Abstracts

A significant minority of patients undergoing surgery for medically refractory non-lesional TLE continue to have seizures, and the reasons for this are uncertain. Flurodeoxyglucose positron emission tomography (FDG-PET) shows hypometabolism in a majority of patients with non-lesional TLE, even in the absence of hippocampal atrophy. It is controversial whether the surgical resection of the region of temporal hypometabolism influences outcome. We examined whether the extent of resection of the area of hypometabolism on the pre-operative FDG-PET scan influenced outcome following surgery for non-lesional TLE. 24 patients who underwent temporal lobectomy for medically refractory TLE with at least 6 months follow-up were studied. The pre-operative FDG PET was compared with 20 non-epileptic controls using SPM-99 to identify regions of significant hypometabolism (p[lt]0.0005, cluster [gt] 200). This image was then co-registered to the post-operative MRI scan using Analyze 7.55 (Mayo Foundation). The volume and brightness area product (BAP) of the FDG-PET hypometabolism that lay within the area of the resected temporal lobe was calculated and expressed as a percentage of the volume and BAP of hypometabolism. Mean follow-up was 3.01 yrs (range 0.7 [ndash] 5.4 yrs). Patients with an excellent outcome had a greater proportion of the FDG-PET hypometabolism volume resected than those with a non-excellent outcome (24.2% vs. 12.0%, p=0.04). Similarly, the percentage of the BAP resected was higher in the excellent outcome group (25.2% vs. 10.6%, p=0.04). Logistic regression demonstrated that the extent of resection of the hypometabolism was significantly correlated with outcome independent of the presence of hippocampal sclerosis ([italic]b=[/italic]8.1, p=0.047 and [italic]b=[/italic]1.5, p=0.22). The extent of resection of the region of hypometabolism on the pre-operative FDG-PET is predictive of outcome following surgery for non-lesional TLE, independent of the presence of hippocampal sclerosis.