Brainstem diseases causing isolated ocular motor nerve palsies

Abstract

There is a significant number of individual patients with ocular motor nerve palsies as the only clinical sign of MRI- and, less frequently, CT-documented small brainstem lesions with a predominance of infarctions and hemorrhages in the 3 rd and 4 th nerves and demyelinating lesions in the 6 th nerve. The 3 rd nerve is most commonly and the 6 th and 4 th nerves less frequently involved. An intra-axial basis for isolated ocular motor nerve palsies may be underestimated if based on MRI-documented lesions only, as electrophysiologic abnormalities indicating brainstem lesions may be independent of MRI-documented lesions.This paper reviews neuroimaging and electrophysiological data on brainstem diseases manifesting as isolated ocular motor nerve palsies. It supports the concept that small pontine and mesencephalic lesions are an underestimated cause of isolated ocular motor nerve palsies and the main cause of nontraumatic 3 rd and 6 th nerve palsies in the middle-aged and elderly population.