Abstracts

Rationale: In recent years, an increasing number of reports have indicated an association between epileptogenicity and amygdala enlargement, rather than sclerosis or atrophy. Since the seizures of these cases are relatively well controlled, few cases received surgical treatment. For this reason also, the physiopathology of this disease remains poorly understood. 11Cmethionine-PET (Met-PET) is considered a useful measure for identifying brain tumors cause epilepsy. Then, we performed non-invasive diagnostic imaging studies including Met-PET, 18F-fluorodeoxyglucose-PET (FDG-PET) and SPECT, in an attempt to gain insight into the physiopathology of this epilepsy. Methods: Nine patients with symptomatic localization-related epilepsy, in whom amygdala enlargement was found on MRI were studied. Met-PET was performed in all patients, and SPECT and FDG-PET were conducted whenever possible. The imaging findings, clinical characteristics and EEG findings were evaluated, and the pathological implications of the findings for epilepsy were discussed. Results: Except 1 case that showed no definitive EEG abnormalities, the laterality of epileptiform EEG abnormalities was the same as that of amygdala enlargement in the other 8 cases. On Met-PET, increased uptake in the amygdala was observed in 1 case, while no increased uptake was detected in the other 8 cases. The same case also showed decreased uptake on SPECT and FDG-PET at the medial side of left temporal lobe, ipsilateral to amygdala enlargement. The 8 cases that had no increased uptake on Met-PET were divided into a group showing decreased uptake on FDG-PET and/or SPECT in the temporal lobe ipsilateral to amygdala enlargement (n = 5), and a group with no decreased uptake (n = 3). Compared to the group with decreased uptake, the group showing no decreased uptake tended to have older epilepsy onset and very good seizure outcome. Four of nine patients had elderly onset epilepsy (above 60 years of age); seizures were not controlled in 1 patient with increased amygdala uptake on Met-PET, while seizures were controlled in all 4 patients who had no uptake. Conclusions: In almost all patients, both interictal and ictal discharges on EEG showed the same laterality as amygdala enlargement, suggesting a strong association between amygdala enlargement and epileptogenicity. In the patient showing uptake on Met-PET, the etiology was probably gliomatosis cerebri based on MRI and other findings. The 5 patients showing no uptake on Met-PET but decreased uptake on FDG-PET and/or SPECT probably had focal cortical dysplasia. In 3 patients with elderly onset epilepsy and no abnormal uptake in all functional imaging studies, the pathology remains unknown. However, because of the high probability of an association between amygdala enlargement and epileptogenicity, amygdala enlargement is important for understanding the pathology of epilepsy, especially in elderly patients. From the viewpoint of differentiating from tumors also, Met-PET study is effective in patients with elderly onset epilepsy showing amygdala enlargement.