4.1 Non-invasive vagus nerve stimulation (nVNS / gammaCore)

4.1.1 What it is

A hand-held device held against the side of the neck over the cervical vagus nerve, delivering a 2-minute low-voltage electrical stimulation. No surgery, no implant. Used both acutely (at attack onset) and preventively (fixed daily doses).

preprint / trial In Australia, the device is the rechargeable gammaCore Sapphire, supplied non-sterile as a single-patient-use device. Each stimulation lasts 2 minutes; the device permits up to 30 stimulations per 24-hour period but the label instructs users not to exceed 24 per 24 hours, because “use of more than 24 stimulations per day has not been evaluated in controlled clinical trials”. Preventive use is two 2-minute stimulations morning and night; acute use is two 2-minute stimulations on the same side of the neck as needed, repeated if pain persists (Medistar Australia — gammaCore for Patients). The device is activated by a refill card that loads a fixed number of therapy days; “the course of therapy decreases by 1 day as every 24-hour period passes after activation” whether or not you use it (Medistar). That last detail matters financially — the clock runs even on good days.

4.1.2 ACT1 — the first sham-controlled acute trial

peer-reviewed ACT1: Silberstein SD et al., Headache 2016;56(8):1317-1332, DOI 10.1111/head.12896, PMID 27593728, NCT01792817. Randomised, double-blind, sham-controlled, US multicentre.

• 150 randomised; ITT population 133 (nVNS 60, sham 73). Of these, 85 had episodic CH (eCH) and 48 chronic CH (cCH).
• Primary endpoint: response defined as pain intensity 0 or 1 at 15 minutes for the first treated attack, with no rescue medication through 60 minutes.

Population	nVNS	Sham	p
All patients (primary endpoint)	26.7% (16/60)	15.1% (11/73)	0.10 — NOT MET
Episodic CH	34.2% (13/38)	10.6% (5/47)	<0.01
Chronic CH	13.6% (3/22)	23.1% (6/26)	0.48

peer-reviewed So ACT1 failed its primary endpoint in the overall population. The episodic subgroup was clearly positive; the chronic subgroup was numerically worse than sham (13.6% vs 23.1%), though not significantly so. Sustained response favoured nVNS in eCH (p=.008) and in the total population (p=.04) (Silberstein 2016, PMID 27593728).

peer-reviewed ACT1 double-blind-period safety: ≥1 adverse event in 18 (24.7%) nVNS vs 31 (40.3%) sham; adverse device effects in 11 (15.1%) nVNS vs 24 (31.2%) sham. Lip/facial drooping, pulling or twitching occurred in 8 (11.0%) nVNS patients and 0 sham. No serious device-related adverse events (Silberstein 2016). Notably, the sham device produced more adverse events than the active device — the sham delivered a perceptible low-frequency current, which is relevant to interpreting the blinding.

4.1.3 ACT2 — the trial that made the episodic/chronic split undeniable

peer-reviewed ACT2: Goadsby PJ et al., Cephalalgia 2018;38(5):959-969, DOI 10.1177/0333102417744362, NCT01958125. European, randomised, double-blind, sham-controlled.

• 102 randomised; efficacy population 92 (nVNS 48, sham 44). eCH 14/13; cCH 34/31 — i.e. 70.6% of the efficacy population had chronic CH, the reverse of ACT1’s composition.
• Primary endpoint: proportion of all treated attacks achieving pain-free status at 15 minutes.

Endpoint	Population	nVNS	Sham	p
Primary — % attacks pain-free at 15 min	All	—	—	0.71 — NOT MET
% attacks pain-free at 15 min	Episodic	48%	6%	<0.01
% attacks pain-free at 15 min	Chronic	5%	13%	0.13
≥50% of attacks pain-free at 15 min	All	23%	15%	0.15
≥50% of attacks pain-free at 15 min	Episodic	36%	8%	0.16
≥50% of attacks pain-free at 15 min	Chronic	9%	7%	1.00
Responder (≥50% of attacks)	All	40%	14%	<0.01
Responder (≥50% of attacks)	Episodic	64%	15%	<0.01
Responder (≥50% of attacks)	Chronic	29%	13%	0.11

peer-reviewed The interaction term between CH subtype and treatment was significant (p=0.04) (Goadsby 2018, DOI 10.1177/0333102417744362). This is the key statistical fact: the difference between episodic and chronic responders was not just a subgroup eyeball — the trial formally demonstrated that treatment effect depended on subtype.

This is the single most important number in this section for a person with chronic daily CH. In ACT2, chronic patients got 5% of attacks pain-free at 15 minutes on active nVNS versus 13% on sham. In ACT1, chronic patients got 13.6% response versus 23.1% on sham. In both trials the chronic subgroup’s point estimate was numerically below sham. Neither difference was statistically significant, and both subgroups were small (48 and 65 chronic patients respectively), so the honest reading is “no detectable acute benefit in chronic CH”, not “harmful”. But it is not a near-miss; it is a flat line.

4.1.4 Pooled analysis of ACT1 + ACT2

peer-reviewed de Coo IF, Marin JC, Silberstein SD, Friedman DI, Gaul C, McClure CK, Tyagi A, Liebler EJ, Načinović Đ, Ferrari MD, Goadsby PJ. Cephalalgia 2019;39(8):967-977, DOI 10.1177/0333102419856607, PMID 31246132 / PMC6637721. Pooled n=225 (eCH 112, cCH 113).

• Episodic CH: absolute difference vs sham of +27% on the ACT1 endpoint and +22% on the ACT2 endpoint, both p<0.01.
• Interaction between subtype and treatment: p=0.0052 (ACT1 endpoint), p=0.0025 (ACT2 endpoint).
• “No treatment difference in cCH for any endpoint.”
• Pooled safety: ≥1 AE in 38 (31%) nVNS vs 45 (35%) sham; serious AEs 2 (2%) vs 1 (1%), none device-related; perioral myokymia 8 (7%) nVNS vs 0 sham; dysgeusia 0 vs 8 (6%) sham; application-site erythema 0 vs 9 (7%) sham. No serious adverse device effects (de Coo 2019).

4.1.5 PREVA — nVNS as a preventive in chronic CH (the one positive chronic trial)

peer-reviewed PREVA: Gaul C et al., Cephalalgia 2016;36(6):534-546, DOI 10.1177/0333102415607070. Prospective, open-label (not sham-controlled), randomised: 97 patients with chronic CH, nVNS + standard of care (n=48) vs standard of care alone (n=49); 92 continued into an extension phase.

• Reduction in attacks per week: −5.9 (nVNS+SoC) vs −2.1 (SoC), p=.02; therapeutic gain 4.2 attacks/week.
• ≥50% responder rate: 40% vs 8.3%, p<.001.
• 57% decrease in abortive medication use, p<.001.
• 100% response (attack-free): 8% vs 0%.
• ≥25% response p<0.001; ≥75% response p=0.009.
• Adverse events ≥5%: headache 8%, dizziness 6%, neck pain 6%. No serious treatment-related AEs.

peer-reviewed Post hoc analysis: Gaul C et al., J Headache Pain 2017;18(1):22, DOI 10.1186/s10194-017-0731-4, PMID 28197844 / PMC5309191.

The tension to hold in mind: nVNS is a failed acute treatment in chronic CH and a positive preventive treatment in chronic CH, and the preventive evidence comes from a single open-label trial where patients knew they were getting the device. Both statements are true simultaneously. The 2021 narrative review’s evidence table records exactly this: preventive nVNS — “one trial positive”; acute nVNS — “two trials negative” (PMC8665918).

4.1.6 Real-world open-label data in refractory chronic CH

peer-reviewed Simmonds L et al., Front Neurol 2023;14:1100426, DOI 10.3389/fneur.2023.1100426 — UCL/National Hospital for Neurology and Neurosurgery, London; 40 patients with refractory chronic CH:

• 43% (17/40) achieved ≥50% reduction in attack frequency at 3 months.
• Attacks fell from 124±67 to 79±63 per month (mean reduction 44.7, 95% CI 25.1–64.3, p<0.001).
• Severity fell by 1.2 points on a verbal rating scale (p=0.001).
• 2 patients achieved complete remission; 5 had no benefit; 2 worsened.

peer-reviewed A separate retrospective UK observational series reported mean chronic CH attack frequency falling from 26.6±17.1 to 9.5±11.0 attacks/week (p<0.01), with reduced attack duration, severity and abortive use (summarised in PMC8665918, 2021).

Minority observation, clearly labelled as such: the Simmonds series is one of the very few places in this literature that reports patients getting worse on a treatment (2/40, 5%). Most device papers do not report deterioration as a category at all. Take the near-universal absence of “worsened” rows in these tables as a reporting artefact rather than evidence that it doesn’t happen.

4.1.7 Guideline positions

peer-reviewed European Academy of Neurology guideline: May A, Evers S, Goadsby PJ, Leone M, Manzoni GC, Pascual J, et al. “European Academy of Neurology guidelines on the treatment of cluster headache.” Eur J Neurol 2023;30(10):2955-2979, DOI 10.1111/ene.15956, PMID 37515405; full PDF.

• Acute treatment: STRONG recommendation, LOW quality evidence, for nVNS in acute attacks in episodic but not chronic CH. Guideline Table 11: 131 participants, RR 4.4 (95% CI 2.7–7.2) in eCH. Table 12: 122 participants, cCH RR 0.4 (95% CI 0.2–0.6) — i.e. the pooled chronic estimate points away from benefit.
• Preventive treatment in chronic CH (PREVA): WEAK recommendation, low/very low evidence; mean 3.9 fewer attacks per week (95% CI 0.5–7.2).
• Consensus statement: “nVNS and SPG stimulation are the most promising approaches and should be discussed with the individual patient.”

preprint / trial NICE (UK) Medical Technologies Guidance MTG46 reviewed 8 studies covering 410 patients and concluded that gammaCore “worked better acutely for episodic than chronic CH”, noting studies were not powered for subgroup analysis and that no serious device-related adverse events were reported. NICE recommends stopping treatment if there is no reduction in the first 3 months (NICE MTG46, evidence chapter). NICE’s committee also concluded gammaCore “appears to be effective in some but not all people” (NICE HTG533 committee discussion).

peer-reviewed NICE health-economic analysis: PharmacoEconomics Open 2021;5(4):577-586, DOI 10.1007/s41669-021-00276-5, PMID 34322861 / PMC8611122 — “Evidence suggests that gammaCore reduces the intensity and frequency of cluster headaches and that the addition of gammaCore to standard care is cost saving.”

preprint / trial Direct conflict, stated plainly. Ontario Health’s 2025 HTA reached the opposite conclusion for acute treatment: “no statistically significant improvement in overall response, pain freedom, or duration”, GRADE Very low. It recomputed ACT1 as RR 1.77 (95% CI 0.89–3.52), p=.10; ACT2 absolute difference 15.1%, p=.05; combined ≥50%-of-attacks endpoint RR 1.85 (0.84–4.07), not significant (Ont Health Technol Assess Ser 2025;25(2):1-177, PMID 40496978 / PMC12148001).

So: NICE says adopt it and it saves money; Ontario Health says the acute evidence is very low quality and not significant; EAN says strong-but-low-evidence yes for episodic, and no for chronic acute. All three read essentially the same two trials. The disagreement is about how much weight to give a subgroup finding from a trial that missed its primary endpoint.

4.1.8 Regulatory status

preprint / trial United States (FDA):

• April 2017 — released for acute treatment of pain associated with episodic cluster headache in adults.
• June 2017 — gammaCore-S 510(k) clearance (K173442).
• January 2018 — acute treatment of migraine.
• 28 November 2018 — FDA clearance for adjunctive preventive treatment of cluster headache (NeurologyLive).
• The label explicitly states: “The safety and effectiveness … has not been established in the acute treatment of chronic cluster headache.” The FDA has essentially codified the ACT1/ACT2 subgroup finding into the labelling.

preprint / trial Europe: CE-marked; gammaCore-S available in the EU since 2015.

preprint / trial Australia (TGA): listed on the ARTG as entry 355575, sponsor Medistar 2 Pty Ltd (trading as Medistar). The TGA granted a s42DF restricted-representation advertising approval on 23 October 2023 (TGA advertising permissions — Medistar 2 Pty Ltd, gammaCore).

The Australian indication is broader than the US one. Medistar states gammaCore is indicated in Australia “for the treatment and/or prevention of primary headache: migraine, cluster headache, and hemicrania continua, and medication overuse headache in adults”, available “on authorisation by a registered healthcare professional” (Medistar patient page). Migraine Australia confirms: “gammaCore is a Vagus Nerve Stimulator (VNS) device that is TGA approved for the management of primary headache conditions such as cluster headache and migraine… available by prescription only… Under Australian law, this device is restricted to sale by or on the order of a licenced healthcare provider” (Migraine Australia — Devices).

Worth flagging honestly: the Australian indication covers chronic cluster headache without the US carve-out, even though the underlying trial evidence for acute chronic CH is null. Regulatory indication breadth is not evidence.

4.1.9 Cost and access — Australia specifically

preprint / trial Medistar’s own prescriber document states: “At this time, there is no available subsidy for gammaCore Sapphire” (Medistar — How to prescribe gammaCore in AU). Kits are supplied as 31-day and 93-day Starter/Refill options.

preprint / trial No AUD price is published on any Medistar page I could fetch. The patient page says only that the healthcare professional “will provide the initial costs” and “ongoing costs”, and that Medistar contacts the patient “regarding payment and shipment” (Medistar patient page). Migraine Australia likewise lists no price (Migraine Australia). The Australian out-of-pocket cost is therefore effectively unpublished — you have to go through a prescriber to find out. That is an access barrier in itself.

preprint / trial For a reference point, the Ontario Health HTA records the North American cash price: “the device costs $650 (plus tax) for a 93-day kit, and 93-day refills cost an additional $650”, with patients obtaining it “through out-of-pocket payment or through private insurance plans” (Ontario Health HTA 2025). At roughly quarterly refills, that is on the order of AU$4,000/year equivalent before shipping — treat as an indicative order of magnitude only, not an Australian quote.

preprint / trial Elsewhere: the NHS in England supports adoption under NICE MTG46. electroCore reported 2025 revenue of $32.0M, up 27%, and announced a reimbursement approval in September 2025 (electroCore investor release). The company is commercially alive, which — as the rest of this chapter shows — is not a given in this field.

4.1.10 Patient community experience and sentiment

community report On the ClusterBusters forum, the only substantive post in the “Has anyone used / had success with GammaCore?” thread is the original question, from user Baby Moth (23 April 2024): “Has anyone used / had success with GammaCore? I am thinking of getting a prescription, but it’s VERY expensive and not covered by insurance. Wanted to see if anyone had experiences with this in the community.” (ClusterBusters forum thread). The thread received no reported user experiences. That silence is itself a data point about penetration in the community.

community report On r/ClusterHeadaches, a 2025 nVNS thread contains discussion but no commenter states that they personally used gammaCore. User Designer_Training_74 wrote: “The gammaCore Sapphire is effective for migraines; if you can obtain coverage, it’s worth trying. The Truvaga Plus is the original gammaCore model, so it may be your next best option.” User Andimatic noted that “GammaCore is specifically designed for cluster headaches” while considering the cheaper consumer device Pulsetto instead (r/ClusterHeadaches — vagus nerve stimulation).

community report Odd finding, minority, flagged as such: in that same thread, user JoeyLongHots reported that the consumer vagus device Pulsetto “seemed to trigger attacks”. Pulsetto is a wellness device, not gammaCore, and is not TGA/FDA cleared for cluster headache — but the report of a vagus-targeting device apparently provoking attacks is worth noting rather than discarding (r/ClusterHeadaches).

community report Another thread member, Sir_Pervert369, described self-triggering the gag reflex to stimulate the vagus nerve and stop attacks, noting “it requires repeated attempts” (r/ClusterHeadaches). Purely anecdotal, no supporting evidence, included because it is a recurring folk technique in the community rather than because it is validated.

[PEER-REVIEWED / registry] A manufacturer-linked prospective registry (“gammaCore Patient Registry”, GPR) exists for episodic CH — Am J Manag Care 2020;26(1 Suppl):S15-S19, PMID 32109020. Treat as sponsor-adjacent evidence with the usual selection caveats.

community report electroCore’s own testimonial page carries uniformly positive quotes (“gammaCore was awesome, and gave me immediate pain relief”) (gammaCore reviews). Curated marketing testimonials; no sentiment weight should be assigned to them.

Sentiment summary, honestly stated: community sentiment towards gammaCore is thin rather than negative. The recurring themes in what does exist are cost and lack of reimbursement, not reports of failure. There is no ClusterBusters or OUCH-run structured survey of gammaCore outcomes that I could locate — so there is no citizen science tier evidence for nVNS, only trials at one end and scattered anecdote at the other.