Long-term memory trajectories in seizure-free patients following epilepsy surgery for hippocampal sclerosis

This study was undertaken to study long-term memory trajectories over the years in patients with temporal lobe epilepsy and unilateral hippocampal sclerosis (TLE/HS) seizure-free since surgery.

This cross-sectional study included patients with TLE/HS from a single-center epilepsy surgery program who had been seizure-free for at least 10 years following anterior temporal lobectomy (ATL) or selective amygdalohippocampectomy (SAH). Memory performance was evaluated preoperatively (T1), 1-4 years postoperatively (T2), and 10-15 years after surgery (T3). Logistic regression evaluated variables correlated with memory function at each point in time. A reliable change index was performed to identify changes in individual measures.

A total of 54 patients were included, of whom 36 (66%) were male and 52 (96%) right-handed. Patients with left HS and normal preoperative Rey Auditory Verbal Learning Test or Wechsler Memory Scale-Revised (WMS-R) logical memory showed worsening at T2 (13% × 52%, p = .029; 0 × 31%, p < .015, respectively) and T3 (27% × 63%, p = .045; 22% × 81%, p < .001, respectively). Visual reproduction (WMS-R) following nondominant surgery also deteriorated at T3 for patients who improved or sustained normal performance between T1 and T2 (33% × 50%, p = .64). The predictive factors for memory decline included normal preoperative memory function (odds ratio [OR] = 15, 95% confidence interval [CI] = 4.03-55.9, p < .001 for logical memory; OR = 1.5, 95% CI = 1.12-2.01, p = .007 for visual reproduction), younger age (OR = 1.2, 95% CI = 1.12-1.28, p < .001), dominant-side surgery (OR = 3.66, 95% CI = 1.49-8.95, p < .01), and lower education level (OR = 8.74, 95% CI 1.77-43.2, p = .008). The SAH technique was associated with better long-term verbal learning outcomes compared to ATL (OR = 3.02, 95% CI = 1.17-7.81, p = .02).

Memory preservation or improvement in the first few postoperative years is usually not sustained in the long term, suggesting that disease progression surpasses plasticity over the years.