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.