Abstracts

Rationale: Cognitive dysfunction in patients with epilepsy may stem from neurophysiological changes related to seizure or to anti-epileptic drugs (AEDs). Previous studies have examined P300 in patients with epilepsy to evaluate cognitive disturbances. However, the effects of epilepsy or AEDs on P300 activity still remain controversial. We examined alteration in P300 activity in patients with temporal lobe epilepsy (TLE). Methods: We examined 14 TLE patients (six females). The mean age was 33.0 12.9 (20 - 50 years). The mean age of onset was 22 12 (3-25 years). Six of 14 were seizure free for more than 20 months. Seven patients took none or one AED, three patients two AEDs, and four patients more than three AEDs. Control data was collected 14 age-matched healthy comparisons (seven females, all right handed). P300 were elicited by a series of pure-tone (1,000 and 1050 Hz). The tones were presented at a rate of one trial per 500 50 ms in a random sequence with the 1050 Hz (rare, target) pure-tone occupying 20% (200 times) and 1000 Hz (frequent, non target) pure-tone occupying 80% (200 times) of the total beeps. The P300 was recorded from four midline electrodes (Fz, Cz, Pz, Oz) and EOG. At least 20 responses for rare stimuli were analyzed in each session. We evaluated the peak amplitude, mean amplitude and peak latency at Fz, Cz and Pz between 250 and 450 ms after onset of stimuli. ANOVA was used to compare P300 parameters between TLE and healthy participants. Clinical parameters (age of onset, numbers of AEDs, seizure frequency) in patients with TLE and P300 parameters were compared using Spearman`s correlation coefficient by rank test. Results: Patients with TLE patients showed significantly reduced mean and peak P300 amplitudes compared to healthy comparisons. (p<0.001) There was no significant difference in peak latency between TLE and healthy comparisons. The patients who had no seizure for more than 20 months showed a trend of even lower amplitudes compared to patients whose seizure were not controlled. In TLE patients, numbers of AEDs or age of onset were not related to P300 parameters. Conclusions: Patients with TLE showed significantly lower P300 amplitudes than healthy participants. Furthermore P300 amplitudes were affected in TLE patients in TLE patients even after seizure remission for more than 20 months.