SSR-40Hz electrogenesis: results of clinical investigation.

This study attempts to provide clinical evidence on the origin of SSR-40Hz auditory evoked potential studying posttrauma coma patients. The SSR-40Hz present two types of morphology: an acute narrow wave, defined as "sharp", and a slow wide curve defined as "rounded". In constant recording of auditory brainstem responses (ABR) the "sharp" wave correlated with the absence of middle latency responses (MLR), and the "rounded" with their presence. In some patients the morphology changed passing grom a "sharp" to a "rounded" wave and a tendency towards widening preceded the appearance of middle latency responses. Perhaps the functional electrophysiologic block may have diminished in sub-cortical neuronal areas not involved in MLR genesis.