Background: It is unknown whether multiple system atrophy of the cerebellar type (MSA-C) and idiopathic cerebellar ataxia with extracerebellar presentation (IDCA-P) represent distinct entities.
Objective: To investigate the discriminative validity of magnetic resonance imaging in sporadic cerebellar ataxia.
Design: Basal ganglia and infratentorial structures were screened for signal abnormalities and atrophic changes. Magnetic resonance imaging raters were masked to the clinical diagnosis.
Setting: Outpatient clinic of a university hospital.
Patients: Forty-one individuals were diagnosed as having MSA-C (n = 30) or IDCA-P (n = 11) based on their clinical features.
Results: Shrinkage of the cerebellar vermis and hemispheres was found in both groups. Atrophy of the brainstem and middle cerebellar peduncles was significantly more frequent in patients with MSA-C (P<.001). Hyperintensities of infratentorial structures were common in patients with MSA-C (middle cerebellar peduncles: 87%; pons: 97%) but were absent in patients with IDCA-P. Hypointensities or hyperintensities of basal ganglia structures did not reliably differentiate the groups.
Conclusions: Patients with MSA-C were characterized by a higher frequency and severity of magnetic resonance imaging abnormalities (atrophic changes and additional hyperintense signal changes) of the middle cerebellar peduncles and pons. The presence of these magnetic resonance imaging features points to the diagnosis of MSA-C and helps differentiate MSA-C from other types of sporadic cerebellar ataxia with extracerebellar features.