Spinocerebellar Ataxia Type 2

Clinical characteristics: Spinocerebellar ataxia type 2 (SCA2) is characterized by progressive cerebellar ataxia, including nystagmus, slow saccadic eye movements, and in some individuals, ophthalmoparesis or parkinsonism. Pyramidal findings are present; deep tendon reflexes are brisk early on and absent later in the course. Age of onset is typically in the fourth decade with a ten- to 15-year disease duration.

Diagnosis/testing: The diagnosis of SCA2 rests on the use of molecular genetic testing to detect an abnormal CAG trinucleotide repeat expansion in ATXN2. Affected individuals have alleles with 33 or more CAG trinucleotide repeats.

Management: Treatment of manifestations: Management is supportive. Affected individuals should maintain activity. Canes and walkers help prevent falls; grab bars, raised toilet seats, and ramps to accommodate motorized chairs may be necessary. Speech therapy and communication devices such as writing pads and computer-based devices may benefit those with dysarthria. Weighted eating utensils and dressing hooks help maintain a sense of independence. When dysphagia becomes troublesome, video swallowing studies can identify the consistency of food least likely to trigger aspiration.

Prevention of secondary complications: Vitamin supplements are recommended; weight control helps minimize difficulties with ambulation and mobility.

Surveillance: Annual examination by a physician experienced in movement disorders and ataxia.

Agents/circumstances to avoid: Alcohol and medications known to affect cerebellar function.

Genetic counseling: SCA2 is inherited in an autosomal dominant manner. Offspring of an affected individual have a 50% chance of inheriting the causative CAG trinucleotide repeat expansion. The repeat may expand significantly, especially when transmitted by the father. Prenatal testing for a pregnancy at increased risk is possible if the diagnosis has been established by molecular genetic testing in an affected family member.