Somatosensory evoked potentials following severe head injury: loss of the thalamic potential with brain death.

The thalamic component (P17) of the short-latency somatosensory evoked potential (SEP) was assessed to determine its usefulness in patients with severe head injury. Subjects were a group of patients admitted to the Auckland Hospital Critical Care Unit who subsequently died from head injury. In all instances where brain death was unequivocally established and a SEP recording made in close temporal proximity to the time of brain death the P17 potential was absent. When there was evidence of continuing brainstem activity and particularly where prolonged survival occurred following the last SEP recording the P17 potential remained intact bilaterally. This study shows that the presence or absence of the thalamic component of the short-latency SEP provides a reliable electrophysiological measure of brainstem function in patients where brain death has been suspected.