Clinical and magnetic resonance image correlation in idiopathic cerebellar ataxia

Sixty-one patients who fulfilled the clinical criteria for idiopathic cerebellar ataxia and who had symptoms at least for 3 years were examined clinically and by magnetic resonance imaging (MRI). Based on the clinical signs, they were divided into patients with pure cerebellar signs (Group 1), patients with additional mild rigidity and/or hyperreflexia (Group 2) and patients with additional severe rigidity and hypokinesia (Group 3). Patients in Group 1 had milder disability and better prognosis than patients in Group 2 or Group 3 (ataxic score: 14.9 vs. 28.6 and 36.0; annual progression ratio: 0.26 vs. 0.65 and 0.70, respectively). We measured the area of the cerebellar vermis, ventral pons and dorsal brainstem on midsagittal T1-weighted MR images for all patients and age- and sex-matched controls. The cerebellar vermis as well as the ventral pons of patients were significantly smaller than corresponding structures in controls (p < 0.001). The ventral pons of patients in Group 2 and Group 3 was significantly smaller than that of patients in Group 1 (p < 0.0001, respectively), and the dorsal brainstem of patients in Group 2 and Group 3 was also significantly smaller than that of patients in Group 1 (p < 0.001, respectively). The ventral pons of patients in Group 3 was significantly smaller than that of patients in Group 2 (p < 0.05) as well. There was a significant correlation between the area of the ventral pons and the annual progression ratio (p < 0.001). With MRI, slight but definite hyperintensities were demonstrated in the pontine base and the medulla of 22 patients on proton density images. In the longitudinal study, patients in Group 2 and Group 3 had atrophy of the ventral pons already at an early stage. The ventral pons of patients in Group 3 was smaller at the initial MR examination than that of patients in Group 2. These observations suggest that patients with smaller ventral pons may have rapid progression and poor prognosis. Thus, even a relatively simple quantitation of the area of the ventral pons may be useful to predict the prognosis of patients, in addition to neurologic assessment at intervals.