cluster headache

EPIDEMIOLOGY/RISK FACTORS: Male > female (~3:1), onset typically 20s–40s. Strong association with tobacco use and alcohol (alcohol triggers attacks during a cluster period, not outside it).

PATHOPHYSIOLOGY: Hypothalamic (posterior hypothalamic gray/suprachiasmatic nucleus) activation explains circadian and circannual periodicity (attacks at the same time each day, often nocturnal/REM; seasonal clusters in spring/fall). Trigeminal-autonomic reflex: activation of the trigeminovascular system (pain) with parasympathetic outflow via the superior salivatory nucleus → sphenopalatine ganglion (autonomic features). Vasodilation of the cavernous sinus/carotid region and CGRP release contribute.

CLINICAL PRESENTATION: Excruciating, stabbing/boring unilateral orbital, supraorbital, or temporal pain. Duration 15–180 min; frequency from every other day to 8/day. Ipsilateral autonomic features: lacrimation, conjunctival injection, nasal congestion/rhinorrhea, eyelid edema, partial Horner syndrome (ptosis, miosis), forehead/facial sweating. Restlessness/agitation: patients pace or rock (contrast with migraine, where patients prefer to lie still in a dark room). Episodic form: clusters last weeks to months with remission ≥3 months. Chronic form: attacks for >1 year with remissions <3 months.

DIAGNOSIS: Clinical (ICHD-3 criteria: ≥5 attacks of severe unilateral orbital/supraorbital/temporal pain lasting 15–180 min with ipsilateral autonomic signs and/or restlessness). Obtain MRI brain (with attention to pituitary/hypothalamic region) at first presentation to exclude secondary causes.

TREATMENT: - Acute: 100% oxygen via non-rebreather mask at 12–15 L/min for 15 min; subcutaneous or intranasal sumatriptan (triptans; contraindicated in CAD/uncontrolled HTN); intranasal zolmitriptan is an alternative. Intranasal lidocaine and DHE are also options. - Prophylaxis: verapamil (first-line; monitor ECG for PR prolongation/heart block); short-term prednisone bridge; lithium and others as second line; galcanezumab (anti-CGRP) is FDA-approved for episodic cluster headache. Occipital nerve stimulation or sphenopalatine ganglion stimulation in refractory cases. - Avoid: Alcohol and other triggers (nitroglycerin) during active cluster periods. Smoking cessation recommended.

HIGH-YIELD DIFFERENTIALS: - Migraine: Female predominance, 4–72 h, pulsatile, photophobia/phonophobia, nausea, aura; prefers to lie still. - Paroxysmal hemicrania: Women; shorter (2–30 min) and more frequent attacks (>5/day); absolute response to indomethacin. - SUNCT/SUNA: Very brief (seconds to minutes), very frequent stabbing attacks with conjunctival injection and tearing. - Hemicrania continua: Continuous unilateral headache, indomethacin-responsive. - Trigeminal neuralgia: Brief electric shock-like pain in V2/V3 triggered by touch/chewing; treat with carbamazepine. - Tension-type headache: Bilateral, band-like, mild-moderate, no autonomic features. - Secondary causes: Pituitary tumor, cavernous sinus lesion, carotid dissection (painful Horner), acute angle-closure glaucoma, giant cell arteritis (older patients).

BOARD PEARL: "Male smoker with excruciating unilateral periorbital pain, tearing, rhinorrhea, and restlessness for 45 minutes each night" → cluster headache → 100% O2 for acute, verapamil for prevention.