Comprehensive Functional Evaluation of the Spectrum of Multi-System Atrophy with ¹⁸F-FDG PET/CT and ^99mTc TRODAT-1...

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.

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.

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.

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.