Objective To investigate the changing pattern of regional cerebral blood flow in patients with multiple system atrophy (MSA) with predominant cerebellar ataxia (MSA-C).Methods Twelve MSA-C patients in the neurology department of our hospital and 25 normal controls were enrolled. Brain single-photon emission computed tomography (SPECT) with technetium-99m ethyl cysteinate dimer as the imaging agent was performed to evaluate their regional cerebral blood flow. The SPECT images of both MSA-C patients and normal controls were analyzed by voxel-based morphometry with SPM8 and xjview9. The regions with significantly different cerebral blood flow compared with normal controls were projected onto the standard brain template, and the main affected cerebral areas, peak positions, and maximum t values were analyzed.Results Compared with the normal controls, the MSA-C patients had significantly reduced regional cerebral blood flow mainly in the bilateral posterior lobe of the cerebellum, the vermis, and the pons (P<0.01_{FDR correction}, cluster level), and there was no significant decrease in the blood flow in the cerebellar cortex and putamen.Conclusions In MSA-C patients, regional cerebral blood flow is reduced mainly in the cerebellum and the pons.