A Proposal for Classification of Retinal Degeneration in Spinocerebellar Ataxia Type 7
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ORIGINAL ARTICLE
A Proposal for Classification of Retinal Degeneration in Spinocerebellar Ataxia Type 7 Bruna Ferraço Marianelli 1,2 & Flávio Moura Rezende Filho 3 & Mariana Vallim Salles 1 & João Brainer Clares de Andrade 3 & José Luiz Pedroso 3 & Juliana Maria Ferraz Sallum 1 & Orlando Graziani P. Barsottini 3 Accepted: 9 November 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract The aim of this study is to propose a classification system for the spinocerebellar ataxia type 7 retinal degeneration (SCA7-RD). Twenty patients with molecularly confirmed SCA7 underwent slit lamp examination, fundus photography, and optical coherence tomography (Spectralis®). Scale for the Assessment and Rating of Ataxia (SARA) and International Cooperative Ataxia Rating Scale (ICARS) were applied, and age, sex, age at symptom onset, and number of CAG expansions were recorded. After analyzing the ophthalmological findings in each participant, a panel of retinal disease experts created a qualitative classification system for SCA7-RD comprising four stages. We assessed the correlations of retinal degeneration severity with SARA and ICARS scores, number of CAG repeats in ATXN7 allele, and age at symptom onset. We graded retinal degeneration as stage 1 in nine participants, as stage 2 in five, and as stage 3 in six. No differences in age and visual symptoms duration were found between groups. SARA and ICARS scores correlated with the severity of SCA7-RD on the classification system (p = 0.024 and p = 0.014, respectively). After adjusting for disease duration, retinal disease stage association with SARA and ICARS scores remained significant (ANCOVA, p < 0.05). The classification system for SCA7-RD was able to characterize different disease stages representing the landmarks in the cone–rod dystrophy natural history. Neurodegeneration appears to occur in parallel in the cerebellum and in the visual pathway. We conclude that retinal degeneration in SCA7 is a potential biomarker of the neurological phenotype severity. Keywords Retinal degeneration . Neurogenetic . Spinocerebellar ataxia type 7 . Optical coherence tomography . Color fundus photographs . Disease staging
Introduction Spinocerebellar ataxia type 7 (SCA7) is an autosomal dominant neurodegenerative disorder resulting from CAG trinucleotide expansions in the ATXN7 gene. The expanded gene Bruna Ferraço Marianelli and Flávio Moura Rezende Filho contributed equally to this work. * Bruna Ferraço Marianelli [email protected] 1
Division of Retina and Vitreous, Department of Ophthalmology, Universidade Federal de São Paulo, São Paulo, SP, Brazil
2
Vitória, Brazil
3
Division of General Neurology and Ataxia Unit, Department of Neurology and Neurosurgery, Universidade Federal de São Paulo, São Paulo, SP, Brazil
codifies a protein rich in polyglutamine residues, ataxin 7, which accumulates ubiquitously in the central and peripheral nervous systems [1]. This mutated protein causes cell death in neurons of the retina, brain, cerebellum, spinal cord,
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