Functional MRI Predicts Memory Performance after Right Mesiotemporal Epilepsy Surgery

Authors


Address correspondence and reprint requests to Dr. F.G. Woermann at MRI Unit, Mara Hospital, Bethel Epilepsy Center, Maraweg 21, Bielefeld 33617, Germany. E-mail: fgw@mara.de

Abstract

Summary: Purpose: Anterior temporal lobe resection (ATR) is a treatment option in drug-resistant epilepsy. An important risk of ATR is loss of memory because mesiotemporal structures contribute substantially to memory function. We investigated whether memory-activated functional MRI (fMRI) can predict postoperative memory loss after anterior temporal lobectomy in right-sided medial temporal lobe epilepsy (MTLE).

Methods: We included 16 patients (10 women) aged 16–54 years. The mean age at epilepsy onset was 12.5 years (range, 1–26 years). The patients' mean Wechsler IQ score was 95.2 (range, 62–125). The activation condition of fMRI consisted of retrieval from long-term memory induced by self-paced performance of an imaginative walk. All but one patient had left-sided speech dominance according to speech-activated fMRI. Outside the scanner, we evaluated the pre- and postoperative visual memory retention by using Rey Visual Design Learning Test.

Results: We found a correlation between the preoperative asymmetry index of memory-fMRI and the change between pre- and postsurgical measures of memory retention. Reduced activation of the mesiotemporal region ipsilateral to the epileptogenic region correlated with a favorable memory outcome after right-sided ATR.

Conclusions: In light of the postoperative results, the theoretical implication of our study is that fMRI based on a simple introspective retrieval task measures memory functions. The main clinical implication of our study is that memory-fMRI might replace the invasive Wada test in MTLE by using a simple fMRI paradigm. Predictive power, however, will be studied in larger patient samples. Other studies are required for left-sided MTLE and neocortical epilepsies to assess the clinical usefulness of memory-fMRI.

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