Abstracts

Rationale: Although FDG-PET hypometabolism is a gold-standard presurgical workup in patients with medically intractable epilepsy (MIE), the significance of FDG-PET hypermetabolism (FPH), especially in FCD, is not well established. Methods: A retrospective study of patients who underwent FDG-PET during presurgical workup for MIE at the Children's Hospital Colorado during the period between January 2010 and December 2013 was performed. Seven patients with FPH were identified. Results: Age at study was between 11 and 183 months (Median 124). Four were male and 3 were female. Six underwent epilepsy surgery (ES). Duration of seizures prior to the surgeries was between 2 and 148 months (Median 67). All patients had FCD, type 1 in five and type 3 in two patients (FCD 1 with remote stroke and Rasmussen encephalitis). MRI showed no abnormalities in 1, focal abnormalities in 3 and multilobar abnormalities in 3 patients. FPH was noted in the left hemisphere in 4 and right cerebral hemispheres (CH) in 3 patients. Two patients had FPH in the cerebellum contralateral to FPH in CH. FPH was concordant in both region and lateralization with MRI abnormalities in all patients. FDG injection was done during ictal EEG activity in 2, during EEGs with no interictal EEG discharges (IEDs) in 1, during occasional IEDs in 1 and during continuous/very frequent IEDs in 3 patients. One patient with FPH without IEDs had epilepsia partialis continua (EPC). Postictal FDG injection was performed within 1 hour of seizures in 2 patients. Two patients had EPC. LGS (n=1), West syndrome (WS) (n=1), CSWS (n=1), Rasmussen encephalitis (n=1), Ohtahara syndrome (n=1) and structural epilepsy (n=2) were seen. Six of seven patients underwent functional hemispherectomy and all have been seizure free. One patient has been scheduled for functional hemispherectomy (FH). Postoperative follow-up is between 6 and 40 months (Median 19). Conclusions: All patients in this study with FPH had catastrophic epilepsy caused by FCD and most of them had either diffuse/multifocal MRI or EEG findings. These findings led to FH despite a circumscribed FPH focus. FPH is a reliable finding in lateralizing the epileptogenic region (ER) (p<0.05) and predicting seizure freedom after ES. The role of EEG in FPH is questionable as only 28.5% of FDG injections were performed during an ictal EEG. Injection of FDG during either postictal EEG, EEG without IEDs in patients with EPC, or occasional or continuous/very frequent IEDs can be associated with FPH. Crossed FPH cerebellar diaschisis can lateralize ER in some patients.