Impact of cerebellar atrophy on cortical grey matter and cerebellar peduncles as assessed by voxel based morphometry and high angular resolution diffusion imaging

Aims: Since recent years the cerebellum has been attributed a more impor¬tant role in higher level functions than previously believed. We examined a cohort of patients suffering from cerebellar atrophy and resulting in ataxia to investigate not only which regions of the cerebrum were affected but also if diffusion magnetic resonance imaging (dMRI) metrics within the medial (MCP) and superior cerebellar peduncle (SCP), namely fractional anisotropy (FA) and radial diffusivity (RD), could be used as a biomarker in patients suf¬fering from this condition. Methods: Structural and dMRI data of 7 patients (2 spinocerebellar atrophy type 2, 1 Friedreichs ataxia, 4 unknown etiol¬ogy) with cerebellar atrophy and without visible cortical lesions and cortical atrophy were investigated with voxel based morphometry (VBM) of both GM as well as MCP and SCP FA maps. Correlation between MCP and SCP mean FA with ataxia scores and subscores was also evaluated. Results: VBM demonstrated significantly lower GM density in patients, notably in the head of the caudate nucleus, posterior cingulate gyrus and orbito-frontal cortex bilaterally, as well as in Brocas area in the left hemisphere, and sig-nificant RD increase in the MCP and SCP of each hemisphere. Correlation was found significant between MCP mean FA and total ataxia score (R=- 0.7, p=0.03), and coordination [R=-0.74 , p=0.03] and oculomotor [R=-0.70, p=0.04] subscores. Discussion and conclusion: Regions of the cerebrum with significantly lower GM density have been described to be involved in initia¬tion of voluntary movements, emotional control, memory retrieval and gen¬eral cognition, which supports recent findings pointing at an important role played by the cerebellum in higher level functions. The significant difference in the MCP and SCP dMRI metrics between patients and controls as well as the significant correlation with ataxia total score and subscores supports the use of dMRI metrics as an imaging biomarker for cerebellar degeneration and ataxia.