Background: Objective biomarkers are required for differential diagnosis of Parkinson's disease (PD), multiple system atrophy (MSA) and progressive supranuclear palsy (PSP).

Objective: We aimed to determine if cerebellar blood flow, measured using N-isopropyl-[123I] p-iodoamphetamine single photon emission computed tomography (123I -IMP-SPECT), was useful for differentiating between PD, MSA and PSP.

Methods: Twenty-four patients with PD, seventeen patients with MSA with predominant parkinsonian features (MSA-P), sixteenth patients with MSA with predominant cerebellar ataxia (MSA-C) and eight patients with PSP were enrolled. Twenty-seven normal controls' data were used for the calculation of z score. All patients underwent 123I -IMP-SPECT, and data were analyzed using a three-dimensional-stereotactic surface projection program.

Results: Cerebellar perfusion in MSA-P (MSA-P vs PD, P = .002; MSA-P vs PSP, P < .001) and MSA-C (MSA-C vs PD, P < .001; MSA-C vs PSP, P < .001) were significantly decreased compared with PD or PSP. There was no significant difference in perfusion between PD and PSP groups (P = .061). The area under the receiver operating characteristic curve for cerebellar perfusion between MSA-P and PD was 0.858.

Conclusions: Our findings revealed that cerebellar perfusion by 123I-IMP-SPECT was useful for differentiating between PD and MSA-P.