spinocerebellar ataxia prognosisataxia telangiectasia prognosiscerebellar ataxia prognosisfriedreich's ataxia prognosiscerebral ataxia prognosisinherited cerebellar ataxiahereditary cerebellar degenerationcerebral ataxia geneticcerebellar degeneration prognosisataxic cerebral palsy prognosiscerebellar ataxia treatmenthereditary cerebellar ataxia