White matter changes and the development of motor phenotypes in de novo Parkinson's Disease

BACKGROUND: Parkinson's Disease (PD) patients are usually divided into Tremor Dominant (TD) and Postural Instability/Gait Difficulty (PIGD) subtypes. The latter is characterized by axial motor symptoms and worse outcomes, possibly also because of comorbid white matter disease. Therefore, the current study investigated the importance of Age-Related White Matter Changes (ARWMCs) in the development of different PD motor phenotypes. METHODS: The present 4-year longitudinal study recruited 63 de novo PD patients, who underwent MRI at the time of the diagnosis to rate ARWMCs. Motor subtypes (PIGD or TD) were evaluated at baseline visit, and after 2 and 4years. Age, gender, UPDRS part III total score, comorbidities and ARWMC total score were included in a mixed effect logistic regression model for repeated measures. RESULTS: The likelihood of being PIGD subtype during the study period was associated with higher ARWMC total score (OR=2.743; 95%CI=1.137-7.802), but not with age (OR=0.967; 95%CI=0.818-1.143), female gender (OR=0.169; 95%CI=0.014-1.970), UPDRS part III total score (OR=1.942; 95%CI=0.888-13.470), and comorbidities (OR=2.979; 95%CI=0.560-15.849). CONCLUSION: Motor dysfunction in PD is apparently multifactorial and, in particular, comorbid white matter disease might concur in the development of axial impairment.