Testing for a malformed vein of Galen is indicated when a patient has heart failure which has no obvious cause. Diagnosis is generally achieved by signs such as cranial bruits and symptoms such as expanded facial veins. The vein of Galen can be visualized using ultrasound or Doppler. A malformed Great Cerebral Vein will be noticeably enlarged. Ultrasound is a particularly useful tool for vein of Galen malformations because so many cases occur in infancy and ultrasound can make diagnoses prenatally. Many cases are diagnosed only during autopsy as congestive heart failure occurs very early.

Vein of Galen aneurysmal malformations (VGAM) and Vein of Galen aneurysmal dilations (VGAD) are the most frequent arteriovenous malformations in infants and fetuses. VGAM consist of a tangled mass of dilated vessels supplied by an enlarged artery. The malformation increases greatly in size with age, although the mechanism of the increase is unknown. Dilation of the great cerebral vein of Galen is a secondary result of the force of arterial blood either directly from an artery via an arteriovenous fistula or by way of a tributary vein that receives the blood directly from an artery. There is usually a venous anomaly downstream from the draining vein that, together with the high blood flow into the great cerebral vein of Galen causes its dilation. The right sided cardiac chambers and pulmonary arteries also develop mild to severe dilation.

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.

The most common signs/symptoms of DAVFs are:

1. Pulsatile tinnitus

2. Occipital bruit

3. Headache

4. Visual impairment

5. Papilledema

Pulsatile tinnitus is the most common symptom in patients, and it is associated with transverse-sigmoid sinus DAVFs. Carotid-cavernous DAVFs, on the other hand, are more closely associated with pulsatile exophthalmos. DAVFs may also be asymptomatic (e.g. cavernous sinus DAVFs).

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.

Just like berry aneurysm, an intracerebral arteriovenous fistula can rupture causing subarachnoid hemorrhage.

An arteriovenous fistula is an abnormal connection or passageway between an artery and a vein. It may be congenital, surgically created for hemodialysis treatments, or acquired due to pathologic process, such as trauma or erosion of an arterial aneurysm.

Most commonly found adjacent to dural sinuses in the following locations:

1. Transverse (lateral) sinus, left-sided slightly more common than right

2. Intratentorial

3. From the posterior cavernous sinus, usually draining to the transverse or sigmoid sinuses

4. Vertebral artery (posterior meningeal branch)

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.

Major symptoms of PWS include:

Birthmarks: Effected PWS patients suffer from large, flat, pink staining on the skin. This staining is a result of the capillary malformations that have the tendency to increase the blood flow near the surface of the skin causing the staining. Because of the staining color they are sometimes referred to as “port-wine stains”. “Port-wine stain” or discoloration of the skin due to vascular malformation is also referred as Nevus flammeus.

Hypertrophy: Hypertrophy refers to excessive growth of the bone and soft tissue. In PWS patients a limb is overgrown and hypertrophy is usually seen in the affected limb.

Multiple arteriovenous fistulas: PWS patients also suffer from multiple AVFs that occur in conjunction with capillary malformations. AVFs occur because of abnormal connections between arteries and veins. Normally, blood flows from arteries to capillaries then to veins. But for AFV patients, because of the abnormal artery and vein connections, blood flows directly from arteries into the veins completely bypassing the capillaries. These irregular connections affect the blood circulation and may lead to life-threatening complications such as abnormal bleeding and heart failure. AVFs can be identified by: large, purplish bulging veins, swelling in limbs, decreased in blood pressure, fatigue and heart failure.

Capillary arteriovenous malformations: Vascular system disorder is the cause of the capillary malformations. Here, the capillaries are enlarged and increase the blood flow towards the surface of the skin. Because of the capillary malformations, the skin has multiple small, round, pink or even red dots. For most of the affected individuals, these malformations occur on the face, arms and or legs. The spots may be visible right from birth itself or they may develop during childhood years. If capillary malformations occur by themselves, it is not a huge threat to life. But when these occur in conjunction with AVFs then it is a clear indicator of PWS and may be serious depending on the severity of the malformations.

The Human Phenotype Ontology (HPO) reports of additional symptoms in PWS patients. HPO is an active database that collects and researches on the relationships between phenotypic abnormalities and biochemical networks. This is an useful database as it has information and data on some of the rarest diseases such as PWS. According to HPO, the symptoms which are reported very frequently in PWS patients include: abnormal bleeding, hypertrophy of the lower limb, hypertrophy of the upper limb, nevus flammeus or staining of the skin, peripheral arteriovenous fistula, telangiectasia of the skin. Frequent to occasional symptoms include: varicose veins, congestive heart failure, glaucoma and headache.

Abnormal bleeding: some skin lesions are prone to bleed easily.

Peripheral arteriovenous fistula: abnormal communication between artery and vein that is a direct result of the abnormal connection or wiring between the artery and vein.

Telangiectasia of the skin: Telangiectasia is a condition where tiny blood vessels become widened and form threadlike red lines and or patterns on the skin. Because of their appearance and formation of web-like patterns they are also known as spider veins. These patterns are referred as telangiectases.

Varicose veins: Enlarged, swollen and twisted veins.

Congestive heart failure: This is a condition in which the heart’s ability to meet the requirements of the body is diminished. The cardiac output is decreased and the amount of blood pumped is not adequate enough to keep the circulation from the body and lungs going.

Glaucoma: Glaucoma is a combination of diseases that cause damage to the optic nerve and may result in vision loss and blindness.

Headache: pain in the head.

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.

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.

Occasionally, there is only the one single umbilical artery (SUA) present in the umbilical cord. Approximately this affects between 1 in 100 and 1 in 500 pregnancies, making it the most common umbilical abnormality. It is more common in multiple births. Its cause is not known.

Most cords have one vein and two arteries. The vein carries oxygenated blood from the placenta to the baby and the arteries carry deoxygenated blood from the baby to the placenta. In approximately 1% of pregnancies there are only two vessels —usually a single vein and single artery. In about 75% of those cases, the baby is entirely normal and healthy and the missing artery isn't missed at all. One artery can support a pregnancy and does not necessarily indicate problems. For the other 25%, a 2-vessel cord is a sign that the baby has other abnormalities—sometimes life-threatening and sometimes not. SUA does increase the risk of the baby having cardiac, skeletal, intestinal or renal problems. Babies with SUA may have a higher likelihood of having other congenital abnormalities, especially of the heart. However, additional testing (high level ultrasound scans) can rule out many of these abnormalities prior to birth and alleviate parental anxiety. Echocardiograms of the fetus may be advised to ensure the heart is functioning properly. Genetic counseling may be useful, too, especially when weighing the pros and cons of more invasive procedures such as chorionic villus sampling and amniocentesis.

Although the presence of an SUA is a risk factor for additional complications, most fetuses with the condition will not experience other problems, either in utero or after birth. Especially encouraging are cases in which no other soft markers for congenital abnormalities are visible via ultrasound. Prior to ultrasound technology, the only method for determining the presence of a SUA was at birth, following an examination of the placenta. Given that the vast majority of expectant mothers do not receive the kind of advanced ultrasound scanning required to confirm SUA in utero, most cases may never be detected antenatally even today.

Doctors and midwives often suggest parents take the added precaution of having regular growth scans near term to rule out intrauterine growth restriction, which can happen on occasion and warrant intervention. Yet the majority of growth restricted infants with the abnormality also have other defects. Finally, neonates with the finding may also have a higher occurrence of renal problems, therefore close examination of the infant may be warranted shortly after birth. Among SUA infants, there is a slightly elevated risk for post-natal urinary infections.

It may be associated with Edwards syndrome.

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.

Pulmonary vein stenosis is a rare cardiovascular disorder. It is recognized as being the stenosis of one or more of the four pulmonary veins that return blood from the lungs to the left atrium of the heart. In congenital cases, it is associated with poor prognosis and high mortality rate. In some people, pulmonary vein stenosis occurs after pulmonary vein ablation for the treatment of atrial fibrillation. Some recent research has indicated that it may be genetically linked in congenital cases.

Symptoms can occur when the aneurysm pushes on a structure in the brain. Symptoms will depend on whether an aneurysm has ruptured or not. There may be no symptoms present at all until the aneurysm ruptures. For an aneurysm that has not ruptured the following symptoms can occur:

- Fatigue

- Loss of perception

- Loss of balance

- Speech problems

- Double vision

For a ruptured aneurysm, symptoms of a subarachnoid hemorrhage may present:

- Severe headaches

- Loss of vision

- Double vision

- Neck pain or stiffness

- Pain above or behind the eyes

NCS is associated with hematuria (which can lead to anemia) and abdominal pain (classically left flank or pelvic pain).

Since the left gonadal vein drains via the left renal vein it can also result in left testicular pain in men or left lower quadrant pain in women. Nausea and vomiting can result due to compression of the splanchnic veins. An unusual manifestation of NCS includes varicocele formation and varicose veins in the lower limbs. Another clinical study has shown that nutcracker syndrome is a frequent finding in varicocele-affected patients and possibly, nutcracker syndrome should be routinely excluded as a possible cause of varicocele and pelvic congestion.

Aneurysm presentation may range from life-threatening complications of hypovolemic shock to being found incidentally on X-ray. Symptoms will differ by the site of the aneurysm and can include:

The nutcracker syndrome (NCS) results most commonly from the compression of the left renal vein between the abdominal aorta (AA) and superior mesenteric artery (SMA), although other variants exist. The name derives from the fact that, in the sagittal plane and/or transverse plane, the SMA and AA (with some imagination) appear to be a nutcracker crushing a nut (the renal vein).

There is a wide spectrum of clinical presentations and diagnostic criteria are not well defined, which frequently results in delayed or incorrect diagnosis.

This condition is not to be confused with superior mesenteric artery syndrome, which is the compression of the third portion of the duodenum by the SMA and the AA.

Parkes Weber Syndrome (PWS) is a congenital disorder of the vascular system. It is an extremely rare disease with only 0.3% of the world's population known to have this syndrome. In 1907, a British dermatologist, Frederick Parkes Weber first described this syndrome and hence this disease was named Parkes Weber Syndrome. In the body, vascular system consists of arteries, veins and capillaries. When abnormalities such as: vascular malformation, capillary arteriovenous malformations (AVMs), arteriovenous fistulas (AVFs) and overgrowth of a limb occur together in combination and disturb the complex network of blood vessels of the vascular system -it is known as PWS. The capillary malformations and AVFs are known to be present from the birth. In some cases PWS is a genetic condition where RASA1 gene is mutated and displays autosomal dominant inheritance pattern. If PWS is genetic then most patients show multiple capillary malformations. Patients that do not have multiple capillary malformations most likely did not inherit PWS and do not have RASA1 mutations. In such cases the cause of PWS is often unknown and is sporadic as most cases often are.

Often times PWS is mixed up with Klippel–Trénaunay syndrome (KTS). These two diseases are similar but they are not quite the same. PWS occurs because of vascular malformation that may or may not be because of genetic mutations, where as Klippel-Trenaunay syndrome is a condition in which blood vessels and or lymph vessels do not form properly. PWS and KTS almost have the same symptoms except PWS patients are seen with both AVMs and AVFs occur together along with lymph hypertrophy.

Vascular occlusion is a blockage of a blood vessel, usually with a clot. It differs from thrombosis in that it can be used to describe any form of blockage, not just one formed by a clot. When it occurs in a major vein, it can, in some cases, cause deep vein thrombosis. The condition is also relatively common in the retina, and can cause partial or total loss of vision. An occlusion can often be diagnosed using Doppler sonography (a form of ultrasound).

Some medical procedures, such as embolisation, involve occluding a blood vessel to treat a particular condition. This can be to reduce pressure on aneurysms (weakened blood vessels) or to restrict a haemorrhage. It can also be used to reduce blood supply to tumours or growths in the body, and therefore restrict their development. Occlusion can be carried out using a ligature; by implanting small coils which stimulate the formation of clots; or, particularly in the case of cerebral aneurysms, by clipping.

In medicine, May-Thurner syndrome (MTS), also known as the iliac vein compression syndrome, is a rare condition in which compression of the common venous outflow tract of the left lower extremity may cause discomfort, swelling, pain or blood clots, called deep venous thrombosis (DVT), in the iliofemoral vein.

The specific problem is compression of the left common iliac vein by the overlying right common iliac artery. This leads to pooling or stasis of blood, predisposing the individual to the formation of blood clots. Uncommon variations of MTS have been described, such as the right common iliac vein getting compressed by the right common iliac artery.

In the 21st century the May-Thurner syndrome definition has been expanded to a broader disease profile known as nonthrombotic iliac vein lesions (NIVL) which can involve both the right and left iliac veins as well as multiple other named venous segments. This syndrome frequently manifests as pain when the limb is dependent (hanging down the edge of a bed/chair) and/or significant swelling of the whole limb.

May-Thurner syndrome (MTS) is thought to represent between two and five percent of lower-extremity venous disorders. May-Thurner syndrome is often unrecognized; however, current estimates are that this condition is three times more common in women than in men. The classic syndrome typically presents in the second to fourth decades of life. In the 21st century in a broader disease profile, the syndrome acts as a permissive lesion and becomes symptomatic when something else happens such as, following trauma, a change in functional status such as swelling following orthopaedic joint replacement.

It is important to consider May-Thurner syndrome in patients who have no other obvious reason for hypercoagulability and who present with left lower extremity thrombosis. To rule out other causes for hypercoagulation, it may be appropriate to check the antithrombin, protein C, protein S, factor V Leiden, and prothrombin G20210A.

Venography will demonstrate the classical syndrome when causing deep venous thrombosis.

May-Thurner syndrome in the broader disease profile known as nonthrombotic iliac vein lesions (NIVLs) exists in the symptomatic ambulatory patient and these lesions are usually not seen by venography. Morphologically, intravascular ultrasound (IVUS) has emerged as the best current tool in the broader sense. Functional testing such as duplex ultrasound, venous and interstitial pressure measurement and plethysmography may sometimes be beneficial. Compression of the left common iliac vein may be seen on pelvic CT.

Arteriovenous malformations (AVMs, larger vascular malformations) occur in larger organs, predominantly the lungs (50%), liver (30–70%) and the brain (cerebral AVMs, 10%), with a very small proportion (<1%) having AVMs in the spinal cord.

Vascular malformations in the lungs may cause a number of problems. The lungs normally "filter out" bacteria and blood clots from the bloodstream; AVMs bypass the capillary network of the lungs and allow these to migrate to the brain, where bacteria may cause a brain abscess and blood clots may lead to stroke. HHT is the most common cause of lung AVMs: out of all people found to have lung AVMs, 70–80% are due to HHT. Bleeding from lung AVMs is relatively unusual, but may cause hemoptysis (coughing up blood) or hemothorax (blood accumulating in the chest cavity). Large vascular malformations in the lung allow oxygen-depleted blood from the right ventricle to bypass the alveoli, meaning that this blood does not have an opportunity to absorb fresh oxygen. This may lead to breathlessness. Large AVMs may lead to platypnea, difficulty in breathing that is more marked when sitting up compared to lying down; this probably reflects changes in blood flow associated with positioning. Very large AVMs cause a marked inability to absorb oxygen, which may be noted by cyanosis (bluish discoloration of the lips and skin), clubbing of the fingernails (often encountered in chronically low oxygen levels), and a humming noise over the affected part of the lung detectable by stethoscope.

The symptoms produced by AVMs in the liver depend on the type of abnormal connection that they form between blood vessels. If the connection is between arteries and veins, a large amount of blood bypasses the body's organs, for which the heart compensates by increasing the cardiac output. Eventually congestive cardiac failure develops ("high-output cardiac failure"), with breathlessness and leg swelling among other problems. If the AVM creates a connection between the portal vein and the blood vessels of the liver, the result may be portal hypertension (increased portal vein pressure), in which collateral blood vessels form in the esophagus (esophageal varices), which may bleed violently; furthermore, the increased pressure may give rise to fluid accumulation in the abdominal cavity (ascites). If the flow in the AVM is in the other direction, portal venous blood flows directly into the veins rather than running through the liver; this may lead to hepatic encephalopathy (confusion due to portal waste products irritating the brain). Rarely, the bile ducts are deprived of blood, leading to severe cholangitis (inflammation of the bile ducts). Liver AVMs are detectable in over 70% of people with HHT, but only 10% experience problems as a result.

In the brain, AVMs occasionally exert pressure, leading to headaches. They may also increase the risk of seizures, as would any abnormal tissue in the brain. Finally, hemorrhage from an AVM may lead to intracerebral hemorrhage (bleeding into the brain), which causes any of the symptoms of stroke such as weakness in part of the body or difficulty speaking. If the bleeding occurs into the subarachnoid space (subarachnoid hemorrhage), there is usually a severe, sudden headache and decreased level of consciousness and often weakness in part of the body.

The following features are observed with VACTERL association:

- V - Vertebral anomalies

- A - Anorectal malformations

- C - Cardiovascular anomalies

- T - Tracheoesophageal fistula

- E - Esophageal atresia

- R - Renal (Kidney) and/or radial anomalies

- L - Limb defects

Although it was not conclusive whether VACTERL should be defined by at least two or three component defects, it is typically defined by the presence of at least three of the above congenital malformations.