Skew deviation: clinical updates for ophthalmologists.

Abstract

This article discusses the current approach in diagnosing skew deviation, as well as recent findings in the lesion localization. Skew deviation can be defined as vertical misalignment of the eyes that does not map to any of cyclovertical muscles, in association with neurologic symptoms and signs and with posterior fossa lesion. It can be differentiated from trochlear nerve palsy by the direction of ocular torsion and the change in the degree of vertical deviation with upright and supine head position. It is commonly caused by ischemia of the posterior paramedian pons, medial thalamus, or cerebellum. Other less common mechanism being demyelinating lesion, mass effect, infection, hemorrhage, or intracranial hypertension. When the vestibular nuclei are involved, skew deviation may occur with acute vestibular syndrome. Ground-in or Fresnel prism may alleviate diplopia in relatively small vertical deviation; however, patient with larger deviation or with the presence of ocular torsion may benefit from surgery of the cyclovertical muscles. Skew deviation can be appropriately diagnosed from the nature of the ocular torsion and the vertical deviation, along with the presence of lesion involving posterior paramedian pons and/or medial thalamus.