Consequences of mesial temporal sparing temporal lobe surgery in medically refractory epilepsy

Abstract

Objective: We compared long-term seizure outcome, neuropsychological outcome, and occupational outcome of anterior temporal lobectomy (ATL) with and without sparing of mesial structures to determine whether mesial sparing temporal lobectomy prevents memory decline and thus disability, with acceptable seizure outcome.

Methods: We studied patients (n = 21) and controls (n = 21) with no evidence of mesial temporal sclerosis (MTS) on MRI who had surgery to treat drug-resistant epilepsy. Demographic and pre- and postsurgical clinical characteristics were compared. Patients had neuropsychological assessment before and after surgery. Neuropsychological analyses were limited to patients with left-sided surgery and available data (n = 14 in each group) as they were at risk of verbal memory impairment. The California Verbal Learning Test II (CVLT-II) (sum of trials 1-5, delayed free recall) and the Logical Memory subtest of the Wechsler Memory Scale III or IV (WMS-III or WMS-IV) (learning and delayed recall of prose passages) were used to assess verbal episodic learning and memory. Seizure and occupational outcomes were assessed.

Results: The chance of attaining seizure freedom was similar in the two groups, so sparing mesial temporal structures did not lessen the chance of stopping seizures. Sparing mesial temporal structures mitigated the extent of postoperative verbal memory impairment, though some of these individuals suffered decline as a consequence of surgery. Occupational outcome was similar in both groups.

Significance: Mesial temporal sparing resections provide a similar seizure outcome as ATL, while producing a better memory outcome. Anterior temporal lobectomy including mesial structure resection did not increase the risk of postoperative disability.

Keywords: Disability; Employment; Hippocampal sparing anterior temporal lobectomy; Verbal memory.

Fig. 1.

Kaplan–Meier graph showing cumulative time-dependent probability of occurrence of the first seizure with altered consciousness after anterior temporal lobectomy with sparing (red) or without sparing (blue) of the mesial temporal structures in patients without MTS on MRI. There is no difference between the two groups (n = 21 for each group at the start).

Fig. 2.

(A–D) pre and postsurgical verbal memory performance for patients who had mesial temporal sparing or standard ATL. CVLT-II sum of trials 1–5 (A), CVLT-II delayed recall (B), Logical Memory I (C), Logical Memory II (D). The change in memory performance over time differed significantly between groups with cases faring better than controls, for CVLT-II delayed recall, Logical Memory I, and Logical Memory II. The group difference in change over time for CVLT-II sum of trials 1–5 did not reach the threshold of statistical significance. n = 28 for CVLT-II. n = 27 for Logical Memory.