Posturo-locomotor markers of preclinical Parkinson's disease.

Parkinson's disease (PD) is known to have a long prodromal stage due to the degeneration of dopaminergic neurons of the substantia nigra pars compacta over the course of many years without clinical manifestations of PD. When the diagnosis is made, the neuropathological process is already well entrenched. Consequently, identifying individuals during this prodromal period could be very helpful for future trials of neuroprotective or disease-modifying therapies, which might slow or prevent the degeneration of dopaminergic neurons. Thus, efforts are needed to determine appropriate early markers of PD. Gait and balance disorders are frequent during the early stages of PD. This systematic review aims to determine if gait and balance disorders occur before the diagnosis of PD and if so, whether they could be used as markers of preclinical PD. Findings reveal that, at the presymptomatic stage of PD, impaired basal ganglia function leads to disorders in gait and balance. Both clinical and instrumental assessments allow early detection of these disorders, particularly when performed under challenging conditions (e.g. dual-task). Among all studied parameters, temporal gait variability and arm kinematics appear to be promising markers of preclinical PD.