Skew deviation is an unusual ocular deviation (strabismus

Strabismus

Strabismus is a condition in which the eyes are not properly aligned with each other. It typically involves a lack of coordination between the extraocular muscles, which prevents bringing the gaze of each eye to the same point in space and preventing proper binocular vision, which may adversely...

), wherein the eyes move upward (hypertropia

Hypertropia

Hypertropia is a condition of misalignment of the eyes , whereby the visual axis of one eye is higher than the fellow fixating eye.Hypotropia is the similar condition, focus being on the eye with the visual axis lower than the fellow fixating eye....

), but in opposite directions. Skew deviation is caused by abnormal prenuclear vestibular

Vestibular

The Vestibular is a competitive examination and is the primary and widespread system used by Brazilian universities to select their students. The Vestibular usually takes place from November to January, right before the start of school year in February or March, although certain universities hold...

 input to the ocular motor nuclei, most commonly due to brainstem or cerebellar stroke

Stroke

A stroke, previously known medically as a cerebrovascular accident , is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by blockage , or a hemorrhage...

. Other causes include multiple sclerosis

Multiple sclerosis

Multiple sclerosis is an inflammatory disease in which the fatty myelin sheaths around the axons of the brain and spinal cord are damaged, leading to demyelination and scarring as well as a broad spectrum of signs and symptoms...

 and head trauma. Skew deviation is usually characterized by torticollis

Torticollis

Torticollis, or wryneck, is a stiff neck associated with muscle spasm, classically causing lateral flexion contracture of the cervical spine musculature...

 (head tilting) and binocular

Binocular vision

Binocular vision is vision in which both eyes are used together. The word binocular comes from two Latin roots, bini for double, and oculus for eye. Having two eyes confers at least four advantages over having one. First, it gives a creature a spare eye in case one is damaged. Second, it gives a...

 torsion

Wiktionary

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. The exact pathophysiology

Pathophysiology

Pathophysiology is the study of the changes of normal mechanical, physical, and biochemical functions, either caused by a disease, or resulting from an abnormal syndrome...

 of skew deviation remains incompletely understood. Skew deviation appears to be a perturbation of the ocular tilt reaction, which is itself probably a vestigial righting response used to keep fish

Fish

Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

and other lateral-eyed animals properly oriented.

Is poorly understood disorder of gaze in which is maintain vertical deviation of one eye above the other. The patient complains of vertical diplopia. Occurs with lesion of brain stem and cerebellum