Spinocerebellar Ataxia Type 13

Excerpt

Clinical characteristics: Spinocerebellar ataxia type 13 (SCA13) is a phenotypic spectrum that includes both non-progressive infantile-onset ataxia and progressive childhood-onset and adult-onset cerebellar ataxia. Three phenotypes are seen:

1. Cerebellar hypoplasia with non-progressive infantile-onset limb, truncal, and gait ataxia with mild-to-moderate intellectual disability and occasionally seizures and/or psychiatric manifestations. Cognition and motor skills improve over time.

2. Childhood-onset slowly progressive cerebellar atrophy with slowly progressive cerebellar ataxia and dysarthria, delayed motor milestones, and mild-to-moderate intellectual disability

3. Adult-onset progressive cerebellar atrophy with progressive ataxia and spasticity

Diagnosis/testing: The diagnosis of spinocerebellar ataxia type 13 (SCA13) is established in a proband with suggestive clinical and brain imaging findings and a heterozygous KCNC3 pathogenic variant identified by molecular genetic testing.

Management: Treatment of manifestations: A multidisciplinary approach to management of ataxia and related neurologic manifestations is recommended including neurology, physical therapy (PT), occupational therapy (OT), speech and language pathology, and feeding team, as well as experts in educational needs and/or social/behavioral issues.

Surveillance: Regular neurologic examinations to evaluate disease progression and response to treatment; PT/OT to assess mobility and activities of daily living; feeding team re nutrition and risk for aspiration; speech and language pathology re dysarthria. Regular assessment of educational / mental health needs.

Agents/circumstances to avoid: Alcohol and sedating drugs, which can exacerbate ataxia.

Genetic counseling: SCA13 is inherited in an autosomal dominant manner. In rare instances, an individual diagnosed with SCA13 has the disorder as the result of a de novo KCNC3 pathogenic variant. Each child of an individual with SCA13 has a 50% chance of inheriting the KCNC3 pathogenic variant. Once the KCNC3 pathogenic variant has been identified in an affected family member, prenatal testing for a pregnancy at increased risk and preimplantation genetic testing are possible.