Invasive monitoring with grid electrodes was associated with significant complications. Most of them were transient. Increased complication rates were related to left-sided grid insertion and longer monitoring with a greater number of electrodes (especially more than 60 electrodes). Improvements in grid technology, surgical technique, and postoperative care resulted in significant reductions in the complication rate.

Summary:Purpose: Focal cortical dysplasia (CD) is increasingly recognized as a common pathologic substrate of medically intractable epilepsy. As these lesions are often localized in the frontal lobe (therefore in potentially eloquent cortex), an understanding of the functional status of the involved region(s) and of its anatomic and pathologic correlates is of prime importance. The purpose of this study is to assess the function of focal CD in relation to magnetic resonance imaging (MRI) and histopathologic features.Methods: Eight patients operated on for medically intractable epilepsy with histologically proven focal CD involving putative eloquent cortex in the frontal lobe (perirolandic and Broca's areas) were included in the study. Functional regions (motor and language) and epileptogenic areas were assessed by extraoperative electrocorticographic recording and electrical cortical mapping. Cortical functions were correlated with the extent of epileptogenicity on electrocorticographic recordings, MRI features, and histologic characteristics.Results: Language or motor areas were colocalized with epileptogenic regions (n ‫ס‬ 6 of 8, 75%), but were not mapped in regions of increased signal on fluid-attenuated inversion recovery (FLAIR) MRI (when they were identified) on preoperative MRI (n ‫ס‬ 5 of 5, 100%). Histologically, balloon cells were almost exclusively found in nonfunctional regions with FLAIR MRI abnormalities. When resected, regions of motor cortex were characterized by cortical dyslamination, columnar disorganization, and dysmorphic neurons, but were devoid of balloon cells. Conclusions:We found an absence of language or motor functions in perirolandic and Broca's areas that showed decreased epileptogenicity, histopathological evidence of CD with balloon cells and FLAIR MRI signal increase. Language and motor functions were present in epileptogenic and dysplastic areas with no balloon cells and no FLAIR signal abnormalities. These findings have implications on options for epilepsy surgery in patients with CD.

Summary:Purpose: Interictal ['XF]fluorodeoxyglucose (FDG) positron emission tomography (PET) reveals regional hypometabolism in 60-80% of patients with mesial temporal lobe epilepsy (MTLE). The extent of hypometabolism generally extends beyond the epileptogenic zone. The pathophysiology underlying this widespread change is unknown. This study evaluated the relation between hippocampal neuronal loss and hypometabolism in patients with MTLE.Methods: Forty-three patients with MTLE after anterior temporal lobectomy were included. Pathology demonstrated mesial temporal sclerosis (n = 41) or endfolium sclerosis (n = 2). Interictal FDG-PET scans were graded by visual analysis on a scale ranging from normal (grade 1) to severe (grade 5) hypometabolism. Neuronal counting was performed in the subiculum, hippocampal subfields, and dentate granular cell layer (DG). Neuronal density of patients was compared with that of seven autopsy controls. Data were compared by using Student's t tests and Kruskal-Wallis one-way analysis of variance (ANOVA).Results: Significant neuronal loss in CAI through CA4 and DG was found in patients compared with controls. Neuronal density in the subiculum, CAI, CA4, and DG did not correlate with severity of hypometabolism. However, patients with abnormal FDG-PET had higher neuronal density in CA2 and CA3 versus patients with normal studies.Conclusions: This study supports a previous observation that degree of FDG-PET hypometabolism does not parallel severity of hippocampal neuronal loss in MTLE. Key Words: FDG-PET-Mesial temporal lobe epilepsy-Mesial temporal sclerosis-Hippocampal neuronal density.Interictal [ '8F]fluorodeoxyglucose positron emission tomography (FDG-PET) demonstrates hypometabolism involving, but not restricted to, the epileptogenic zone in 60-90% of patients with mesial temporal lobe epilepsy (MTLE; 1,2). The pathophysiology of this finding is unknown. Hippocampal atrophy and FDG-PET hypometabolism have been shown to be reliable predictors of outcome after anterior temporal lobectomy (ATL; 3-5). Several investigators have found a significant correlation between hippocampal volume on magnetic resonance imaging (MRI) and severity of hippocampal cell loss in the resected tissue (6-8). Conflicting results were obtained when hippocampal volume was correlated with FDG-PET hypometabolism in patients with MTLE Accepted Aprii 20, 1998. Address correspondence and reprint requests to Dr. N. Foldvary at The Cleveland Clinic Foundation, Section of Epilepsy and Sleep Disorders, Department of Neurology, 9500 Euclid Avenue, S-5 I , Cleveland, OH 44195, U.S.A. (9,lO). In addition, Engel et al. ( 1 1) found no relation between degree of hypometabolism and frequency of interictal discharges during PET by using scalp, sphenoidal, and depth electrode recordings, suggesting that hypometabolism is unrelated to epileptiform activity. Henry et al. (12) found no correlation between severity of hypometabolism measured quantitatively and hippocampal neuronal density in 40 patients with TLE. Further to eval...

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