Abstracts

Rationale: Patients with medically refractory epilepsy may be successfully treated with surgical resection of seizure foci especially if the area can be precisely identified. For this purpose, a very careful comprehensive pre-surgical evaluation is completed at Epilepsy Monitoring Unit using scalp electroencephalography (EEG), video monitoring, and imaging (MRI) of the brain. Some patients may require further evaluation by utilizing functional imaging to precisely identify the seizure foci such as single-photon emission computed tomography (SPECT). To achieve optimal SPECT scan quality, tracer injection should be done as quickly as possible after seizure onset and under highest safety conditions. Methods: Patient records admitted to University of Michigan Epilepsy Monitoring Unit for ictal SPECT between January 2005 and December 2005 were analyzed utilizing inpatient charts, VEEG, monitoring data, monitoring reports generated by physicians. Results: Between January 2005 and March 2006, 45 patients were admitted to University of Michigan Epilepsy Monitoring Unit for ictal SPECT. The average age was 36 years, 31 female and 14 male, and 20 patients had MRIs with no focal or structural abnormality. The number of patients who had epilepsy surgery was 23 (51%). The reason patient did not have surgery: 2 patients responded to medication, 1 patient did not have seizures during gird mapping, 6 patients decided not to have surgery, 7 patients were not candidates based on diagnostic testing, 6 patient postponed surgery or pending further investigation. The patients who had epilepsy surgery: 9 had non lesional MRIs, 1 patient had brain tumor (oligodendroglioma), 2 patient had AVM (1 had hemorrhage), 4 patient had mesial temporal sclerosis, 2 temporal lobe dysplasia, 1 increased signal in temporal lobes, 1 patient with porencephalic cyst with congenital hydrocephalus, 1 porencephalic cyst, and 1 with cortical dysplasia. Second phase testing: 15 patients underwent grid mapping, and 3 patients had ECOG prior to surgery. The outcome of surgery was 18 (78%) of the patients became seizure free for up to 2 year after surgery. The patients with abnormal MRI and temporal lobe onset seizures showed seizure free outcome rate of (7/8) 88%. Four of the five patients who did not become seizure free showed 75% reduction in their seizure frequency. Conclusions: Ictal SPECT can be very useful in identifying the site of seizure onset. In our series, 78% of patients who underwent this procedure became seizure free, and all but one of the patients who was not seizure free had a 75% reduction in seizure frequency. Our results are somewhat better than those previously reported. This excellent outcome may be the result of a rapid injection time, or careful selection of patients for this procedure. We advocate ictal SPECT strongly as a means for identifying ictal onset zone in patients with cortical MRI abnormalities, normal MRI or difficult lateralization of temporal lobe epilepsy.