Long latency auditory evoked potentials in nonlesional partial epilepsy

Event-related potentials have been occasionally investigated in epilepsy. We recorded slow vertex responses or long-latency auditory evoked potentials (LLAEPs) to auditory stimuli in patients with complex partial and secondarily generalized seizures. Fifty consecutive neurologically-normal patients with normal imaging studies and 50 controls were compared. Slow vertex response (SVR) recordings utilized monaural condensation clicks presented at 0.5 Hz and 100 dB sound pressure level (SPL) with 40 dB contralateral masking; filter bandpass was 1-50 Hz, analysis time was 500 mseconds, and 200 averages were recorded and replicated. Long-latency auditory evoked potentials were recorded from Fz and Ct to linked-ear and ipsilateral-ear reference. Long-latency auditory evoked potential latencies of N100 potentials were significantly prolonged in patients as compared to controls, while P180 and N200 were longer in latency among patients but did not achieve statistical significance. N100 and P180 were significantly prolonged in latency on the side of the electroencephalogram (EEG)-documented epileptogenic focus in the seizure patients. These findings support previous suggestions of frontal or temporal cortical origin for SVRs, and suggest that LLAEP components may be prolonged in latency on the side of an irritative focus. Long-latency auditory evoked potential latency prolongation or asymmetry may therefore assist in the noninvasive neurophysiologic assessment of epilepsy patients.