Objective: To examine the anatomical integrity of the motor cortex in Friedreich ataxia (FRDA).

Background: FRDA is an inherited neurodegenerative disorder characterised by progressive gait and limb incoordination, dysarthria, and cardiomyopathy. The primary neuropathology associated with FRDA involves the spinal cord and cerebellum; however, recent brain connectivity, functional neuroimaging, and behavioural studies suggest additional involvement of the cerebral cortex.

Methods: Using structural magnetic resonance imaging (MRI), cerebral grey matter thickness and grey matter volume were measured in 31 adults with FRDA and 37 healthy age and gender matched controls using semi-automated procedures (Freesurfer and Voxel-Based Morphometry). Between group comparisons were undertaken using ANCOVA models (controlling for age, gender, and hemisphere) in four motor regions-of-interest: primary motor, dorsal premotor, ventral premotor, and supplementary motor areas. Whole-brain exploratory analyses were also conducted.

Results: Individuals with FRDA showed significantly thinner cortex in the dorsal premotor, ventral premotor, and supplementary motor areas relative to controls, with a trending difference in the primary motor area. No significant differences in cortical volume were evident in these regions, although trend-level reductions were apparent in the ventral premotor cortex. Exploratory analyses additionally revealed significant thinning and volume loss in the precuneus, insula, and frontal operculum in individuals with FRDA compared to controls.

Conclusions: Structural neuropathology in FRDA extends to the cerebral components of the motor system. These alterations appear particularly weighted to premotor and supplementary motor areas. Specific measures of cortical thickness also appear to be more sensitive to disease expression than more gross measures of cortical volume (of which cortical thickness is one determinant). These findings contribute to more complete characterizations of the neurobiological substrates of FRDA.

Friedreich Ataxia Research Association (Australia), December 2015, Melbourne, Australia.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/cortical-grey-matter-atrophy-in-the-motor-system-in-friedreich-ataxia-the-image-frda-study/