Phenotype of postural instability/gait difficulty in Parkinson disease: relevance to cognitive impairment and mechanism relating pathological proteins and neurotransmitters.

Parkinson disease (PD) is identified as tremor-dominant (TD) and postural instability and gait difficulty (PIGD) phenotypes. The relationships between motor phenotypes and cognitive impairment and the underlying mechanisms relating pathological proteins and neurotransmitters in cerebrospinal fluid (CSF) are unknown. We evaluated the motor symptoms and cognitive function by scales, and detected the levels of pathological proteins and neurotransmitters in CSF. TD group and PIGD group had significantly higher levels of total tau, tau phosphorylated at the position of threonine 181(P-tau181t), threonine 231, serine 396, serine 199 and lower β amyloid (Aβ)(1-42) level in CSF than those in control group; PIGD group had significantly higher P-tau181t level and lower Aβ(1-42) level than those in TD group. In PD group, PIGD severity was negatively correlated with MoCA score and Aβ(1-42) level in CSF, and positively correlated with Hoehn-Yahr stage and P-tau181t level in CSF. In PIGD group, PIGD severity was negatively correlated with homovanillic acid (HVA) level in CSF, and HVA level was positively correlated with Aβ(1-42) level in CSF. PIGD was significantly correlated with cognitive impairment, which underlying mechanism might be involved in Aβ(1-42) aggregation in brain and relevant neurochemical disturbance featured by the depletion of HVA in CSF.