All fast-flow malformations are malformations involving arteries. They constitute about 14% of all vascular malformations.

- Arterial malformation

- Arteriovenous fistula (AVF) : a lesion with a direct communication via fistulae between an artery and a vein.

- Arteriovenous malformation : a lesion with a direct connection between an artery and a vein, without an intervening capillary bed, but with an interposed nidus of dysplastic vascular channels in between.

Vascular malformation is a collective term for different disorders of the vasculature (errors in vascular development). It can be a disorder of the capillaries, arteries, veins and lymphatic vessels or a disorder of a combination of these (lesions are named based on the primary vessel that is malformed). A vascular malformation consists of a cluster of deformed vessels, due to an error in vascular development (dysmorphogenesis). However, endothelial turnover is stable in these defects. Congenital vascular malformations are always already present at birth, although they are not always visible. In contrast to vascular tumors, vascular malformations do not have a growth phase, nor an involution phase. Vascular malformations tend to grow proportionately with the child. Vascular malformations never regress, but persist throughout life.

Vascular malformations can be divided into slow-flow, fast-flow and complex-combined types.

Sinus pericranii typically present as soft palpable masses along midline skull, which may fluctuate in size depending on body positioning. Classically, these lesions are not associated with color change of the overlying skin, such as with other vascular lesions such as hemangioma.

Sinus pericranii (SP) is a rare disorder characterized by a congenital (or occasionally, acquired) epicranial venous malformation of the scalp. Sinus pericranii is an abnormal communication between the intracranial and extracranial venous drainage pathways. Treatment of this condition has mainly been recommended for aesthetic reasons and prevention of hemorrhage.

The birth defect is diagnosed by the presence of a combination of these symptoms (often on approximately ¼ of the body, though some cases may present more or less affected tissue):

- One or more distinctive port-wine stains with sharp borders

- Varicose veins

- Hypertrophy of bony and soft tissues, that may lead to local gigantism or shrinking, most typically in the lower body/legs.

- An improperly developed lymph system

In some cases, port-wine stains (capillary port wine type) may be absent. Such cases are very rare and may be classified as "atypical Klippel–Trenaunay syndrome".

KTS can either affect blood vessels, lymph vessels, or both. The condition most commonly presents with a mixture of the two. Those with venous involvement experience increased pain and complications, such as venous ulceration in the lower extremities.

Those with large AVMs are at risk of formation of blood clots in the vascular lesion, which may migrate to the lungs (pulmonary embolism). If there is large-volume blood flow through the lesion, "high-output heart failure" may develop due to the inability of the heart to generate sufficient cardiac output.

Clinical symptoms of CNS origin include recurrent headaches, focal neurological deficits, hemorrhagic stroke, and seizures, but CCM can also be asymptomatic. The nature and severity of the symptoms depend on the lesion's location.

Klippel–Trénaunay syndrome (KTS or KT), formerly Klippel–Trénaunay–Weber syndrome and sometimes angioosteohypertrophy syndrome and hemangiectatic hypertrophy, is a rare congenital medical condition in which blood vessels and/or lymph vessels fail to form properly. The three main features are nevus flammeus (port-wine stain), venous and lymphatic malformations, and soft-tissue hypertrophy of the affected limb. It is similar to, though distinctly separate from, the less common Parkes-Weber syndrome.

The classical triad of Klippel-Trenaunay syndrome consists of:

1. vascular malformations of the capillary, venous and lymphatic vessels;

2. varicosities of unusual distribution, particularly the lateral venous anomaly; and

3. unilateral soft and skeletal tissue hypertrophy, usually the lower extremity.

A developmental venous anomaly (DVA, formerly known as venous angioma) is a congenital variant of the cerebral venous drainage. On imaging it is seen as a number of small deep parenchymal veins converging toward a larger collecting vein.

Central nervous system cavernous hemangioma is a cavernous hemangioma that arises in the central nervous system (CNS). It can be considered to be a variant of hemangioma, and is characterized by grossly large dilated blood vessels and large vascular channels, less well circumscribed, and more involved with deep structures, with a single layer of endothelium and an absence of neuronal tissue within the lesions. These thinly walled vessels resemble sinusoidal cavities filled with stagnant blood. Blood vessels in patients with cerebral cavernous malformations (CCM) can range from a few millimeters to several centimeters in diameter. Most lesions occur in the brain, but any organ may be involved.

DVA can be characterized by the Caput medusae sign of veins, which drains into a larger vein. The drains will either drain into a Dural venous sinuses or into a deep ependymal vein. It appears to look like a Palm tree.

Double aortic arch (DAA) is a relatively rare congenital cardiovascular malformation. DAA is an of the aortic arch in which two aortic arches form a complete vascular ring that can compress the trachea and/or esophagus. Most commonly there is a larger (dominant) right arch behind and a smaller (hypoplastic) left aortic arch in front of the trachea/esophagus. The two arches join to form the descending aorta which is usually on the left side (but may be right-sided or in the midline). In some cases the end of the smaller left aortic arch closes (left atretic arch) and the vascular tissue becomes a fibrous cord. Although in these cases a complete ring of two patent aortic arches is not present, the term ‘vascular ring’ is the accepted generic term even in these anomalies.

The symptoms are related to the compression of the trachea, esophagus or both by the complete vascular ring. Diagnosis can often be suspected or made by chest x-ray, barium esophagram, or echocardiography. Computed tomography (CT) or magnetic resonance imaging (MRI) show the relationship of the aortic arches to the trachea and esophagus and also the degree of tracheal narrowing. Bronchoscopy can be useful in internally assessing the degree of tracheomalacia. Treatment is surgical and is indicated in all symptomatic patients. In the current era the risk of mortality or significant morbidity after surgical division of the lesser arch is low. However, the preoperative degree of tracheomalacia has an important impact on postoperative recovery. In certain patients it may take several months (up to 1–2 years) for the obstructive respiratory symptoms (wheezing) to disappear.

People with visible marks generally feel fine (physically) and can act normally, but when it is mentioned, they may become withdrawn and self-conscious. Some children may have low self-esteem due to the condition.

CMTC is an uncommon, sporadic congenital vascular malformation characterized by a generalized or localized reticulated cutaneous vascular network.

Cutaneous lesions described in patients with CMTC include nevus flammeus, hemangioma, nevus anemicus, café-au-lait spots, melanocytic nevus, aplasia cutis and acral cyanosis.

It has a marbled bluish to deep-purple appearance. The dark skin lesions often show a palpable loss of dermal substance. The reticulated mottling frequently appears more prominent in a cold environment (physiologic cutis marmorata), but tends not to disappear with warming. Hence, the erythema may be worsened by cooling, physical activity, or crying.

CMTC frequently involves the extremities, with the lower extremities involved most commonly, followed by the upper extremities, and then the trunk and face. The lower extremities often show atrophy and seldom show hypertrophy resulting in limb circumference discrepancy.

When located on the trunk, the lesions of CMTC tend to show mosaic distribution in streaks with a sharp midline demarcation seen across the abdomen. The lesions are primarily localized, but can be segmental or generalized, often unilateral in appearance. Diffuse involvement of the skin is usually not observed.

Although its course is variable, the majority of lesions in mild cases fade by adolescence. Ulceration and secondary infection are complications in severe cases and can be fatal if present in the neonatal period.

Symptoms are caused by vascular compression of the airway, esophagus or both. Presentation is often within the first month (neonatal period) and usually within the first 6 months of life. Starting at birth an inspiratory and expiratory stridor (high pitch noise from turbulent airflow in trachea) may be present often in combination with an expiratory wheeze. The severity of the stridor may depend on the patient’s body position. It can be worse when the baby is lying on his back rather than its side. Sometimes the stridor can be relieved by extending the neck (lifting the chin up). Parents may notice that the baby’s cry is hoarse and the breathing noisy. Frequently a persistent cough is present. When the airway obstruction is significant there may be episodes of severe cyanosis (“blue baby”) that can lead to unconsciousness. Recurrent respiratory infections are common and secondary pulmonary secretions can further increase the airway obstruction.

Secondary to compression of the esophagus babies often feed poorly. They may have difficulties in swallowing liquids with choking or regurgitating and increased respiratory obstruction during feeding. Older patients might refuse to take solid food, although most infants with severe symptoms nowadays are operated upon before they are offered solid food.

Occasionally patients with double aortic arches present late (during later childhood or adulthood). Symptoms may mimic asthma.

Aberrant subclavian artery, or aberrant subclavian artery syndrome, is a rare anatomical variant of the origin of the right or left subclavian artery. This abnormality is the most common congenital vascular anomaly of the aortic arch, occurring in approximately 1% of individuals.

The signs and symptoms of diastematomyelia may appear at any time of life, although the diagnosis is usually made in childhood. Cutaneous lesions (or stigmata), such as a hairy patch, dimple, Hemangioma, subcutaneous mass, Lipoma or Teratoma override the affected area of the spine is found in more than half of cases. Neurological symptoms are nonspecific, indistinguishable from other causes of cord tethering. The symptoms are caused by tissue attachments that limit the movement of the spinal cord within the spinal column. These attachments cause an abnormal stretching of the spinal cord.

The course of the disorder is progressive. In children, symptoms may include the "stigmata" mentioned above and/or foot and spinal deformities; weakness in the legs; low back pain; scoliosis; and incontinence. In adulthood, the signs and symptoms often include progressive sensory and motor problems and loss of bowel and bladder control. This delayed presentation of symptoms is related to the degree of strain placed on the spinal cord over time.

Tethered spinal cord syndrome appears to be the result of improper growth of the neural tube during fetal development, and is closely linked to spina bifida.

Tethering may also develop after spinal cord injury and scar tissue can block the flow of fluids around the spinal cord. Fluid pressure may cause cysts to form in the spinal cord, a condition called syringomyelia. This can lead to additional loss of movement, feeling or the onset of pain or autonomic symptoms.

Cervical diastematomyelia can become symptomatic as a result of acute trauma, and can cause major neurological deficits, like hemiparesis, to result from otherwise mild trauma.

The following definitions may help to understand some of the related entities:

- Diastematomyelia (di·a·stem·a·to·my·elia) is a congenital anomaly, often associated with spina bifida, in which the spinal cord is split into halves by a bony spicule or fibrous band, each half being surrounded by a dural sac.

- Myeloschisis (my·elos·chi·sis) is a developmental anomaly characterized by a cleft spinal cord, owing to failure of the neural plate to form a complete neural tube or to rupture of the neural tube after closure.

- Diplomyelia (diplo.my.elia) is a true duplication of spinal cord in which these are two dural sacs with two pairs of anterior and posterior nerve roots.

This condition is usually asymptomatic. The aberrant artery usually arises just distal to the left subclavian artery and crosses in the posterior part of the mediastinum on its way to the right upper extremity. In 80% of individuals it crosses behind the esophagus. Such course of this aberrant vessel may cause a vascular ring around the trachea and esophagus.

Dysphagia due to an aberrant right subclavian artery is termed dysphagia lusoria, although this is a rare complication. In addition to dysphagia, aberrant right subclavian artery may cause stridor, dyspnoea, chest pain, or fever. An aberrant right subclavian artery may compress the recurrent laryngeal nerve causing a palsy of that nerve, which is termed Ortner's syndrome.

The aberrant right subclavian artery frequently arises from a dilated segment of the proximal descending aorta, the so-called Diverticulum of Kommerell (which was named for the German Radiologist, Burkhard Friedrich Kommerell (1901–1990), who discovered it in 1936). It is alternatively known as a lusorian artery.

During the first few weeks after birth, when the lesions are not very reticulated, CMTC may look very similar to vascular lesions such as port-wine stains. However, during follow-up, CMTC lesions become characteristic in their appearance. They must be differentiated from other causes of persistent reticulated vascular lesions, such as those in the following table:

Adult presentation in diastematomyelia is unusual. With modern imaging techniques, various types of spinal dysraphism are being diagnosed in adults with increasing frequency. The commonest location of the lesion is at first to third lumbar vertebrae. Lumbosacral adult diastematomyelia is even rarer. Bony malformations and dysplasias are generally recognized on plain x-rays. MRI scanning is often the first choice of screening and diagnosis. MRI generally give adequate analysis of the spinal cord deformities although it has some limitations in giving detailed bone anatomy. Combined myelographic and post-myelographic CT scan is the most effective diagnostic tool in demonstrating the detailed bone, intradural and extradural pathological anatomy of the affected and adjacent spinal canal levels and of the bony spur.

Prenatal ultrasound diagnosis of this anomaly is usually possible in the early to mid third-trimester. An extra posterior echogenic focus between the fetal spinal laminae is seen with splaying of the posterior elements, thus allowing for early surgical intervention and have a favorable prognosis. Prenate ultrasound could also detect whether the diastematomyelia is isolated, with the skin intact or association with any serious neural tube defects. Progressive neurological lesions may result from the "tethering cord syndrome" (fixation of the spinal cord) by the diastematomyelia phenomenon or any of the associated disorders such as myelodysplasia, dysraphia of the spinal cord.

Usually the cerebellum and brain stem are formed normally, although in some cases the cerebellum may also be absent. An infant with hydranencephaly may appear normal at birth or may have some distortion of the skull and upper facial features due to fluid pressure inside the skull. The infant's head size and spontaneous reflexes such as sucking, swallowing, crying, and moving the arms and legs may all seem normal, depending on the severity of the condition. However, after a few weeks the infant sometimes becomes irritable and has increased muscle tone (hypertonia). After several months of life, seizures and hydrocephalus may develop, if they did not exist at birth. Other symptoms may include visual impairment, lack of growth, deafness, blindness, spastic quadriparesis (paralysis), and intellectual deficits.

Some infants may have additional abnormalities at birth including seizures, myoclonus (involuntary sudden, rapid jerks), limited thermoregulation abilities, and respiratory problems.

Still other infants display no obvious symptoms at birth, going many months without a confirmed diagnosis of hydranencephaly. In some cases a severe hydrocephalus, or other cephalic condition, is misdiagnosed.

Congenital vertebral anomalies are a collection of malformations of the spine. Most around 85% are not clinically significant, but they can cause compression of the spinal cord by deforming the vertebral canal or causing instability. This condition occurs in the womb. Congenital vertebral anomalies include alterations of the shape and number of vertebrae.

Local gigantism or localised gigantism is a condition in which a certain part of the body acquires larger than normal size due to excessive growth of the anatomical structures or abnormal accumulation of substances. It is more common in fingers and toes, where it is termed macrodactyly. However, sometimes an entire limb may be enlarged.

Anomalous left coronary artery from the pulmonary artery (ALCAPA or Bland-White-Garland syndrome or White-Garland syndrome) is a rare congenital anomaly in which the left coronary artery (LCA) branches off the pulmonary artery instead of the aortic sinus. After birth, the pressure in other coronary arteries (namely the RCA) will have a pressure that exceeds the LCA and collateral circulation will increase. This, ultimately, can lead to blood flowing from the RCA into the LCA (retrograde) and into the pulmonary artery, thus forming a left-to-right shunt.

The syndrome is named for Edward Franklin Bland, Paul Dudley White, and Joseph Garland.

When a patient has multiple abnormalities (multiple anomaly, multiple deformity), they have a congenital abnormality that can not be primarily identified with a single system of the body or single disease process. Most medical conditions can have systemic sequelae, but multiple abnormalities occur when the effects on multiple systems is immediately obvious.

Midline cervical clefts are a rare congenital anomaly resulting from incomplete fusion during embryogenesis of the first and second branchial arches in the ventral midline of the neck. The condition presents as a midline cutaneous defect of the anterior neck with a skin projection or sinus, or as a subcutaneous erythematous fibrous cord. Surgical excision is the preferred treatment.

A capillary hemangioma (also known as an Infantile hemangioma, Strawberry hemangioma, and Strawberry nevus) is the most common variant of hemangioma which appears as a raised, red, lumpy area of flesh anywhere on the body, though 83% occur on the head or neck area. These marks occur in about 10% of all births, and usually appear between one and four weeks after birth. It may grow rapidly, before stopping and slowly fading. Some are gone by the age of 2, about 60% by 5 years, and 90–95% by 9 years. Capillary hemangioma is a vascular anomaly.

Capillary hemangiomas occur 5 times more often in female infants than in males, and mostly in Caucasian populations. Additionally, low birthweight infants have a 26% chance of developing a hemangioma.

It is the most common tumor of orbit and periorbital areas in childhood. It may occur in the skin, subcutaneous tissues and mucous membranes of oral cavities and lips as well as in the liver, spleen and kidneys. While this birthmark may be alarming in appearance, physicians generally counsel that it be left to disappear on its own, unless it is in the way of vision or blocking the nostrils.