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Venous Angioma

Developmental Venous Anomalies (Venous Angiomas) and Their Potential Relationship to Cerebral Cavernous Malformations

While great strides have been made in the understanding and treatment of cerebral cavernous malformations (CCM), the creation mechanism behind these lesions remains poorly understood. In the same vein (pun intended), another lesion called a venous angioma (a.k.a. developmental venous anomaly or DVA) has received increased scrutiny in recent years. Even though the neurosurgical community has categorized DVAs as benign lesions, there are burgeoning concerns that DVAs may be involved in the genesis or growth of cerebral cavernous malformations and other brain lesions such as arteriovenous malformations (AVM).

 

Definition, Incidence Rate, Function, Diagnosis, and Treatment

A DVA is a radial arrangement of veins usually draining into one slightly enlarged, main or central vein. Sometimes you will hear the descriptive term “caput medusae” (Latin for “head of Medusa”) used to describe this feature, since the vein pattern resembles the snakes of hair from the Medusa character of Greek mythology. DVAs have the highest prevalence rate (over 60%) of all intracranial vascular malformations.[1] They may appear anywhere in the body. Like CCMs, multiple DVAs may exist within the same individual. It is thought that one person in fifty has at least one DVA.

The brain’s venous network acts as a conduit to drain blood from the brain so that this blood can be re-oxygenated by the lungs. Even though DVAs are anomalous structures, they are fully integrated with the body’s venous system and provide the brain with normal blood drainage function.

Diagnosis is either via an incidental finding during imaging of other lesions, or during autopsy. Conventional computed tomograms (CTs) may not always document DVAs sufficiently, although newer high resolution CT scans with thin cuts and contract enhancement, and CT angiogram (CTA) reconstructions can image these lesions, as well as MRI/MRA and conventional angiograms. With these non-invasive modalities, the vast majority of suspected DVAs should not be subjected to the risk of catheter angiography, except in rare instances where a true AVM may be suspected clinically

The generally passive nature of DVAs requires an expectant course of management. Because these anomalies provide a useful and important blood draining function, in no case should they be excised or radiated. Doing so during surgery, either by accident or intent, has resulted in venous infarction and patient death. This includes those instances of CCM resection in association with a DVA. While the CCM can be safely removed, the DVA must remain undisturbed. Both clinical and radiographic information must be integrated when considering diagnosis and treatment of mixed vascular malformation such as DVA-CCM.[2]

 

DVA Implications for Other Lesions

Neurosurgeons classify DVAs as benign lesions because they normally do not present with any clinical symptoms during one’s lifespan. However, there are a few case studies that point to potential DVA-associated hemorrhage due to blockage or narrowing of the structure’s drainage channel, causing a transient rise in pressure within the draining veins [3] Whether or not the hemorrhage originated from the DVA or from an associated, poorly visualized (or post-hemorrhage obliterated) CCM or AVM remains controversial.

The most sinister aspect of DVAs is their potential role in the genesis of other types of vascular malformations that cause clinical symptoms. The literature has documented DVA association in conjunction with other malformations such as CCMs or AVMs.[4] With the recent advent of higher resolution imaging techniques, this association has become a more common finding.[5] Solitary non-familial CCMs are much more likely associated with DVA than multifocal familial CCMs, but few other differences in clinical profile are evident otherwise.[6] Once again, the importance of using gradient-echo MRI sequences as a diagnostic tool to identify punctate CCMs adjacent to DVAs cannot be over-emphasized.

A similar line of reasoning to the above DVA bleed theory has been postulated for the formation of CCMs in association with DVAs. Basically, obstruction or stenosis of the draining vein alters blood flow and venous pressure, somehow inducing an adjacent CCM. Since CCMs communicate freely with the venous system, anything that negatively affects venous system pressure or drainage can have dire consequences for the CCM itself.[7] Again, this is a generally accepted theory that has not been definitively proven.

This CCM inducement theory reinforced the medical community’s recent discounting of the congenital nature of CCM formation. Instead it is now widely acknowledged that CCMs can develop in a “de novo” fashion. Pre and post radiation treatment MRI sequences confirm that CCM’s do indeed develop where previously no CCM had been present. The exact mechanism leading to CCM formation has not been found, so until proven otherwise, the DVA-CCM link will continue to garner great interest.

 

References

[1] Ciricillo SF, Dillon WP, Fink ME, et al: Progression of multiple cryptic vascular malformations associated with anomalous venous drainage. Case report. J Neurosurg 81:477--481, 1994.

[2] Robinson JR Jr, Awad IA, Masaryk TJ, et al: Pathological heterogeneity of angiographically occult vascular malformations of the brain. Neurosurgery 33:547–555, 1993.

[3] Field LR, Russell E. Spontaneous hemorrhage from a cerebral venous malformation related to thrombosis of the central draining vein: demonstration with angiography and serial MR. AJNR AmJ Neuroradiol 1995;16:1885–1888.

[4] Abe T, Singer RJ, Marks MP, Norbash AM, Crowley RS, Steinberg GK. Coexistence of occult vascular malformations and developmental venous anomalies in the central nervous system: MR evaluation. American Journal of Neuroradiology 19:51-57, 1998.

[5] Maeder P, Gudinchet F, Meuli R, de Tribolet N, Development of a cavernous malformation of the brain. Am J Neuroradiol 19, pp. 1141-1145, 1998.

[6] Abdulrauf SI, Keynar M and Awad IA. A comparison of the clinical profile of cavernous malformations with and without associated venous malformations. Neurosurgery 44: 41-47, 1999.

[7] Little JR, Awad IA, Jones SC, Ebrahim ZY. Vascular pressures and cortical blood flow in cavernous angioma of the brain. Journal of Neurosurgery. 73(4): 555-9, Oct 1990.


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