Headache, Cluster 

Cluster headache, also known as histamine headache, is a form of neurovascular headache. Attacks usually are severe and unilateral and typically are located at the temple and periorbital region. The pain is typically associated with ipsilateral lacrimation, nasal congestion, conjunctival injection, miosis, ptosis, and lid edema. Each headache is brief in duration, typically lasting a few moments to 2 hours. Cluster refers to a grouping of headaches, usually over a period of several weeks. To fulfill criteria for diagnosis, patients must have had at least 5 attacks occurring from 1 every other day to 8 per day and no other cause for the headache.

The 2 existing forms of cluster headache are (1) episodic clusters with at least 2 cluster phases lasting 7 days to 1 year separated by a cluster-free interval of 1 month or longer, and (2) chronic form, in which the clusters occur more than once a year without remission or the cluster-free interval is less than 1 month.

The pathophysiology of cluster headaches is not well understood. Some proposed mechanisms are described here.

Hemodynamic: Vascular dilatation may play a role, but blood flow studies are inconsistent. Extracranial blood flow (hyperthermia and increased temporal artery blood flow) increases but following the onset of pain. Vascular change is considered secondary to primary neuronal discharge.

Trigeminal nerve: The trigeminal nerve may be responsible for neuronal discharge causing cluster headaches. Substance P neurons carry sensory and motor impulses in the maxillary and ophthalmic divisions of the nerve. These connect with the sphenopalatine ganglion and interior carotid perivascular sympathetic plexus. Somatostatin inhibits substance P and reduces the duration and intensity of cluster headaches.

Autonomic nervous system: Sympathetic (eg, Horner syndrome, forehead sweating) and parasympathetic (eg, lacrimation, rhinorrhea, nasal congestion) effects occur.

Circadian rhythm: Cluster headaches often recur at the same time every day, suggesting that the hypothalamus, which controls circadian rhythms, may be the site of activation.

Serotonin: This is not as striking as in migraines, but some changes are seen.

Histamine: Although evidence supporting a causative role is inconsistent, cluster headaches may be precipitated with small amounts of histamine. Antihistamines do not abort cluster headaches.

Mast cells: Increased numbers of mast cells have been found in the skin of painful areas of some patients, but this finding is inconsistent.

Frequency

United States

Incidence is estimated to be 2-9% of migraine sufferers, making it relatively uncommon compared with classic migraines. Prevalence in males is 0.4-1%.

International

Incidence in the United Kingdom is equivalent to that of multiple sclerosis.

Mortality/Morbidity

No reported mortality is directly associated with cluster headaches, although suicides have been reported in cases where attacks are frequent and severe. The intensity of the attacks often leads those who experience cluster headaches to miss time from activities such as work or school.

Race

Cluster headaches may be underdiagnosed in black women, but ethnic differences have not been studied.

Sex

This condition is more common in males than in females. The male-to-female ratio was 6:1 in the 1960s but now is 2:1.

Age

Cluster headaches usually begin in middle adult life. The mean age of onset is 30 years for men and later for women.