Internuclear ophthalmoplegia caused by subdural hematoma.

Internuclear ophthalmoplegia (INO) is caused by lesions in the median longitudinal fasciculus. It is generally the result of primary intraaxial disorders, most commonly multiple sclerosis in young adults and infarction in older adults. Rarely, extraaxial disorders cause INO by compressing the brainstem. We report two patients with INO resulting from subdural hematoma with transtentorial herniation. These cases demonstrate that INO is a reliable, but not a pathognomonic, sign of a primary intraaxial disorder.