4.3 Occipital nerve stimulation (ONS)

4.3.1 What it is

Subcutaneous electrodes placed across the back of the head at the level of the greater occipital nerves (usually bilaterally), connected to an implanted pulse generator, typically below the clavicle. Unlike SPG stimulation this is a preventive, continuous therapy, not an abortive one.

peer-reviewed Uniquely among invasive CH options, “Occipital nerve stimulation for refractory CCH is the only available invasive approach with a Conformité Européenne (CE) mark” (PMC8665918, 2021). This is important: it is the only implantable CH device you can actually get in Europe. It is also — see below — the one guidelines are most negative about.

4.3.2 Early evidence base — open-label case series

peer-reviewed ONS with implanted electrodes in CCH was first reported in 2007 in a case series of 8 patients, with attack-frequency reductions ranging from 25% to 95% (summarised in PMC8665918). Other early series:

Series	n	Result
Burns et al.	14	10 reported benefit; 3 >90%; 3 >40% (PMC4119587)
Magis et al.	14	11 with ≥90% attack reduction at mean 37 months (PMC4119587)
Unnamed series	13	Mean attack frequency −68%, intensity −49%; 1 infection requiring hardware removal (PMC8665918)
Miller et al. 2016	51	≥50% improvement in attack frequency in 53% (PMC8665918)
Long-term observational	—	Median follow-up 6.1 years; 67% responders (≥50% reduction in attacks/day); of those, 40% had only sporadic attacks (PMC8665918)
Large observational	105	>50% attack reduction in 69%; mean weekly attacks 22.5 → 9.9; preventive and abortive medication significantly reduced; efficacy sustained at 1 year and last follow-up (PMC8665918)
EAN-cited uncontrolled study	35	59% responders (≥50% frequency reduction), mean follow-up 48.8 months (EAN 2023)

These open-label numbers (53–69% responders) are the ones patients usually hear. The controlled trials below tell a much more complicated story.

4.3.3 ICON — the phase 3 dose-controlled trial

peer-reviewed Wilbrink LA, de Coo IF, Doesborg PGG, Mulleners WM, Teernstra OPM, Bartels EC, Burger K, Wille F, van Dongen RTM, Kurt E, Spincemaille GH, Haan J, van Zwet EW, Huygen FJPM, Ferrari MD, ICON study group. “Safety and efficacy of occipital nerve stimulation for attack prevention in medically intractable chronic cluster headache (ICON): a randomised, double-blind, multicentre, phase 3, electrical dose-controlled trial.” Lancet Neurol 2021;20(7):515-525, DOI 10.1016/S1474-4422(21)00101-0, PMID 34146510, NCT01151631.

Design — and this is the crux. Because ONS causes paraesthesia, a true sham is impossible. ICON therefore randomised patients to 100% versus 30% of the individually determined range between paraesthesia threshold and near-discomfort, hypothesising similar paraesthesia but different efficacy. 150 enrolled, 131 randomised (65 at 100%, 66 at 30%, one not implanted). Sites: four hospitals in the Netherlands, one each in Belgium, Germany and Hungary. Enrolment Oct 2010 – Dec 2017. Funded by the Netherlands Organisation for Scientific Research, the Dutch Ministry of Health, the NutsOhra Foundation, and Medtronic.

Group	Baseline weekly attacks (median, IQR)	Weeks 21–24	Median change
All	15.75 (9.44–24.75)	7.38 (2.50–18.50)	−5.21 (IQR −11.18 to −0.19), p<0.0001
100% ONS	17.58 (9.83–29.33)	9.50 (3.00–21.25)	−4.08 (−11.92 to −0.25)
30% ONS	15.00 (9.25–22.33)	6.75 (1.50–16.50)	−6.50 (−10.83 to −0.08)

Between-group difference: −2.42 (95% CI −5.17 to 3.33) — no difference between doses.

peer-reviewed The 30% “low-dose” arm did just as well as the 100% arm. As the L-ICON authors put it: “The 30% stimulation was assumed to be clinically ineffective or much less effective… [it] was found to be as effective as the 100% stimulation” and “because there was no difference between treatment groups, a placebo response could not be formally ruled out, but was considered highly unlikely by the authors” (L-ICON, eBioMedicine 2023, DOI 10.1016/j.ebiom.2023.104895, PMC10755111).

State the conflict explicitly: the trialists interpret the equal-dose result as “low-dose ONS is also therapeutic”. The alternative interpretation — that both arms reflect regression to the mean plus placebo in an unblindable procedure — cannot be excluded by this design. The EAN guideline, reading the same data, sided with scepticism (§3.6). Reasonable experts genuinely disagree here.

peer-reviewed ICON masked-phase safety: 129 adverse events with 100% ONS versus 95 with 30%; 17 versus 8 serious adverse events, requiring brief hospital admission for minor hardware-related issues. Named event types: local pain, impaired wound healing, neck stiffness, hardware damage (Wilbrink 2021).

4.3.4 L-ICON — long-term extension (2–8 years)

peer-reviewed Brandt RB, Wilbrink LA, De Coo IF, Haan J, Mulleners WM, Huygen FJPM, van Zwet EW, Ferrari MD, ICON study group. “A prospective open label 2–8 year extension of the randomised controlled ICON trial on the long-term efficacy and safety of occipital nerve stimulation in medically intractable chronic cluster headache.” eBioMedicine 2023, DOI 10.1016/j.ebiom.2023.104895, PMC10755111.

• 88/103 eligible Dutch participants started L-ICON; mean follow-up 4.2±2.2 years; 370 person-years observed (84% of potential).
• Followed ≥2 years: 73/88 (83%); ≥3 years: 61/88 (69%); ≥5 years: 33/88 (38%); ≥8.5 years: 3/88 (3%).

Efficacy:

Time point	Pooled geometric mean weekly attacks	95% CI
Baseline	16.2	14.4–18.3
1 year	4.2	2.8–6.3
2 years	5.1	3.5–7.6
5 years	4.1	3.0–5.5

Responder analysis	n/N	%
≥50% responders at end of ICON	49/88	56%
Retained ≥50% response for ≥half of L-ICON follow-up	35/49 or 36/49	71% or 73%
ICON non-responders who became ≥50% responders	15/39	38%
All L-ICON participants with ≥50% response for ≥half of follow-up	52/88	59%
≥30% responders at end of ICON	57/88	65%
Retained ≥30% response	47/57	82%
≥75% responders at end of ICON	36/88	41%
Retained ≥75% response	24/36	67%

Minor internal inconsistency, flagged: the paper reports 35/49 (71%) in its Summary and 36/49 (73%) in its Results for the same quantity (PMC10755111). Trivial, but worth noting for a source-of-truth document.

Patient-reported outcomes at last follow-up: 69/88 (78%, 95% CI 68–86%) reported subjective improvement; 9/88 (10%) no change; 4/88 (5%) worsening; 6/88 (7%) could not answer. 70/88 (81%) would recommend ONS to other patients; 2/88 (2%) would not (PMC10755111).

Long-term safety — the number that should govern the decision:

Category	Events	Participants	%	Incidence rate (per person-year)	95% CI
All serious adverse events	202	63/88	72%	0.62	0.54–0.71
Hardware-related SAEs	122	48/88	55%	0.37	0.31–0.45
Non-hardware-related SAEs	79	40/88	45%	0.24	0.19–0.30
All hardware-related AEs	593	71/88	81%	1.83	1.68–1.98

• 112/122 (92%) of hardware-related SAEs required additional surgery, affecting 44/88 participants (50%), at 0.35 per person-year. Two-thirds were lead replacements, one-third battery replacements (PMC10755111).
• Follow-up was prematurely terminated in 34/88 (39%): explantation 8, device switched off for lack of efficacy 3, lost to follow-up 10, personal reasons 4, death from another disease 4, attack freedom 3, “no effect but scared to stop ongoing stimulation” 2.
• The authors state that “no biological SAEs occurred” — no infections, no neurological injury. All SAEs were hardware/hospitalisation events.

Read that honestly: half of long-term ONS patients needed at least one further operation, and 81% had some hardware-related adverse event, but essentially none of it was biologically dangerous. It is a high-nuisance, low-catastrophe profile — the opposite of DBS. The authors’ own conclusion is that ONS is “safe, well-tolerated and long-term effective”. A patient may reasonably weigh “50% chance of repeat surgery” differently from how the authors do.

4.3.5 Fogh-Andersen 2026 — the placebo-controlled Danish trial (newest evidence)

peer-reviewed Fogh-Andersen IS, Sørensen JCH, Petersen AS, Jensen RH, Meier K. “Safety and efficacy of occipital nerve stimulation as treatment of chronic cluster headache: an investigator-initiated, double-blind, randomized, placebo-controlled study.” J Headache Pain 2026 Mar 9;27(1):77, DOI 10.1186/s10194-026-02312-3, PMID 41803706 / PMC12980930, NCT05023460. Aarhus University Hospital + Danish Headache Center; funded by the Novo Nordisk Foundation. Danish, non-Anglophone-led.

Design: 4-week baseline → 12 weeks open-label TENS → ONS implantation → 14-day grace period → 12 weeks double-blind burst ONS (n=19) vs placebo/no stimulation (n=19) → 12 weeks open-label tonic ONS. Primary endpoint: proportion achieving ≥30% reduction in attack frequency.

Endpoint	Burst ONS	Placebo
≥30% responders, randomised phase	18.81% (95% CI 0.28–37.89)	50.02% (95% CI 26.87–73.09)
≥30% responders, open-label tonic phase	42.09% (19.91–64.34)	51.11% (27.32–74.88)

The chance of achieving ≥30% reduction was 31.20% HIGHER in the placebo group (95% CI 1.29–61.23), p=0.042. In the open-label phase there was no difference (p=0.63) (Fogh-Andersen 2026).

Weekly attack frequency did fall in both arms — burst ONS from 20.57 to 13.87 (−31.10% from baseline, 95% CI −56.78 to +10.14); placebo from 12.75 to 6.67 (−44.32%, 95% CI −64.69 to −12.13). PGIC “much/very much improved”: 4 (21%) burst vs 9 (50%) placebo in the randomised phase; 11 (58%) vs 13 (72%) in the open-label phase.

peer-reviewed The authors’ conclusion: both burst and tonic ONS reduced attack frequency, but burst ONS was not superior to placebo (Fogh-Andersen 2026).

This is the most important recent result in the ONS literature and it deserves emphasis. In a properly blinded, placebo-controlled design — the implant present but switched off — the placebo arm outperformed the active arm on the primary endpoint. Combined with ICON’s finding that 30% dose equals 100% dose, there are now two independent controlled designs in which varying or removing the actual stimulation made no difference to outcome, while outcomes improved substantially from baseline in everyone.

The most parsimonious reading: a large part of the benefit patients experience from ONS may come from implantation, expectation, regression to the mean and intensive specialist care, rather than from the electrical stimulation itself. That reading is contested — burst stimulation specifically may simply be the wrong waveform, the trial was small (38 patients), and the groups were imbalanced at baseline (burst arm had 20.6 attacks/week versus placebo 12.8). But it cannot be waved away.

4.3.6 Complication rates across the wider literature

Different series report wildly different complication rates, largely reflecting era and surgical technique.

peer-reviewed Falowski S, Wang D, Sabesan A, Sharan A. “Occipital Nerve Stimulator Systems: Review of Complications and Surgical Techniques.” Neuromodulation 2010;13(2):121-125, DOI 10.1111/j.1525-1403.2009.00261.x. Retrospective single-centre chart review, 28 patients implanted 2003–2007, mean follow-up 21 months (range 2–60):

• Average 2.1 surgeries per patient; 59 total surgeries, 41 lead-related; 1–5 surgeries per patient over 60 months.
• Lead migration in 7/28 patients (25%); 13 lead-migration revisions (32% of procedures in that series).
• Average time to revision for lead migration 26 weeks; 54% of revisions within 8 weeks, 39% within 4 weeks, 31% within 2 weeks.
• Cited from Schwedt et al.: lead migration 33% at 6 months, 60% at 2 years, 100% at 3 years (Falowski 2010).

peer-reviewed The 105-patient observational series recorded: 67 patients experienced at least one complication; 29 required additional surgery. Infection 6%, lead migration 12%, lead fracture 4.5%, hardware dysfunction 8.2% (PMC8665918).

peer-reviewed Modern technique looks markedly better. Meier K, Fogh-Andersen IS, Sørensen JCH. “Occipital nerve stimulation: A detailed description of a surgical approach and a discussion on implantation techniques.” Pain Pract 2025;25(1):e13444, DOI 10.1111/papr.13444, PMID 39607056. Aarhus, Denmark; 45 CCH patients implanted March 2018 – June 2024; 86.3 patient-years:

• 22 adverse events in 17 patients; 9 required revision surgery.
• No lead migration. No lead breakage. No muscle/neck stiffness.
• Most frequent non-surgical AE: temporary occipital dysaesthesia, resolving spontaneously within weeks.
• Serious adverse event rate: one per 9.6 patient-years.
• 6 patients had the system explanted for lack of efficacy.

The contrast between Falowski’s 25% lead migration (2003–2007, older leads, single lead anchoring) and Meier’s zero lead migrations (2018–2024, tined leads, single lead from behind the ear across the back of the head, IPG below the right clavicle, sleep-awake anaesthetic with perioperative patient feedback) is one of the more encouraging findings in this chapter. The L-ICON authors say the same: more flexible electrodes reduced fracture risk and tined leads reduced dislocation risk (PMC10755111). Old complication rates in reviews and patient forums substantially overstate the risk of a modern implant.

Battery depletion: peer-reviewed originally a major driver of reoperation, “overcome by the introduction of rechargeable batteries” (PMC4119587). ICON used non-rechargeable IPGs; rechargeables were used for replacements during follow-up (PMC10755111).

Side-shift: peer-reviewed some series reported a shift of attacks to the other side when unilateral stimulation was used, which is why bilateral lead placement became standard (PMC4119587). The modern Danish technique uses a single lead crossing the back of the head (Meier 2025).

4.3.7 Guideline position — the most negative in this chapter

peer-reviewed The EAN 2023 guideline: “No recommendation for greater ONS based on a very low level of evidence”, and states ONS is “not recommended due to side effect profile”. Table 18 records the expert consensus that ONS is a “method of third choice” with an “unfavourable efficacy/side-effect profile” — while also conceding it “could be discussed with patients before DBS is planned”. The evidence base cited is 181 participants (Miller 2016 n=51; Wilbrink 2021 n=130) (EAN 2023 PDF).

peer-reviewed A 2021 review is blunter about the practicalities: “GON stimulation for the treatment of refractory CCH and chronic migraine has been regarded as a cost-intensive treatment option with a significant complication rate” and “the highest rate of technical problems after implantation has been reported for GON stimulation” (PMC8665918).

So: ONS is the only implantable CH device you can actually obtain in Europe, and it is the one the European guideline declines to recommend. That is an uncomfortable but accurate summary of the current position.

4.3.8 Community experience

community report Community reports on ONS specifically for cluster headache are sparse. One r/migraine poster who has both chronic cluster headaches and migraines reported on a 60-day trial of a percutaneous occipital stimulator (SPRINT PNS, a temporary system, not a permanent implant): “about a 50% decrease in the intensity” (r/migraine — Experience with occipital nerve stimulation?). A 2025 r/ClusterHeadaches nVNS thread contains no ONS reports at all (r/ClusterHeadaches).

[PEER-REVIEWED — patient-reported, closest thing to structured patient sentiment] The strongest structured patient-sentiment data for ONS is inside L-ICON: 81% would recommend it to other patients, 78% reported subjective improvement, 2% would not recommend, 5% reported worsening (PMC10755111). Two participants continued stimulation despite “no effect but scared to stop ongoing stimulation” — a small, human, and telling category that almost never appears in trial reporting.

Note the gap: 81% of ONS patients would recommend it, and the European guideline does not recommend it. Both are defensible. The patients are reporting on their own experience of a package that includes implantation, intensive follow-up, and possibly placebo; the guideline is reporting on whether the electricity is proven to be the active ingredient.