DISTURBANCES OF PRECISION GRIP IN HUNTINGTONS-DISEASE

Disturbed motor control of the fingers, as revealed by the response to unexpected loading of an object held in a precision grip, or to finge r perturbation during isometric holding, has been studied in patients with Huntington's disease (HD) and in normal subjects. In normal subje cts unexpected loading elicited a reflex response (mean latency 73 ms) in the first dorsal interosseus muscle (FDI). This was accompanied by a clear increase in grip force, reaching a maximum at 200 ms, which s tabilised block position. Index finger perturbation led to a long-late ncy reflex response in the FDI of all normal subjects. No such respons e was seen in the HD patients. The response to object loading, in cont rast, was present, but significantly delayed (mean onset 95 ms; P = 0. 0135). The response was qualitatively normal, with grip force reaching a maximum at 220-230 ms. It is suggested that the absence of the long -latency stretch reflex and the delay in the response to loading in HD patients may represent a reduction in somatosensory input to the cort ex caused by disruption of basal ganglia structures.