Auditory brain-stem responses in comatose patients: relationship with brain-stem reflexes and levels of coma.

Auditory brain-stem responses (BSR) were recorded in 20 comatose patients in whom the level of brain-stem dysfunction was defined by clinical assessment of brain-stem reflexes and posture. No BSR abnormalities were found in the 10 cases with cortico-subcortical or diencephalic levels. The other 10 patients showed a clear relationship between alteration of the different components of the BSR and the clinical levels of brain-stem dysfunction caused by the rostro-caudal evolution. Alteration of wave P5 seems related to a midbrain dysfunction, of P3 to a pontine dysfunction and of P1 or P2 to a lower brain-stem dysfunction.