Vascular malformations are localized collections of blood vessels that are abnormal in structure or number, lead to altered blood flow, and are not cancerous (nonneoplastic). While it was originally believed that most vascular malformations are present at birth (congential), cavernous malformation lesions may develop throughout the lifetime of the affected individual. Other vascular malformations are not congenital, but are caused by trauma, radiation, or other injury to the spinal cord. Vascular malformations are typically classified by size, location, and type of change, with the four most common being capillary telangiectasias, cavernous malformations, venous malformations, and arteriovenous malformations.
Cavernous malformations are dilated blood vessels that are characterized by multiple distended "caverns" of blood-filled vasculature through which the blood flows very slowly. Vessels of a cavernous malformation lesion have a tendency to leak because they lack the proper junctions between neighboring cells as well as the necessary structural support from smooth muscle and stretchable material (elastin). Leakage (bleeding) from these vascular lesions is the underlying cause of clinical symptoms associated with the illness. Cavernous malformations are primarily located in the brain, but can also be found in the spinal cord, on the skin, and more rarely in the retina.
Cerebral cavernous malformations (CCMs) are usually located in the white matter (cortex) of the brain. CCM do not have brain tissue within the malformation like other lesions such as arteriovenous malformations, and they usually do not have defined borders (are not encapsulated). CCM are dynamic structures, changing in size and number over time and they can range in size from a few millimeters to several centimeters.
CCM are present in up to 0.5% of the general population, and they account for a large proportion (8-15%) of all brain and spinal vascular malformations. While the prevalence of individuals with at least one CCM lesion is quite high, as many as 40% of affected individual may never experience symptoms or become diagnosed with cavernous malformation. A majority of these cases are individuals with only a single lesion and no family history of the disease. (These cases are termed 'sporadic' and are not caused by an inherited genetic mutation). Individuals with the familial (genetic) form of cavernous malformation are likely to have multiple lesions and may be more likely to experience symptoms associated with the disorder. While adults are most often diagnosed with CCM, people of all ages may be affected by cavernous malformations, and approximately 25% of all diagnosed cavernous malformations are found in children.
CCM lesions are commonly associated with developmental venous anomalies (DVA) also called, venous malformations or venous angiomas. A DVA is a type of vascular malformation that, on its own, does not cause any clinical symptoms. However, when found in combination with a CCM lesion, the DVA complicates the option for surgical intervention because disturbing the DVA during surgery could cause dangerous bleeding. Association of CCMs with DVAs is uncommon in familial cavernous malformation; however, at least 40% of sporadic cavernous malformations may develop within the vicinity of a DVA. Rarely, multiple sporadic cavernous malformations are found nearby an associated DVA. The significance of DVA association with sporadic lesions is currently under investigation; perhaps this observation may suggest a difference in developmental mechanisms between sporadic and familial cavernous malformations.