Objective: To evaluate the diagnostic accuracy of middle cerebellar peduncle (MCP) width measurements in the differential diagnosis of neurodegenerative parkinsonian disorders including multiple system atrophy (MSA), Parkinson’s disease (PD) and Progressive Supranuclear Palsy (PSP).

Background: A previous study reported that a mean diameter of the two middle cerebellar peduncles (MCP) of less than 8 mm classifies all MSA patients correctly. This analysis was performed in a small cohort of patients with neurodegenerative parkinsonism (16 MSA patients and 26 PD patients) and was never replicated thereafter.

Methods: We exploited two independent cohorts which recruited patients to study risk markers for neurodegenerative parkinsonism: (1) a prospective neuroimaging study and a retrospective cohort study involving patients with neurodegenerative parkinsonism who underwent MRI during their routine diagnostic work-up. The MCP width was measured on sagittal T1-weighted images. The linear distance between the superior and inferior borders of the MCP as delimited by the peripeduncular cerebrospinal fluid spaces of pontocerebellar cisterns was measured. The prospective cohort was exploited to determine the optimal local cut-off. The diagnostic accuracy was determined in the second cohort. All data are presented as mean±standard deviation (SD). The optimal cut-off was determined using receiver operating characteristic curves.

Results: The prospective cohort involved 22 MSA patients, 42 PD patients and 21 PSP patients. There was no significant age difference (p=0.229). The disease duration was significantly shorter in MSA and PSP patients as compared with PD patients (p<0.001). The retrospective cohort included 74 MSA patients, 249 PD patients and 72 PSP patients. MSA patients were significantly younger than PD and PSP patients (p=0.001). The mean disease duration was significantly shorter in MSA and PSP patients (p<0.001).

The optimal local cut-off was 7.95mm as derived by ROC analysis in the prospective cohort. This cut-off yields a sensitivity and specificity of 62.7 % (95% CI 50.7%-73.6%) and 90.3% (95% CI 86.6%-93.3%), respectively, in the retrospective cohort.

Conclusions: We could confirm the high specificity of reduced MCP width for a clinical diagnosis of MSA, but in our series sensitivity of MCP width alterations was suboptimal. Normal MCP width should therefore not be taken as an exclusionary criterion for MSA.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/middle-cerebellar-peduncle-width-in-multiple-system-atrophy/