Eye-head coordination in moderately affected Huntington's Disease patients: do head movements facilitate gaze shifts?

In addition to many other symptoms, Huntington's Disease (HD) also causes an impairment of oculomotor functions. In particular, saccadic eye movements become progressively slower and more difficult to initiate; ultimately, patients are forced to recur to large head thrusts as means to initiate gaze shifts. We wondered whether, as a precursor of this condition, head movements would facilitate gaze shifts already in early stages of the disease. We studied horizontal head movements and eye-head coordination in 29 early stage HD patients (Ps) and 24 age matched controls (Cs). Subjects tracked random horizontal steps of visual or auditory targets while their heads were either stabilised (saccade amplitudes