Preoperative fMRI predicts memory decline following anterior temporal lobe resection

Abstract

Background Anterior temporal lobe resection (ATLR) benefits many patients with refractory temporal lobe epilepsy (TLE) but may be complicated by material specific memory impairments, typically of verbal memory following left ATLR and non-verbal memory following right ATLR. Preoperative memory fMRI may help in the prediction of these deficits. Objective To assess the value of preoperative fMRI in the prediction of material specific memory deficits following both left and right sided ATLR. Methods We report 15 patients with unilateral TLE undergoing ATLR; 8 underwent dominant hemisphere ATLR and 7 non-dominant ATLR. Patients performed an fMRI memory paradigm which examined the encoding of words, pictures and faces. Results Individual patients with relatively greater ipsilateral compared to contralateral medial temporal lobe activation had greater memory decline following ATLR. This was the case for both verbal memory decline following dominant ATLR and for non-verbal memory decline following non-dominant ATLR. For verbal memory decline, activation within the dominant hippocampus alone was predictive of postoperative memory change whereas activation in the non-dominant hippocampus was not. Conclusion These findings suggest that preoperative memory fMRI may be a useful non-invasive predictor of post-operative memory change following ATLR and provide support for the functional adequacy theory of hippocampal function. They also suggest that fMRI may provide additional information, over that provided by neuropsychology, for use in the prediction of postoperative memory decline.