Arteriovenous malformations (AVMs) are abnormal collections of blood vessels in the brain or spinal cord. AVMs are congenital, meaning patients are typically born with them, though they often do not cause symptoms until later in life. They are abnormal ‘tangles’ of vessels in which one or more arteries provide blood supply, and they drain into enlarged veins. AVMs are much less common than intracranial aneurysms; they are estimated to be present in approximately 0.14% of the population.
The most common way in which AVMs present is by bleeding and causing neurologic symptoms; these can include weakness, numbness, visual changes, changes in speech, and lethargy/coma. These symptoms can mimic a stroke. In addition, AVMs may also cause seizures, and, occasionally, headaches. The yearly risk of bleeding from an AVM is estimated to be approximately 2-4%, though may vary significantly.
AVMs may be evaluated using a number of tests including CT and MRI. However, the best method for understanding the anatomy of an AVM is cerebral angiography. Options for treatment include surgical resection (typically approached via craniotomy in the head or laminectomy in the spine), endovascular embolization (gluing of the AVM from the inside), and radiosurgery. In some cases, an AVM may require more than one treatment, or even a combination of treatments (embolization + surgery, for example). After treatment, cerebral angiography is the best method to assess whether the lesion has been completely treated.
Justin F. Fraser, MD
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