Skew deviation is an unusual ocular deviation (

strabismus Strabismus is an eye disorder in which the eyes do not properly align with each other when looking at an object. The eye that is pointed at an object can alternate. The condition may be present occasionally or constantly. If present during a ...

), wherein the eyes move upward (

hypertropia Hypertropia is a condition of misalignment of the eyes (strabismus), 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 fello ...

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

vestibular The Vestibular (from , "entrance hall") is a competitive examination and is the primary and widespread entrance system used by Brazilian universities to select the students admitted. The Vestibular usually takes place from November to January, ...

input to the ocular motor nuclei, most commonly due to

brainstem The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is conti ...

cerebellar The cerebellum (: cerebella or cerebellums; Latin for 'little brain') is a major feature of the hindbrain of all vertebrates. Although usually smaller than the cerebrum, in some animals such as the mormyrid fishes it may be as large as it or e ...

stroke Stroke is a medical condition in which poor cerebral circulation, blood flow to a part of the brain causes cell death. There are two main types of stroke: brain ischemia, ischemic, due to lack of blood flow, and intracranial hemorrhage, hemor ...

. Other causes include

multiple sclerosis Multiple sclerosis (MS) is an autoimmune disease resulting in damage to myelinthe insulating covers of nerve cellsin the brain and spinal cord. As a demyelinating disease, MS disrupts the nervous system's ability to Action potential, transmit ...

and

head trauma A head injury is any injury that results in trauma to the skull or brain. The terms ''traumatic brain injury'' and ''head injury'' are often used interchangeably in the medical literature. Because head injuries cover such a broad scope of inj ...

. Skew deviation is usually characterized by

torticollis Torticollis, also known as wry neck, is an extremely painful, dystonic condition defined by an abnormal, asymmetrical head or neck position, which may be due to a variety of causes. The term ''torticollis'' is derived . The most common case ha ...

(head tilting) and

binocular Binocular may refer to: Science and technology * Binocular vision, seeing with two eyes * Binoculars, a telescopic tool * Binocular microscope, binocular viewing of objects through a single objective lens Other uses * Binocular (horse), a thoroug ...

torsion Torsion may refer to: Science * Torsion (mechanics), the twisting of an object due to an applied torque * Torsion of spacetime, the field used in Einstein–Cartan theory and ** Alternatives to general relativity * Torsion angle, in chemistry Bio ...

. The exact

pathophysiology Pathophysiology (or physiopathology) is a branch of study, at the intersection of pathology and physiology, concerning disordered physiological processes that cause, result from, or are otherwise associated with a disease or injury. Pathology is ...

of skew deviation remains incompletely understood. Skew deviation appears to be a perturbation of the

ocular tilt reaction The ocular tilt reaction (OTR) comprises skew deviation, head tilt and ocular torsion involving structures of the inner ear responsible for maintenance of balance of the body i.e. the semi-circular canals (SCC), utricle and saccule. Each ant ...

, which is itself is most likely a

vestigial Vestigiality is the retention, during the process of evolution, of genetically determined structures or attributes that have lost some or all of the ancestral function in a given species. Assessment of the vestigiality must generally rely on co ...

righting response used to keep

fish A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...

and other lateral-eyed animals properly oriented. There are three types of skew deviations: Type 1: Upward deviation of both eyes; sound-induced vestibular symptoms; both eyes show counterclockwise rotary upward rotation Type 2: Hypertropia in one eye; dorsolateral medullary infarctions; excyclotropia in the ipsilateral eye; hypertropia in the contralateral eye Type 3: Simultaneous hypertropia one eye and hypotropia in the other eye; upper brainstem lesion

References

Further reading