Current Developments on [¹⁸F]FDG PET/CT in Inflammatory Disorders of the Central Nervous System

2-Deoxy-2-[¹⁸F]fluoro-D-glucose positron emission tomography (FDG-PET) is widely used to study cerebral glucose metabolism and may be useful in several inflammatory disorders of the central nervous system. Emerging literature suggests that [¹⁸F]FDG may be more sensitive to detect abnormalities in auto-immune encephalitis (AIE) in comparison to MRI, especially in NDMA receptor encephalitis. Distinct patterns of regional abnormalities in AIE have been reported, depending on the auto-antibody involved. Predominant findings are hypermetabolism of the mediotemporal lobe and hypometabolism in parietal and occipital lobes. The possibility for whole body imaging in the setting of malignancy screening further strengthens the importance of [¹⁸F]FDG PET in AIE when associated with paraneoplastic syndromes. Other inflammatory conditions of the central nervous system where [¹⁸]FDG PET may facilitate diagnosis include neurosarcoidosis and potential neuropsychiatric manifestations of systemic lupus erythematodes. More recently, [¹⁸F]FDG PET has been used in patients to evaluate postacute sequelae of COVID-19, allowing assessment of specific neuronal impairments at the individual level and determination of time-dependent metabolic alterations.