[Regional cerebral glucose metabolism associated with ataxic gait--an FDG-PET activation study in patients with olivopontocerebellar atrophy].

We studied changes in regional cerebral glucose metabolism during bipedal gait in 7 patients with olivopontocerebellar atrophy (OPCA) and 7 control subjects without neurological disease. All OPCA patients in this study were able to walk on the treadmill without a support or handrails. We used 18F-2-fluoro-2-deoxy-D-glucose (18F-FDG) and positron emission tomography (PET) to evaluate glucose metabolism under two different conditions; 30 minutes' treadmill walking, and supine resting. The two sets of PET images were three-dimensionally registered to the magnetic resonance image (MRI) in each subject. Then, the PET images were normalized by the global value. Regions of interest (ROIs) were drawn on the cerebellar vermis, cerebellar hemispheres, pons, and thalamus, and FDG uptake was obtained to calculate the activation ratio (= [FDG uptake under walking]/[FDG uptake under resting]) for each region. We used unpaired t-test for statistical analysis to compare the OPCA patients and the normal control subjects. Normalized resting FDG uptake had no significant difference between control subjects and OPCA patients in any region. Activation ratio of OPCA patients was significantly decreased in the cerebellar vermis compared with the control subjects. In the control subjects, FDG uptake had little difference between resting and walking in the cerebellar hemisphere, pons and thalamus. On the other hand, the FDG uptake of OPCA patients was moderately increased by walking in these regions. In the cerebellar vermis, in spite of no significant difference between the normals and the patients during resting, the activation ratio in OPCA patients was significantly decreased. We speculate that the reduction of activation ratio in the cerebellar vermis reflects the dysfunction caused by degeneration. The result suggests that the PET activation study can demonstrate cerebellar dysfunction in the early phase of OPCA, in which other neuro-imaging methods cannot detect the tissue atrophy, hypometabolism or hypoperfusion in the resting state. In the cerebellar hemisphere, pons and thalamus, the activation ratio was nearly equal to one in control subjects, while it was larger in OPCA patients. We speculate that the instability during the ataxic gait increases the inputs from the vestibular, somatosensory and visual systems to these regions and outputs from these regions to the other neural systems. In conclusion, PET activation study is a useful and noninvasive technique for investigating the brain function associated with human gait.