(A) Cluster headache # Cluster headache (CH) is an idiopathic syndrome consisting of recurrent brief attacks of sudden, severe, unilateral periorbita pain> Attacks of CH are typically short in duration (5-180 min) and occur with a frequency from once every other day to 8 times a day, particularly during sleep. As opposed to migraine, CH is not preceded by aura, affording patients little or no warning.> Pain generally is described as excruciating, penetrating, and not throbbing.> It may radiate to other areas of the face and neck but is typically periorbital.> It may be triggered by stress, relaxation, extreme temperatures, glare, allergic rhinitis, and sexual activity.> CH rarely is triggered by ingestion of specific foods, although tobacco or alcohol products may precipitate an attack.> An attack of CH is a dramatic event during which the patient may be extremely restless. In desperation, CH patients may rock, sit, pace, or bang themselves against a hard surface.> The association of prominent autonomic phenomena is a hallmark of CH. Such signs include ipsilateral nasal congestion and rhinorrhea, lacrimation, conjunctival hyperemia, facial diaphoresis, palpebral edema, and complete or partial Horner syndrome (which may persist between attacks). Tachycardia is a frequent finding.> A distinctive CH face is described as follows: leonine facial appearance, multifurrowed and thickened skin with prominent folds, a broad chin, vertical forehead creases, and nasal telangiectasias.> Persons affected by CHs often are tall and rugged-looking.