Pre- and post-operative fMRI and clinical memory performance in temporal lobe epilepsy

Abstract

Objective: The present study aimed to examine and compare memory processing in patients with unilateral temporal lobe epilepsy (TLE) before and after surgery using functional magnetic resonance imaging (fMRI).

Methods: Seventeen pre-operative patients with unilateral TLE (nine left, eight right) and eight healthy controls were recruited. They performed a complex visual scene-encoding task during fMRI to measure memory activation in the mesial temporal lobe. Their memory performance was evaluated using standardized neuropsychological tests. After unilateral temporal lobe resection (either temporal lobectomy, selective amygdalohippocampectomy or lesionectomy), the same fMRI paradigm and neuropsychological tests were administered to the patient group.

Results: Left-TLE patients demonstrated decline in verbal memory after left temporal lobe resection. Their post-operative verbal and visual memory performance was positively associated with post-operative functional activation in the right mesial temporal lobe whereas post-operative memory performance of right-TLE patients was positively associated with post-operative functional activation in the left mesial temporal lobe, contralateral to their respective side of resection.

Conclusion: Post-operative memory performance was significantly associated with functional activation contralateral to the side of resection in patients with unilateral TLE and the function of the contralateral mesial temporal lobe seems to play an important role in supporting memory performance after temporal lobe resection.