Adult-onset autosomal recessive ataxia with thalamic lesions in a Finnish family.

Objective: To describe an unusual kindred with adult-onset ataxia and thalamic lesions detected by brain MRI. Methods: The authors characterized clinical, laboratory, and pathologic features of the disease and sought linkage to previously recognized ataxia loci. Results: Two sisters and a brother developed progressive ataxia, dysarthria, mild cognitive impairment, and sensorimotor neuropathy at age 30, combined with epilepsy in one sibling. MRI showed symmetric thalamic lesions, changes in brainstem gray matter, and white matter changes in the cerebellum. Autopsy in one of the patients revealed neuronal degeneration with a peculiar vacuolar change in thalamus, probably representing transsynaptic degeneration in response to deafferentation. Neuronal and secondary tract degeneration was observed in the spinal cord, cerebellum, and brainstem suggesting a spinocerebellar degeneration. The disorder appears to be transmitted as an autosomal recessive trait. Genetic and sequence analysis of the FRDA gene and comprehensive laboratory examinations excluded Friedreich's ataxia and other similar recessive diseases. Conclusion: Adult-onset recessive ataxia with bilateral thalamic lesions in this family may represent a distinct hereditary spinocerebellar ataxia.