Bilateral internuclear ophthalmoplegia after intrathecal chemotherapy and cranial irradiation

A 26-year-old man developed transient bilateral internuclear ophthalmoplegia with exotropia after cranial irradiation and intrathecal administration of methotrexate for lymphoma. Resolution of the ophthalmoplegia and the decrease in abnormally high levels of cerebrospinal fluid myelin basic protein after discontinuation of intrathecal medication suggested demyelination from chemotherapy and irradiation.