DOI: 10.1093/brain/awh281 Brain (2004), 127, 2286–2298 Functional MRI predicts post-surgical memory following temporal lobectomy Marcie L. Rabin, 1 Veena M. Narayan, 1 Daniel Y. Kimberg, 1,2 Daniel J. Casasanto, 1 Guila Glosser, 1 Joseph I. Tracy, 3 Jacqueline A. French, 1 Michael R. Sperling 3 and John A. Detre 1,2 Correspondence to: John A. Detre, MD, Department of Neurology, University of Pennsylvania School of Medicine, 3W Gates Bldg, 3400 Spruce Street, Philadelphia, PA 19104, USA E-mail: detre@mail.med.upenn.edu 1 Departments of Neurology and 2 Center for Functional Neuroimaging, University of Pennsylvania School of Medicine and 3 Department of Neurology, Thomas Jefferson University School of Medicine, Philadelphia, Pennsylvania, USA Summary Temporal lobectomy is an effective therapy for medically refractory temporal lobe epilepsy (TLE), but may be complicated by amnestic syndromes. Therefore, pre-surgical evaluation to assess the risk/benefit ratio for surgery is required. Intracarotid amobarbital testing (IAT) is currently the most widely used method for assessing pre-surgical memory lateralization, but is relatively invasive. Over the past decade functional MRI (fMRI) has been shown to correlate with IAT for language lateralization, and also for memory lateraliza- tion in a small number of patients. This study was carried out to compare fMRI during memory encoding with IAT testing for memory lateralization, and to assess the predictive value of fMRI during memory encoding for post-surgical memory outcome. Thirty-five patients with refractory TLE undergoing pre-surgical evaluation for temporal lobectomy and 30 normal subjects performed a complex visual scene-encoding task during fMRI scanning at 1.5 T using a 10-min protocol. Encoding performance was evaluated with subsequent recognition testing. Twenty-three patients also completed the same task again outside the scanner, an average of 6.9 months following surgery. A region of interest (ROI) analysis was used to quantify activation within hippocampal and a larger mesial temporal lobe ROI consisting of hippocampus, parahippocampus and fusiform gyrus (HPF) as defined by a published template. Normal subjects showed almost symmetrical activation within these ROI. TLE patients showed greater asymmetry. Asymmetry ratios (ARs) from the HPF ROI correlated significantly with memory lateralization by intracarotid amobarbital testing. HPF ARs also corre- lated significantly with memory outcome, as determined by a change in scene recognition between pre-surgical and post-surgical trials. When absolute activation within the HPF ROI was considered, a significant inverse correlation between activation ipsilateral to temporal lobectomy and memory outcome was observed, with no significant correlation in the contralateral HPF ROI. Although further technical improvements and prospective clinical validation are required, these results suggest that mesial temporal memory activation detected by fMRI during complex visual scene encoding correlates with post- surgical memory outcome and supports the notion that this approach will ultimately contribute to patient management. Keywords: functional MRI; episodic memory; temporal lobe epilepsy; temporal lobectomy Abbreviations: AR = asymmetry ratio; fMRI = functional MRI; H = hippocampus; HPF ROI = hippocampal–parahippocampal– fusiform ROI; H ROI = hippocampal ROI; IAT = intracarotid amobarbital test; mTL = mesial temporal lobe; ROI = region of interest; SPM = statistical parametric map; TL = temporal lobectomy; TLE = temporal lobe epilepsy; TR = repetition time; WMS-III = Wechsler Memory Scale III Received April 5, 2004. Revised June 17, 2004. Accepted June 22, 2004. Advanced Access publication August 25, 2004 Introduction Anterior temporal lobectomy (TL) eliminates seizures or improves seizure control in 80–90% of patients (Engel et al., 1993), and has been prospectively validated as an effective therapy for medically refractory temporal lobe epilepsy (TLE) (Wiebe et al., 2001). However, the hippo- campus (H) and adjacent anatomically related mesial Brain Vol. 127 No. 10 # Guarantors of Brain 2004; all rights reserved