ModifiedColorado Rocky Mountain Health PlansPolicy 2026T0101NN

Vagus and External Trigeminal Nerve Stimulation

Policy governing use and coverage of implantable and nonimplantable vagus nerve stimulation (VNS) and external/transcutaneous trigeminal nerve stimulation (TNS) for UnitedHealthcare Commercial and Individual Exchange plans; applies to providers and members under those plans.

Policy Summary

PayerColorado Rocky Mountain Health Plans

PolicyVagus and External Trigeminal Nerve Stimulation

Policy CodePolicy 2026T0101NN

Change TypeAdministrative/template updatesshared-version creation

Effective DateJanuary 1, 2026

Next Review Date

Key ActionObtain prior authorization that documents failure of two or more antiepileptic drug trials and that resective surgery was considered or ruled out before implantable VNS is approved.

SourceLink

POLICY UPDATE CHANGES

Updated reference link to reflect the current policy title for Transcranial Magnetic Stimulation for Treating Physical Health Conditions.

Created shared policy version to support application to Oxford plan membership.

Archived previous policy version 2025T0101MM and SURGERY 073.30.

5randomized trials (epilepsy)

67.6%5‑year cumulative VNS response (registry)

27.4%hoarseness incidence

>20

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non‑epilepsy indications listed

~40+references cited

Coverage Criteria for VNS, tVNS, and eTNS

inv-01: Implantable VNS — Medically Necessary Indications

Covered when ALL of the following are met:

Implantable VNS — Medically Necessary Indications: (1) Medically refractory epileptic seizures with failure of two or more trials of single or combination antiepileptic drug therapy or intolerable side effects of antiepileptic drug therapy; and (2) The individual is not a candidate for epilepsy surgery, has failed epilepsy surgery, or refuses epilepsy surgery after shared decision‑making discussion; and (3) No history of left or bilateral cervical vagotomy (contraindication per FDA).

FDA identifies left or bilateral cervical vagotomy as a contraindication to VNS.

inv-02: Unproven / Not Medically Necessary Indications

Not covered / considered unproven when ANY of the following apply:

Implantable VNS for non‑epilepsy conditions: Implantable VNS is unproven and not medically necessary for treating other conditions including but not limited to Alzheimer's disease, anxiety disorder, autism spectrum disorder, autoimmune disorders, back and neck pain, bipolar disorder, bulimia, cerebral palsy, chronic pain syndrome, cluster headaches, depression, fibromyalgia, heart failure, migraines, morbid obesity, musculoskeletal disorders, narcolepsy, obsessive‑compulsive disorder, paralysis agitans, sleep disorders, Tourette's syndrome, and upper limb impairment related to stroke.

List is illustrative, not exhaustive.

Transcutaneous and external devices: Transcutaneous (non‑implantable) vagus nerve stimulation devices and external/transcutaneous trigeminal nerve stimulation devices are considered unproven and not medically necessary for preventing or treating all indications listed (including ADHD, depression, epilepsy, and headache) due to insufficient evidence of efficacy.

Specific devices (e.g., gammaCore, Cefaly, Monarch) are described in the evidence but considered unproven for many indications per policy.

inv-03: Implantable VNS for epilepsy (initial)

Covered when ALL of the following are met:

Initial implant — epilepsy candidacy: Patient has medically intractable partial seizures or drug‑resistant epilepsy with multiple antiseizure medication trials without adequate control; the patient is not a candidate for potentially curative resective epilepsy surgery (e.g., lesionectomy, mesial temporal lobectomy) or has failed or refused surgery after shared decision‑making; and shared decision‑making documenting risks and benefits has occurred.

AAN recommends VNS for adults/adolescents >12 when resection is not viable; prior failure of two or more AED trials is required for implant consideration.

inv-04: Noninvasive VNS for cluster headache (acute/prophylactic)

Covered when ALL of the following are met for non‑invasive VNS in cluster headache prophylaxis or acute treatment:

Cluster headache — indication and subtype specification: Device use is for cluster headache and the intended use (acute abortive vs prophylactic) and cluster subtype (episodic versus chronic) are specified in the documentation.

Evidence supports efficacy for episodic cluster headache (nVNS superior to sham) but is inconsistent for chronic cluster headache; trials such as ACT1/ACT2 and PREVA inform these distinctions.

Prescribing clinician and baseline documentation: Device is prescribed by a clinician managing headache disorders and baseline headache/attack diaries are documented to permit outcome assessment.

Trial-of-therapy documentation (baseline and follow-up diaries) is recommended to assess response.

Response monitoring and limited continuation: A defined trial period (for example, an initial trial of several weeks as used in trials) with documented clinical benefit is required to continue therapy; lack of symptomatic improvement should prompt discontinuation (NICE recommends stopping prophylactic treatment if no reduction within first 3 months).

inv-05: Implantable VNS for treatment‑resistant depression

Use considered investigational/limited when ALL of the following apply:

Implantable VNS — treatment‑resistant depression (TRD): VNS is considered investigational/limited for treatment‑resistant depression when evidence is limited or mixed: randomized sham‑controlled trials have not consistently met primary endpoints, although some secondary and long‑term observational data suggest benefit; therefore use should be limited to individuals with TRD, ideally within research or registry settings with informed consent and clinical governance.

NICE recommends use only with special arrangements; large RCTs have had mixed results though registry data (Aaronson 2017) suggest long‑term benefit.

inv-06: Investigational/Experimental indications

Not covered / experimental when ANY of the following apply:

Other investigational indications: Indications such as Alzheimer's disease, anxiety, autism spectrum disorder, obsessive‑compulsive disorder, chronic pain, sleep disorders, heart failure, asthma, fibromyalgia, stroke rehabilitation (upper limb impairment), autoimmune/musculoskeletal disorders, and many other psychiatric and neurologic conditions have insufficient evidence to conclude safety and effectiveness and are considered experimental or investigational.

Policy cites limited studies, small samples, and weak designs across these indications.

Transcutaneous and external modalities for unsupported indications: Transcutaneous (non‑implantable) VNS and external TNS for indications without supportive high‑quality evidence are considered experimental/investigational and not covered for routine care.

Chunk 30 states insufficient evidence for tVNS; external TNS evidence for DRE is insufficient per systematic reviews.

inv-07: Conditional coverage concepts (evidence-informed)

Covered when ALL of the following are met (examples derived from evidence summaries):

General preconditions: Device is FDA‑cleared for the indicated use where applicable; prescribing clinician documents baseline severity and headache/migraine diaries; and shared decision‑making and consent are documented where required.

FDA clearance and clinician oversight are referenced in device trials and guidance; documentation supports governance and outcome tracking.

Indications with evidence‑informed conditional coverage: Examples include: episodic cluster headache — acute nVNS shows benefit versus sham (ACT1/ACT2, Goadsby) and prophylactic adjunctive nVNS reduced attacks in PREVA; acute episodic migraine — some RCTs show pain‑freedom at 30–60 minutes with nVNS. Conditional coverage may be considered for these contexts with strict documentation and trial‑of‑therapy criteria.

Supportive trials: ACT1/ACT2, Goadsby, PREVA, Tassorelli, PREMIUM post hoc adherent analyses.

Limitations and continuation criteria: Coverage continuation should require documented adherence and clinical improvement during an initial trial period; lack of adherence or benefit should prompt discontinuation (e.g., reassess at 3 months).

inv-08: Indications with positive trial evidence

Evidence summary and contexts where device therapy showed benefit in trials:

Randomized sham‑controlled trial evidence: sTMS demonstrated significant 2‑hour pain‑free response versus sham in an acute migraine pivotal study; external trigeminal nerve stimulation (e‑TNS) showed significant headache pain reduction at 1 hour in a randomized sham‑controlled ACME trial; trigeminal nerve stimulation showed efficacy signal for pediatric ADHD in a blinded sham‑controlled trial (McGough et al.).

Pivotal studies summarized in Reuter et al. and individual trial reports provide the evidence base for these positive trial signals.

inv-09: Indications lacking robust evidence

Contexts with insufficient or conflicting evidence:

Insufficient or conflicting evidence contexts: Prevention of migraine: evidence quality/quantity is limited and NICE recommends use only with special arrangements; trigeminal nerve stimulation for drug‑resistant epilepsy lacks sufficient data to support efficacy; depression studies and many other indications have small samples, heterogeneous designs, and limited long‑term follow‑up, making benefit and durability uncertain.

Reuter et al., Generoso et al., and NICE guidance highlight heterogeneity and limitations across studies.

Refer to the Medical Policy titled Bariatric Surgery for any requests specifically addressing vagus nerve blocking for the treatment of obesity; that topic is managed under that policy rather than here. Additionally, note that this policy treats transcutaneous (non‑implantable) vagus nerve stimulation (tVNS) as unproven and not medically necessary for preventing or treating indications listed in this document; tVNS devices are called out in the policy as non‑covered across many uses and should be considered separately from implantable VNS when reviewing benefits.

Implantable VNS and non‑implantable neuromodulation therapies have been studied for many indications beyond refractory epilepsy, but the evidence is insufficient for routine coverage for a wide range of conditions. Examples explicitly listed include Alzheimer disease, autism spectrum disorder, anxiety disorders, obsessive‑compulsive disorder, chronic pain syndromes, fibromyalgia, heart failure, migraines, cluster headaches, narcolepsy, sleep disorders, stroke‑related upper limb impairment, and various autoimmune and musculoskeletal disorders. These examples are illustrative, not exhaustive, and additional indications are discussed in the literature but lack definitive evidence of effectiveness.

Transcutaneous (non‑implantable) VNS is considered investigational/insufficient evidence for a broad range of conditions identified in the policy, including but not limited to atrial fibrillation, epilepsy, depression, heart failure, premature ventricular contractions, impaired glucose tolerance, tinnitus, and various pain and psychiatric conditions. The policy explicitly states that transcutaneous VNS devices are unproven and not medically necessary for preventing or treating all indications listed and that larger, higher‑quality studies are needed before these uses could be considered proven.

Evidence quality for external/transcutaneous trigeminal nerve stimulation (eTNS/TNS) is low or limited for some migraine and epilepsy indications. Systematic reviews and evidence assessments report potential symptom improvement in selected trials, but overall the body of evidence is small, heterogeneous, and of low certainty, preventing firm conclusions about routine effectiveness for migraine prevention or for drug‑resistant epilepsy.

Professional guidance referenced in the policy includes the American Academy of Pediatrics, which does not recommend eTNS as a treatment for ADHD because the supporting evidence is sparse, and the National Institute for Health and Care Excellence (NICE), which advises that certain transcutaneous electrical stimulation procedures for migraine should be used only with special arrangements for clinical governance, consent, and audit or research (acute use) and that preventive use be limited to research settings due to inadequate evidence for prevention.

This Medical Policy is provided for informational purposes to assist interpretation of UnitedHealthcare standard benefit plans. Member‑specific benefit plan documents govern coverage determinations and take precedence in the event of a conflict; providers should verify applicable member plan terms, prior authorization requirements, and any federal or state mandates before proceeding.

The policy states that implantable VNS is unproven and not medically necessary for indications other than medically refractory epilepsy because of insufficient evidence of efficacy. Implantable VNS should not be considered established therapy for the many non‑epilepsy conditions listed in the policy until higher‑quality evidence demonstrates safety and clinical benefit.

For indications without supportive high‑quality evidence, including many headache and neurologic or psychiatric conditions, the policy considers transcutaneous (non‑implantable) VNS investigational or not medically necessary. Specific examples called out include cluster headache and migraine, where study limitations and low‑quality bodies of evidence preclude routine coverage in many settings.

The policy concludes that available data for noninvasive vagus nerve stimulation (nVNS) and external/transcutaneous trigeminal nerve stimulation (eTNS) in migraine are insufficient to support routine coverage. Although some trials report benefit for select outcomes, the overall evidence is heterogeneous, limited in size and quality, and lacks definitive replication, so routine coverage is not supported by the current evidence base.

A recent systematic review and related evidence assessments cited in the policy found that data are currently insufficient to support trigeminal nerve stimulation as an established therapy for drug‑resistant epilepsy (DRE). While some small studies report seizure reductions and acceptable tolerability, the small number of trials, heterogeneous designs, and variable reporting prevent definitive conclusions about sustained efficacy and clinical role; larger comparative studies are needed.

Billing and Product Codes

Procedural CPT CodesCPT

61885	Insertion or replacement of cranial neurostimulator pulse generator or receiver, direct or inductive coupling; with connection to a single electrode array.
61886	Insertion or replacement of cranial neurostimulator pulse generator or receiver, direct or inductive coupling; with connection to 2 or more electrode arrays.
64553	Percutaneous implantation of neurostimulator electrode array; cranial nerve.
64568	Open implantation of cranial nerve (e.g., vagus nerve) neurostimulator electrode array and pulse generator.
64570	Removal of cranial nerve (e.g., vagus nerve) neurostimulator electrode array and pulse generator.

Durable Medical Equipment / HCPCSHCPCS

A4541	Monthly supplies for use of device coded at E0733.
E0733	Transcutaneous electrical nerve stimulator for electrical stimulation of the trigeminal nerve.
E0735	Noninvasive vagus nerve stimulator.
E0770	Functional electrical stimulator, transcutaneous stimulation of nerve and/or muscle groups, any type, complete system, not otherwise specified.
E1399	Durable medical equipment, miscellaneous.

Implantable Device L-CodesHCPCS

L8679	Implantable neurostimulator, pulse generator, any type.
L8680	Implantable neurostimulator electrode, each.
L8682	Implantable neurostimulator radiofrequency receiver.
L8683	Radiofrequency transmitter (external) for use with implantable neurostimulator radiofrequency receiver.
L8685	Implantable neurostimulator pulse generator, single array, rechargeable, includes extension.
L8686	Implantable neurostimulator pulse generator, single array, nonrechargeable, includes extension.
L8687	Implantable neurostimulator pulse generator, dual array, rechargeable, includes extension.
L8688	Implantable neurostimulator pulse generator, dual array, nonrechargeable, includes extension.

Implantable Vagus Nerve Stimulator product codesmixed

LYJ	Example product code for implantable VNS devices (PMA)
MUZ	Example product code for implantable VNS devices (PMA)
QPY	Example product code for implantable VNS devices (PMA)

Transcutaneous (non-implantable) VNS product codesmixed

PKR	Product code for transcutaneous (non-implantable) VNS (PMN/510(k) reference)
QAK	Product code for transcutaneous (non-implantable) VNS (PMN/510(k) reference)

External/Transcutaneous Trigeminal Nerve Stimulation product codesmixed

PCC	Product code for external/transcutaneous trigeminal nerve stimulation (PMN/510(k) reference)
QGL	Product code for external/transcutaneous trigeminal nerve stimulation (PMN/510(k) reference)

Responder definition — VNS

Responder threshold (standard)≥ 50% reduction in seizure frequency (common trial/registry definition)

Higher-threshold reports≥ 80% seizure reduction reported in some analyses as a more stringent responder definition

Timepoints reportedResponder rates reported at multiple follow-up intervals (3, 6, 12, 24, 36, 48, 60 months) in pooled analyses

Typical pooled responder ratesOverall pooled responder rates around 40–51% across timepoints in meta-analysis

Prior Authorization, Documentation, and Operational Notes

Prior Authorization

Prior Authorization Required for Implantable VNS (Epilepsy)

Prior authorization is required for implantable VNS devices and related implantation procedures for epilepsy. Requests should document drug-resistant epilepsy (failure of AED therapy) and that the member is not a candidate for resective epilepsy surgery, has failed surgery, or refuses surgery after a shared decision-making discussion.

Applicable codes may imply PA — verify plan tools for codes such as 64568, 64570, L8679, L8680 when submitting prior authorization requests.
FDA device approvals are informational only and do not substitute for PA or coverage determination.

Documentation Required

Trial-of-Therapy Documentation and Review

Document the trial-of-therapy during pre-implantation review: specify duration of VNS trial (if applicable), adherence to prior antiseizure medication (AED) regimens, seizure frequency diaries or other objective measures, and clear evidence of clinical improvement or lack thereof. Requests lacking adequate trial documentation may be delayed or denied.

Background and Scope

Vagus nerve stimulation (VNS) refers to therapies that deliver electrical stimulation to the vagus nerve via implanted pulse generators (implantable VNS) or by noninvasive surface stimulation targeting auricular or cervical branches (transcutaneous VNS), while external or transcutaneous trigeminal nerve stimulation (eTNS/TNS) delivers stimulation via electrodes applied to the forehead to target trigeminal branches. Implantable VNS is an established adjunctive treatment for medically refractory epilepsy when patients meet the policy criteria; noninvasive approaches are under investigation for a range of neurologic and psychiatric indications but currently lack consistent high‑quality evidence for many uses.

Definitions and Terminology

Shared Decision Making

DefinitionA collaborative process in which a provider/clinician and a patient (including caregivers and family) work together to make healthcare decisions by comparing benefits, harms, risks, and considering patient values and preferences.

PurposeTo ensure decisions reflect evidence-based information, clinician experience, and what matters most to the patient.

ParticipantsPatient, clinician, and when appropriate caregivers or family members.

Transcutaneous VNS (tVNS)

DefinitionNon‑invasive stimulation delivered through surface electrodes placed on areas targeting auricular or cervical branches of the vagus nerve; e.g., handheld prescription devices such as gammaCore.

Typical uses described

Policy Revision History & Changes

Summary of Changes: 02/01/2026 — Administrative update to a related policy reference link was recorded in the policy history (non‑material). 01/01/2026 — Template/shared‑policy creation was recorded when a shared policy version was created to support application to Oxford plan membership. Prior policy versions were archived as noted in the policy history; these archival entries are informational and non‑material edits to the record.

Policy Summary

PayerColorado Rocky Mountain Health Plans

PolicyVagus and External Trigeminal Nerve Stimulation

Policy CodePolicy 2026T0101NN

Change TypeAdministrative/template updatesshared-version creation

Effective DateJanuary 1, 2026

Next Review Date

Key ActionObtain prior authorization that documents failure of two or more antiepileptic drug trials and that resective surgery was considered or ruled out before implantable VNS is approved.

SourceLink

On This Page

reassess at 3 months

PREVA and other studies suggest early response; NICE guidance supports trial governance and stopping rules.

reassess at 3 months

Trials reported adherence issues and NICE recommends stopping prophylactic cluster headache treatment if no improvement in first 3 months.

Include AED trial details: names, doses, dates, and reasons for discontinuation or intolerance.
Provide seizure frequency baseline and follow-up data (diaries, EEG/monitoring results) and any device trial parameters and outcomes.

Prior Authorization

Prior Authorization — Transcutaneous / Non‑Implantable Devices

No special prior authorization rules are specified for non-implantable/transcutaneous devices within this policy excerpt; however, transcutaneous devices are considered unproven/not medically necessary for many indications and may require additional review or denial if requested.

Transcutaneous (non-implantable) VNS/tVNS is listed as unproven/not medically necessary for many indications — expect denial risk without strong evidence.
FDA clearance alone is informational and not a coverage criterion.

Prior Authorization

Follow Plan‑Specific Prior Authorization Procedures

Follow plan-specific prior authorization procedures and any third‑party tools used by the payer (e.g., InterQual). Always verify member-specific benefit documents and applicable mandates before submitting requests.

Check the member-specific benefit plan for coverage differences and state/federal mandates.
Use payer tools and PA portals as required by Colorado Rocky Mountain Health Plans.

Denial Risk

Denial Risk for Insufficient Prior Therapy or Surgery Candidacy

Requests missing documentation of adequate prior therapy (failure of two or more AED trials) or documentation that the member was evaluated for and is not a candidate for resective epilepsy surgery may be denied.

Ensure documentation of at least two AED trials (names, durations, outcomes) or intolerable side effects.
Document evaluation for resective surgery, reasons surgery is not viable, failed surgery, or documented refusal after Shared Decision Making.

Documentation Required

Shared Decision‑Making Documentation

Document that shared decision-making occurred prior to VNS implantation when surgery is not a viable option — include discussion of risks, benefits, alternatives, and the member’s values and preferences.

Record who participated (patient, family/caregivers) and the topics discussed (benefits, risks, alternatives including resective surgery, and expected outcomes).
Note the member’s informed choice if they refuse surgery after discussion.

Denial Risk

Insufficient or Heterogeneous Evidence May Trigger Denial

When evidence is limited, heterogeneous, or inadequate (for example, transcutaneous approaches for many indications), the request may be denied or coverage limited, or require special arrangements for governance, consent, audit, or research (per NICE guidance).

NICE recommends special arrangements for tVNS and some transcutaneous procedures — expect payers to require governance/consent/audit or to deny outside those frameworks.
Heterogeneous clinical evidence for migraine and other indications may trigger additional review or denial.

Note

Member‑Specific Benefit Reference

Always verify the member-specific benefit document — it governs in case of conflict with this policy. Coverage determinations must defer to plan terms and any applicable state or federal mandates.

If a Medicare NCD/LCD or state mandate applies, follow that guidance where it overrides this policy.
Document relevant benefit plan citations in the authorization request.

Documentation Required

Pre‑Implantation Documentation Requirements

Pre‑implantation documentation must include: confirmation of drug‑resistant epilepsy with details of AED trials, evaluation for resective surgery and rationale if not pursued, absence of contraindications (e.g., left/bilateral cervical vagotomy), and infection risk considerations.

Include past surgical evaluations, neurosurgical notes, and any diagnostic testing supporting nonsurgical candidacy.
Document absence of left or bilateral cervical vagotomy (contraindication to implantation).

Documentation Required

NICE Governance and Trial‑of‑Therapy Documentation

NICE guidance indicates certain transcutaneous procedures should only be used with special arrangements for clinical governance, consent, and audit (or research). When applicable, include documentation of governance arrangements or participation in approved programs.

For devices like gammaCore or other t‑VNS approved under NICE recommendations, provide evidence of adherence to NICE special‑arrangement requirements if available.
If care is part of a research program or audit, include protocol and consent documentation.

Note

Device Approval Reference (Informational)

FDA device approval information is provided for reference only. For device-specific approval and product code information, include the FDA PMA/510(k)/PMN reference in the request when available.

Reference FDA product codes (e.g., LYJ, MUZ, QPY for implantable VNS; PKR, QAK for transcutaneous VNS) and include PMA or 510(k)/PMN numbers if known.
State that FDA clearance is informational and not a guarantee of coverage.

Documentation Required

Pharmacologic Failure Requirement

Pharmacologic failure requirement: Implantable VNS for epilepsy requires failure of two or more trials of single or combination AED therapy or documented intolerable AED side effects prior to approval consideration.

Document each AED trial (agent, dose, duration, clinical response, reason for discontinuation).

Note

Clinical Sequencing — When to Consider VNS

Clinical sequencing: VNS is appropriate after adequate AED trials have failed and when resective surgery is not viable or is declined; VNS is less effective than curative resective surgery but may provide meaningful seizure reduction and quality‑of‑life benefit.

Consider VNS as adjunctive therapy alongside ongoing antiseizure medications for drug‑resistant epilepsy.
Document rationale for selecting neuromodulation over other options.

Note

Neuromodulation After Pharmacotherapy Failure

Neuromodulation (including VNS and select noninvasive devices) may be considered for individuals who have failed pharmacotherapy or cannot tolerate medications; treatment plans should be individualized and supported by documentation of prior pharmacologic failure and candidacy.

AHS supports consideration of neuromodulation for patients who failed or cannot tolerate pharmacotherapy; ensure individualized plan and documentation.
For noninvasive neuromodulation, demonstrate prior pharmacologic failure and rationale for device selection.

Step Therapy

Step Therapy — None Specified

No step‑therapy requirements are specified in this policy excerpt. However, some governance recommendations suggest specialized oversight for transcutaneous devices; verify plan‑level step therapy requirements before submitting a request.

If the member’s plan uses step therapy tools, follow those processes.
For transcutaneous devices, expect possible specialized governance rather than conventional step‑therapy pathways.

Acute treatment of episodic cluster headache; also explored for depression, epilepsy, chronic pain, migraine, tinnitus, insomnia, and inflammatory disorders.

Example devicegammaCore (ElectroCore, LLC) — noninvasive handheld prescription device

External Trigeminal Nerve Stimulation (TNS/eTNS)

DefinitionNon‑invasive therapy that delivers electrical stimulation via electrodes applied to the forehead/face to target trigeminal nerve branches.

Device examplesMonarch external Trigeminal Nerve Stimulation (eTNS) System; Cefaly supraorbital stimulator.

Investigational usesStudied for ADHD, epilepsy, depression, and migraine prevention/acute treatment; evidence quality varies and is generally limited.

AAN Level C (evidence level)

AAN Level C meaningPossibly effective or possibly useful (or possibly ineffective/harmful); requires at least one Class II study or two consistent Class III studies.

Implication for practiceSuggests limited/uncertain evidence—benefit not firmly established and further higher-quality studies needed.

Evidence thresholdAt least one Class II study or two consistent Class III studies required for Level C assignment.

nVNS (noninvasive vagus nerve stimulation)

DefinitionTranscutaneous/non‑invasive stimulation of the vagus nerve (cervical or auricular approaches) used for acute or preventive treatment, commonly referred to as nVNS; may be delivered by handheld or external devices.

Clinical contextsStudied for cluster headache (acute and prophylactic), migraine prevention/acute treatment, and other neurologic or psychiatric indications.

Example devicegammaCore is cited as a noninvasive VNS device used for cluster headache and other indications.

eTNS / TNS (external/transcutaneous trigeminal nerve stimulation)

DefinitionNon‑invasive stimulation of the trigeminal nerve via an external device applied to the forehead/face (supraorbital/infraorbital branches) for migraine, epilepsy, and other indications.

Evidence summarySystematic reviews identify potential benefit for migraine and some trials report reductions in migraine days or pain vs sham, but quality is low and findings are heterogeneous.

Device examplesCefaly (supraorbital stimulator) and Monarch eTNS system are cited as examples under study or development.

External or transcutaneous trigeminal nerve stimulation — short form

Short forme‑TNS

Alternate short formTNS

Usage noteRefers to external or transcutaneous trigeminal nerve stimulation applied to the forehead/face.

Transcutaneous/Non-implantable Vagus Nerve Stimulation — short form

Short formtVNS / nVNS

Usage noteRefers to transcutaneous or non‑implantable vagus nerve stimulation (cervical or auricular stimulation), delivered externally without implantation.

Common contextsUsed interchangeably in literature for noninvasive vagus stimulation in headache and other investigational indications.

References — key studies, reviews, and guidelines

Representative randomized trials/guidelinesSilberstein et al. ACT1 (nVNS acute cluster headache), PREVA (Gaul et al.) for prophylactic nVNS in chronic CH, PRESTO (Tassorelli) for acute migraine, PREMIUM (Diener) for migraine prevention.

Systematic reviews/meta-analysesReuter et al. 2019 systematic review of noninvasive neuromodulation; Mao et al. 2021 meta-analysis of implantable VNS for DRE; Cochrane reviews by Panebianco et al. on VNS for partial seizures.

Guideline sourcesAmerican Headache Society guidance and American Academy of Neurology evidence level definitions cited among references.

Other referenced topicsStudies and reviews cover migraine, cluster headache, epilepsy, depression, ADHD, heart failure, and rehabilitation outcomes (see reference list).