Abstracts

Rationale: The preoperative investigation in patients with temporal lobe epilepsy with hippocampal sclerosis (TLE-HS) is usually expensive and time-consuming. Although video-EEG is unquestionably valuable in epilepsy surgical evaluation, it may delay surgery due to the need of hospitalization and the fact that ictal scalp EEG recordings are often obscured by artifacts. Previous studies have shown that interictal EEG findings may offer sufficient information for lateralization of the epileptic zone in selected cases of TLE-HS, however, there has been no evidence based on surgical outcome. Our objective was to compare surgical outcome in patients with unilateral TLE-HS with and without preoperative video-EEG.Methods: We included 99 refractory TLE-HS, who underwent surgery. All patients had clinical and EEG diagnosis of TLE with MRI signs of unilateral HS by visual analysis. All underwent neuropsychological evaluation and had long term follow-up in our service (mean 8.3 years). They were followed for at least two years post operatively. We excluded individuals with confirmed or suspected non-epileptic events, patients with MRI lesions other than HS and individuals with bilateral HS or normal MRI. Surgical outcome was classified according to Engel scale. Patients were divided into two groups. 1. vEEG+ group (n=53): if they performed video-EEG before surgery and 2. vEEG- group (n=46): if they underwent surgery, with concordant serial interictal EEGs (defined as more than 85% of EEG with unilateral epileptiform activity) or ictal routine EEG concordant with the HS side without performing video-EEG monitoring. The statistical analysis was done using chi-square and Mann–Whitney U test.Results: In vEEG+ group, 37 patients (69.8%) had ictal recordings, while 9 (19.6%) patients of the vEEG- group had seizures during the routine EEG. The average number of routine EEG performed was 12 for both groups (at least 25 minutes each). Both groups were similar regarding gender, age at surgery, age of seizures onset, duration of epilepsy and preoperative frequency of seizures. The mean postoperative follow up time was 6.5 years. Surgical outcome in both groups was similar: 82.6% of patients from the vEEG- group and 79.2% from the vEEG+ group were classified as Engel I. Time lag between the first neurology appointment and surgery was statically shorter in vEEG- group (mean 83.9 months) when compared with vEEG+ (113.6 months) (p=0.004).Conclusions: We demonstrated that patients with unilateral HS with typical mesial TLE semiology, concordant neuropsychological evaluation and clearly lateralized serial routine EEGs that were operated without vEEG monitoring had similar seizure outcome when compared with those who performed video-EEG monitoring. This is strong evidence supporting the concept that prolonged video-EEG monitoring may be obviated in a selected group of patients with unilateral TLE-HS.