Spinocerebellar Ataxia Type 31

An autosomal dominant cerebellar ataxia type III that is characterized by the late-onset of ataxia, dysarthria and horizontal gaze nystagmus, and that is occasionally accompanied by pyramidal signs, tremor, decreased vibration sense and hearing difficulties.

Epidemiology

Spinocerebellar ataxia type 31 (SCA31) is the third most common form of ADCA in Japan, where more than 20 families have been reported to date. It is rarely found in other Asian countries and is extremely rare in Western countries.

Clinical description

The mean age of disease onset is 58 years but it can present between the ages of 8 to 83 years. Ataxia, dysarthria, and horizontal gaze nystagmus are the common manifestations of SCA31, and the disease duration can be more than 10 years. Less common manifestations include pyramidal signs, tremor, decreased vibration sense, hearing difficulties, and blepharospasm

Etiology

SCA31 is due to non-coding pentanucleotide repeat expansions in the BEAN1 gene (16q21), encoding protein BEAN1.

Diagnostic methods

Diagnosis is based on the characteristic clinical findings and molecular genetic testing. As the manifestations of SCA31 are not specific, diagnosis is only confirmed with the finding of a mutation in the BEAN1 gene

Differential diagnosis

Differential diagnosis includes other types of ADCA.

Genetic counseling

SCA31 is inherited autosomal dominantly with incomplete penetrance and genetic counseling is possible. Genetic counseling should be proposed to individuals having the disease-causing mutation informing them that there is 50% risk of passing the mutation to offspring.

Management and treatment

There is no cure for SCA31 and treatment is supportive. Physical therapy, as well as the use of canes and walkers, should be offered in order to maximize strength and maintain activity. Wheelchairs are eventually necessary. Speech therapy and communication devices may be useful to those with dysarthria. Dysphagia should be monitored to decrease the risk of aspiration pneumonia. In those with vertigo, vestibular suppressants may be beneficial. Annual neurological examinations are recommended to monitor disease progression.

Prognosis

Disease progression is very slow. Life expectancy is not reduced but the quality of life can be significantly affected. According to recent reports, patients can become wheelchair bound at age of 79 years, and died at age of 89 years.