The analysis of 18F-FDG PET/MRI, electroencephalography, and semiology in patients with gray matter heterotopia: A pilot study

Objectives To describe F-18-fluorodeoxyglucose positron emission tomography/magnetic resonance imaging (F-18-FDG PET/MRI) along with semiology and electroencephalography (EEG) in patients with gray matter heterotopia (GMH); to evaluate the concordance between F-18-FDG PET/MRI and clinical epileptogenic zone (EZ). Materials & Methods GMH (subcortical heterotopia [SCH] and periventricular nodular heterotopia [PNH]) patients with epilepsy who underwent F-18-FDG PET/MRI were retrospectively enrolled. Two radiologists evaluated brain MRI, while two nuclear medicine specialists assessed the F-18-FDG PET. The SUVmax values of visually hypometabolic cortical areas were compared to the contralateral cortex using a SUVmax threshold value of 10%; the SUVmax values of GMH lesions were compared with that of the right precentral gyrus. The cortex or GMH with hypometabolism on F-18-FDG PET/MRI was considered representative of the EZ. The clinical EZ was identified using EEG and semiology. Results Thirty patients (19 PNH; 11 SCH) with a mean age of 28.46 +/- 9.52 years were enrolled. The heterotopic nodules were ametabolic in 3 patients (10%), hypometabolic in 16 (33.33%), isometabolic in 13 (26.66%), and hypermetabolic in 4 (10%). F-18-FDG PET/MRI demonstrated hypometabolism in the cortex and GMH in 22/30 (73.33%) and 16/30 (53.33%). We could identify a clinical EZ in 18 patients, and 15 out of 18 (83.33%) had concordant F-18-FDG PET/MRI findings. Conclusion Heterotopic nodules in GMH patients show different metabolic patterns on F-18-FDG PET/MRI, with nearly three-quarters of the patients having cortical hypometabolism. F-18-FDG PET/ MRI findings are mostly concordant with the clinical EZ.