Rare form of primary headache; population frequency 0.1%. Characterized by episodes of recurrent, deep, unilateral, retroorbital searing pain. Unilateral lacrimation and nasal and conjunctival congestion may be present. Visual complaints, nausea, or vomiting is rare. Unlike migraine, pts with cluster tend to move about during attacks. A core feature is periodicity. Typically, daily bouts of one to two attacks of relatively short-duration unilateral pain for 8-10 weeks a year; usually followed by a pain-free interval that averages a little less than a year. Alcohol may provoke attacks.

• Prophylaxis with verapamil (40-80 mg twice daily to start), lithium (400-800 mg/d), or prednisone (60 mg/d for 7 days followed by a taper over 21 days).
• High-flow oxygen (10-12 L/min for 15-20 min) or sumatriptan (6 mg SC or 20-mg nasal spray) is useful for the acute attack.
• Deep-brain stimulation of the posterior hypothalamic gray matter is successful for refractory cases as is the less-invasive approach of occipital nerve stimulation.