 We therefore propose to perform a prospective observational study of individuals at risk for the most common SCA disorders, SCA1, SCA2, SCA3 and SCA6 RISCA. It is our aim to answer the following questions: 1 What is the incidence of disease manifestation in mutation carriers? 2 Which clinical signs precede the onset of manifest ataxia in SCA1, SCA2, SCA3 and SCA6? 3 What are the prevalence and incidence of preceding signs? 4 Are the prevalence and incidence of preceding signs affected by genotype, gender, age, estimated time until disease manifestation and repeat length? 5 Does the presence of certain preceding signs predict the manifestation of ataxia ? 6 Are there MRI alterations that precede the onset of ataxia? It is planned to enroll 480 study participants and to follow them at regular intervals over six years. At each visit, study participants are asked in a structured interview for a number of predefined clinical signs that potentially precede the onset of ataxia. In addition, the following self-assessment scales will be applied: Pittsburgh Sleep Quality Index PSQI, Diagnostic Criteria for Restless Legs Syndrome, Patient s Health Questionnaire PHQ-9. All study participants will undergo a physical examination including the Scale for the Assessment and Rating of Ataxia SARA. Study participants will further perform the SCA Functional Composite SCA-FC which is a comprehensive measure of functional capacity based on results in quantitative tests related to gait 8m timed walk, speech PATA rate and hand function 9 hole pegboard. In a subset of study participants, we will record eye movements and obtain volumetric MRIs. The study will also be used to collect and store blood and urine samples for proteomic and gene expression studies. 