Ocular Oscillations

See-saw nystagmus is a conjugate, pendular, torsional oscillation with a superimposed disjunctive vertical vector. The intorting eye rises and the opposite (extorting) eye falls. Repetition of this sequence in the reverse direction provides the see-saw effect. The majority of patients with acquired see-saw nystagmus have bitemporal hemianopsias and large parasella tumors expanding within the third ventricle. Upper brainstem vascular disease is the next most common etiology. This nystagmus reflects diencephalic dysfunction. In certain positions, the vertical vectors are not prominent and large amplitude tortional nystagmus alone is present. The see-saw is then usually best manifest in downward gaze.