CT findings in spinocerebellar degeneration.

Thirty-five CT scans were studied from patients with several forms of spinocerebellar degeneration. Atrophy was determined by objective measurements of the number and width of cerebellar sulci, transverse diameter and surface area of the fourth ventricle, brainstem ratio, cerebellopontine angle cistern, and Evans' index. Two-thirds of the patients with Friedreich's ataxia showed moderate cerebellar atrophy and an increase in the surface area of the fourth ventricle. Severe cerebellar atrophy and enlargement of the cerebellopontine angle cistern was seen in patients with olivopontocerebellar (OPC) atrophy and idiopathic cortical cerebellar atrophy. In the OPC atrophy group there was also prominent atrophy of the brainstem and an increase in the fourth ventricle parameters. Alcoholic cerebellar degeneration showed a specific pattern of cerebellar atrophy most prominent in the superior vermis, together with a slight increase in the fourth ventricle surface, a reduction in the size of the brainstem, and an enlargement of the cerebellopontine angle cistern. Supratentorial atrophy was present only in the OPC and alcoholic atrophy groups. In one patient with spastic ataxia, CT was normal but MR imaging revealed prominent atrophy of the spinal cord. These CT patterns appear to be distinctive enough to permit the diagnosis and classification of the various forms of spinocerebellar degeneration.