[Significance of somatosensory evoked potentials in determining brain death]

Electrophysiological examinations are useful to confirm the clinical diagnosis of brain death and to substantiate the loss of brain function and of brain stem function. In addition to the EEG, which has been an useful ancillary test for many years to diagnose brain death, auditory and somatosensory evoked potentials are other electrophysiological techniques that give useful information on the assessment of brain death. In this study, short-latency somatosensory evoked potentials following median nerve stimulation were recorded in 20 patients who fulfilled the clinical criteria of brain death. The primary cortical responses N 20/P 25 recorded above the somatosensory cortex disappeared in all patients. Furthermore, except in two patients, there was a loss of the N 13 b component recorded above the spinous process C2 (N 13 b is assumed to originate in the cervicomedullary junction). Nine patients in whom brain death had occurred exhibited additionally changes of N 13 a - recorded above the spinous process C7 - a potential generated in the lower cervical cord. These data point to the occasional involvement of the cervical cord in the loss of function in patients in whom brain death had become manifest.