MR features of diseases involving bilateral middle cerebellar peduncles

BACKGROUND AND PURPOSE: Distribution of lesions or involvement of specific anatomic sites can suggest the diagnosis of disease. The purpose of this study was to investigate what diseases affect both middle cerebellar peduncles (MCPs) and to evaluate other MR features for differential diagnosis.METHODS: MR findings of 27 patients (14 male and 13 female; age range, 4–77 years [mean, 48.5 years]) with bilateral MCP lesions were retrospectively studied.RESULTS: Neurodegenerative diseases were the most frequent diagnoses (n = 11 [41%]: sporadic olivopontocerebellar atrophy, eight; Shy-Drager syndrome, one; spinocerebellar ataxia, two). Also included were metabolic diseases (n = 6 [22%]: adrenoleukodystrophy, two; Wilson disease, two; cirrhosis of the liver, one; and hypoglycemia, one); cerebrovascular diseases, including posterior reversible encephalopathy syndrome (n = 3 [11%]: infarction, one; hypertensive encephalopathy, one; cyclosporin-A encephalopathy, one), demyelinating and inflammatory diseases (n = 4 [15%]: multiple sclerosis, one; acute disseminated encephalomyelitis, one; Behçet disease, one; and HIV encephalopathy, one), and neoplasms (n = 3 [11%]: lymphoma, one; glioma, one; meningeal carcinomatosis, one). All patients showed symmetrical T2 hyperintensity in both MCPs, except for one with malignant lymphoma. Marked atrophy in the posterior fossa was characteristically seen in neurodegenerative diseases. Enlargement of the pons was observed in hypertensive encephalopathy and neoplasms but absent in meningeal carcinomatosis. Lesions were restricted in the posterior fossa in eight patients with neurodegenerative diseases and one with brain stem glioma. Other patients had supratentorial lesions.CONCLUSION: Symmetricity of MCP lesions, morphologic change of the posterior fossa structures, and distribution of other lesions are helpful in the differential diagnosis.

MR imaging is the most sensitive imaging technique to depict brain lesions as altered signal intensities. Most of the lesions are demonstrated as hyperintensities on T2-weighted MR images, and the signal intensity itself is nonspecific. Characteristic distribution of lesions or involvement of specific anatomic sites, however, can suggest the diagnosis or narrow the differential diagnosis.The middle cerebellar peduncle (MCP) consists of the transversely coursing pontocerebellar fibers that arch across the midline and gather on each side (1). The MCPs can be evaluated by routine MR examination, and normal MCPs show homogeneous white matter signal intensity. Bilateral involvement of the MCPs is well known in olivopontocerebellar atrophy (OPCA) (2) but is relatively rare in other diseases. We retrospectively reviewed the MR findings and the clinical charts of the patients with bilateral MCP lesions to investigate what disorders affect both MCPs and to evaluate other MR features for differential diagnosis. A literature review on bilateral involvement of MCPs is also presented.