Association between third ventricular width assessed by transcranial sonography and plasma homocysteine in Parkinson's disease with cognitive impairment and their potential to predict conversion to dementia.

Background: Cognitive impairment (CI) is a prevalent non-motor symptom in Parkinson's disease (PD) that often leads to disability. This study aimed to explore the association between plasma homocysteine (Hcy) and the width of third ventricle (V3) in PD patients with CI and their potential to predict dementia conversion. Methods: Totals of 118 PD patients with normal cognition (PD-NC), 81 PD patients with mild CI (PD-MCI), 58 PD patients with dementia (PDD), and 35 healthy controls (HCs) were retrospectively recruited. V3 width was measured using transcranial sonography (TCS), plasma Hcy level was quantified using cyclase assay, and cognitive function was analyzed using the Montreal Cognitive Assessment (MoCA). Results: Both V3 width and plasma Hcy concentration were negatively correlated with MoCA scores in PD (r=-0.358, P<0.001; r=-0.187, P=0.013, respectively). Receiver operating characteristic (ROC) analysis suggested that V3 width and Hcy were able to discriminate PDD and PD without dementia [area under the curve (AUC) =0.767 and 0.628, respectively], PD-NC and PD with cognitive decline (AUC =0.735 and 0.657, respectively), and PD-NC and PD-MCI (AUC =0.683 and 0.664, respectively). Following an average follow-up period of 31.04±18.84 months, PD-MCI patients with a V3 width ≥6.55 mm were at a 4.085 times higher risk of developing dementia, whereas PD-NC patients with a V3 width ≥5.75 mm had nearly double the risk of progressing to MCI. However, baseline plasma Hcy levels were unsuitable to predict cognition alternation over time. Conclusions: Plasma Hcy level and V3 width are associated with cognition function severity in PD patients, a V3 width is an independent predictor of MCI-dementia conversion in PD.