Etiology and prognosis of alpha coma.

We reviewed our experience with alpha coma, the finding of predominantly alpha-frequency rhythms in the EEGs of unconscious patients, and identified 50 patients. Cardiac arrest, either inside (n = 25) or outside (n = 24) the hospital, was the cause of unconsciousness in all except one patient who had hyperglycemic, hyperosmolar coma. After out-of-hospital cardiac arrest, the risk of never regaining consciousness or dying during hospitalization did not differ significantly between unconscious patients with (n = 24) and without (n = 69) alpha frequencies in their EEGs. A review of the literature supports our findings that alpha coma most commonly follows cardiac arrest and does not preclude the possibility of neurologic recovery. We conclude that alpha coma is a descriptive term and lacks prognostic significance in itself.