title: Rare nocturnal headaches.
abstract: OBJECTIVE
  This review describes rare headaches that can occur at night or during sleep, with a focus on cluster headaches, paroxysmal hemicrania, short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing, hypnic headache and exploding head syndrome.
  
  
  RESULTS
  It is known that cluster headaches and hypnic headache are associated with rapid eye movement sleep, as illustrated by recent polysomnographic studies. Functional imaging studies have documented hypothalamic activation that is likely to be of relevance to circadian rhythms. These headache syndromes have been shown to respond to melatonin and lithium therapy, both of which have an indirect impact on the sleep-wake cycle.
  
  
  CONCLUSIONS
  There is growing evidence that cluster headache and hypnic headache are chronobiological disorders.
authors.affiliation: Department of Clinical Neurology, Institute of Neurology, London, UK.
authors.forename: Anna S
authors.initials: AS
authors.lastname: Cohen
authors.forename: Holger
authors.initials: H
authors.lastname: Kaube
mesh_terms: D000818:Animals; D002940:Circadian Rhythm; D003027:Cluster Headache / Q000175:diagnosis / Q000503:physiopathology; D003228:Conjunctiva / Q000503:physiopathology; D006261:Headache / Q000175:diagnosis / Q000503:physiopathology*; D006801:Humans; D007031:Hypothalamus / Q000378:metabolism; D017286:Polysomnography; D012890:Sleep; D012895:Sleep, REM; D013577:Syndrome; D013666:Tears / Q000378:metabolism