Evolution of Clinical Outcome Measures and Biomarkers in Sporadic Adult-Onset Degenerative Ataxia

Abstract

ABSTRACT Background Sporadic adult‐onset ataxias without known genetic or acquired cause are subdivided into multiple system atrophy of cerebellar type (MSA‐C) and sporadic adult‐onset ataxia of unknown etiology (SAOA). Objectives To study the differential evolution of both conditions including plasma neurofilament light chain (NfL) levels and magnetic resonance imaging (MRI) markers. Methods SPORTAX is a prospective registry of sporadic ataxia patients with an onset >40 years. Scale for the Assessment and Rating of Ataxia was the primary outcome measure. In subgroups, blood samples were taken and MRIs performed. Plasma NfL was measured via a single molecule assay. Regional brain volumes were automatically measured. To assess signal changes, we defined the pons and middle cerebellar peduncle abnormality score (PMAS). Using mixed‐effects models, we analyzed changes on a time scale starting with ataxia onset. Results Of 404 patients without genetic diagnosis, 130 met criteria of probable MSA‐C at baseline and 26 during follow‐up suggesting clinical conversion to MSA‐C. The remaining 248 were classified as SAOA. At baseline, NfL, cerebellar white matter (CWM) and pons volume, and PMAS separated MSA‐C from SAOA. NfL decreased in MSA‐C and did not change in SAOA. CWM and pons volume decreased faster, whereas PMAS increased faster in MSA‐C. In MSA‐C, pons volume had highest sensitivity to change, and PMAS was a predictor of faster progression. Fulfillment of possible MSA criteria, NfL and PMAS were risk factors, CWM and pons volume protective factors for conversion to MSA‐C. Conclusions This study provides detailed information on differential evolution and prognostic relevance of biomarkers in MSA‐C and SAOA. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.