls) or class III (PMA), it may be subject to additional controls. Existing major regulations affecting your device can be found in the Code of Federal Regulations, Title 21, Parts 800 to 898. In addition, FDA may publish further announcements concerning your device in the Federal Register.

Please be advised that FDA's issuance of a substantial equivalence determination does not mean that FDA has made a determination that your device complies with other requirements of the Act or any Federal statutes and regulations administered by other Federal agencies. You must comply with all the Act's requirements, including, but not limited to: registration and listing (21 CFR Part 807); labeling (21 CFR Part 801); medical device reporting of medical device-related adverse events) (21 CFR 803) for

{1}------------------------------------------------

devices or postmarketing safety reporting (21 CFR 4, Subpart B) for combination products (see https://www.fda.gov/combination-products/guidance-regulatory-information/postmarketing-safety-reportingcombination-products); good manufacturing practice requirements as set forth in the quality systems (QS) regulation (21 CFR Part 820) for devices or current good manufacturing practices (21 CFR 4, Subpart A) for combination products; and, if applicable, the electronic product radiation control provisions (Sections 531-542 of the Act); 21 CFR 1000-1050.

Also, please note the regulation entitled, "Misbranding by reference to premarket notification" (21 CFR Part 807.97). For questions regarding the reporting of adverse events under the MDR regulation (21 CFR Part 803), please go to https://www.fda.gov/medical-device-safety/medical-device-reportingmdr-how-report-medical-device-problems.

For comprehensive regulatory information about medical devices and radiation-emitting products, including information about labeling regulations, please see Device Advice (https://www.fda.gov/medicaldevices/device-advice-comprehensive-regulatory-assistance) and CDRH Learn (https://www.fda.gov/training-and-continuing-education/cdrh-learn). Additionally, you may contact the Division of Industry and Consumer Education (DICE) to ask a question about a specific regulatory topic. See the DICE website (https://www.fda.gov/medical-device-advice-comprehensive-regulatoryassistance/contact-us-division-industry-and-consumer-education-dice) for more information or contact DICE by email ([e-mail]) or phone [phone] or 301-796-7100).

Sincerely,

Patrick Antkowiak Acting Assistant Director DHT5B: Division of Neuromodulation and Physical Medicine Devices OHT5: Office of Neurological and Physical Medicine Devices Office of Product Evaluation and Quality Center for Devices and Radiological Health

Enclosure

{2}------------------------------------------------

# Indications for Use

510(k) Number (if known) Not yet known

Device Name gammaCore Sapphire

#### Indications for Use (Describe)

The gammaCore Sapphire Non-invasive Vagus Nerve Stimulator is intended to provide non-invasive vagus nerve stimulation (nVNS) on the side of the neck. The gammaCore Sapphire device is indicated for:

- · The preventive treatment of migraine headache in adolescent (aged 12 and older) and adult patients
- The acute treatment of pain associated with migraine headache in adolescents (aged 12 and older) and adult patients
- · Adjunctive use for the preventive treatment of cluster headache in adult patients
- · The acute treatment of pain associated with episodic cluster headache in adult patients
- · Treatment of hemicrania continua in adults
- · Treatment of paroxysmal hemicrania in adults

Type of Use (Select one or both, as applicable)

X Prescription Use (Part 21 CFR 801 Subpart D)

Over-The-Counter Use (21 CFR 801 Subpart C)

#### CONTINUE ON A SEPARATE PAGE IF NEEDED.

This section applies only to requirements of the Paperwork Reduction Act of 1995.

#### *DO NOT SEND YOUR COMPLETED FORM TO THE PRA STAFF EMAIL ADDRESS BELOW.*

The burden time for this collection of information is estimated to average 79 hours per response, including the time to review instructions, search existing data sources, gather and maintain the data needed and complete and review the collection of information. Send comments regarding this burden estimate or any other aspect of this information collection, including suggestions for reducing this burden, to:

> Department of Health and Human Services Food and Drug Administration Office of Chief Information Officer Paperwork Reduction Act (PRA) Staff [e-mail]

"An agency may not conduct or sponsor, and a person is not required to respond to, a collection of information unless it displays a currently valid OMB number."

{3}------------------------------------------------

## 510(K) SUMMARY

The following information is provided as required by 21 CFR §807.92 for the electroCore gammaCore Sapphire 510(k) premarket notification. In response to the Safe Medical Devices Act of 1990, the following is a summary of the information upon which the substantial equivalence determination is based.

### Applicant: electroCore, Inc. 200 Forge Way, Suite 205 Rockaway, New Jersey 07866 Ph: 888-903-2673 Fax: [phone]

#### Establishment Registration Number: 3015529603

| Contact: | Mike Romaniw |
|---------------------------|----------------------------------------------|
| | VP, Quality Assurance & Regulatory Affairs |
| | Office: 973-355-6702 |
| | Fax: [phone] |
| | [e-mail] |
| Alternate Contact: | Eric J. Liebler |
| | SVP, Neurology |
| | Mobile: [phone] |
| | [e-mail] |
| Alternate Contact: | Deborah Lavoie Grayeski |
| | Sr. Project Manager |
| | M Squared Associates, Inc. |
| | Office: 347-954-0418 |
| | Fax: [phone] |
| | [e-mail] |
| Date of Submission: | June 15, 2021 |
| Proprietary Name: | gammaCore Sapphire |
| Common Name: | External vagal nerve stimulator for headache |
| Classification Status: | Class II |
| Product Codes: | PKR, QAK |
| Primary Predicate Device: | gammaCore Sapphire, K203546 |

{4}------------------------------------------------

Indication for Use: The gammaCore Sapphire Non-invasive Vagus Nerve Stimulator is intended to provide non-invasive vagus nerve stimulation (nVNS) on the side of the neck. The gammaCore Sapphire device is indicated for:

- . The preventive treatment of migraine headache in adolescent (aged 12 and older) and adult patients
- . The acute treatment of pain associated with migraine headache in adolescents (aged 12 and older) and adult patients
- . Adjunctive use for the preventive treatment of cluster headache in adult patients
- The acute treatment of pain associated with episodic cluster headache in adult patients .
- . Treatment of hemicrania continua in adults
- Treatment of paroxysmal hemicrania in adults .

Device Description: The gammaCore Sapphire (gammaCore) is a multi-use, handheld, rechargeable, portable device consisting of a rechargeable battery and signal-generating and -amplifying electronics, with a slide control switch for user/operator control of the signal amplitude (relative range, 0-40 continuous).

The gammaCore Sapphire:

- . Includes a charging station incorporated into the "clamshell" storage case connected to a power adapter for charging of the device as necessary by the end user.
- Provides visible (light and display) and audible (beep) feedback regarding device and stimulation . status.
- Allows for multiple stimulations or doses; each stimulation or dose lasts 120 seconds, after . which the device automatically turns off unless turned off earlier by the user/operator. Note: One dose is defined as one stimulation cycle lasting 120 seconds (2 minutes).
- Delivers up to a fixed number of doses within a 24-hour period; once the maximum daily number . of doses has been reached, the device will not deliver any more doses until the following 24-hour period.
- Indicates on the display the number of remaining doses available in a 24-hour period.

The device will be provided to the patient/user with an initial 10-, 31-, or 93-day RFID card on the basis of the health care provider's prescription. Additional (refill/reload) cards will be provided in response to a user/patient request based on a prescription from his or her health care provider. The refill/reload RFID

{5}------------------------------------------------

cards will be programmed by electroCore or its authorized agent. This is a specialized application for dispensing the device therapy.

When a 10-, 31-, or 93-day refill/reload card is requested by a patient/user (in accordance with a prescription from a health care provider) for a unique device serial number, an RFID card is encoded with the appropriate dosage according to the prescription. The gammaCore RFID card-loading application uses a proprietary encoding algorithm to encrypt the therapy days and doses per day on the refill/reload RFID card using near field communication protocols.

The encoded refill/reload RFID card is then provided to the user/patient who requested the refil/reload of the device, along with 1 to 6 additional tubes of conductive gel (the number of conductive gel tubes provided is based on the 10-, 31-, or 93-day refill/reload being provided). On receipt of the RFID card, the user/patient refills/reloads his or her gammaCore device by placing the RFID card across the face of the device (with the device turned on). The device will display "rd" and the "refill" icon as the device reads the RFID card. The device will signal (beeping twice) when it has been loaded with the programmed doses. The device will now be ready for use as treatment. The RFID card can be used for only one refill/reload; upon completion of the device refill/reload, the card can be thrown away.

In addition, a Bluetooth® feature will be enabled to facilitate diagnostics of any devices returned by patients/users to the manufacturer, to allow determination of the number of days the device was used and/or the number of doses as well as any days/doses remaining on the device. The Bluetooth feature will not be accessible to the patient/user; it is accessible only to the device manufacturer.

The subject device delivers the same energy and maintains the same operational characteristics as the gammaCore Sapphire device cleared in K203546. No changes in design or manufacturing process have been made that could affect device functionality. All functional aspects of the device remain the same as K203546, including the strength and nature of the device outputs.

## Summary of Technological Characteristics:

There are no changes to the technological characteristics of the gammaCore Sapphire for this expanded labeling.

{6}------------------------------------------------

#### Summary of Nonclinical Testing:

There are no changes to the technological characteristics of the gammaCore Sapphire for this expanded labeling; no additional nonclinical or performance testing is required.

### Summary of Clinical Data:

Clinical data demonstrating the safety and effectiveness of the gammaCore Sapphire for the treatment of hemicrania continua and paroxysmal hemicrania in adults were extrapolated from randomized controlled trials of nVNS for the acute and preventive treatment of cluster headache' (DEN150048 and K182369) and collected from clinical audits and case series/case reports that included patients with hemicrania continua or paroxysmal hemicrania.2510 These included a total of 19 patients with hemicrania continua and 14 patients with paroxysmal hemicrania.5-10 The duration of nVNS therapy in these patients (where specified) ranged from 8 weeks to 5 years.610 Fifteen of the 19 patients with hemicrania continua (79%)68.00 and 11 of the 14 patients with paroxysmal hemicrania 210 experienced clinically meaningful benefits with nVNS therapy, including decreases in the severity of persistent pain and/or reductions in the frequency, severity, and/or duration of exacerbations or attacks. No serious or unexpected adverse events were reported.5-10

## Substantial Equivalence Discussion:

gammaCore Sapphire technology is identical to the device technology cleared under K203546. There have been no changes in the technological characteristics or intended use of the gammaCore Sapphire. Therefore, there are no new issues of safety or effectiveness; thus, the subject gammaCore Sapphire is substantially equivalent to the predicate gammaCore Sapphire device.

#### Summary:

The following table establishes the substantial equivalence of the subject device to that of the predicate device.

{7}------------------------------------------------

# Substantial Equivalence Comparison Table

| | gammaCore Sapphire<br>(predicate device) | gammaCore Sapphire<br>(subject device) | Substantial equivalence |
|----------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| 510(k) Number | K203546 | TBD | |
| Intended use | The gammaCore Sapphire is a device that<br>provides non-invasive vagus nerve<br>stimulation (nVNS) when applied to the<br>side of the neck. This is a mild electrical<br>stimulation of the vagus nerve, which<br>runs through the neck and carries<br>information to the central nervous<br>system. Each stimulation with<br>gammaCore lasts 2 minutes. The patient<br>controls the stimulation strength. | The gammaCore Sapphire is a device that<br>provides nVNS when applied to the side<br>of the neck. This is a mild electrical<br>stimulation of the vagus nerve, which<br>runs through the neck and carries<br>information to the central nervous<br>system. Each stimulation with<br>gammaCore lasts 2 minutes. The patient<br>controls the stimulation strength. | Same; no change in intended use |
| Indication for use | The gammaCore Sapphire is indicated<br>for:<br>• The preventive treatment of migraine<br>headache in adolescent (aged 12 and<br>older) and adult patients<br>• The acute treatment of pain associated<br>with migraine headache in adolescents<br>(aged 12 and older) and adult patients<br>• Adjunctive use for the preventive<br>treatment of cluster headache in adult<br>patients<br>• The acute treatment of pain associated<br>with episodic cluster headache in adult<br>patients | The gammaCore Sapphire is indicated<br>for:<br>• The preventive treatment of migraine<br>headache in adolescent (aged 12 and<br>older) and adult patients<br>• The acute treatment of pain associated<br>with migraine headache in adolescents<br>(aged 12 and older) and adult patients<br>• Adjunctive use for the preventive<br>treatment of cluster headache in adult<br>patients<br>• The acute treatment of pain associated<br>with episodic cluster headache in adult<br>patients<br>• Treatment of hemicrania continua in<br>adults in adolescents (aged 12 and<br>older) and adult patients<br>• Treatment of paroxysmal hemicrania<br>in in adolescents (aged 12 and older)<br>and adult patients | Clinical data support the expanded<br>labeling. Questions of safety or<br>effectiveness have been addressed in the<br>supporting data. |
| Rx vs OTC | Prescription use | Prescription use | No change |
| | gammaCore Sapphire<br>(predicate device) | gammaCore Sapphire<br>(subject device) | Substantial equivalence |
| 510(k) number | K203546 | TBD | |
| | Acute treatment of migraine:<br>120-second stimulation cycle, 2 bilateral<br>stimulations up to 3<br>times a day | Acute treatment of migraine:<br>120-second stimulation cycle, 2 bilateral<br>stimulations up to 3<br>times a day | Change in treatment protocol to reflect<br>different forms of primary headache |
| Treatment<br>recommendations | Preventive treatment of migraine:<br>120-second stimulation cycle,<br>2 consecutive stimulations on either side<br>of the neck as follows:<br>• First daily treatment: within 1 hour of<br>waking<br>• Second daily treatment:<br>4-6 hours after the first daily treatment<br>• Third daily treatment: within 1 hour<br>before going to sleep | Preventive treatment of migraine:<br>120-second stimulation cycle,<br>2 consecutive stimulations on either side of<br>the neck as follows:<br>• First daily treatment: within 1 hour of<br>waking<br>• Second daily treatment:<br>4-6 hours after the first daily treatment<br>• Third daily treatment: within 1 hour<br>before going to sleep<br>Acute treatment of eCH:<br>120-second stimulation cycle,<br>3 consecutive stimulations up to<br>8 times a day<br>Preventive treatment of CH:<br>120-second stimulation cycle,<br>3 consecutive stimulations on<br>either side of the neck as follows:<br>• First daily treatment: within 1 hour of<br>waking<br>• Second daily treatment: 7-10 hours<br>after the first daily treatment<br>Treatment of hemicrania continua:<br>120-second stimulation cycle,<br>2 stimulations ipsilateral to the side of pain<br>up to 3 times a day | |
| | gammaCore Sapphire<br>(predicate device) | gammaCore Sapphire<br>(subject device) | Substantial equivalence |
| | Treatment of paroxysmal hemicrania:<br>120-second stimulation cycle,<br>2 stimulations ipsilateral to the side of pain<br>up to 3 times a day | | |
| Patient-contacting<br>materials | SS, ABS-PC, SignaGel electrode gel | SS, ABS-PC, SignaGel electrode gel | No change in materials |
| Electrical<br>classification | UL 60601-1 Class III Type BF Applied<br>Part | UL 60601-1 Class III Type BF Applied<br>Part | No change in classification |
| Waveform/frequency | Sinusoidal wave, symmetrical biphasic<br>5000-Hz pulses at a rate of 25 Hz | Sinusoidal wave, symmetrical biphasic<br>5000-Hz pulses at a rate of 25 Hz | No change in waveform or frequency |
| Maximum output | 30 V (peak), 60 mA(peak) | 30 V (peak), 60 mA(peak) | No change in outputs |
| Load impedance | 450-550 ohms | 450-550 ohms | No change in impedance |
| Power supply | 3V LiFePo4 battery | 3V LiFePo4 battery | No change in power supply voltage |
| Service life | 3 years from date of manufacture | 3 years from date of manufacture | No change in service life |
| Controls | Control slide<br>Increase slide up/decrease slide down | Control slide<br>Increase slide up/decrease slide down | |
| Output regulation | Device software and control slide | Device software and control slide | No change in circuitry or controls of the<br>subject and predicate devices |
| Device status display | LED screen | LED screen | |
| Battery charger | Qi-compatible wireless charger in<br>clamshell storage case | Qi-compatible wireless charger in<br>clamshell storage case | |
| RFID refill/reload<br>capability | Allows refilling/reloading of the number<br>of days/doses for which the device can<br>provide treatment; allows for continued<br>use of same device for extended periods<br>of time | Allows refilling/reloading of the number of<br>days/doses for which the device can<br>provide treatment; allows for continued<br>use of same device for extended periods of<br>time | |
| | gammaCore Sapphire<br>(predicate device) | gammaCore Sapphire<br>(subject device) | Substantial equivalence |
| Device diagnostics,<br>Bluetooth | Provides for diagnostics by manufacturer<br>of returned devices, including number of<br>days device was used, number of doses<br>delivered, and remaining days/doses | Provides for diagnostics by manufacturer<br>of returned devices, including number of<br>days device was used, number of doses<br>delivered, and remaining days/doses | |
| Startup | Yes | Yes | No change in available alarm signals |
| Session complete | Yes | Yes | |
| Errors/depleted<br>battery | Yes | Yes | |
| No doses left | Yes | Yes | |
| Expired/no days left | Yes | Yes | |
| Start-up<br>(powered on) | Light on | Light on | No change to display/message in the<br>subject and predicate devices |
| Unit ready (powered<br>on) | LED doses remaining for 24-h period | LED doses remaining for 24-h period | |
| Dose complete | LED days and doses remaining and last<br>amplitude | LED days, doses remaining, and last<br>amplitude | |
| Errors/depleted<br>battery | E# display | E# display | |
| No doses remaining | LED doses 00 | LED doses 00 | Differences between the subject device<br>and reference device represent changes<br>in the user interface. These changes do<br>not impact the safety or effectiveness of<br>the device. |
| Expired/no days left | LED doses/days remaining | LED doses/days remaining | |
| Low battery | LED display battery charge indicator | LED display battery charge indicator | |
| Reloading error | LED display if refill process fails | LED display if refill process fails | |
| Card error | LED display if refill card fails | LED display if refill card fails | |

{8}------------------------------------------------

{9}------------------------------------------------

{10}------------------------------------------------

{11}------------------------------------------------

#### Conclusion:

The gammaCore Sapphire device is the same as the predicate device and no technological or intended use changes have occurred. Therefore, no new issues of safety or effectiveness are raised. Thus, gammaCore Sapphire is substantially equivalent to the predicate device.

### References

- 1. de Coo IF, Marin JC, Silberstein SD, et al. Differential efficacy of non-invasive vagus nerve stimulation for the acute treatment of episodic and chronic cluster headache: a meta-analysis. Cephalalgia. 2019;39(8):967-977. doi:10.1177/0333102419856607
- 2. Gaul C, Diener HC, Silver N, et al. Non-invasive vagus nerve stimulation for prevention and acute treatment of chronic cluster headache (PREVA): a randomised controlled study. Cephalalgia. 2016;36(6):534-546. doi:10.1177/0333102415607070
- 3. Goadsby PJ, de Coo IF, Silver N, et al. Non-invasive vagus nerve stimulation for the acute treatment of episodic and chronic cluster headache: a randomized, double-blind, sham-controlled ACT2 study. Cephalalgia. 2018;38(5):959-969. doi:10.1177/0333102417744362
- 4. Silberstein SD, Mechtler LL, Kudrow DB, et al. Non-invasive vagus nerve stimulation for the acute treatment of cluster headache: findings from the randomized, double-blind, sham-controlled ACT1 study. Headache. 2016;56(8):1317-1332. doi:10.1111/head.12896
- న. Davies B, Chatterton K. Non-invasive vagus nerve stimulation for hemicrania continua: a case series of 3 patients. Cephalalgia. 2016;36(1S):93.
- 6. Eren O, Straube A, Schoberl F, Schankin C. Hemicrania continua: beneficial effect of noninvasive vagus nerve stimulation in a patient with a contraindication for indomethacin…