Pendular see saw nystagmus

See saw nystagmus is characterized by its 1) oppositely directed vertical components (e.g., one eye elevates while the other depresses), and 2) conjugate torsion. For example, the right eye elevates and incycloducts while the left eye depresses and excycloducts, and then the right eye depresses and excycloducts while the left eye elevates and incycloducts. See saw nystagmus is pendular in this patient, because there are back-to-back-to-back slow phases. The best way to appreciate that the vertical components of the nystagmus are oppositely directed is to focus on the bridge of the nose rather than either eye individually. Compare to hemi-see saw nystagmus, where a slow phase of oppositely directed vertical and conjugate torsion is followed by a fast phase. Pendular see saw nystagmus almost always indicates a disorder in the mesodiencephalic/sellar region (e.g., pituitary macroadenoma with a bitemporal hemianopia), and this patient had a thalamic/rostral midbrain hemorrhage with subsequent hydrocephalus. Visual fields were normal without a bitemporal hemianopia. There were alternating hypertropias and a V-pattern strabismus, presumably due to bilateral 4th nerve palsies (more likely peripheral and due to hydrocephalus and intracranial pressure rather than central given the rostral location of the hemorrhage). There was convergence-retraction nystagmus with upward gaze, suggesting dorsal midbrain (posterior commissure) involvement, and slow downward more than upward saccades, suggesting rostral interstitial medial longitudinal fasciculus involvement. Finally, there was oculopalatal tremor (but without a clear OPT pendular nystagmus, which is usually vertical and/or torsional, not see saw) as evidenced by palatal tremor, presumably due to involvement of fibers of Mollaret's triangle as they wrap around the red nucleus and descend ipsilaterally to the inferior olive of the medulla.