Different types of skew deviation.

Although all manifest skew deviations appear the same for the clinician, skew deviation can result from different combinations of dysconjugate vertical ocular deviations. Evidence is presented for three different types of skew deviation when it occurs as a feature of an ocular tilt reaction. In type 1 (utricle) there is upward deviation of both eyes with different amplitudes, as described for otolith Tullio phenomenon in humans. In Type 2 (dorsolateral medulla oblongata) hypertropia of one eye occurs while the other eye remains in the primary position, the hypothetical mechanism of skew deviation in Wallenberg's syndrome. In Type 3 (midbrain tegmentum) there is simultaneous hypertropia of one eye and hypotropia of the other eye, as described for electrical stimulation of midbrain tegmentum in monkeys and observed in clinical cases with a paroxysmal ocular tilt reaction.