Contents of This Section:

1. What is a venous angioma (Developmental Venous Anomaly, DVA)?
2. How common are venous angiomas?
3. Why do venous angiomas develop?
4. What are the symptoms of venous angiomas?
5. More about venous angioma hemorrhage.
6. What are the complications of venous angiomas?
7. How are venous angiomas detected?
8. How are venous angiomas treated?
9. Radiological images of a venous angioma.

1. What is a venous angioma (Developmental Venous Anomaly, DVA)?

A venous angioma, also referred to as a "developmental venous anomaly" (DVA) or sometimes "venous malformation" is basically an extreme variation of veins draining normal brain tissue in that region. That is, a venous angioma (DVA) by itself is not necessarily "abnormal"; it's rather a variation of normal. However, having stated this, it should be noted that some studies have found that some veins (or all veins) that comprise a venous angioma have structural abnormalities compared with more normal veins. Regardless, most neurosurgeons regard venous angiomas by themselves as extreme variations of normal venous drainage.

The veins that comprise a venous angioma usually form a little cluster ("star burst" or "caput Medusae" - looks like a "head of snakes"), and these veins generally drain into a larger "collector" vein. The collector vein is usually on the surface of the brain, but sometimes there may be deep drainage too. The pattern (arrangement) of these veins is frequently simple, but may at times be more complex looking. Between the veins that make us the venous angioma is normal brain tissue. Sometimes one or more of these veins can appear extra dilated and may be more thin walled than other veins in the brain. Venous angiomas tend to occur near the frontal horns of the ventricles (fluid filled spaces of the brain) and also in the cerebellum (small part of the brain at the lower back part of the head).

Importantly, venous angiomas are frequently associated with cavernous malformations (cavernomas) and it is through this association that trouble potentially arises ( take me to the section on Cavernomas now). Venous angiomas on their own don't tend to cause any trouble and, with few (reported) exceptions, should generally be left alone (see Section 8., below).

2. How common are venous angiomas?

The true prevalence of venous angiomas is not known, but autopsy series indicate that they are much more common than cavernous hemangiomas, aneurysms and arteriovenous malformations. The prevalence of venous angiomas (i.e., their presence at any one time in the general population) is probably somewhere between 5-10%; it is higher in imaging series compared with autopsy series. Venous angiomas therefore represent the most common blood vessel (vascular) "anomaly" in the central nervous system.

3. Why do venous angiomas develop?

There are no well established risk factors for venous angioma formation. They are thought to be nonhereditary (i.e., not inherited from your parents). Venous angiomas are considered "congenital anomalies", i.e., persons are born with these lesions, they don't simply "develop" these in later life. Some venous angiomas may themselves undergo evolutionary changes over the years that they are observed (i.e., the lesion itself changes radiologically, or in rare instances may have a second type of vascular anomaly develop in close proximity) but this is uncommon and it is therefore thought that most venous angiomas do not undergo any significant change at all. Most venous angiomas occur alone, while some are associated with other vascular malformations such as cavernous hemangiomas. Some venous angiomas occur in multiple sets within the brain (i.e., several of them may be found rather than just one, as in "blue rubber bleb nevus syndrome").

4. What are the symptoms of venous angiomas?

Alone, venous angiomas tend not to cause any symptoms. That is, the majority of venous angiomas are thought to remain dormant or silent throughout life. However, some do cause problems such as seizures or brain hemorrhage. Hemorrhage from these vessels, although very rare, can cause sudden onset of headache, associated with one or more of the following: nausea, vomiting, sleepiness ("somnolence" or "obtundation") and weakness in one or more limb(s), or some other neurological disability. They are typically not associated with chronic headaches or migraines, however, theoretically, one or more veins comprising the angioma can spontaneously "clot off" (thrombose), leading to local venous hypertension (back pressure buildup in the region's venous system) that can manifest as headache. Interestingly, if the venous angioma occurs in association with a cavernoma ( take me to the section on Cavernomas now), it is the cavernoma that usually causes a problem, and not the venous angioma.

5. More about brain venous angioma hemorrhage.

Hemorrhage from a venous angioma is a very rare event. It is more likely to occur if the venous angioma is associated with a cavernous hemangioma, and in such a setting, it is the cavernous hemangioma that usually bleeds, not the venous hemangioma ( take me to the section on Cavernomas now). If the venous angioma itself is thought to have bled, it is probable that one or more of abnormal-walled vein comprising the angioma ruptured. Again, this has been reported in the literature, but is rare.

6. What are the complications of venous angiomas?

As mentioned above, the two main complications (both relatively rare) are seizures and hemorrhage. It cannot be overstressed that most venous angiomas cause no complications whatsoever; some of course do.

7. How are venous angiomas detected?

Most venous angiomas are never detected unless the patient has a brain scan for another reason. This is because most venous angiomas cause no problems. They are best detected through cerebral angiography, but can also be seen in contrast-enhanced MRI scans and contrast-enhanced CAT scans, or in CT-angiography (CTA). Magnetic resonance angiography (MRA) is not a good way to look for venous angiomas because MRA looks at the arterial side of the circulation, not the venous side. Magnetic resonance venography (MRV) may pick up a venous angioma if it is not small. If there is hemorrhage associated with the venous angioma, regular (nonenhanced) CAT scans can usually detect the area of hemorrhage.

In general, an MRI with and without contrast is an excellent way through which a venous angioma can be detected. The multiple imaging sequences used in the MRI scan can show the venous angioma along with any other vascular abnormality. CT-angiography (CT) can also be carried out as an alternative, but is not as good at picking up a commonly associated vascular malformations such as cavernous hemangioma (cavernoma) if that cavernoma is small. If a venous angioma appears "complex", it may be worth considering formal cerebral angiography to exclude the possibility of another vascular lesion such as an arteriovenous malformation (AVM; take me to the section on AVMs now).

8. How are venous angiomas treated?

Most neurosurgeons agree that for most persons, venous angiomas should not be directly treated (i.e., one avoids venous angioma surgery or "radiation" whenever possible). However, this should be discussed with your surgeons and physicians. If the angioma is thought to be causing seizures, one approach is to make sure there is no underlying arteriovenous malformation and, if there is not, the seizures can be treated using conventional oral anti-seizure medications such as Phenytoin (Dilantin) or another equivalent agent. If the seizures are debilitating and not controlled medically, surgery can be carried out to remove the angioma. However, the main risk of surgery is venous stroke, as such lesions are thought to drain normal brain tissue. This is something that should be discussed in detail with your physicians. It is very important that other types of blood vessel abnormalities that may exist with (e.g., cavernoma) or mimic (e.g., AVM) venous angiomas are ruled out by appropriate consultation and investigation.

There is no effective radiation treatment (conventional or stereotactic) for venous angiomas, and as mentioned above, no treatment whatsoever is recommended for the vast majority of venous angiomas (there may be some exceptions).

Surgery can be carried out if the venous angioma is thought to have ruptured. At the time of surgery, a previously undetected cavernous malformation or AVM may be found. In surgeries for symptomatic or enlarging cavernous malformations (cavernomas) that have an associated venous angioma (this association is common), the venous angioma is not disturbed by the neurosurgeon, but the cavernoma is removed.

9. Radiological images of a venous angioma.

Top left: An axial MRI scan with contrast shows a typical appearance of a venous angioma/developmental venous anomaly (DVA; circled in red). This particular one is located in the left cerebellum. Bottom left: An MR arteriogram in the same patient failed to show the DVA (as expected) because the "anomaly" is venous not arterial. A normal loop of the posterior inferior cerebellar artery (PICA) is seen as expected. Right image: The same patient's coronal MRI scan with contrast shows the classic small cluster of tributary veins (TV) draining into a dilated collector vein (CV). There was no cavernous malformation associated with this particular DVA and it was asymptomatic (diagnosed "incidentally" while screening for another condition). Appropriately, no treatment was required or offered.