No abstract

Surface and depth EEG seizure patterns were compared in 34 patients with intractable temporal lobe epilepsy in whom depth EEG electrodes had been chronically implanted in order to localize epileptogenic sites with a view to surgery. EEG records accompanied by clinical seizures, auras, no behavioral changes, as well as records for which no behavioral observations had been made, were judged with respect to the manner in which seizure activity originating unilaterally in the depth of one of the temporal lobes spread to the surface. For each EEG record, the onset of seizure activity in depth was classified as being focal or regional in form, and seizure activity was judged as: (1) not spreading to the surface, (2) spreading bilaterally and synchronously to the surface, (3) spreading initially to the surface ipsilateral to the depth site(s) in which the electrographic seizure first appeared, or (4) spreading initially to the surface contralateral to the depth site(s) in which the seizure activity initially occurred. EEG seizure activity was found to be less likely to propagate to the surface for those records that were either unaccompanied by behavior changes or accompanied only by auras than for those records accompanied by clinical seizures. In records accompanied by clinical seizures, seizure activity commonly propagated to the surface in a bilateral and synchronous fashion and was also found to spread initially to the ipsilateral but not to the contralateral surface. Anatomical and electrophysiological data accounting for the occurrence of ipsilateral spread were discussed. Diagnostic usefulness of surface recordings during clinical seizures in temporal lobe epilepsy was discussed.

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HE clinical manifestations of discharges of seizures now termed temporal-lobe epilepsy, have been recognized since the article of Jackson TM in 1888. That the origin is in the uncinate region was reported by Jackson and Cohnan 1~ in 1898. The development of electroencephalography was necessary to provide a confirmatory test and a reliable means to distinguish these states of seizures. Jasper and Kershman 12 observed in 1941 that patients with psychomotor episodes usually had sharp waves and rhythms of 6 per sec., often synchronous bilaterally, and sometimes localized in the frontotemporal regions. It seemed clear to them from the nature of these disturbances that the temporal lobe and subjacent structures in the archipallium were the regions involved primarily. The first clear correlation of the clinical features and the loci of anteriortemporal spikes either unilaterally or bilaterally, as well as their detection by recording during sleep, came from Gibbs et al. 6 in 1948. With the identification of states of focal seizures in the temporal regions some afflicted patients who were not relieved by anticonvulsant medication were given surgical therapy by Penfield and Flanigin TM in 1950 and by Bailey and Gibbs 3 in 1951. Subsequent long-term follow-up studies and confirmation of similar results by numerous other surgeons 2,4,7-9,i6,19 have established this method of treatment for clearly focal temporal epilepsy. The consensus of results is that at least two-thirds of patients have complete or very good relief from seizures