Pathological stimulus-related slow wave arousal responses in the EEG.

A group of 55 patients were studied who showed in their EEGs prolonged episodes of delta activity, in response to either auditory or tactile stimuli or both. This unusual pattern occurred with states ranging from drowsiness to deep coma but never in alert patients. It was found in a variety of conditions, most commonly following head injury. The EEG phenomenon disappeared within 5 weeks and over half of the patients had a favourable outcome.