Characteristic magnetic resonance imaging findings in spinocerebellar ataxia 6

Objective: To clarify the characteristic magnetic resonance imaging (MRI) findings in patients with spinocerebellar ataxia 6 (SCA6) diagnosed by genetic analysis. Patients and Methods: Using MRI, we examined 10 patients genetically diagnosed as having SCA6 and 40 control subjects. Results: The mean (+/- SD) CAG repeat length in 10 patients with SCA6 was 22.9 +/- 1.3. There was a significant inverse correlation between the CAG repeat size and age at onset in the SCA6 group (r=-0.86, P=.003). In patients with SCA6, the areas of the cerebellar vermis and hemispheres in sagittal MRI were significantly smaller than those in the control subjects. In transaxial MRI, the anteroposterior diameter of the pens and the diameter of the middle cerebellar peduncle were mildly decreased and the red nucleus was slightly atrophied in patients with SCA6. There was no significant difference in the diameter of the midbrain, medulla oblongata, fourth ventricle, superior cerebellar peduncles, dentate nucleus, or globus pallidus between the SCA6 and control groups, A high-signal intensity in the transverse pontine fibers was not observed in any of the patients with SCA6 on T-2-weighted and/or proton-weighted axial MRI. Conclusions: The cerebellum and its afferent and efferent systems were affected in patients with SCA6, These results seem to distinguish the MRI findings of SCA6 from those of other forms of spinocerebellar ataxia.