Spinocerebellar Ataxia 1

Clinical Characteristics
Ocular Features: 

Early manifestations include gaze-evoked nystagmus and saccadic hypermetria.  Ophthalmoplegia develops later in the disease process.  Some patients experience a decrease in acuity and dyschromatopsia.  The ERG shows evidence of generalized rod and cone photoreceptor dysfunction in some patients.  Optic atrophy, central scotomas, central RPE changes, retinal arteriolar attenuation, and blepharospasm have also been reported.

Time-domain OCT has revealed microscopic changes in the macula with thinning of the inner-outer segment junction and nuclear layer in areas with RPE hypopigmentation. 

Systemic Features: 

This is a progressive cerebellar syndrome characterized by systems of ataxia, dysarthria, and bulbar palsy.  Speech is often scanning and explosive.  DTRs can be exaggerated, and dysmetria is common.  The mean age of onset is about age 40.  Some cognitive decline may occur.  Muscle atrophy, and symptoms of peripheral neuropathy can be present.  MRI shows atrophy in the cerebellum, spinal cord, and brainstem.  There is considerable variation in clinical expression.  Individuals with adult onset of symptoms can survive for 10-30 years whereas those with a juvenile-onset often do not live beyond the age of 16 years.


This disorder is caused by an expanded CAG repeat in the ataxin-1 gene (ATXN1) at 6p23.  It is an autosomal dominant disorder.  Alleles with 39-44 or more CAG repeats are likely to be associated with symptoms. 

A male bias and the phenomenon of anticipation have been demonstrated in this disorder as in spinocerebellar ataxia 7 (SCA7) (164500), in which affected offspring of males with SCA develop disease earlier and symptoms progress more rapidly than in offspring of females.  This is often explained by the fact that males generally transmit a larger number of CAG repeats.

SCA7 (164500), also inherited in an autosomal dominant pattern and caused by expanded CAG repeats on chromosome 3, has many similar ocular and neurologic features.

Treatment Options: 

Supportive care is often required.          

Article Title: 


Lebranchu P, Le Meur G, Magot A, David A, Verny C, Weber M, Milea D. Maculopathy and Spinocerebellar Ataxia Type 1: A New Association? J Neuroophthalmol. 2013 Apr 11. [Epub ahead of print]

PubMedID: 23584155

Vaclavik V, Borruat FX, Ambresin A, Munier FL. Novel maculopathy in patients with spinocerebellar ataxia type 1 autofluorescence findings and functional characteristics. JAMA Ophthalmol. 2013 Apr 1;131(4):536-8.

PubMedID: 23579607

Thurtell MJ, Biousse V, Newman NJ. Rod-cone dystrophy in spinocerebellar ataxia type 1. Arch Ophthalmol. 2011 Jul;129(7):956-8.

PubMedID: 21746990

B?ork K, Fetter M, Abele M, Laccone F, Brice A, Dichgans J, Klockgether T. Autosomal dominant cerebellar ataxia type I: oculomotor abnormalities in families with SCA1, SCA2, and SCA3. J Neurol. 1999 Sep;246(9):789-97.

PubMedID: 10525976

Buttner N, Geschwind D, Jen JC, Perlman S, Pulst SM, Baloh RW. Oculomotor phenotypes in autosomal dominant ataxias. Arch Neurol. 1998 Oct;55(10):1353-7.

PubMedID: 9779665

Rivaud-Pechoux S, D?orr A, Gaymard B, Cancel G, Ploner CJ, Agid Y, Brice A, Pierrot-Deseilligny C. Eye movement abnormalities correlate with genotype in autosomal dominant cerebellar ataxia type I. Ann Neurol. 1998 Mar;43(3):297-302. Review.

PubMedID: 9506545

Stricker S, Oberwahrenbrock T, Zimmermann H, Schroeter J, Endres M, Brandt AU, Paul F. Temporal retinal nerve fiber loss in patients with spinocerebellar ataxia type 1. PLoS One. 2011;6(7):e23024. Epub 2011 Jul 29.

PubMedID: 21829579