Characteristics of Structural Changes in the Cerebrum of Patients with Spinocerebellar Degeneration

Hiroyuki Hamada, Yutaka Kikuchi, Wen Wen, Qi An, Atsushi Yamashita and Hajime Asama

Spinocerebellar degeneration (SCD) is a neurodegenerative disease of the cerebellum and its input-output pathways, causing ataxia. Although degeneration of the cerebellum, brainstem, and spinal cord was conventionally thought to be the main pathophysiology, an increase in cerebral volume has been reported, suggesting that the cerebral cortex compensates for the cerebellar dysfunction. However, the relationship between the characteristics of the volume changes and cerebellar syndromes has not been fully elucidated. Hence, we aimed to statistically classify the characteristics of structural changes in the cerebrum in patients with SCD in order to understand compensation by the cerebrum. A total 50 patients with SCD and 11 healthy adults were included. Cerebellar volume was calculated by Voxel-based morphometry and cerebral volume (68 areas) was calculated by Surface-based morphometry from structural T1 images acquired using a 3T MR Scanner. We used an unpaired t-test to compare cerebellar volume between the SCD and healthy groups, and Spearman's rank correlation coefficient for the relationship between cerebellar volume, disease duration, and the Scale for the Assessment and Rating of Ataxia (SARA) score. Furthermore, the volume of each region of the cerebrum of each patient was subjected to principal component analysis (PCA) to extract components whose cumulative contribution ratio exceeded 80%, and the scores of the components were classified by hierarchical clustering (Ward's method). The results showed a significant decrease in cerebellar volume in the SCD group compared to the healthy group (p < 0.05), and a significant negative correlation between the disease duration and cerebellar volume in the SCD group (p < 0.01), but no correlation between cerebellar volume and SARA score, or between the disease duration and the SARA score. Nine components were extracted from the volume of each cerebral region in the SCD group by PCA, and the scores of each component were classified into four characteristics by clustering. The first cluster, characterized by increased left and right superior frontal, temporal, and parietal regions, showed a significantly lower SARA score than the third cluster (p < 0.05), but there were no significant differences in cerebellar volume and the disease duration. These results indicate that cerebellar volume changes in SCD patients can be classified into multiple characteristics. Increased volumes of motor- and sensory-related areas may be associated with the cerebellar syndromes expressed in the SARA.