Abstracts

Since the introduction of high resolution magnetic resonance imaging (MRI) for the assessment of patients with hippocampal sclerosis, the value of pre-surgical video-EEG telemetry has been brought into question. In a previous study (Scott CA and Fish DR, Epilepsia 2000,41(S7) 201),we have shown that video-EEG telemetry adds little novel information in patients with MRI defined unilateral hippocampal sclerosis (UHS). However the results obtained from investigations carried out pre-operatively are used not only to determine who should proceed to surgery but as an aid in predicting the post-operative outcome. Whilst patients with UHS generally have a good prognosis for seizure freedom following temporal lobectomy, a minority group have persistent seizures post-operatively. We reviewed our operative cases to determine which features could be considered predictors of good outcome.
We reviewed the details of all patients who had MRI evidence of UHS and had had video-EEG telemetry between 1995 and 1998 for assessment for epilepsy surgery at the National Hospital for Neurology and Neurosurgery. We determined the influence of ictal EEG features and the clinical semiology of the seizures on the post-operative outcome following a standard temporal lobectomy.
Of the 190 patients with unequivocal UHS 125 proceeded to surgery,and of these 104 had a good outcome, Engel Class I or II, with a median follow up of 4 years, range 1 [ndash] 6 years. We found there was no ictal EEG feature that was independently predictive of a good outcome in this selected group of patients although in comparison to other imaging groups the combination of UHS and temporal seizure type show a significant association with a good outcome. Of the UHS patients whose clinical ictal semiology was of a temporal type seizure, 94/111 had a good outcome. In contrast to other recent studies, only half of the 17 patients with UHS and temporal seizures had a history of frequent generalised seizures and only 1 patient had a history of status epilepticus. There were no clinical features associated with these patients that might have predicted the poor outcome, although their median age at time of assessment was higher than those with a good outcome (not statistically significant). The 14 patients with UHS and other clinical seizure types did not show a significant difference in post-operative outcome to those with temporal clinical seizures, but pre-operative tests had added information to aid in the decision whether to proceed to surgery.
Ictal EEG-video telemetry adds little information that helps to predict post-operative outcome in patients with unequivocal UHS and clearly documented seizures with temporal type clinical semiology.
[Supported by: University College Hospital NHS Trust]