Prognostic factors determining poor postsurgical outcomes of mesial temporal lobe epilepsy

Abstract

Objectives: To investigate the long-term postoperative outcomes and predictive factors associated with poor surgical outcomes in mesial temporal lobe epilepsy (MTLE).

Materials and methods: We enrolled patients with MTLE who underwent resective surgery at single university-affiliated hospital. Surgical outcomes were determined using a modified Engel classification at the 2nd and 5th years after surgery and the last time of follow-up.

Results: The mean duration of follow-up after surgery was 7.6 ± 3.7 years (range, 5.0-21.0 years). 334 of 400 patients (83.5%) were seizure-free at the 5th postoperative year. Significant predictive factors of a poor outcome at the 5th year were a history of generalized tonic clonic (GTC) seizures (odds ratio, OR; 2.318), bi-temporal interictal epileptiform discharge (IED) (OR; 3.107), bilateral hippocampal sclerosis (HS) (OR; 5.471), unilateral HS and combined extra-hippocampal lesion (OR; 5.029), and bi-temporal hypometabolism (BTH) (OR; 4.438). Bi-temporal IED (hazard ratio, HR; 2.186), BTH (HR; 2.043), bilateral HS (HR; 2.541) and unilateral HS and combined extra-hippocampal lesion (HR; 2.75) were independently associated with seizure recurrence. We performed a subgroup analysis of 208 patients with unilateral HS, and their independent predictors of a poor outcome at the 5th year were BTH (OR; 5.838) and tailored hippocampal resection (OR; 11.053).

Conclusion: This study demonstrates that 16.5% of MTLE patients had poor long-term outcomes after surgery. Bilateral involvement in electrophysiological and imaging studies predicts poor surgical outcomes in MTLE patients.

Fig 1. Kaplan-Meier survival curves according to (a) MRI findings and (b) PET hypometabolism patterns.

(a) The Kaplan-Meier survival curves show statistically significant associations of bilateral HS and unilateral HS combined with extra-hippocampal lesion with seizure recurrence. (b) The survival curves show significantly more frequent recurrence in patients with BTH or temporal plus extratemporal hypometabolism compared with patients with UTH involving only mesial temporal and temporal pole structures. HS, hippocampal sclerosis; UTH, unilateral temporal hypometabolism; BTH, bilateral temporal hypometabolism.