title: Clinical features of headache at altitude: a prospective study.
abstract: BACKGROUND
  Headache is the most common nervous system complication at altitude; however, there have been few attempts to characterize clinical features of high-altitude headaches (HAH).
  
  
  OBJECTIVE
  To measure prospectively the incidence of HAH and to determine its risk factors and characteristics.
  
  
  METHODS
  Members of an expedition to Kanchenjunga base camp in Nepal (5,100 m) were prospectively studied. Subjects were interviewed prior to the trip and while trekking recorded headaches experienced at >3,000 m using a structured questionnaire incorporating International Headache Society (IHS) and acute mountain sickness (AMS) criteria. In addition, clinical features of headaches in 19 trekkers in other groups above 3,000 m were recorded using the same questionnaire.
  
  
  RESULTS
  Eighty-three percent (50/60) reported at least 1 HAH (median 2, range 0 to 10). Those who developed HAH were younger (p = 0.04); women and persons with headaches in daily life were more likely to report severe headaches (p = 0.03 and p = 0.07). One hundred thirty-eight HAH, experienced by 69 persons, are described. The mean altitude at which headaches occurred was 4,723 m. Twenty-six percent of headaches woke subjects at night or occurred upon awakening. HAH reported by migraineurs were accompanied by more phonophobia (p = 0.008). There were no IHS accompanying symptoms in 44% of headaches or symptoms of AMS in 52% of headaches.
  
  
  CONCLUSIONS
  Headaches are a frequent complication of ascent to altitude. Older age appears to offer some protection, whereas headaches were more severe in women and persons with headaches in daily life. There is a wide clinical spectrum, with some suggesting intracranial hypertension. There is a need for evidence-based diagnostic criteria for headaches at altitude.
authors.affiliation: King's Regional Neuroscience Center, London, UK. eli.silber@kcl.ac.uk
authors.forename: E
authors.initials: E
authors.lastname: Silber
authors.forename: P
authors.initials: P
authors.lastname: Sonnenberg
authors.forename: D J
authors.initials: DJ
authors.lastname: Collier
authors.forename: A J
authors.initials: AJ
authors.lastname: Pollard
authors.forename: D R
authors.initials: DR
authors.lastname: Murdoch
authors.forename: P J
authors.initials: PJ
authors.lastname: Goadsby
mesh_terms: D000222:Adaptation, Physiological; D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000531:Altitude; D015331:Cohort Studies; D005260:Female; D006261:Headache / Q000150:complications / Q000175:diagnosis* / Q000188:drug therapy; D006801:Humans; D008297:Male; D008875:Middle Aged; D009051:Mountaineering; D009325:Nausea / Q000209:etiology; D009390:Nepal; D011446:Prospective Studies; D012307:Risk Factors; D012737:Sex Factors; D012890:Sleep; D011795:Surveys and Questionnaires