Are gait initiation parameters early markers of Huntington's disease in pre-manifest mutation carriers?

Huntington's disease (HD) pre-manifest mutation carriers (PMCs) present early-onset gait disturbances. Gait initiation encompasses the preparation and execution of the first step. By using paradigms with and without external cues, a gait initiation analysis can highlight the interaction between motor and cognitive aspects of movement preparation and execution. Hence, gait initiation disorders may constitute particularly interesting early markers of HD. The objective of the present study was to quantify gait initiation in PMCs. In a case-control study, 17 PMCs (median age: 36.5) were compared with a group of 25 healthy controls (HCs, median age: 36) for gait initiation and a group of 57 HCs (median age: 38) for gait. Presymptomatic mutation carriers displayed a shorter first step duration and lower-amplitude postural adjustments. For the first step duration and speed, these impairments were more pronounced under self-triggered (ST) conditions. The PMCs displayed a lower gait speed, cadence and stride length and higher stride-to-stride variability. The latter parameter seemed capable of differentiating between PMCs and HCs with adequate sensitivity (0.81) and specificity (0.87). We confirmed the early-onset impairment of gait in general and first step execution in particular in PMCs (particularly under ST conditions). The temporal parameters of step execution (e.g. duration) and spatial parameters of postural adjustment (e.g. a backward shift in the centre of pressure) may be worth investigating as early markers of HD. However, two such parameters (stride-to-stride variability and first step duration under ST conditions) already appear to be sufficiently reliable diagnostic tools for differentiating between PMCs and HCs.