Jerky Seesaw Nystagmus in Isolated Internuclear Ophthalmoplegia

ABSTRACT

The authors report jerky seesaw nystagmus, extorsional downbeating in the right eye and intorsional upbeating in the left eye, in a patient with right internuclear ophthalmoplegia (INO). This pattern of nystagmus may occur by disrupting pathways from contralateral posterior and anterior semicircular canals by a lesion in the medial longitudinal fasciculus. Depending on damage to the pathways from contralateral vertical canals, various patterns of dissociated torsional-vertical nystagmus may accompany INO.