High altitude cerebral oedema.

High altitude cerebral oedema is a severe form of acute mountain sickness occurring at heights above 4500 metres. The clinical features are of headache, impairment of consciousness and a variety of neurological signs. The condition occurs during acclimatisation and also at extreme altitudes above 7500 metres when it is often fatal. Case histories of cerebral oedema patients, pathological findings and treatment are reviewed. Other forms of altitude-related illness are also reviewed, including stroke and retinal haemorrhage.