A vascular malformation is a

blood vessel The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away ...

or lymph vessel

abnormality Abnormality refers to any deviation from the normal, the noun form of the adjective ''abnormal''. Abnormality may refer to: __NOTOC__ Medicine and physiology *Chromosome abnormality, atypical number of chromosomes or a structural abnormality in ...

. Vascular malformations are one of the classifications of

vascular anomalies A vascular anomaly is any of a range of lesions from a simple birthmark to a large tumor that may be disfiguring. They are caused by a disorder of the vascular system. A vascular anomaly is a localized defect in blood or lymph vessels. These defects ...

, the other grouping is

vascular tumor A vascular tumor is a tumor of vascular origin; a soft tissue growth that can be either benign or malignant, formed from blood vessels or lymph vessels. Examples of vascular tumors include hemangiomas, lymphangiomas, hemangioendotheliomas, Ka ...

s. They may cause aesthetic problems as they have a growth cycle, and can continue to grow throughout life. Vascular malformations of the brain (VMBs) include those involving capillaries, and those involving the veins and arteries. Capillary malformations in the brain are known as cerebral cavernous malformations or ''capillary cavernous malformations'' (CCMs). Those involving the mix of vessels are known as

cerebral arteriovenous malformation A cerebral arteriovenous malformation (cerebral AVM, CAVM, cAVM) is an abnormal connection between the arteries and veins in the brain—specifically, an arteriovenous malformation in the cerebrum. Signs and symptoms The most frequently observed ...

s (AVMs or cAVMs). The arteriovenous type is the most common in the brain.

Types

A simple division of the vascular malformations is made into ''low-flow'' and ''high-flow'' types. Low-flow malformations involve a single type of blood or lymph vessel, and are known as ''simple vascular malformations''; high-flow malformations involve an artery. There are also malformations that are of mixed-flow involving more than one type of vessel, such as an arteriovenous malformation. Low-flow vascular malformations include ''capillary malformations'', ''venous malformations'', and ''lymphatic malformations''.

Capillary malformation

Capillary malformations involve the

capillaries A capillary is a small blood vessel from 5 to 10 micrometres (μm) in diameter. Capillaries are composed of only the tunica intima, consisting of a thin wall of simple squamous endothelial cells. They are the smallest blood vessels in the body: ...

, and are the most common type. They used to refer only to

port-wine stain A port-wine stain (''nevus flammeus'') is a discoloration of the human skin caused by a vascular anomaly (a capillary malformation in the skin). They are so named for their coloration, which is similar in color to port wine, a fortified red wi ...

s but now include others. Capillary malformations are limited to the superficial layers of the skin but they can thicken, become nodular, and sometimes become disfiguring. It has been proposed that the category of capillary malformations, also called vascular stains, be classified into seven major clinical types including

nevus flammeus nuchae Naevus flammeus nuchae, or colloquially stork bite, is a congenital capillary malformation present in newborns. It is a common type of birthmark in a newborn. Prevalence and symptoms Stork bites occur in a significant number of newborns, with est ...

also known as nevus simplex, commonly known as ''stork bite'' or ''salmon patch''. A capillary malformation is also a feature of the disorder

macrocephaly-capillary malformation Macrocephaly-capillary malformation (M-CM) is a multiple malformation syndrome causing abnormal body and head overgrowth and cutaneous, vascular, neurologic, and limb abnormalities. Though not every patient has all features, commonly found signs ...

Venous malformation

Venous malformations are typically ill-defined masses, coloured from pale to dark blue. They can affect any tissue in the body. The mass is soft, and easily compressed, and their blue colouring is due to the dilated anomalous involved veins. They are most commonly found in the head and neck. Venous malformations can often extend deeper from their surface appearance, reaching underlying muscle or bone. In the neck they may extend into the lining of the mouth cavity or into the

salivary gland The salivary glands in mammals are exocrine glands that produce saliva through a system of ducts. Humans have three paired major salivary glands (parotid, submandibular, and sublingual), as well as hundreds of minor salivary glands. Salivary gla ...

s. A severe venous malformation can involve the lymph vessels as a ''lymphaticovenous malformation''.

Lymphatic malformation

Lymphangioma of the left side of the tongue Wellcome L0062760

Lymphatic malformations are congenital, developing from badly-formed lymphatic vessels in early

embryonic development An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sperm ...

. Abnormal development of the lymph vessels results in their failure to connect and drain into the venous system. These lymph vessels can become blocked due to the collection of lymph which forms a cyst as a mass, and are known as

lymphangioma Lymphangiomas are malformations of the lymphatic system characterized by lesions that are thin-walled cysts; these cysts can be macroscopic, as in a cystic hygroma, or microscopic. The lymphatic system is the network of vessels responsible for ...

s. They can be macrocystic, microcystic, or a combination of the two. Macrocystic have cysts greater than , and microcystic lymphangiomas have cysts that are smaller than . A macrocystic lymphangioma is also known as a

cystic hygroma A cystic hygroma is an abnormal growth that usually appears on a baby's neck or head. It consists of one or more cysts and tends to grow larger over time. The disorder usually develops while the fetus is still in the uterus, but can also appear a ...

. Cystic hygromas most often occur in the neck where they are known as ''nuchal hygromas''. A severe venous malformation is known as a lymphaticovenous malformation that also involves the lymph vessels.

Arteriovenous malformation

Arteriovenous malformations occur between an artery and a vein. In the brain a

causes arterial blood to be directly shunted into the veins as there is an absence of a capillary bed. This carries a high risk of an

intracranial hemorrhage Intracranial hemorrhage (ICH), also known as intracranial bleed, is hemorrhage, bleeding internal bleeding, within the Human skull, skull. Subtypes are intracerebral bleeds (intraventricular bleeds and intraparenchymal bleeds), subarachnoid bleed ...

References