Vertebral artery loop formations occur when a portion of the vertebral artery contains an unusual coil. It can be a rare anatomical variant or can be acquired.
Vertebral artery loops tend to be mostly diagnosed in the 5th and 6th decades. Its prevalence is uncertain but is thought...
Vertebral artery thrombosis results in complete or partial occlusion of the vertebral artery and alteration of blood flow to the posterior cerebral circulation. Ischemia or infarction to structures supplied by these arteries may result in a range of symptoms.
The vertebral venous plexus is a highly anastomotic network of valveless veins running along the entire length of the vertebral column from the foramen magnum to the sacral hiatus.
The vertebral venous plexus is comprised of three interconnected divisions:
internal vertebral ven...
A vestibule is an anatomical term and refers to a small cavity at the proximal end of a tube. It may refer to:
History and etymology
Vestibule derives ultimate...
There are two arteries passing through Vidian canal from the pterygopalatine fossa to the petrous portion of the ICA. One is a branch of the internal maxillary artery (itself a branch of the ECA) and the other is from the C2 segment of the ICA. It therefore forms one of the ICA to ECA anastamoses.
Virchow triad refers to the factors which can promote thrombosis, these are useful to consider when thinking about the possible causes in a particular situation. They are:
factor V Leiden
protein S deficiency
protein C deficiency
antithrombin III de...
Visceral artery aneurysms are abnormal focal dilatations of arteries supplying abdominal organs. Visceral artery aneurysms include both true aneurysms and pseudoaneurysms.
Owing to different clinical manifestations and a unique, specific, pathology, renal artery aneurysms are discussed separate...
Wells criteria for deep venous thrombosis is a risk stratification score and clinical decision rule to estimate the pretest probability for acute deep venous thrombosis (DVT). It is intended to be combined with noninvasive diagnostic tests (e.g. ultrasound or D-dimer) for suspected cases. D-dime...
Westermark sign is a sign of pulmonary embolus seen on chest radiographs. It is one of several described signs of pulmonary embolus on chest radiographs.
The theory behind the sign is either obstruction of the pulmonary artery or distal vasoconstriction in hypoxic lung 3.
In one stu...
The WFNS (World Federation of Neurosurgical Societies) grading system uses the Glasgow Coma Scale and presence of focal neurological deficits to grade the severity of subarachnoid hemorrhage. This grading system was proposed in 1988, and this is one of the accepted systems (although not consider...
The white coat effect, not to be confused with white coat hypertension, is a measure of change that is commonly defined as the difference between in-clinic and out-of-clinic blood pressure readings 1,2.
Alternatively, the white coat effect can be defined as the increase in the arterial blood p...
White coat hypertension (abbreviated alternatively as WCH or WCHT), not to be confused with the white coat effect (WCE), is commonly defined as typical in-clinic blood pressure (BP) measurements of 140/90 mm Hg or more in the presence of multiple daytime out-of-clinic home or ambulatory BP readi...
Williams syndrome (WS) is characterized by some or all of the following features:
craniofacial dysmorphism (e.g. elfin facies)
short stature (50% of cases)
mild to moderate intellectual disability
supravalvular aortic stenosis 2
pulmonary artery stenosis 3
The windsock sign refers to appearances seen in type A thoracic aortic dissections on contrast CT. It results from intimo-intimal intussusception between the true and false dissected lumens of the thoracic aorta. The altering density of contrast between the dissection lumens which taper distally...
Wyburn-Mason syndrome (also known as Bonnet-Dechaume-Blanc syndrome) is a rare, nonhereditary neurocutaneous disorder that typically presents with unilateral vascular malformations that primarily involve the brain, orbits and facial structures. It is currently classified as a craniofacial arteri...
The Yasargil classification is one of the two common systems for classifying vein of Galen malformations that is currently in use at the time of writing (mid 2016).
type I: small pure cisternal fistula between the vein of Galen (voG) and either the pericallosal arteries (anteri...
The yellow nail syndrome (YNS) is a rare disorder principally affecting the lymphatic system.
It is characterized by a clinical triad:
nail discolouration: yellow slow-growing dystrophic nails (scleronychia)
pulmonary disease: see yellow nail syndrome (pulmona...
The yin-yang sign, also known as the Pepsi sign, is a radiological sign described in both true and false aneurysms on various imaging modalities.
On Doppler ultrasound, the yin-yang sign indicates bidirectional flow due to the swirling of blood within the true...