Altered coupling between resting‐state glucose metabolism and functional activity in epilepsy

OBJECTIVE: Altered functional activities and hypometabolism have been found in medial temporal lobe epilepsy patients with hippocampal sclerosis (mTLE‐HS). Hybrid PET/MR scanners provide opportunities to explore the relationship between resting‐state energy consumption and functional activities, but whether repeated seizures disturb the bioenergetic coupling and its relationship with seizure outcomes remain unknown. METHODS: (18)F‐FDG PET and resting‐state functional MRI (rs‐fMRI) scans were performed with hybrid PET/MR in 26 patients with mTLE‐HS and in healthy controls. Energy consumption was quantified by (18)F‐FDG standardized uptake value ratio(SUVR) relative to cerebellum. Spontaneous neural activities were estimated using regional homogeneity (ReHo), fractional amplitude of low frequency fluctuations (fALFF) from rs‐fMRI. Between‐group differences in SUVR and rs‐fMRI derived metrics were evaluated by two‐sample t test. Voxel‐wise spatial correlations were explored between SUVR and ReHo, fALFF across gray matter and compared between groups. Furthermore, the relationships between altered fALFF/SUVR and ReHo/SUVR coupling and surgical outcomes were evaluated. RESULTS: Both the patients and healthy controls showed significant positive correlations between SUVR and rs‐fMRI metrics. Spatial correlations between SUVR and fMRI‐derived metrics across gray matter were significantly higher in patients with mTLE‐HS compared with healthy controls (fALFF/SUVR, P < 0.001; ReHo/SUVR, P = 0.022). Higher fALFF/SUVR couplings were found in patients who had Engel class IA after surgery than all other (P = 0.025), while altered ReHo/SUVR couplings (P = 0.097) were not. CONCLUSION: These findings demonstrated altered bioenergetic coupling across gray matter and its relationship with seizure outcomes, which may provide novel insights into pathogenesis of mTLE‐HS and potential biomarkers for epilepsy surgery planning.