Electro-oculography of smooth pursuit and optokinetic nystagmus eye movements in type I Duane's retraction syndrome.

Introduction: These two eye movements have not been previously studied in this condition by this method.

Methods: Five cases were studied. Both visual acuity and eye examination of anterior and posterior segments were normal. A Nicolet Nystar Plus system with chloride silver electrodes was used to record the EOG.

Results: Of the two systems under study, the smooth pursuit system showed the most relevant anomalies, both in the Duane's eye and in the apparently healthy eye. No correlation was found between the pursuit and optokinetic nystagmus disorders. In some cases, more significant abnormalities were observed in the clinically normal eye.

Conclusions: The results clearly demonstrated a significant impairment of the pursuit system. This suggests that this motor disorder is not exclusively caused by hypoplasia or aplasia of the nucleus of the abducens nerve (VIth cranial nerve). These abnormalities might be related to a poor development of the rhombencephalon since both supramotor nuclei as well as the pathways of this system arise from this region of the embryonic brain. In the particular case of OKN, the supramotor nuclei have a different origin. Therefore, these systems might be affected differently.