We sought retrospectively to assess outcomes in bilateral temporal lobe epilepsy (BTLE) patients undergoing resective temporal lobe surgery following invasive EEG lateralization in comparison to unilateral TLE (UTLE).

Patients undergoing surgical intervention for TLE (the vast majority being mesial temporal lobe epilepsy) during a 7-year period were retrospectively categorized as suspected BTLE (sBTLE) or UTLE. Temporal lobectomy was performed in the sBTLE group on the side of maximum number of intracranial EEG seizure onsets. EEG, MRI, laterality of iEEG ictal onset (in sBTLE), seizure outcome and drug tapering data were retrospectively analyzed.

Of 148 adult patients undergoing temporal lobe epilepsy surgery, 24 (16.2 %) fit the criteria of sBTLE, amongst whom iEEG ictal onset proved to be unilateral in 14 (uBTLE, 58.3 %) and bilateral in 10 (dBTLE, 41.7 %). Of operated patients in the dBTLE group, the first seizure onset was ipsilateral to the resection in 4 patients (57.1 %) and contralateral in 3 (42.9 %). In the UTLE group, seizure freedom (Engel 1) was achieved in 87.8 % at mean follow-up of 59.2 ± 27.9 months. Seizure freedom was achieved in 92.9 % of uBTLE patients at 52.8 ± 36.6 months. Seven of 10 dBTLE patients underwent resection on the side of maximum number of iEEG seizure onset, and 6 (85.7 %) remained seizure-free at 40.14 ± 25 months. There was no statistically significant difference in seizure-free outcome between UTLE and sBTLE (Pearson Chi-Square test, p-value = 0.67).

High seizure freedom rates were observed in both unilateral and bilateral disease following standard temporal lobectomy. However, the study lacks pre- and post-resection neuropsychological data to conclude on the cognitive sequelae of resective surgery in established bilateral mesiotemporal epilepsy.