Clinical features of headache at altitude: a prospective study

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).

To measure prospectively the incidence of HAH and to determine its risk factors and characteristics.

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.

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.

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.