Objective: To assess the usefulness of cranial nerves V (CNV) and VIII (CNVIII) atrophy as a neuroradiological sign to differentiate RFC1-related disorder from spinocerebellar ataxias (SCA) and multiple system atrophy cerebellar type (MSA-C).
Background: RFC1-related disorder is now recognized as an important cause of late-onset ataxia, such as SCA and MSA-C. Due to its clinical interface, it may be difficult to differentiate between them in clinical practice. Thinning of CNV and CNVIII has been lately reported in magnetic resonance imaging (MRI) scans of RFC1-related disorder, but its specificity has not been studied.
Method: Eighty-two patients with late-onset ataxia were enrolled, including 17 individuals with RFC1-related disorder, 55 with SCA (types 2,3 and 6) and 10 with MSA-C defined by clinical criteria. Ten healthy controls were also assessed. All subjects underwent MRI scans on the same 3-Tesla scanner and clinical evaluation on the same day. We acquired the balanced steady-state gradient echo sequence for qualitative assessment of CNV and CNVIII. Images were reviewed by a neuroradiologist blinded to patient and clinical data to classify these nerves as atrophic or normal. We analyzed the frequencies of combined and isolated atrophy of CNV and CNVIII for each subject. These frequencies were compared between groups using Fisher exact test. Level of significance was set at 0.05.
Results: Mean age of patients in RFC1, SCA and MSA groups were 62±8, 54±16 and 65±10 years, respectively. Atrophy of CNV and CNVIII was significantly more frequent in the RFC1 group when compared to SCA (CNV: 82% vs 16%, p<0.001; CNVIII: 65% vs 24%, p=0.003), MSA (CNV: 82% vs 0%, p<0.001; CNVIII: 65% vs 10%, p=0.014) and controls (CNV: 82% vs 0%, p<0.001; CNVIII: 65% vs 0%, p=0.001). In an exploratory sub-analysis assessing each SCA subtype, simultaneous atrophy of both nerves was also more frequent in the RFC1 group than in SCA2 (65% vs 21%, p=0.029), SCA3 (65% vs 13%, p<0.001) and SCA6 (65% vs 6%, p<0.001) subgroups. Our findings had a sensitivity and specificity of, respectively: 82% and 88% for CNV atrophy, 65% and 81% for CNVIII atrophy, and 65% and 91% for combined CNV and CNVIII atrophy.
Conclusion: MRI evaluation of CNV and CNVIII using a dedicated sequence is an easy-to-use tool that helps to distinguish RFC1-related disorder from SCA and MSA-C. This new neuroradiological sign should be sought in the routine evaluation of late-onset ataxias.
To cite this abstract in AMA style:C. Lobo, G. Wertheimer, T. Rezende, PC. Matos, L. Branco, J. Silva, F. Borba, O. Barsottini, JL. Pedroso, W. Marques Jr, M. França Jr. atrophy of cranial nerves v and viii is a hallmark of rfc1-related disorder [abstract]. Mov Disord. 2023; 38 (suppl 1). https://www.mdsabstracts.org/abstract/atrophy-of-cranial-nerves-v-and-viii-is-a-hallmark-of-rfc1-related-disorder/. Accessed September 27, 2023.
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MDS Abstracts - https://www.mdsabstracts.org/abstract/atrophy-of-cranial-nerves-v-and-viii-is-a-hallmark-of-rfc1-related-disorder/