The diagnostic value of eye movement recordings in patients with Huntington's disease and their offspring.

Eye movements were studied with EOG in a large number of Huntington's disease (HD) patients (N = 48) and their offspring (subjects at risk, N = 97). The following oculomotor paradigms were investigated: horizontal and vertical saccades of different sizes (10-80 degrees), smooth pursuit eye movements, optokinetic and vestibular nystagmus. It was found that 75% of the HD patients had pathologically slow saccades. This number rose to 87% if other oculomotor deficits were included. Thus a small, but definite number of HD patients had normal eye movements. This included patients with disease durations of more than 14 years. A comparison with the results of clinical and evoked potential studies on these patients showed that they were clinically only mildly affected but did not form a different group of HD patients. Subjects at risk had statistically (P less than 0.01) slower horizontal saccades (average 427 deg/sec) than the controls (455 deg/sec). For 11% of the subjects at risk horizontal saccade velocity was pathological and altogether 22% had some oculomotor deficits. Subjects with pathological slow horizontal saccades also had a high incidence (64%) of pathological evoked potentials. Thus, subjects with pathological slow horizontal saccades can be considered to have a high risk of developing the clinical symptoms of HD.