Articles are a collaborative effort to provide a single canonical page on all topics relevant to the practice of radiology. As such, articles are written and edited by countless contributing members over a period of time. A global group of dedicated editors oversee accuracy, consulting with expert advisers, and constantly reviewing additions.

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Wackenheims line

Wackenheims line (also known as the clivus canal line or basilar line) is formed by drawing a line along the clivus and extending it inferiorly to the upper cervical canal. Normally the tip of the dens is ventral and tangential to this line. In basilar invagination odontoid process transects th...

Waldeyer's ring

Waldeyer's ring is a ring of lymphoid tissue located in the nasopharynx and oropharynx at the entrance to the aerodigestive tract. Gross anatomy The structures composing this ring are: palatine tonsils (also called the faucial tonsils) adenoid tonsils (nasopharyngeal tonsils) the lateral ba...

Warthin tumour

Warthin tumours (or papillary cystadenoma lymphomatosum) are benign, sharply demarcated tumours of the salivary gland. They are of lymphoid origin and most commonly arise from parotid gland tail. They may be bilateral or multifocal in up to 20% of cases and are the most common neoplastic cause o...

Widening of diploic space

Widening of diploic space refers to diffuse, most commonly bilateral, calvarium widening secondary to extramedullary hematopoiesis within the skull. Causes Most commonly caused by systemic underlying pathologies such as: chronic haemolytic disorders: may be associated with vertical striations...

Widow's peak hair anomaly

Widow's peak hair anomaly refers to a frontal hairline projection. Clinical features Prominent V shaped hairline projection. Ocular hypertelorism might be noted. On examination a bony prominence may be present. Pathology It is purported that the periorbital fields of hairless region or hairg...

Williams syndrome

Williams syndrome (WS) is characterised by some or all or the following features: craniofacial dysmorphism (e.g. elfin facies) oral abnormalities short stature (50% of cases) mild to moderate mental retardation supravalvular aortic stenosis 2 pulmonary artery stenosis 3 renal insufficienc...

Wolff-Chaikoff effect

Wolff-Chaikoff effect is an autoregulatory phenomenon, whereby a large amount of ingested iodine acutely inhibits thyroid hormone synthesis within the follicular cells, irrespective of the serum level of thyroid-stimulating hormone (TSH) 1.  Pathology The Wolff-Chaikoff effect is thought to be...

Wormian bones

Wormian bones are a subset of the small intrasutural bones that lie between the cranial sutures formed by the bones of the skull vault. The title Wormian bones is reserved for abnormal intrasutural bones that are typically found around the lambdoid suture. Some consider them abnormal only if gr...

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