Short-term cognitive changes after surgery in patients with unilateral mesial temporal lobe epilepsy associated with hippocampal sclerosis

Abstract

We investigated the short-term postoperative cognitive function of patients with unilateral mesial temporal lobe epilepsy associated with hippocampal sclerosis (MTLE/HS). Fourteen unilateral MTLE/HS patients who had undergone selective amygdalohippocampectomy (SAH) or anterior temporal lobectomy (ATL) were enrolled. Cognitive functions related to the frontal and temporal lobes were evaluated using a battery of neuropsychological tests administered before surgery and 3months after surgery. The battery included the Verbal Fluency Test (VFT), Boston Naming Test (BNT), Stroop Color-Word Test (TST), Trail Making Test (TMT) and Wechsler Memory Scale (WMS). MTLE/HS patients demonstrated significantly improved postoperative performance on the TST regardless of the surgical method or side of resection. There was no significant difference in any of the other neuropsychological tests before and after surgery. After left-side resection, performance on the VFT and the TMT-B was worse than at baseline. After right-side resection, performance on the VFT and WMS short-term memory improved; however, these differences were not statistically significant. SAH patients exhibited improved TST performance but worse TMT-A performance; however, performance on all tests was not significantly different after surgery in ATL patients. In summary, MTLE/HS patients demonstrated improved frontal lobe-related cognitive function after surgery, but no such improvement in temporal lobe-related function was observed. Based on cognitive evaluation, right-sided MTLE/HS patients may be more appropriate surgical candidates than left-sided MTLE/HS patients. SAH may not be better than ATL in improving cognitive function. We hypothesise that postoperative cognitive changes depend on whether the excised cerebral regions are related to the neuropsychological functions examined by specific assessment instruments.