Abstract
Eye movements in an 8-year-old with congenital oculomotor apraxia were recorded and analyzed. The predominant defects were increased latencies and decreased amplitudes of voluntary saccadic eye movements in the horizontal plane. Abnormalities of eye movement were greatest when the oculomotor task required motor volition. In this patient complete loss of the quick phase of vestibular nystagmus was elicited by cold caloric irrigation and a moderate defect in the initiation of the slow and quick phases of optokinetic nystagmus were also present. However, the slow phase of vestibular nystagmus was demonstrated by caloric test and pendular rotation test to be preserved.
Eye and head movements began nearly synchronously. The saccade did not occur consistently even after the head began moving and instead, compensatory eye movement occurred as the patient moved his head toward the target.
Overshooting head movements were frequently observed. CT scan of the brain revealed atrophy of the cerebellar vermis.
Our findings indicate that the patterns of eye-head coordination in this patient depend upon the nature of the defect in the production of voluntary saccade. The main lesions are probably in the PPRF and cerebellar vermis. These two lesions are believed to be congenital associated disorders of hypogenesis of myelination.
