A cerebral arteriovenous malformation (AVM) is an abnormal connection between the arteries and veins in the brain.
An AVM diagnosis is established by neuroimaging studies after a complete neurological and physical examination.
Three main techniques are used to visualize the brain and search for AVM: computed tomography (CT), magnetic resonance imaging (MRI), and cerebral angiography.
A CT scan of the head is usually performed first when the subject is symptomatic. It can suggest the approximate site of the bleed.
MRI is more sensitive than CT in the diagnosis of AVMs and provides better information about the exact location of the malformation.
More detailed pictures of the tangle of blood vessels that compose an AVM can be obtained by using radioactive agents injected into the blood stream.
If a CT is used in conjunction of dye this is called a computerized tomography angiogram while if MRI is used it is called magnetic resonance angiogram.
The best images of an AVM are obtained through cerebral angiography.
This procedure involves using a catheter, threaded through an artery up to the head, to deliver a contrast agent into the AVM.
As the contrast agent flows through the AVM structure, a sequence of X-ray images are obtained.
A common method of grading cerebral AVMs is the Spetzler-Martin grade.
This system was designed to assess the patient’s risk of neurological deficit after open surgical resection, based on characteristics of the AVM itself.
Based on this system, AVMs may be classified as grades 1 – 5.
|AVM size||Adjacent eloquent cortex||Draining veins|
|Under 3 cm = 1||Non-eloquent = 0||Superficial only = 0|
|3-6 cm = 2||Eloquent* = 1||Deep veins = 1|
|Over 6 cm = 3|
Such as sensory or motor cortex, language or visual areas, brain stem, etc.
The risk of post-surgical neurological deficit (difficulty with language, motor weakness, vision loss) increases with increasing Spetzler-Martin grade.