The role of evoked potentials in anoxic-ischemic coma and severe brain trauma

The early recognition of comatose patients with a hopeless prognosis-regard less of how aggressively they rue managed-is of utmost importance. Median s omatosensory evoked potentials supplement and enhance neurologic examinatio n findings in anoxic-ischemic coma and severe brain trauma, and are useful as an early guide to outcome. The key finding is that bilateral absence of cortical evoked potentials, generated by thalamocortical tracts, reliably p redicts unfavorable outcome in comatose patients after cardiac arrest, and correlates strongly with death or persistent vegetative state in severe bra in trauma. The author studied 50 comatose patients with preserved brainstem function after cardiac arrest. All 23 patients with bilateral absence of c ortical evoked potentials died without awakening. Neuropathologic study in seven patients disclosed widespread ischemic changes or frank cortical lami nar necrosis. The remaining 27 patients with normal or delayed central cond uction times had an uncertain prognosis because some died without awakening or entered a persistent vegetative state. The majority of patients with no rmal central conduction times had a good outcome, whereas a delay in centra l conduction times increased the likelihood of neurologic deficit or death. This report includes a systematic review of the literature concerning adul ts in anoxic-ischemic coma and severe brain trauma, in which somatosensory evoked potentials were used as an early guide to predict clinical outcome. Greater use of somatosensory evoked potentials in anoxic-ischemic coma and severe brain trauma would identify those patients unlikely to recover and w ould avoid costly medical care that is to no avail.