QUANTIFIED EEG AND CORTICAL EVOKED-RESPONSES IN PATIENTS WITH CHRONICTRAUMATIC FRONTAL LESIONS

Eighteen frontal trauma patients and 17 age-matched control subjects h ad quantified EEGs and measurements of sensory (SEP) and auditory evok ed potentials (P300) using a Biologic Brain Atlas Ill system. The find ings were compared to the conventional paper EEG, and to the frontal l esion volumes, severity of head injury, and outcome variables. The qua ntified EEG confirmed the pathological findings detected by visual ins pection, but some regional abnormalities were more easily detected by topographic mapping. The regional distribution of pathological slowing corresponded well with the morphological lesions in most patients. Th e modal frequency of EEG correlated both with lesion volume and injury severity and with the outcome variables. There were no pathological f indings in the SEPs, and all but one patient had clearly distinguishab le P300 responses. There was a significant reduction in P300 amplitude in the frontal patients at the anterior, but not at the posterior ele ctrodes. The topographical distribution of the P300 changes correspond ed well with the morphological lesions. Our findings indicate that the P300 potential is, in part, dependent upon the prefrontal cortical ar eas. The present study thus supports P300 investigations which have sh own amplitude reduction in other disorders (e.g., schizophrenia) with a presumed prefrontal dysfunction.