Abstracts

Rationale: This case-series study aims to assess the efficacy of surgery and investigate factors associated with poor outcome in patients with mesial temporal lobe epilepsy (MTLE).

Methods: This study reviewed a total of 175 MTLE patients who underwent resective surgery at a single university-affiliated hospital between January 2008 and December 2021. Surgical outcomes were assessed using a modified Engel classification at two years and five years post-operation, as well as at the last follow-up visit. Poor outcome was defined as Engel III-IV.

Results: Thirteen (7.4% [13/175]; 38.3 +- 9.7 years, 4 males) patients were classified as having a poor surgical outcome at the five-year post-surgical mark. After 5 years post-surgery, the mean seizure reduction for the 13 patients was 63.0% at the 5th year. Among them, 3 reported no change in seizure frequency, while the 10 had an average reduction of 81.8%. No patient reported increased seizure frequency after surgery.

On presurgical evaluation of the 13 patients, six (46.1%) showed unilateral temporal interictal epileptiform discharges (IEDs) and seven (53.9%) showed bi-temporal IEDs. Eleven (84.6%) showed hippocampal sclerosis (HS), with two (15.4%) having HS combined extratemporal lesion, and two (15.4%) had normal MRI findings. Nine (9/13, 69.2%) showed unilateral hypometabolism on PET, while four (30.8%) had hypometabolism not confined to the unilateral temporal area on PET. Regarding the surgical procedure, eleven (84.6%) patients received complete resection of the hippocampus, while three (23.1%) received partial hippocampal resection (remaining hippocampal tail) to avoid postoperative memory disturbance. Pathology tests revealed HS in eleven (84.6%) patients, focal cortical dysplasia (FCD) in the lateral temporal lobe in addition to HS in ten (76.9%) patients, and FCD only in two (15.4%) patients.

Among the three patients showing no seizure reduction, one had three preoperative episodes of status epilepticus but underwent partial resection of the hippocampus. Another patient had suspected HS on MRI, but pathology did not confirm HS; moreover, combined extratemporal lesions with non-localized hypometabolism were identified. The remaining patient exhibited IEDs and ictal onset from bi-temporal areas.


Conclusions: Although classified within the poor surgical outcome group, they experienced meaningful seizure reduction. It suggests that resective surgery remains a viable option for MTLE patients with at least for palliative purposes. Incomplete resection of hippocampus and combined extratemporal lesions likely contribute to very poor surgical outcomes (=no seizure reduction).

Funding: This work was not supported by any funding.