Postural deficits in Huntington's disease when performing motor skills involved in daily living.

Previous studies of Huntington's disease (HD) have reported motor control deficits for selected fine and gross motor skills. However, no studies have metrically assessed postural control in this clinical group when performing motor skills involved in daily living. Therefore, the purpose of the present study was to evaluate and compare postural control of individuals with confirmed Huntington's disease and non-gene carriers when completing three functional postural tasks. Eleven individuals with HD (mean age=47.1 years: UHDRS mean=34.5: mean age of HD onset 34.6 years: mean CAG repeat=44.1) and 17 non-gene carriers (NGC) (mean age=39.2 years: UHDRS mean=0.13: mean CAG repeat=20.5) completed three tests on a force plate interfaced with a computer. The tests were a step up and over an obstacle (SUO) test, a sit-to-stand (STS) test, and a step and turn (ST) test. Selected kinematic and kinetic variables were used to quantify postural control. Data were analyzed using MANOVA procedures and discriminant function analysis. HD patients were significantly slower in completing all three tests (HD SUO=2.3 s vs. NGC SUO=1.6 s; HD STS=0.8 s vs. NGC STS=0.5 s; HD ST=1.7 s vs. NGC ST=0.9 s) and developed less rising force during the step up and over test (HD=25.8% body weight vs. NGC=39.4% body weight) but not for the sit-to-stand test. Additionally, sway velocity of the center of gravity (COG) was significantly higher for HD patients when performing the sit-to-stand (HD=4.1°/s vs. NGC=2.9°/s) and step and turn tests (HD=33.7°/s vs. NGC=21.7°/s). HD patients manifest significant postural control deficits when performing motor skills typical of daily living activities.

Impaired postural stability as a marker of premanifest Huntington's disease.

Subtle changes in fine motor control have been observed in individuals who carry the Huntington's disease (HD) mutation but have not yet manifested symptoms, referred to as premanifest HD (preHD). However, few studies have examined gross motor impairments in this population. This study sought to examine the role of sensory involvement in maintaining postural stability during the premanifest and manifest stages of HD using computerized dynamic posturography. Eleven HD participants, 22 preHD subdivided into "preHD Near" (<5 years from estimated clinical onset) and "preHD Far" (>5 years from estimated clinical onset), and 17 nongene carriers (NGC) completed a sensory organization test (SOT) to assess postural control when vestibular, visual, and somatosensory information was systematically degraded. The HD group demonstrated greater postural sway than the NGC and preHD Far groups on all conditions including baseline, and greater postural sway than the preHD Near group when sensory information was manipulated. The preHD Near group showed significantly greater postural sway than the preHD Far group when visual and somatosensory information was degraded and only vestibular information was available and reliable for maintaining postural stability. The results of this study highlight subtle postural deficits in the face of changing sensory conditions in preHD up to 5 years before estimated disease onset. The findings suggest that the SOT may be a highly sensitive indicator of early motor impairment and subsequent phenoconversion to manifest HD in preHD.