An Arteriovenous Malformation (AVM) is an abnormal tangle of blood vessels where arteries and veins connect directly, bypassing normal tissues. These malformations usually develop before birth or shortly thereafter.
Essentially, instead of blood flowing from arteries to capillaries and then to veins, in an AVM, the blood rushes directly from arteries into veins. This can put the veins under high pressure and increase the risk of rupture. It also deprives the surrounding tissues of the normal blood supply delivered through the capillary network.
Here's a more detailed breakdown:
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Abnormal Connection: AVMs are characterized by an atypical connection between arteries and veins. Normally, arteries carry oxygen-rich blood from the heart to the body, and veins return oxygen-depleted blood to the heart. Capillaries, small blood vessels, connect the arteries and veins, allowing for nutrient and oxygen exchange. In an AVM, this capillary network is bypassed.
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Developmental Issue: These malformations usually arise during fetal development or shortly after birth. The exact cause remains unknown.
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Location: AVMs can occur in various parts of the body, but they are most common in the brain and spinal cord.
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Risk Factors: While AVMs are generally congenital (present at birth), some genetic conditions may increase the risk. However, most AVMs occur sporadically without a known cause.
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Symptoms: Symptoms vary depending on the AVM's location and size. Some AVMs may not cause any symptoms, while others can lead to serious complications such as:
- Headaches
- Seizures
- Hemorrhage (bleeding)
- Neurological deficits (weakness, numbness, speech difficulties)
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Diagnosis: AVMs are typically diagnosed using imaging techniques such as:
- Magnetic Resonance Imaging (MRI)
- Computed Tomography (CT) Scan
- Angiography
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Treatment: Treatment options depend on the size, location, and symptoms of the AVM. Options include:
- Surgery: Removing the AVM surgically.
- Embolization: Blocking the AVM with coils or glue.
- Stereotactic Radiosurgery: Using focused radiation to shrink the AVM.
In summary, an AVM is a congenital vascular anomaly where arteries and veins are directly connected without the intervening capillary network, potentially leading to serious health problems.
