Molecular Imaging in CANVAS: A Contribution for Differential Diagnosis?

Phenotypes of CANVAS are increasingly diversified, including bradykinesia and dysautonomia, so that its primary differential diagnoses are multiple system atrophy-cerebellar type (MSA-c), and spinocerebellar ataxia type 3 (SCA3). This case series aims to highlight key molecular imaging findings in CANVAS.

We report a case series of six patients with CANVAS who underwent nuclear medicine examinations in our center and 13 patients from the literature. These include ¹⁸F-FDG brain positron emission tomography (PET), single photon emission computed tomography (SPECT) of dopamine transporter (DaT) activity, and ¹²³I-MIBG cardiac scintigraphy of noradrenergic transmission.

In CANVAS, ¹⁸F-FDG brain PET mainly shows cerebellar hypometabolism, with preserved brainstem and striatum metabolism, contrasting with SCA3 and MSA-c. Dopaminergic denervation on scintigraphy seems to be associated with clinical parkinsonism, ranging from normal to severely impaired DaT SPECT. Additionally, ¹²³I-MIBG cardiac scintigraphy might show denervation in CANVAS, similar to SCA3, but not in most MSA-c patients.