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W

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1. Symbol for the element tungsten (wolfram). 2. Watt.

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w

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week; wife; with.

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Waardenburg syndrome

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(var′dĕn-bŭrg″) [Petrus Johannes Waardenburg, Dutch ophthalmologist, 1886–1979] ABBR: WS. Any of several related autosomal dominant disorders that may produce dermatological, neurological, ophthalmic, and auditory deficits, and abnormalities in skin pigmentation.

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INCIDENCE: WS occurs in 1 in approx 44,000 births. About 1 in 30 students in schools for the deaf have the syndrome. All races and both sexes are affected approx. equally.

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CAUSES: Mutations in transcription factors in cells from the embryonic neural crest, esp. melanocytes, cause the skin changes found in WS and the loss of normal development of the stria vascularis of the cochlea of the inner ear.

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SYMPTOMS AND SIGNS: Most patients have patches of pale skin (albinism), or hair (white forelocks) in association with congenital deafness. Some variants of WS (type II) are characterized by abnormally small eyes (microophthalmia) or pale blue eyes, often with coloring that does not match bilaterally; other examples of WS are associated with loss of normal innervation of the gastrointestinal tract (type IV WS with Hirschsprung disease). Type 3 WS is accompanied by abnormal development of the limbs. Type 1 WS is marked by dystopia canthorum.

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DIAGNOSIS: The disease is usually diagnosed when a blood relative is identified with both patchy loss of skin or hair pigment and hearing loss from birth. Hearing loss can be confirmed with audiometry.

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PREVENTION: Genetic testing and counseling can be used to identify offspring who may be at risk for WS.

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TREATMENT: There are no specific treatments for the disease.

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PATIENT CARE: Hearing amplification helps patients with deafness. Patients with type 4 disease, who may suffer episodes of megacolon, may require either medical therapies for constipation or bowel surgeries.

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Wada test

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(wod′ă) [Juhn Atsushi Wada, Japanese-born Canadian neurosurgeon, b. 1924] A test to identify which side of the brain is used for what purposes, e.g., primarily language and memory. The test is employed before neurosurgery to prevent injury to essential parts of the brain. A dose of a barbiturate is injected into an internal carotid artery. After that side of the brain is sedated, the patient is asked to speak and to identify cards imprinted with pictures or words. After the first hemisphere of the brain recovers from sedation, the patient is asked to recall those objects or words that were shown. The test is then repeated on the opposite hemisphere.

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wafer

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(wā′fĕr) A thin envelope or disk used to enclose a medication or to separate two structures from one another.

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WAGR syndrome

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