Cerebellar lesions in multiple system atrophy: postmortem MR imaging-pathologic correlations.

BACKGROUND AND PURPOSE Cerebellar atrophy and white matter T2-hyperintensities have been characterized as cerebellar lesions of multiple system atrophy (MSA). The aim of the study was to correlate MR images with histologic findings in cerebellar lesions of MSA. MATERIALS AND METHODS Postmortem T2-weighted images using 1.5T were compared with histologic findings in 7 postmortem-proved cases with MSA. The MR imaging findings in the cerebellar cortices and deep white matter dentate nucleus regions were compared with their histologic findings in each case. RESULTS We detected 3 types of cerebellar changes: type 1, no apparent atrophy or signal-intensity changes; type 2, cerebellar atrophy and inhomogeneous (patchy and/or confluent) cerebellar white matter hyperintensities; and type 3, cerebellar atrophy and diffuse white matter hyperintensities. Hypointensities were seen in the dentate nucleus regions. Atrophy of the cerebellar white matter was more severe than that of cerebellar cortices, and this anatomy was well depicted on coronal images. Histologically, degeneration was more severe in the cerebellar white matter than in the cerebellar cortices. Hyperintensities in the cerebellar white matter showed loss of myelinated fibers and gliosis. Hypointensities in the dentate nucleus regions revealed diffuse ferritin deposition in preserved dentate nuclei and white matter both around and within the nuclei. CONCLUSIONS Hyperintensities in the cerebellar white matter reflect degenerated white matter associated with loss of myelinated fibers and gliosis, whereas hypointensities in the dentate nucleus regions reflect diffuse ferritin deposition in preserved dentate nuclei and white matter around and within the nuclei. Degeneration is more severe in the cerebellar white matter than in the cerebellar cortices.