Temporal lobectomy: long-term seizure outcome, late recurrence and risks for seizure recurrence

Abstract

There is little information available relevant to long-term seizure outcome after anterior temporal lobectomy, particularly at extended postoperative periods. The aim of this study was an in-depth examination of patterns of longitudinal outcome and potential risk factors for seizure recurrence after lobectomy, utilizing a large patient sample with long follow-up. Included were 325 patients who underwent anterior temporal lobectomy between 1978 and 1998 (mean follow-up 9.6 +/- 4.2 years). Retrospective data were analysed using survival analysis and multivariate regression with Cox proportional hazard models. The probability of complete seizure freedom at 2 years post-surgery was 55.3% [95% confidence interval (CI) 50-61]; at 5 years, 47.7% (95% CI 42-53); and at 10 postoperative years it was 41% (95% CI 36-48). Patients with discrete abnormalities preoperatively (i.e. lesions and hippocampal sclerosis) had a significantly higher probability of seizure freedom than patients without obvious abnormality. The latter group had a pattern of recurrence similar to that in patients with lesions outside the area of excision. After adjustment for preoperative pathology, only the presence of preoperative secondarily generalized seizures had a significant association with recurrence [occasional preoperative generalized seizures, hazard ratio (HR) 1.6, 95% CI 1.1-2.3; frequent seizures, HR 2.0, 95% CI 1.4-2.9 compared with absence of preoperative generalized seizures]. Duration of preoperative epilepsy, age of seizure onset and age at surgery did not have an effect on outcome. Patients with two seizure-free postoperative years had a 74% (95% CI 66-81) probability of seizure freedom by 10 postoperative years. This late seizure recurrence was not associated with any identified risk factors. Specifically, patients with hippocampal sclerosis were not at higher risk. Surprisingly, complete discontinuation of anti-epileptic drugs (AEDs) after two postoperative years was not associated with an increased risk of recurrence (HR 1.03, 95% CI 0.5-2.1). This may be because selection of patients for AED discontinuation is biased towards those individuals perceived as 'low risk'. The results of this study indicate that the lack of an obvious abnormality or the presence of diffuse pathology, and preoperative secondarily generalized seizures are risk factors for recurrence after surgery. Late recurrence after initial seizure freedom is not a rare event; risk factors specific to this phenomenon are as yet unidentified.

Preoperative Factors Associated With Antiepileptic Drug Withdrawal Following Surgery for Intractable Temporal Lobe Epilepsy

“…Several other recent studies have reported similar findings of seizurefree, drug-free status in 22% to 42% of patients after temporal lobe resection. 1,[4][5][6][7]12) Differences in pathologies, surgical procedures, and AED reduction policies in these other studies can explain the differences in the reported rates of postoperative AED cessation.…”

“…Only a few studies have focused on the relationships between surgical procedures and the overall rate of seizure-free outcome without drugs. 1,7) The type of surgery (ATL, AHE, or lesionectomy) was not a predictive factor in patients with seizure recurrence after AED cessation. 1) Similarly, in our study, hippocampectomy was not a predictive factor if the focus was correctly identified.…”

“…Patients with TLE who undergo surgery hope to become seizure-free, but also to be completely cured and to discontinue antiepileptic drugs (AEDs). 13) While several recent papers have discussed this issue, 1,[4][5][6][7]12) there have been difficulties in assessing the rates or predictors of postoperative drug treatment. Differences in the postoperative AED reduction criteria, pathologies, and medico-social environments among the published reports create considerable difficulties for this type of assessment.…”

Not all that glitters is gold: A guide to surgical trials in epilepsy

“…Late seizures are milder in severity and lower in frequency,53, 54, 55 easier to control with AEDs,54 and more likely to “run down” than their earlier counterparts 54. Also, late seizure recurrences usually arise from the edge of the original resection in patients with normal preoperative brain MRI,55 nonspecific surgical pathology,53 or long epilepsy duration 43. This is in contrast to early recurrences, which usually localize to brain regions distant to the site of resection or to residual incompletely resected epileptic lesions, implicating a localization or resection challenge.…”

“…No clinical predictors could a priori predict patients whose seizures will recur during AED reduction as opposed to those whose seizures will recur after complete AED discontinuation 63. Similarly, although low seizure frequency, lack of secondary generalization, unilateral preoperative EEG and MRI findings, and lack of need for invasive EEG recordings correlate with early seizure freedom after surgery for TLE,46, 53 only the presence of a specific pathological diagnosis predicts long‐term seizure freedom: 40% of patients with gliosis or nonspecific pathology were seizure free 10 years after TLE surgery in the one series that investigated early versus late outcomes independently, as opposed to 80% of those with a specific pathological abnormality 46. Overall, a lot remains to be understood about the determinants of cure (defined by seizure freedom off AEDs) or long‐term seizure remission after epilepsy surgery.…”