Variability of FP-CIT PET Patterns Associated With Clinical Features of Multiple System Atrophy

To validate the role of the dopamine transporter (DAT) imaging as a biomarker in multiple system atrophy (MSA), we analyzed the association between spatial patterns of [¹⁸F]fluoro-propyl-carbomethoxy-iodophenyl-tropane ([¹⁸F]FP-CIT) PET and the clinical characteristics of MSA.

Sixty-five patients with MSA who underwent [¹⁸F]FP-CIT PET between 2009 and 2018 were retrospectively enrolled. To identify spatial patterns of [¹⁸F]FP-CIT PET, principal component (PC) analysis was used and correlated with the clinical presentation.

Of the 65 patients, 42 presented with parkinsonian subtype of MSA, and 23 presented with cerebellar subtype of MSA (mean age 63.7 ± 9.3 years; disease duration, 1.8 ± 1.8 years). Each PC represents a specific pattern of degeneration: PC1 and PC2 were associated with the DAT binding of the entire putamen and the posterior putamen, respectively. PC3 was associated with increased [¹⁸F]FP-CIT uptake of the caudate and decreased uptake of the dorsal pons. PC2 was significantly correlated with the presence of parkinsonism (p = 5.34 × 10^-5) and a positive levodopa response (p = 0.044), with age as a cofactor. PC3 was correlated with the presence of urinary incontinence (p = 0.036). Onset age was significantly correlated with both PC2 (R = 0.48, p = 5.0 × 10^-5) and PC3 (R = -0.39, p = 0.0013).

The spatial pattern of DAT binding can reflect distinct clinical features of MSA and provides insight into the underlying pathophysiology of a broad spectrum of clinical features in MSA.