Objective: To analyze corpus callosum (CC) volumes on MRI in patients under follow-up for confirmed or suspected hereditary cerebellar ataxia

Background: It is recognized that HCA and hereditary spastic paraplegia (HSP) are extremes for the same spectrum of neurodegenerative disease, showing phenotypic, pathophysiological and genetic overlap.⁽¹⁾ Some studies previously evaluated CC volume in specific diagnoses such as Frederich’s ataxia ⁽²⁾, but in general terms, CC atrophy is not a common marker for HCA, as it is for some HSP.

Method: We recruited 35 patients with a diagnosis of hereditary cerebellar ataxia who were under follow-up in our Movement Disorders Unit and had a brain MRI suitable for volumetric analysis. 20 patients (56%) had a late disease onset (> 40 years) and 15 patients (44%) had an early onset. Regarding the pattern of inherence, 9 patients were autosomal dominant (AD), 4 were autosomal recessive (AR), and 22 were sporadic cases. We identified the following confirmed diagnoses, in the AD group: SCA3, SCA37, SCA48 and episodic ataxia 1 and 2, in the AR group: XCT, SPG7, ATX/POLG, ATX/ANO10, and we have not confirmed a genetic diagnosis in sporadic cases. Volumetry of the CC was performed using an automated atlas-based volumetry approach implemented in SPM12 software. Volumetric differences in CC volume between groups were assessed using ANCOVA, covarying by age.

Results: Average disease duration at the time of MRI scanning was 13.86 ± 12.75 years and did not differ between the different groups. Volume of the right CC was significantly higher in the AD group compared to the other groups (p=0.037), but no significant differences were observed between the AR and sporadic groups. With respect to clinical characteristics, the AD group presented pyramidalism in 2/9 cases (22.2%) and none with spastic paraparesis, while the AR/sporadic group presented pyramidalism in 11/26 cases (42.3%) and spastic paraparesis in 2/26 cases (7.7%).

Conclusion: While being limited by the relatively small sample size, these preliminary findings suggest more pronounced CC atrophy in patients with AR or sporadic forms of cerebellar ataxia compared to AD cases.

References: 1. Synofzik M, Schule R. Overcoming the divide between ataxias and spastic paraplegias: Shared phenotypes, genes, and pathways. Movement disorders : official journal of the Movement Disorder Society. 2017;32(3):332-45.
2. Rezende TJ, Silva CB, Yassuda CL, Campos BM, D’Abreu A, Cendes F, et al. Longitudinal magnetic resonance imaging study shows progressive pyramidal and callosal damage in Friedreich’s ataxia. Movement disorders : official journal of the Movement Disorder Society. 2016;31(1):70-8.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/volumetric-analysis-of-the-corpus-callosum-in-hereditary-cerebellar-ataxia/