| cerebral arteriovenous malformations | Vascular anomalies in which tangles of arteries are connected directly to veins without intervening capillaries. The resulting vessels are thin-walled owing to poorly developed elastic and muscle tissue within the media. They can be located anywhere in the brain and can produce headaches, seizures, focal neurologic deficits, or intracranial haemorrhage. Familial cases are rare, indicating that the problem reflects sporadic abnormalities in embryologic development. (12 Dec 1998) |
|---|
| arteriovenous malformation | <anatomy, embryology> A tangled collection of abnormal blood vessels where there is an abnormal communication between the arterial and venous systems. The afferents flow directly into the venous efferents without the usual resistance of an intervening capillary bed. They are mostly congenital. If large enough, they may produce a shunt of sufficient magnitude to raise the cardiac output. Common sites include; skin, liver, brain, brainstem and spinal cord, where they may cause headaches, seizures or bleeding (subarachnoid haemorrhage). See: arteriovenous fistula, cerebral arteriovenous malformations. Synonym: haemangioma (20 Jun 2000) |
|---|---|
| arnold-chiari malformation | <radiology> Chiari I herniation of medulla and cerebellar tonsils, 4th ventricle in normal position, Chiari II herniation of medulla, tonsils, vermis, 4th ventricle at foramen magnum, myelomeningocele, aqueductal stenosis most likely to be hydrocephalus, Chiari III further herniation, 4th ventricle below foramen magnum, encephalocele or myelomeningocele associated with: agenesis of corpus callosum, syrinx (12 Dec 1998) |
| A-V malformation | <anatomy, embryology> A tangled collection of abnormal blood vessels where there is an abnormal communication between the arterial and venous systems. The afferents flow directly into the venous efferents without the usual resistance of an intervening capillary bed. They are mostly congenital. If large enough, they may produce a shunt of sufficient magnitude to raise the cardiac output. Common sites include; skin, liver, brain, brainstem and spinal cord, where they may cause headaches, seizures or bleeding (subarachnoid haemorrhage). See: arteriovenous fistula, cerebral arteriovenous malformations. Synonym: haemangioma (20 Jun 2000) |
| malformation | <embryology> A morphologic defect resulting from an intrinsically abnormal developmental process. Origin: L. Malus = evil, formatio = a forming (18 Nov 1997) |
| cerebellomedullary malformation syndrome | <radiology> Chiari I herniation of medulla and cerebellar tonsils, 4th ventricle in normal position, Chiari II herniation of medulla, tonsils, vermis, 4th ventricle at foramen magnum, myelomeningocele, aqueductal stenosis most likely to be hydrocephalus, Chiari III further herniation, 4th ventricle below foramen magnum, encephalocele or myelomeningocele associated with: agenesis of corpus callosum, syrinx (12 Dec 1998) |
| congenital malformation | Abnormal formation of a structure evident at birth. (12 Dec 1998) |
| cystic adenomatoid malformation of lung | <radiology> Only true pulmonary cystic disease of newborn, three X-ray types: multicystic, walls of varying thickness, multicystic, one large dominant thin-walled cyst, solid, mediastinal shift common, cysts often contain foetal lung fluid, Treatment: surgery Cf: congenital lobar emphysema (12 Dec 1998) |
| cystic adenomatoid malformation of lung, congenital | A developmental anomaly that usually becomes apparent in the neonatal period with progressive respiratory distress. This malformation is a focal pulmonary dysplasia characterised by a multicystic mass of terminal bronchiolar structures. Ccam is classified into 3 separate types (I, II, III) depending on cyst size. (12 Dec 1998) |
| arteriovenous | <anatomy> Both arterial and venous, pertaining to or affecting an artery and a vein. (18 Nov 1997) |
| arteriovenous anastomosis | <anatomy> A vessel that directly interconnects an artery and a vein, and that acts as a shunt to bypass the capillary bed. Not to be confused with surgical anastomosis, nor with arteriovenous fistula. (12 Dec 1998) |
| arteriovenous aneurysm | <anatomy> A dilated arteriovenous shunt where there is communication between an artery and a vein, sometimes congenital. (05 Mar 2000) |
| arteriovenous carbon dioxide difference | <physiology> The difference in carbon dioxide content (in ml per 100 ml blood) between arterial and venous blood. (05 Mar 2000) |
| arteriovenous fistula | <surgery> The surgical joining of an artery and a vein under the skin for the purpose of haemodialysis. Larger arteriovenous shunts can place strain on the heart since arterial blood is diverted back to the venous circulation before it has a chance to deliver nutrients and oxygen to the body tissues. (27 Sep 1997) |
| arteriovenous oxygen difference | <physiology> The difference in the oxygen content (in ml per 100 ml blood) between arterial and venous blood. (05 Mar 2000) |
| arteriovenous shunt | <anatomy, surgery> A direct connection between an artery and vein. Most often due to the surgical joining of an artery and a vein under the skin for the purpose of haemodialysis. Larger arteriovenous shunts can create significant extra workload on the heart since arterial blood is diverted back to the venous circulation before it has a chance to deliver nutrients and oxygen to the body tissues. (20 Jun 2000) |