Significance of Cognitive Evoked Potentials in Patients with Mild to Moderate Head Injury

Cognitive evoked potential(CEP) is the result of endogenous brain response following cognitive stimulus. Only P3 wave is widely applicated in clinical fields among several kinds of waves. We examined the CEP in 53 patients with mild to moderate head injury and 59 control subjects for evaluation of the relationship between P3 finding and head injury with respect to severity of head injury, CT or MRI findings, psychometric diagnosis, and EEG findings. The results are followings: 1) The patients with moderate head injury had significant prolongation of P3 latency compared with mild head injured patients. However there was no statistical difference in latencies and amplitudes between mild head injured patients and controls. 2) The patients with abnormal CT or MRI findings had significant prolongation of P3 latency compared with the patients with normal finding. And the patients with normal finding displayed significant abnormalities of the P3 latency and amplitude compared with normal controls. 3) The patients with organic brain syndrome had significant prolongation of P3 latency compared with the patients with post-traumatic stress disorder. And the patients with post-traumatic stress disorder displayed significant abnormalities of the P3 latency and amplitude compared with normal controls. 4) Abnormalities of electroencephalogram were not correlated with pronlongation of P3 latencies. On the basis of these data, we conclude that cognitive evoked potential can be used as an objective index of cognitive function in patients with mild to moderate head injury.

Normal Value of Cognitive Evoked Potentials in Koreans

Cognitive evoked potential(CEP) is the result of endogenous brain response following cognitive stimulus. There are several kinds of waves, including N1, P2, P3 and slow, but only P3 has wide clinical application. In order to obtain normal data, we studied CEP in 174 normal Koreans using the odd-ball paradigm, and our results concerning the latencies and amplitudes of P3 waves, and their relation to age., were were as follows: 1) The average latency of P3 waves of Fz, Cz and Pz was 332.95, 333.34 and 333.66 msec, respectively, in those aged over 60, P3 latency was more delayed than in other age groups. 2) Among teenager, the average latency of P3 waves of Fz, Cz and Pz decreased by 8.35, 9.58 and 9.58msec/year, respectively, but among those aged over 20, increased by 0.87, 0.90 and 0.91msec/year, respectively. 3) The average amplitude of P3 waves of Fz, Cz and Pz was 14.41, 15.37 and 15.12uV, respectively, and in those aged over 60, P3 amplitude showed a greater decrease. 4) The average amplitude of P3 waves of Fz, Cz and Pz decreased by 0.31, 0.32 and 0.23 uV/year in those aged under 29, decreased by 0.65, 0.63 and 0.67uV/year in those over 50, but was stationary in those aged 30 to 49. 5) Due to wide variation and poor constancy, the amplitude of P3 waves does not appear to be especially useful for initial evaluation of cognitive function; it may, however, be useful for follow-up evaluation of a single subject. For each age group, relatively constant P3 latency data can be obtained, and for the evaluation of cognitive function, P3 waves could therefore be useful.