Temporal lobectomy is an effective therapy for medically refractory temporal l obe epilepsy (TLE), but may be complicated by amnestic syndromes. Therefore, pre surgical evaluation to assess the risk/benefit ratio for ...
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Temporal lobectomy is an effective therapy for medically refractory temporal l obe 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. O ver the past decade functional MRI (fMRI) has been shown to correlate with IAT f or language lateralization, and also for memory lateralization 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 asse ss the predictive value of fMRI during memory encoding for post surgical memory outcome. Thirty five patients with refractory TLE undergoing pre surgical eva luation 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. En coding performance was evaluated with subsequent recognition testing. Twenty th ree 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 co nsisting of hippocampus, parahippocampus and fusiform gyrus (HPF) as defined by a published template. Normal subjects showed almost symmetrical activation with in 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 correlated 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 s ignificant inverse correlation between activation ipsilateral to temporal lobect omy and memory outcome was
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