Since the first description of see-saw nystagmus in 1914 by Maddox1 only seven cases have been reported in the literature. The phenomenon is rare but unmistakable; the eyes move vertically, symmetrically, and rhythmically in dissociated fashion, one looking up while the other looks down (hence the appellation "see-saw"). In addition, as the globe rises it intorts, and as it falls it extorts. When the gaze is directed upward, the movements tend to become faster but smaller. The sign is apparently not dependent upon reduction in visual acuity; however, nearly all patients have a bitemporal hemianopsia. Fixation on a near object or the presence of bright light (as from a flood lamp) diminishes or abolishes the sign.2 Smith points out that the nystagmus is most easily observed by having the patient look down and then noting the lid movements.3
The responsible lesion appears in most cases to be