Phenotypes, Biomarkers and Pathophysiology in Spastic Ataxias

The investigators will perform a registry-based standardized prospective Natural History Study (NHS) in SPAX and related disorders. Participants will be seen annually. At study visits a standardized clinical examination will be performed including application of clinical rating scales (selection of rating scales may vary depending on the individual phenotype and specific genotype); data will be entered into a clinical database (HSP Registry; https://www.hsp-registry.net and ARCA Registry; www.ARCA-registry.org). At all study visits, patients will be asked to donate biosamples; biomaterial collection is optional and participants can elect to participate in sampling of blood, urine, CSF, and/or a skin biopsy. Optionally, additional examinations may be performed including imaging, quantitative movement analysis, neuropsychological examinations, analysis of patient or observer reported outcomes and OMICS analysis to characterize molecular biomarkers. In participants without a genetic diagnosis, next generation sequencing may be performed. Thus this study will establish a model of disease progression and mechanistic evolution in SPAX, which will allow to track and understand selective as well as overlapping dysfunction of the cerebellum and corticospinal tract. In a transatlantic natural history study we will longitudinally validate clinician- and patient-reported, digital and molecular outcomes. In addition, we will improve on existing and develop new outcome parameters that show superior sensitivity to change. These include a novel clinical SPAX composite score, a smartphone mHealth toolbox combining remote assessment of daily living by wearable sensors with app-based patient-entered outcomes (SPAX.app), and multimodal MRI radiomics with an innovative machine learning approach for multisite MRI analysis, including in particular the infratentorial space. Longitudinal validation of targeted fluid biomarker candidates will aslo be an important part.