Oral motor dysfunction in individuals at risk of Huntington disease.

We studied the performance of 34 as yet undiagnosed individuals known to be at risk of Huntington disease (HD), on a maximum-effort oral-motor task. Results were compared with those from a normal control group matched for age and sex. The at-risk-of-HD population was significantly slower overall than the normal group on all 5 of the oral-motor tasks. This is interpreted as indicating that the presence of HD in the one half of the population expected to have it, affected the group's overall performance even though the clinical signs associated with HD had not yet appeared. In addition, rankings of repetition rates in both groups indicate that approximately one half of the at-risk population was consistently associated with the slowest 25% of the combined groups forming, in essence, a subgroup of the at-risk population. The performance of the other one half of the at-risk group did not differ systematically from that of the normal control persons. Minimal repetition rates were identified on each oral-motor task that may serve as early clinical "indicators" for the presence of HD in the population known to be at risk.