Aim: To elucidate the patterns of characteristic hypometabolism on 18F- fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) in multisystem atrophy (MSA) and their correlation with the patterns of uptake on dopamine transporter imaging with 99mTc TRODAT-1 SPECT.
Material and methods: A retrospective analysis of 67 patients with clinically diagnosed MSA was performed. All the subjects underwent 99mTc TRODAT-1 SPECT and 18F-FDG PET/CT scanning on two separate days. The 99mTc-TRODAT-1 scans were analyzed visually for asymmetry and rostro-caudal gradient. The FDG uptake patterns were recorded, and areas of hypometabolism that were two standard deviations from the mean were considered abnormal.
Results: All the subjects had an abnormal pattern of FDG uptake on PET scan, both on a visual inspection and semiquantitative analysis. In MSA-P subjects (n = 29), diffuse predominant hypometabolism of the globus pallidus-putamen complex was noted, with relative sparing of the caudate nuclei. In MSA-C subjects (n = 25), characteristic hypometabolism was noted in the cerebellum and brainstem. In mixed subtypes (n = 13), variable involvement of the basal ganglia, cerebellum, and brainstem was noted with frontoparietal hypometabolism. A statistically significant difference between MSA-P and MSA-C for gradient reduction and asymmetry with gradient reduction was observed.
Conclusion: Dopamine transporter imaging with 99mTc TRODAT-1 SPECT not only helps in confirmation of parkinsonian disorders but also demonstrates varying patterns of distribution in different subtypes of MSA. Characteristic patterns of hypometabolism in 18F-FDG PET may help in the differentiation of the subtypes of MSA in the presence of clinically overlapping symptoms.
Keywords: 18F-FDG PET/CT; 99mTc TRODAT-1 SPECT; multisystem atrophy.
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