Cluster headache is a separate primary headache disorder from migraine — different mechanism, different presentation, different treatment. Cluster falls into the ICHD-3 category of trigeminal autonomic cephalalgias (3.1). It’s much less common than migraine (lifetime prevalence ~0.1% vs ~14% for migraine) but more severe in the acute phase — sometimes called “suicide headache” historically because of the pain intensity.
This page covers the distinguishing features, the treatment approach, and why it’s important not to confuse the two.
The distinctive cluster pattern
ICHD-3 3.1 criteria require:
- At least 5 attacks meeting B–D.
- Severe or very severe unilateral pain, orbital, supraorbital, or temporal, lasting 15–180 minutes untreated.
- At least one of:
- Conjunctival injection AND/OR lacrimation (red and tearing eye on the same side)
- Nasal congestion AND/OR rhinorrhoea (stuffy/runny nose on the same side)
- Eyelid oedema (puffy eyelid on the same side)
- Forehead and facial sweating (same side)
- Miosis AND/OR ptosis (small pupil and/or drooping eyelid on the same side)
- A sense of restlessness or agitation
- Frequency of 1 every other day to 8 per day.
Two patterns:
- Episodic cluster (most common) — attacks occur in “cluster periods” lasting 1 week to 1 year, with at least 1 month pain-free between periods. Often seasonal.
- Chronic cluster — no remission of >1 month for at least 1 year.
The distinctive feature is the circadian rhythm of attacks — they often strike at the same time of day during a cluster period, frequently at night, waking the patient from sleep.
How it differs from migraine
| Feature | Migraine | Cluster |
|---|---|---|
| Pain intensity | Moderate–severe | Very severe (often worst pain ever) |
| Location | Often unilateral, variable | Strictly unilateral, orbital/supraorbital |
| Duration | 4–72 hours | 15–180 minutes |
| Pattern | Random or cycle-linked | ”Clusters” with circadian timing |
| Autonomic symptoms | Rare | Defining (tearing, runny nose, ptosis) |
| Patient behaviour | Lie still in dark room | Pacing, agitation |
| Prevalence | ~14% | ~0.1% |
| Sex predominance | Female (~3:1) | Male (~3:1) historically |
The most diagnostically useful features: the autonomic symptoms (red watery eye, runny nose on the painful side) and the patient’s behaviour during the attack — cluster patients typically pace and rock; migraine patients lie still.
Treatment
Acute and preventive approaches differ from migraine substantially:
Acute
- High-flow oxygen — 12–15 L/min via non-rebreather mask for 15–20 minutes. Aborts attacks in roughly 70 percent of patients. Often the first-line option because of speed and safety.
- Subcutaneous sumatriptan injection — 6 mg subQ. Faster onset than oral and very effective. Limited to 2 doses per 24 hours.
- Intranasal zolmitriptan — alternative when injection not available.
Preventive
- Verapamil — calcium channel blocker, first-line for both episodic and chronic cluster.
- Lithium — particularly for chronic cluster.
- Galcanezumab — CGRP monoclonal antibody, FDA-approved for episodic cluster prevention.
- Short corticosteroid courses — useful to bridge to preventive efficacy.
- Greater occipital nerve block — peripheral injection that helps many patients.
Why Hermly doesn’t address cluster
Hermly’s model and UX are built for migraine specifically:
- The 26-feature vector and cohort training are migraine-trained.
- The “Today” surface assumes once-daily prediction relevance — cluster’s multiple-attacks-per-day pattern doesn’t fit.
- The acute medication logging is migraine-medication-shaped (oral triptans, gepants, NSAIDs) — not oxygen and injectable sumatriptan.
A patient with cluster headache needs a headache specialist (specifically). Cluster headache support groups (Cluster Busters in the US, OUCH UK) are also useful for peer information.
What this isn’t
Not a diagnostic checklist for self-diagnosis. The cluster pattern is distinctive but specific features — particularly the autonomic symptoms — need clinician assessment, not just self- report. If the description above matches your experience, see a neurologist or headache specialist.