[EEG in the prognosis of toxic coma: reflections apropos of unusual data].

During acute intoxications, the first EEG may show persistence or abolition of cerebral activity, but the possibility of recovery after isoelectric tracing in toxic comas must be emphasized. EEG patterns frequently suggest the probability of hypnotic tranquilizer poisoning; 4 types of EEG are encountered corresponding to different grades of toxic coma. Recurrent periods of electrical silence alternating with bursts of activity are habitually recorded in carus comas with hypothermia due to acute barbiturate intoxication, with good prognosis. The possibility of a neurological disturbance associated with drug overdose must be raised whenever an asymmetric tracing is encountered. Serial recordings may detect complications such as: a localized lesion, anoxia or, very rarely, typical paroxysmal abnormalities reappearing in comitial patients before emergence from a toxic coma. Paradoxical monomorphic delta activity corresponding to improvement must not be considered as an aggravation. Peculiar EEG findings occur after oral trichlorethylene poisoning, with temporary clinical deterioration and intermittent periods of electrical silence; recovery is possible. An alpha-like pattern after cardiac arrest of toxic origin has a poor prognosis. The appearance of alternating patterns suggests the development of irreversible brain damage.