Evaluation of amygdala pathology using 11C-methionine positron emission tomography/computed tomography in patients with temporal lobe epilepsy and amygdala enlargement

• Amygdala enlargement (AE) has been increasingly reported to be associated with TLE.
• AE lesions sometimes contain neoplasm, which cannot be detected by MRI.
• We explored AE pathology using 11C-methionine PET.
• Histopathological findings were almost consistent with the results of 11C-methionine PET.
• 11C-methionine PET may be useful for detecting neoplasm in AE lesions.

SummaryObjectiveThe association between amygdala enlargement (AE) and temporal lobe epilepsy (TLE) has increasingly been reported. However, the pathology of AE remains poorly understood. The purpose of this study was to explore AE pathology using 11C-methionine (Met) positron emission tomography (PET)/computed tomography (CT) in patients who have TLE with AE.Materials and methodsTwenty-six TLE patients with AE and 18 TLE patients without AE underwent 11C-Met PET/CT and magnetic resonance imaging (MRI). 11C-Met uptake in amygdala was evaluated by both visual inspection and semi-quantitative measurement. MRI was assessed visually and semi-quantitatively for AE. Laterality index (LI) was obtained by comparing the amygdala volumes of ipsilateral and contralateral sides. The clinical course and histopathological findings of all patients were also analyzed.ResultsOn 11C-Met PET/CT images, visual examination detected increased uptake in the enlarged amygdala in 7 of 26 (27%) TLE patients with AE, and the results were confirmed by semi-quantitative analysis. Among six TLE patients with AE who underwent surgery, histopathology revealed neoplasms (low grade astrocytoma and gangliocytoma) in two patients and focal cortical dysplasia in one patient with increased 11C-Met uptake, but non-neoplastic lesions (focal cortical dysplasia, vacuolar degeneration, and hamartoma) in all three patients with no increased 11C-Met uptake. On MRI, volume of the affected amygdala was significantly larger compared to the contralateral amygdala. LI was significantly higher in the group with AE than in the group without AE.ConclusionsThis study revealed that some TLE patients with AE showed increased 11C-Met uptake in the enlarged amygdala. 11C-Met PET/CT is potentially useful for the evaluation of AE pathology, and may provide beneficial information for appropriate decision-making.