Oculomotor defects in patients with Huntington's disease and their offspring

We recorded saccadic, pursuit and fixation eye movements in patients (n = 5) with moderately advanced Huntington's disease (HD), offspring of HD patients (n = 22) and control subjects (n = 15), using the scleral sensor coil technique. Saccadic slowing was seen in all patients, no controls and (marginally) in a few at-risk subjects. Fixational stability was lower in patients than in the other groups; a structured background enhanced the difference and revealed decreased stability in a number of at-risk subjects. Smooth pursuit showed large errors in most patients and several controls but none of the at-risk subjects. Sporadic follow-up data show that at least two of the at-risk subjects developed manifest HD within a few years after passing the oculomotor test with entirely normal results. The material as a whole suggests that oculomotor dysfunction does not develop prior to, but concurrently with and as a part of generalized, progressive deterioration of motor control. The implication is that oculomotor screening of clinically healthy at-risk subjects does not reliably contribute to an earlier diagnosis of future HD.