Spinocerebellar ataxias
The spinocerebellar ataxias are the autosomal dominant hereditary ataxias, presenting as a slowly progressive cerebellar syndrome of ataxic gait, dysarthria, limb dysmetria, and abnormal eye movements in a patient with an affected parent. The diagnosis is confirmed by genetic testing only after treatable acquired ataxias (alcohol, drugs, thiamine, vitamin E, vitamin B12, copper, hypothyroidism, celiac disease, and paraneoplastic antibodies) have been excluded; treatment is physical, occupational, and speech therapy.
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What this article covers
- Overview
Definition: the spinocerebellar ataxias are the autosomal dominant hereditary ataxias, genetic degenerative disorders of the cerebellum and its connections that produce a chronic, slowly progressive cerebellar syndrome.
- Epidemiology
Genetic ataxias by inheritance: autosomal recessive, autosomal dominant, X-linked, and mitochondrial forms exist; Friedreich ataxia, which is autosomal recessive, is the most common hereditary ataxia overall.
- Risk factors
Affected parent: autosomal dominant transmission gives each child of an affected parent a 50% risk, with the disease seen in successive generations.
- Pathophysiology
Progressive cerebellar degeneration: genetic degeneration of the cerebellum and its connections produces inaccurate, uncoordinated voluntary movement.
- Clinical features
Slowly progressive cerebellar syndrome is the hallmark: unsteady gait, slurred speech, clumsy limbs, and diplopia, worsening over years.
- Differential diagnosis
Cerebellar stroke, tumor, or demyelination: sudden or acute ataxia with headache, emesis, or cranial nerve palsies and a focal lesion on neuroimaging.
- Diagnosis
Diagnosis is established by genetic testing for the autosomal dominant spinocerebellar ataxias in a patient with a chronic progressive cerebellar syndrome and a positive family history, after…
- Management
First, treat any reversible cause found before labeling the ataxia hereditary: suspected Wernicke encephalopathy: thiamine 500 mg IV three times daily for 2 to 3 days, then 250 mg IV or IM once daily…
- Complications
Loss of independent ambulation and falls: progressive gait and truncal ataxia eventually require assistive devices.
- Prognosis
Slowly progressive and irreversible: primary genetic ataxias typically progress slowly over years, and no therapy alters the course.
- Prevention
No primary prevention exists for the inherited disease; prevention centers on genetic counseling, since each child of an affected parent has a 50% risk.
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