Abstracts

Rationale: 1C-Methionine PET (MET-PET) is useful neuroimaging tool for the diagnosis and preoperative grading of glioma.  But the clinical significance of MET-PET in detection of epileptogenic zone has not been known well.  We here assess the findings of MET-PET in patients with intractable epilepsy. Methods: Met-PET were performed in 24 patients with intractable epilepsy who underwent epilepsy surgery.  MET-PET was also done in 6 patients, three with FCD and three with tuberous sclerosis (TSC), who did not undergo resective epilepsy surgery. Results: Among 24 patients who underwent epilepsy surgery, MET-PET demonstrated MET accumulation in epileptogenic zone in 16 patients; with FCD in 7, TSC in 6, hemimegaloencephaly in 1, postoperative gliosis in 1, oligodendrogliomas in 1.  The MET accumulation was also seen one un-operated FCD patients with frequent seizure.  L/C ratio of SUVmax was 1.09-2.3 with mean of 1.36.  The accumulation was not seen in 8 patients; with temporal lobe epilepsy in 3, MRI-invisible lesion in 2, type 1 FCD in 1, TSC without detectable epileptogenic focus in 1, TSC in 1, and ulegyria in 1. The accumulation was also negative in two patients with FCD and three patients with TSC showing no seizure activities.  Immunohistochemical investigation showed resected tissue with MET accumulation showed higher Iba-1 (indicator of activated microglia) positive cell population than those with MET non-accumulated tissue; 50.6/HPF vs. 26.2/HPF.  Vimentin was positive in these microglial activated tissue, which was not true in GFAP, TNF-α, or mTOR.  Conclusions: MET accumulation was seen in epileptogenic zone in FCD type 2, TSC, and hemimegaloencephaly.  Considering the accumulation was negative in patients without seizures instead of presence of these kind of lesions and immunohistochemical microglial activity in MET accumulated lesions, MET-PET positivity seems indicate the inflammatory process in epileptogenic lesions. Funding: No particular funding for this study