EVENT-RELATED POTENTIALS AS AN INDEX OF COGNITIVE FUNCTION DURING RECOVERY FROM SEVERE CLOSED-HEAD INJURY

Objective: To evaluate the utility and neuropsychological correlates o f serially performed recordings of event-related potentials (ERPs) in patients recovering from a severe closed head injury (CHI). Design: Pr ospective longitudinal study. Setting: Brain injury rehabilitation uni t based in a national rehabilitation hospital. Subjects: Sixteen patie nts with severe CHI (significant degree of impaired consciousness grea ter than 24 hours) subclassified into two severity groups according to initial Glasgow Coma Scale (GCS) score: those with initial GCS score < 9, consistent with a more severe injury; and those with initial GCS score > 8, indicating a less severe injury. Methods: ERPs were elicite d using the standard auditory P300 ''oddball'' detection paradigm. ERP recordings were carried out three times: 2 months after injury, 1 mon th later, and 2.5 months or more after the initial study. Parameters a nalyzed included latencies and amplitudes of the P3, N2, P2, and N1 co mponents of the ERPs. Correlations between changes in these ERP parame ters and specific neuropsychological test results were evaluated. Resu lts: Initial P3 latencies in the more severely injured group were sign ificantly longer (P < .05) than those recorded in the less severely in jured patients. In subsequent recordings, P3 latency was found to be s ignificantly shorter compared with the initial P3 latency, and the dif ference in P3 latency between the two patient groups was no longer sta tistically significant by the time of the third recording. For the gro up as a whole, P3 latency decreased significantly on each repeated rec ording. N2 latency was found to be significantly shorter (P < .05) bet ween the first and third recordings. Cognitive performance significant ly improved between the first and third recordings. P3 latency shorten ing was correlated with improvement in neuropsychological test scores for short-term and long-term story recall and for word recall. N2 late ncy shortening was correlated with improvement in the neuropsychologic al test scores for word recall only. Conclusion: ERP recordings perfor med in the subacute stage after CHI may assist in evaluating injury se verity. Moreover, serially performed recordings of P3 latency may be u sed as a physiologic index of brain activity that correlates with reco very from CHI.