NEUROPSYCHOLOGICAL AND COGNITIVE STUDIES IN EPILEPSY

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We have used neuroimaging techniques in patients with temporal lobe epilepsy to perform non-invasive evaluation of functional cortex. This information is crucial for surgical planning in patients with intractable epilepsy. In 12 adults, we compared 150-H2O PET blood flow studies for language activation with the intracarotid sodium amytal (Wada) test. Six injections were performed during auditory and visual confrontation naming. Scan results were co-registered with the patients' MRI scans. Region 44 was most frequently activated in both the auditory and visual naming tasks. Regions 39 and 22 were also activated in the auditory task, and region 17 and 39 in the visual task. When compared with the Wada test, 15O-H2O PET, gave accurate results for language lateralization. More specific localizing data are often obtained using implanted subdural electrodes and electrical stimulation mapping. We compared 15O-H2O PET to this procedure by co-registration of PET with MRI and CT obtained with implanted electrodes, which were digitized to allow matching of points at which stimulation led to functional impairment and PET activation occurred during cognitive tasks. We found a significant relation between the two parameters. PET showed much wider regions of functional involvement, although some of the activated regions may have participated in, but not have been crucial for, task performance. PET has the ability to survey the entire brain, while electrodes can only detect function where they are implanted. Imaging procedures are particularly appropriate for children. We used fMRI In 11 children with epilepsy, FRI language lateralization matched Wada test results for lateralization of speech dominance. Our preliminary data in control subjects suggests that hemispheric language dominance may be affected by age-and sex-related factors. Children show more widespread activation of frontal cortex during naming, with a larger number of pixels involved, than do adults. In addition, females, both adults and children, show greater activation than males. Most recently, we used transcranial magnetic stimulation (TMS) to map memory function and language localization in patients with left hemisphere speech dominance. Left frontal stimulation led to speech arrest, and left temporal to picture naming errors. Both right and left frontal stimulation disrupted memory for pictures; left posterior temporal TMS disrupted naming during encoding but not memory. TMS is a useful tool for investigation of language and memory organization.