Abstracts

To determine the effect of normal MRI findings on seizure free outcomes following epilepsy surgery We reviewed the results of epilepsy surgeries performed in Milwaukee from 1991 to 2001. In 362 evaluations of epilepsy, we found 214 surgical resections. We found 176 cases with valid MRI results, surgery locations, and 6 month seizure-free outcomes. We divided patients into seizure-free versus non-seizure-free at their 6 month assessment. Surgery locations were defined as lobar or multi-lobar. MRIs were collapsed into normal or abnormal resuilts. We performed an analsis using Pearson[apos]s Chi-squared technique on the relationship between normal versus abnormal MRI results and the patient[apos]s seizure outcome, including analysis by surgery location. Of the 176 surgeries performed, 136 were temporal and 22 were frontal. Seizure freedon coccurred in 103 of temporal resections (76%) and 8 of frontal resections (37%). Abnormal MRIs were found in 92 temporal resections (67%) and 15 frontal resections (68%). Seizure freedom was no different in patients with normal versus abnormal MRIs (p=0.991). Seizure freedom rates for temporal resections were 70% in normal MRI versus 77% in abnormal MRI (p=0.43). Seizure freedom rates for frontal resections in normal MRI were 42% versus 33% in abnormal MRIs. Normal MRI in the evaluation of localization-related epilepsies did not influence seizure-free rates in our surgical experience. Previous studies suggest the presence of MRI abnormalities improves surgical outcomes and we have previously reported abnormalities of prognostic significance. Patients presenting for epilepsy surgery should not be discouraged that normal MRI findings may influence their outcome.