[Alpha coma: rectrospective presentation of 20 cases].

Alpha coma is a relatively rare variety of EEG resulting from diffuse cerebral anoxia, focal brainstem lesions, metabolic disturbances or intoxications. It is a monotonous, unreactive and anteriorly predominant activity of less than 50 microV and of 8 to 13 Hz. Twenty cases of alpha coma are reported: 16 resulting from anoxic encephalopathy, 2 from brain stem strokes, and 2 from metabolic encephalopathy. Cardiac arrest was the main cause of alpha coma (10 cases); a large number of patients (7 cases) died, or have survived with severe neurologic deficits (2 cases). In 2 cases there was a metabolic-toxic cause (benzodiazepines and parathion intoxication). The 2 patients with pontomesencephalic haemorrhage died. The physiopathogenicity of alpha coma, which remains obscure, is also discussed.