An arteriovenous malformation (AVM) is a congenital (present from birth) disorder characterised by a complex, tangled web of arteries and veins that develop anywhere in your body but occurs most often in the brain or spine. The arteries are responsible for taking oxygen-rich blood from the heart to the brain. Veins carry the oxygen-depleted blood back to the lungs and heart. A brain AVM disrupts this vital process. An AVM may have several forms, such as a direct connection between an artery and vein, an AV fistula. Unusual formations of veins which bleed and cause seizures are cavernous angiomas. Abnormalities of very small vessels are capillary angiomas. The most important (and dangerous) are AVM’s which have both arterial and venous components. These AVM’s have a 3 to 4 percent chance of spontaneous haemorrhage each year. Roughly 10 percent of the haemorrhages will be fatal and about 15 percent of victims will suffer a continuing neurological deficit, such as weakness, sensory or visual loss, speech abnormality, etc.
Symptoms of AVM’s
They may cause symptoms such as seizure, headache or progressive neurological deficits. Most importantly they can spontaneously bleed resulting in a stroke with lasting neurological problems or even death.
What are the causes?
We don’t know why AVMs occur. Brain AVMs are usually congenital, meaning someone is born with one. But they’re usually not hereditary. People probably don’t inherit an AVM from their parents, and they probably won’t pass one on to their children. AVMs are almost always congenital (present at birth), although they are often not very obvious at birth.There is no evidence to suggest that AVMs are the result of something you did or did not do.
How common are AVMs?
Brain AVMs occur in less than 1 percent of the general population and the incidence of all types of AVM taken together is thought to be approximately 1.4 in every 100,000.
Some people with brain AVMs experience signs and symptoms, such as headache or seizures. AVMs are commonly found after a brain scan for another health issue or after the blood vessels rupture and cause bleeding in the brain (hemorrhage). Most AVMs are detected with either a computed tomography (CT) brain scan or a magnetic resonance imaging (MRI) brain scan. These tests are very good at detecting brain AVMs. They also provide information about the location and size of the AVM and whether it may have bled. A doctor may also perform a cerebral angiogram.
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