CHEMOSENSORY EVENT-RELATED POTENTIALS IN PATIENTS WITH TEMPORAL-LOBE EPILEPSY

We investigated chemosensory functions in patients with temporal lobe epilepsy (TLE) to discover whether olfactory and trigeminal stimuli ap plied either ipsilaterally or contralaterally to the epileptic focus a re processed differently. Twenty-two patients were investigated, 12 of whom had epilepsy with a focus located in left temporal lobe (LTL). T he remaining 10 patients had a right temporal lobe (RTL) focus. Input from the trigeminal system was examined by use of CO2; input from the olfactory system was evaluated with vanillin and hydrogen sulfide as s timuli. Chemosensory function was assessed by evaluation of chemosenso ry event-related potentials (CSERP) and the patients' verbal reports i n an odor identification test. In both groups of patients, prolonged C SERP latencies were noted after stimulation of the left nostril with C O2 as compared with stimulation of the right nostril. In contrast, a d ifferent pattern emerged for olfactory stimuli. After right-sided olfa ctory stimulation, latencies were prolonged in patients with right-sid ed epileptical foci. Similarly, when the left nostril was stimulated i n patients with a left-sided focus, CSERP latencies were prolonged. Th us, neocortical processing of olfactory, but not trigeminally mediated information evidently is affected by functional lesions of the tempor al lobe. After olfactory stimulation in patients with a right-sided fo cus, the distribution of amplitudes was different from normal. Moreove r, analyses showed nonoverlapping 95% confidence intervals (CI) for la tency N1 when vanillin was applied to the right nostril. These results indicate that RTL may play a different role in processing of olfactor y information as compared with LTL.