-> eye move in an opposed vertical fashion (one goes up while the other goes down) with same direction torsion of the eyes. (eye moving up intorts, eye moving down extorts)
The wave form can be either pendular (seesaw) or jerk (semi seesaw).
Seesaw nystagmus is a sequence of abnormal eye movements in which one eye moves up as the other moves down. In addition to the alternating opposed vertical movements, there is rotation (torsion) of the eyes. The eyes rotate synchronously with the up and down movements, both eyes rotating in the same direction; the eye moving up intorts, and the eye moving down extorts.
There are many etiologies of SSN including: most commonly parasellar masses, mesodiencephalic disease, brainstem stroke, head trauma, lack or loss of crossing fibers in the optic chiasm, multiple sclerosis, arnold-chiari malformation, congenital, whole brain irradiation, and intrathecal methotrexate.
Video by Kathleen B. Digre, M.D. - Moran Eye Center
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