Relative pupil-sparing third nerve palsy: etiology and clinical variables predictive of a mass.

The causes of ophthalmoplegia in 24 consecutive patients with neurologically isolated, relative pupil-sparing third nerve palsy included infarction in 10 patients, compression by tumors or aneurysms in 10 patients, and miscellaneous disorders in four patients. There was no significant difference in the proportion of patients with pain, degree of external ophthalmoplegia, or degree of internal ophthalmoplegia between the groups with infarction or mass lesions. Therefore, screening for mass lesions using neuroimaging is indicated in patients with this presentation of third nerve palsy.