Evaluation of brain function in severe human head trauma with multimodality evoked potentials

Abstract

Electrophysiological investigations were undertaken in 51 comatose patients with severe head trauma to locate areas of brain dysfunction and to relate the loci of dysfunction to the patient''s posttraumatic neurological condition. On the basis of evoked potential data, the presence of decortication or decerebration depended on cerebral hemispheric dysfunction. Brain-stem dysfunction, defined by evoked potentials, did not correlate with posturing. Impaired oculocephalic responses and bilateral abnormal pupillary light responses were associated with brain-stem dysfunction, while hemispheric dysfunction did not correlate with either. Duration of coma was dependent on hemispheric dysfunction. Brain-stem dysfunction was not significantly associated with prolonged coma. Of the head trauma patients who had Grade I or II multimodality evoked brain-injury potentials recorded in the acute period following head trauma (mean Day 3), 80% became responsive within 30 days of their injury. Graded somatosensory brain injury potentials appeared to be a powerful prognostic tool as they significantly correlated with the patient''s final outcome even when recorded early after injury. Abnormal multimodality evoked potentials recorded acutely consistently defined dysfunction of the visual, auditory and motor systems in comatose patients, and were considerably more effective than the clinical neurological examination in diagnosing persisting focal deficits of these systems.