The spectrum of preclinical gait disorders in early Parkinson's disease: subclinical gait abnormalities and compensatory mechanisms revealed with dual tasking.

Patients with early Parkinson's disease (PD) may not complain of gait difficulties but subtle gait abnormalities may be revealed as part of a "preclinical gait syndrome" when they are challenged by dual tasks. 21 early PD patients (n = 21, mean age 63.5 years, H&Y 1.62, disease duration <5 years, mean UPDRS-III 7.7) who did not have gait complaints were as compared to age- and gender-matched healthy controls (n = 21). Memory function was not different between the two groups. Under normal walking conditions, there were no significant differences in gait parameters between the patients and the control group. In both groups, normalized gait velocity decreased in response to dual tasking in a parallel fashion (p < 0.001). Similarly, gait variability increased in both groups with dual tasking although not statistically significant. In PD patients, the performance of an additional task resulted in an increased number of cadences (p = 0.04), a reduction in swing time (p = 0.02) and cycle time (p = 0.04) compared with the control group but there was no significant reduction in normalized velocity. Stride width also increased in the PD patients. The addition of a cognitive task may affect certain aspects of gait and is able to elicit subclinical deficits in early PD patients. In an attempt to maintain velocity, early PD patients develop compensatory mechanisms by increasing cadence and decreasing swing time and cycle time. Increased step width helps support balance, and prevents going beyond the base-of-support which may predispose to unsteadiness and falls. We propose that these findings occur as part of a spectrum of a "preclinical gait syndrome" and longitudinal studies are needed to assess the predictive values of these early markers of gait deficits.