Cluster Headache

Definition (ICHD-3). A trigeminal autonomic cephalalgia characterised by attacks of severe, strictly unilateral orbital, supraorbital and/or temporal pain lasting 15–180 minutes, occurring from once every other day to eight times a day, accompanied by ipsilateral cranial autonomic features and/or a sense of restlessness or agitation.

Classification and epidemiology. Male predominance of about 3:1; onset usually between 20 and 40 years, but it can begin in old age. Episodic cluster headache (80–90%) — bouts lasting weeks to months separated by remissions of at least 3 months; chronic cluster headache (10–20%) — no remission, or remissions shorter than 3 months within a year.

Clinical features. The pain is excruciating, boring or stabbing and retro-orbital, with striking circadian and circannual periodicity — attacks wake the patient 1–2 hours after falling asleep and recur at the same time each day (“alarm-clock headache”), with bouts recurring in the same season each year. Ipsilateral autonomic features: lacrimation, conjunctival injection, nasal congestion or rhinorrhoea, eyelid oedema, forehead and facial sweating, and miosis with ptosis (partial Horner’s syndrome). Unlike migraine, the patient is restless and pacing, not lying still. Alcohol reliably triggers attacks during a bout but not during remission.

Differential diagnosis. Migraine; other trigeminal autonomic cephalalgias — paroxysmal hemicrania (shorter, more frequent, and absolutely responsive to indomethacin) and SUNCT/SUNA (attacks lasting seconds); trigeminal neuralgia; acute angle-closure glaucoma; giant cell arteritis; sinusitis; and secondary cluster-like headache from a pituitary lesion or carotid dissection. A first presentation over the age of 50, or any abnormal neurological sign, mandates MRI brain with pituitary views.

Acute (abortive) treatment. High-flow 100% oxygen at 12–15 L/min through a non-rebreathing mask for 15– 20 minutes aborts about 70% of attacks (avoid in severe COPD with carbon dioxide retention), and subcutaneous sumatriptan 6 mg (fastest acting; maximum two doses in 24 hours) or intranasal zolmitriptan 5 mg. Oral triptans and simple analgesics act far too slowly to be useful. Triptans are contraindicated in uncontrolled hypertension, ischaemic heart disease, previous stroke and peripheral vascular disease — a major limitation in older patients, for whom oxygen becomes the treatment of choice.

Preventive treatment. Verapamil is first line (240–960 mg/day in divided doses); an ECG must be done before starting and before every dose increase because of bradycardia and heart block — critically important in older patients. Give transitional therapy with a short tapering course of oral prednisolone, or a greater occipital nerve block, to break the bout while verapamil is titrated. Alternatives: lithium (especially for the chronic form), topiramate and melatonin. For refractory chronic disease: occipital nerve stimulation or sphenopalatine ganglion stimulation.

Galcanezumab — the only agent specifically approved for the prevention of episodic cluster headache. A monoclonal antibody against calcitonin gene-related peptide (CGRP), given as 300 mg subcutaneously at the onset of a bout and repeated monthly through the cluster period; it failed to show benefit in chronic cluster headache. Real-world data and an expert consensus published in 2024 (Journal of Headache and Pain) support its use as an add-on when verapamil is ineffective, not tolerated, or contraindicated — precisely the situation in older patients with conduction disease, in whom high-dose verapamil is hazardous. This sits alongside the American Headache Society 2024 position statement establishing CGRP-targeting therapies as a first-line option in migraine prevention. Converting this to the 6-Mark Version (5 textbook points + 1 update) Omit point 4 (differential diagnosis) and retain points 1, 2, 3, 5 and 6 plus the latest update — giving exactly 6 points. Carry the one indispensable line from point 4 into point 1 instead: “A first presentation after the age of 50 requires MRI brain with pituitary views to exclude secondary cluster-like headache.” Keep the numbers — 15–180 minutes, up to 8 attacks a day, oxygen 12–15 L/min, sumatriptan 6 mg SC, verapamil 240–960 mg — whichever version is asked.