Centripetal, rebound and gaze-evoked nystagmus

Gaze-evoked and rebound nystagmus is commonly seen in disorders that involve the posterior fossa (especially the cerebellum), but centripetal nystagmus is rare. Gaze-evoked nystagmus (e.g., right-beating in right gaze, left-beating in left gaze) typically reduces in intensity to some degree over seconds as adaptative processes set in. Rebound nystagmus is a manifestation of this adaptation, and occurs when nystagmus reverses direction after the patient looks back to primary gaze - e.g., right-beating in right gaze and then left-beating nystagmus when the patient looks back to center. Rarely, gaze-evoked nystagmus will not only slow but reverse direction and beat centripetally when the patient is still looking in lateral gaze - e.g., right-beating in right gaze that slows and then becomes left-beating while the patient is still looking to the right, which intensifies when the patient looks back to center. Centripetal nystagmus is rare (for unclear reasons) but may result from over-adaptation, and it will probably be missed if the patient is held in eccentric gaze for a short time (e.g., <5-10 seconds). This young patient experienced dizziness and imbalance due to an acute cerebellar syndrome, along with diplopia due to a 6th nerve palsy. There was a lymphocytic pleocytosis, but no specific viral or antibody-mediated disorder could be identified to explain her rhombencephalitis. This video was taken months after the onset, when she was markedly improved, although cerebellar ocular motor signs remained.