Table 5.

Notable autosomal dominant cerebellar ataxia syndromes

Genetic Disorder	Mutation	Other Movement Disorder Features	Neurologic Features
SCA1	CAG expansion ATXN1		Early bulbar symptoms Dysarthria, dysphagia Hypermetric saccades
SCA2	CAG expansion ATXN2	Parkinsonism Truncal titubation Postural & rest tremors	Slowed saccades Ophthalmoplegia Hyporeflexia Motor neuron disease
SCA3 (Machado-Joseph disease)	CAG expansion ATXN3	Parkinsonism Dystonia Restless leg syndrome	Fasciculations Bulging eyes Ophthalmoplegia
SCA6	CAG expansion CACN1A	Pure cerebellar syndrome	Downbeating nystagmus
SCA7	CAG expansion ATXN7		Pigmentary retinal macular degeneration Slowed saccades Spasticity
SCA17 (Huntington disease-like)	CAG expansion TBP	Parkinsonism Chorea	Early dysarthria Early dementia Psychiatric disorder

Abbreviation: SCA, spinocerebellar ataxia.