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Article History

Received: 8 February 2026

Accepted: 29 April 2026

First Online: 23 May 2026

Declarations

:

: Each participant and parent of the participating children received detailed study information and gave written informed consent. The study was conducted according to the Declaration of Helsinki and was approved by the Ethics Committee of the University of Medicine Greifswald (BB096/22a, October 26 2022) and all local ethics committees of participating study sites (RWTH Aachen, Faculty of Medicine: 22-014; University of Bonn: 440/22; Innsbruck: Medical University of Innsbruck: 1379/2022, Munich, Medical Faculty: 22–1095; Paris: Comité de Protection des Personnes Est III: 2023-A00315-40; and Tübingen, University Tübingen Faculty of Medicine: 672/2022BO2).

: CE received honoraria from Biogen. JF was funded within the Advanced Clinician Scientist Programme (ACCENT, funded by the Federal Ministry of Research, Technology and Space (BMFTR) under the funding code (FKZ): 01EO2107) and as a PI of the iBehave Network, sponsored by the Ministry of Culture and Science of the State of North Rhine-Westphalia and received funding from the National Ataxia Foundation (NAF). She has received consultancy honoraria from Vico therapeutics and Biogen, travel support from NAF, FARA, Euro-Ataxia and AGI and participated in advisory boards for Vico. SBoe received consulting fees from Biogen and Biohaven, honoraria from Ipsen, Abbvie, Merz Pharma and participated on advisory boards for Vico Therapeutics, Biogen and Biohaven. EI received honoraria from Biogen and Merz. JS received research support from Biogen, Lilly, and Eisai, consulting fees from Biogen, Reata, Lilly ans Eisai, honoraria from Biogen, Lilly and Eisai, and travel support from Lilly, Biogen, and Eisai. He is Speaker German Network of Memory Clinics and the Commission “Dementia” of the German Society of Neurology. KR received research support from Friedreich’s Ataxia Research Alliance (FARA); Interdisciplinary Center for Clinical Research within the Faculty of Medicine at the RWTH Aachen University, Germany (OC2). TK received research support from Servier, UCB, Biogen, and the German Ministry of Research and Consulting Fees from Arrowhead, Bristol-Myer Squibb and UCB. MGE received research support from the National Ataxia Foundation and Ataxia UK, honoraria from Biogen, and travel support from Aparito. All unrelated to this study. BM received research support from the German Federal Joint Committee (G-BA), the German Ministry of Research, the Worch Foundation, the EuroQol Research Foundation and Biogen, and Consulting Fees from Biogen, the EuroQol Research Foundation and Lilly. AD received research support from the National Institute of Health (U01 NS104326), from ANR PROFA, ANR Cortex, Servier, Mavelife, Enroll (CHDI), Vico therapeutics, ASKIBO, and PTC therapeutics, and conculting fees from Biogen, UCB and HUNTIX. She participated in Boards for HUNTIX, Biogen and FRM, holds shares in patent B 06291873.5 and is president of the Société Francophone de Neurogénetique. SBor received consulting fees from Biogen, unrelated to this study. All other authors declare no conflicts of interest.