Arteriovenous malformations or AVMs of the brain or spinal cord are high-flow tangles of blood vessels that are formed before or near birth.  The natural transition between high flow arteries and low flow veins called capillaries are missing.  The result is a large tangle of thin walled blood vessels with very fast flowing blood coursing through the 'nidus' or nest.  In classic AVMs, the nidus has no normal brain in between the coils of dilated vessels.  AVMs of the brain or spinal cord are thought to affect about 300,000 Americans.


Symptoms and Presentation of an AVM

Because of the high flow and thin walled nature of AVM vessels, the most dangerous presentation is that of HEMORRHAGE in the brain.  This might cause severe headache, vomiting, loss of consciousness, or paralysis.  The bleeding can be outside the brain or spinal cord (SAH, subarachnoid hemorrhage) or inside the brain or spinal cord.  The latter condition is usually associated with profound and long lasting disabilities.

Although bleeding is the most dangerous presentation of an AVM, HEADACHE is the most common symptom.  Any type of headache can be associated with AVMs of the brain, but typically they are pulsatile in nature and are located on the side of the head that harbors the malformation.  In that regard the symptoms of an AVM can mimic migraine. 

EPILEPTIC SEIZURES are a very common symptom of an underlying brain AVM.  The irritation from tiny microhemorrhages and/or the lack of nutrients that result from such fast flowing blood cause the local brain cells to become unstable.  This can result in a single seizure or even multiple hard to stop seizures. 

A less common but nonetheless ominous symptom of brain AVMs is temporary paralysis or numbness.  This results from the fact that blood is rushing so fast through the AVM that nutrients like glucose and oxygen can't be transferred from the blood to the adjacent brain.  Whatever area of brain contains the AVM temporarily stops functioning.  This is known as STEAL PHENOMENON.  Depending on the location of the AVM, those disabilities can be loss of speech, memory, vision, or strength.


Diagnosis of an AVM

Patients with any of the above symptoms or presentations will frequently undergo a CAT SCAN or MRI SCAN.  CAT Scans will show the hemorrhage if one has occurred, but may not show the malformation itself.  The MRI will frequently show evidence of enlarged or misshapen vessels suggesting the presence of an AVM. 

Symptomatic patients or those with a high degree of suspicion for a brain or spinal cord AVM, will undergo a CATHETER ANGIOGRAM, where dye is injected into the brain or spinal cord blood vessels and rapid fire pictures are taken.  This allows the definition of those vessels that 'feed' the AVM and those that 'drain' it.  This gives the treating team a roadmap as to how to potentially treat or remove the lesion. 


Treatment of an AVM

Some of the symptoms of AVMs can be treated without treating the AVM itself.  Headaches can be ameliorated with pain MEDICINES.  Care should be taken not to overuse medicines that can be associated with bleeding, such as aspirin or ibuprophin.  Seizures that are associated with AVMs are treated with ANTIEPILEPTICS.  It is only when these medicines fail to stop or control the seizures that definitive treatment of the AVM is warranted.