ATROPHY OF THE CEREBELLUM AND BRAIN-STEM IN DENTATORUBRAL PALLIDOLUYSIAN ATROPHY - INFLUENCE OF CAG REPEAT SIZE ON MRI FINDINGS

To elucidate how the size of the expanded CAG repeat of the gene for d entatorubral pallidoluysian atrophy (DRPLA) and other factors affect t he atrophy of the brainstem and cerebellum, and the appearance of high -intensity signals on T2-weighted MRI of the cerebral white matter of patients with DRPLA, we quantitatively analyzed the MRI findings of 26 patients with DRPLA, the diagnosis of which was confirmed by molecula r analysis of the DRPLA gene. When we classified the patients into two groups based on the size of the expanded CAG repeat of the DRPLA gene (group 1, number of CAG repeat units greater than or equal to 66; gro up 2, number of CAG repeat units less than or equal to 65), we found s trong inverse correlations between the age at MRI and the areas of mid sagittal structures of the cerebellum and brainstem in group 1 but not in group 2. Multiple regression analysis, however, revealed that both the patient's age at MRI and the size of the expanded CAG repeat corr elated with the areas of midsagittal structures. Involvement of the ce rebral white matter as detected on T2-weighted images was observed mor e frequently in patients belonging to group 2 than in group 1 patients . Furthermore it was demonstrated that high-intensity signals can be d etected on T2-weighted images of the cerebral white matter of patients with a largely expanded CAG repeat (group I) in their thirties. These results suggest that patient age as well as the size of the expanded CAG repeat are related to the degree of atrophy of the brainstem and c erebellum, and the white matter changes in patients with DRPLA.