Detection of metabolic and perfusion changes in the hippocampus and temporal lobe regions in patients with temporal lobe epilepsy (TLE) via hybrid 18F-FDG PET/MRI

Purpose: To investigate and compare metabolic and perfusion alterations in temporal lobe epilepsy (TLE) patients via hybrid ¹⁸ F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/magnetic resonance imaging (MRI). Methods: Twenty-one TLE patients (15 with left-sided TLE (LTLE) and 6 with right-sided TLE (RTLE)) who underwent brain ¹⁸ F-FDG PET/MRI, and eight healthy controls (Hc) who had ¹⁸ F-FDG PET/MRI for health examination, were included. Brain regions were segmented based on the automated anatomical labeling (AAL) template, and the hippocampus and temporal lobe were isolated for further analysis. Left and right sides of these structures were analyzed separately. Accordingly, the maximum standardized uptake value (SUV _max ), mean standardized uptake value (SUV _mean ) and cerebral blood flow (CBF) were compared between the two sides via paired t test. Asymmetry indexes (AI) were calculated and statistically compared between the TLE patients and Hc, along with PET and Arterial spin labeling (ASL)-derived AI. Results: LTLE patients showed significant asymmetrical differences in SUV _max , SUV _mean, and CBF within the hippocampus region (p<0.01). In RTLE patients, only SUV _mean showed significant asymmetrical in both the hippocampus (p=0.009) and temporal lobe (p=0.018). The PET-derived AI in the hippocampus nearly doubled in the TLE group compared to Hc group. Similarly, ASL-derived AI in the hippocampus also increased (7.22% vs 3.86%) in the TLE group compared to Hc group (p=0.051). In the temporal lobe, both PET and ASL-derived AIs increased in the TLE group; however, these increases were not statistically significant (p=0.260, p=0.364). In the hippocampus, a significant difference existed for the AI between PET and ASL (p=0.001), while the temporal lobe showed a significant correlation for the AI between PET and ASL (r=0.49, p=0.024). Conclusion: TLE patients exhibited distinct patterns of brain metabolism and perfusion between LTLE and RTLE. And the AIs derived from PET was more accurate than those of ASL in detecting abnormalities in the hippocampus. Meanwhile, metabolism and perfusion in TLE patients differed significantly in the hippocampus, while revealing a correlation in the temporal lobe.