[Electrophysiological monitoring of the brainstem function in impending brain death--serial changes of blink reflex and brainstem auditory evoked potential]

Abstract

Serial changes of EEG, BR and BAEP recordings were obtained over a period of two days on two patients who had suffered massive cerebral hemorrhage while their clinical condition evolved from coma with evidence of preserved cerebral and brainstem functions to a state meeting the criteria of brain death. As clinical evidence of deteriorating brainstem function became apparent in case 1, first wave IV and V components of BAEP disappeared while waves I to III were normal. Finally, when clinical criteria of brain death were fulfilled, the BAEP response was restricted to wave I with small amplitude to stimulation of left ear only. These serial changes were likely consistent with gradual dissolution of brainstem function in a rostrocaudal direction. By contrast, in case 2, the BAEP response was restricted to waves I and II and was stationary in the whole process of impending brain death in no association with some preservation of cerebral and brainstem function. The changes of BAEP was not parallel to the progressive deterioration of EEG and BR. After meeting clinical criteria of brain death, complete abolition of waves II and I was sequential in that order, and then Babinski sign besides withdrawal and deep tendon reflexes may revive in the extremities. Monitoring of serial electrophysiological changes is helpful in the course of impending brain death to determine whether revival of Babinski sign is due to recovery of cerebral-brainstem dysfunction or due to establishment of spinal autonomy.