Abstract

Background
Ocular lateropulsion refers to a syndrome of ocular motor bias toward (ipsipulsion) or away from(contrapulsion) the lesion side without limitation of eye motion. It comprises static ocular deviation and asymmetries in the saccades, smooth pursuit, and optokinetic nystagmus. Ocular lateropulsion has been ascribed to damage to the neural pathways connecting the inferior olivary nucleus, cerebellar Purkinje cell, fastigial nucleus, and paramedian pontine reticular formation. Objective: To report clinical and radiological characteristics of ocular lateropulsion.
Methods
We analyzed clinical and radiological characteristics of 11 patients who had been diagnosed as having ocular lateropulsion. In all patients, the eye movements were evaluated by the senior author, and were recorded with electro- or video-oculography. Brain lesions were documented with magnetic resonance imaging.
Results
Ocular ipsipulsion was observed in 9 patients with lesions in the dorsolateral medulla or with infarcts of medial posterior inferior cerebellar artery. Ocular contrapulsion occurred in two patients, one with medial medullary syndrome and the other with infarction in the rostral cerebellum.
Conclusion
Ocular ipsipulsion is a sign of lesions in the dorsolateral medulla or in the caudal cerebellum while ocular contrapulsion may occur with lesions in the medial medulla or rostral cerebellum. Ocular ipsipulsion may be caused by damage to the crossed climbing fiber in the dorsolateral medulla or caudal cerebellum. Damage to the climbing fibers before crossing in the medial medulla and involvement of the uncinate fasciculus in the rostral cerebellar lesion may be underlying mechanisms of the contrapulsion.