Corpus Callosum Damage and Motor Function in Parkinson’s Disease (P2.006)

OBJECTIVE: To investigate corpus callosum (CC) microstructural damage and its relationship with motor impairment in patients with Parkinson's disease (PD) at different disease stages. BACKGROUND: In PD, CC diffusion tensor (DT) MRI metrics may be valuable markers to asses disease evolution and motor function worsening. DESIGN/METHODS: We enrolled 173 PD patients (98 with Hoehn and Yahr score [HY]=1-1.5, 37 with HY=2-2.5, 29 with HY=3-3.5, 9 with HY=4-5) and 39 matched healthy controls (HC). Diffusion tensor (DT) MRI tractography was performed to obtain the CC and its main three partitions: CC-genu, CC-body, and CC-splenium. Mean tract fractional anisotropy (FA) and mean diffusivity (MD) values were measured. Between group comparisons adjusting for age were assessed. Pearson's correlations were used to explore the relationship between CC DT MRI metrics and UPDRS III score. RESULTS: All PD patients relative to HC showed decreased FA and increased MD of the whole CC and its partitions. Such a microstructural damage to the CC is more marked with increasing PD severity, being only mild in PD patients with HY=1-1.5 (who showed the greatest damage in the CC-body) and severe (same degree of damage in all CC partitions) in patients at the later stages of the disease. UPDRS III score correlated significantly (p<0.001) with FA values of the whole CC (r=-0.399), CC-genu (r=-0.199), CC-body (r=-0.481), and CC-splenium (r=0.270) and MD values of the whole CC (r=0.367), CC-body (r=0.438), and CC-splenium (r=0.257). CONCLUSIONS: PD is associated with microstructural damage to the CC that becomes more significant with disease worsening. In PD patients, the best predictor of CC deterioration of motor functions is the involvement of the CC-body, which includes the transcallosal motor tracts. Assessing CC microstructural alterations may improve the understanding of the pathogenetic mechanisms associated with motor impairment in PD. Study Supported by: Italian Ministry of Health (#GR-2009-1577482); Ministry of Science and Technology of the Republic of Serbia (#175095).