See-saw nystagmus

See-saw ocular movements are described in two patients, one having obstructive hydrocephalus and the other a thalamic infarct. Electro-oculographic studies demonstrated that the eye movements in patient 1 moved in and out of phase at irregular intervals, in both a horizontal and a vertical direction. The disconjugate eye movements were exaggerated in bright light and less evident during fixation. We suggest a lesion impairing the function of that circuitry of cells thought to include the nucleus centromedianus of the thalamus, the zona incerta, the interstitial nucleus of Cajal and eye movement related cells in the mid brain and pons, causes the disconjugate eye movements but that the controlling influence of multiple connections with other parts of the brain results in the ever changing pattern of disconjugate eye movement.