Internuclear ophthalmoplegia from intracranial tumor.

Bilateral internuclear ophthalmoplegia (INO) is most often demyelinative in origin. Rarely, structural lesions may present with this finding, but in these cases the age at onset and the associated signs of increased intracranial pressure and widespread brainstem dysfunction usually make the distinction. This report describes the 13th published case of tumor-induced INO, produced by an atypical adult medulloblastoma. Potential pathophysiologic mechanisms are discussed.