Ocular motor dysfunction in Lesch-Nyhan disease.

Eye movements were assessed in 22 patients with varying degrees of hypoxanthine-guanine phosphoribosyltransferase deficiency. Ocular motility was clinically normal in seven patients with moderate enzyme deficiency but grossly abnormal in 15 patients with severe enzyme deficiency. In patients with severe deficiency, fixation was interrupted by frequent unwanted saccades toward minor visual distractions. Voluntary saccades were associated with an initial head movement and/or eyeblink in all of these patients. When head motion was prevented, voluntary saccades were often delayed and sometimes absent. In contrast, saccade speed, reflexive saccades, and other reflexive eye movements appeared clinically normal. Four patients with severe enzyme deficiency also experienced mild blepharospasm, and two had ocular tics. These disturbances of ocular motility are consistent with dysfunction of the basal ganglia or its connections with ocular motor centers in the prefrontal cortex or midbrain.