spinocerebellar ataxia prognosishereditary ataxia prognosiscerebellar ataxia prognosisfriedreich's ataxia prognosiscerebral ataxia prognosiscerebellar degeneration prognosisataxic cerebral palsy prognosiscerebellar ataxia treatmentataxia diagnosisexercises for ataxiahereditary cerebellar ataxiaataxia of gait