Typically unilateral, very painful (stabbing), periorbital, frontal, or temporal headache associated with ipsilateral tearing, rhinorrhea, sweating, nasal stuffiness, and/or a droopy eyelid. Usually lasts for minutes to hours. Typically recurs once or twice daily for several weeks, followed by a headache-free interval of months to years. The cycle may repeat. Predominantly affects men. Headache awakens patients, whereas migraine does not.

Ipsilateral conjunctival injection, facial flush, or Horner syndrome (third-order neuron etiology) may be present. Ptosis may become permanent.

Precipitating Factors

Alcohol, nitroglycerin.

• Migraine headache: Typically unilateral headache possibly associated with visual and neurologic symptoms. See 10.27, MIGRAINE.
• Chronic paroxysmal hemicrania: Several attacks of pain and cranial autonomic features (e.g., tearing, ocular injection, rhinorrhea) occurring throughout the day and typically lasting no more than 30 minutes. Patients have dramatic improvement with indomethacin.
• Idiopathic stabbing “ice pick” headache: Episodic, momentary sharp pain, or stabbing sensations lasting less than a second that may occur in patients with preexisting migraine or cluster headache history. Lack the classic autonomic features of cluster headaches.
• Short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing: A trigeminal autonomic cephalgia that presents with burning or stabbing pain felt unilaterally, primarily around the eye. Pain lasts for seconds to minutes and may occur >100 times per day. May have tearing, ptosis, eyelid edema, and conjunctival injection. Episodes last days to months and often recur. Distinguish from cluster headaches due to shorter duration, increased frequency, and more prominent autonomic findings.
• Others: See 10.26, HEADACHE.

1. Avoid alcoholic beverages or cigarette smoking during a cluster cycle.
2. Refer patient to neurologist to help coordinate pharmacologic therapy.
3. Abortive therapy for acute attack:
   • Oxygen, 5 to 8 L/min by face mask for 10 minutes at onset of attack. Relieves pain in 70% of adults.
   • Sumatriptan used subcutaneously (6 mg) or intranasally (20 mg) is often effective in relieving pain.
   • Zolmitriptan 5 or 10 mg intranasally also appears to be effective.
   • Less frequent medications used include ergotamine inhalation, dihydroergotamine, or corticosteroids.
4. When headaches are moderate to severe and are unrelieved by nonprescription medication, one of the following drugs may be an effective prophylactic agent during cluster periods:
   • Calcium channel blockers (e.g., verapamil 360 to 480 mg/day p.o. in divided doses).
   • Lithium 600 to 900 mg p.o. daily is administered in conjunction with the patient’s medical doctor. Baseline renal (blood urea nitrogen, creatinine, urine electrolytes) and thyroid function tests (triiodothyronine, thyroxine, TSH) are obtained. Lithium intoxication may occur in patients using indomethacin, tetracycline, or methyldopa.
   • Ergotamine 1 to 2 mg p.o. daily.
   • Methysergide 2 mg p.o. b.i.d. with meals. Do not use for longer than 3 to 4 months because of the significant risk of retroperitoneal fibrosis. Methysergide is not recommended in patients with coronary artery or peripheral vascular disease, thrombophlebitis, hypertension, pregnancy, or hepatic or renal disease.
   • Oral steroids (e.g., prednisone 40 to 80 mg p.o. for 1 week, tapering rapidly over an additional week if possible) and an antiulcer agent (e.g., omeprazole 20 mg p.o. daily or ranitidine 150 mg p.o. b.i.d.).
   • Galcanezumab is a monoclonal antibody to CGRP, which received FDA approval for prevention of cluster headaches and migraines.
5. If necessary, an acute, severe attack can be treated with i.v. diazepam.

1. Patients started on systemic steroids are seen within a few days and then every several weeks to evaluate the effects of treatment and monitor intraocular pressure.
2. Patients taking methysergide or lithium are reevaluated in 7 to 10 days. Plasma lithium levels are monitored in patients taking this agent.