The methods used to diagnose AVMs mainly rely on various imaging procedures. In some cases, clinical symptoms may be able to differentiate AVMs from other neurological ailments, but CT, MRI, and arteriography is essential to the confirmation of the diagnosis.
Arteriograms
Cerebral arteriography was developed by in 1927 by Egas Moniz. Arteriography involves injecting a radioactive dye with a short half-life into the arterial blood stream and taking x-rays as the blood passes through the cerebral vasculature. It has traditionally been the imaging technique of choice to determine the exact location of the AVM and its feeding vessels.
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Arteriogram of the left carotid system. The large irregular mass is an AVM in the inferoposterior portion of the temporal lobe. |
Arteriogram of the same AVM through the vertebrobasilar system. Notice that the AVM has feeder arteries from both major arterial systems. |
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CT scans and MRI are also widely used in the diagnosis of AVMs. On CT scans AVMs will appear as a heterogeneous area with poor demarcation, whereas MRI will show the AVM as a honeycomb area with feeding arteries and draining veins.
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CT scan of the patient pictured in the above
arteriogram. |
MRI is the best technique for differentiating between the AVM and the ventricular system, deep nuclei, and white matter, but CT is important for showing calcification of past hemorrhages. CT and MRI are equally important and complementary in diagnosing AVMs.
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Two MRI images of above patient. The AVM is clearly visible in the posterior portion of the left inferior temporal lobe. |
All
images from Kim, M. (1997). Stereotaxically assisted resection of an
arteriovenous malformation of the dominant temporal lobe. Cerebrovascular Division of the NYU
Department of Neurosurgery.
Click here to
go to their page.
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To go the Harvard Whole Brain Atlas site to see an MRI series of an AVM click here.
Other Diagnosic Techniques
Other techniques that have limited applications in diagnosing AVMs include perfusion and blood pool scintigraphy and Magnetic Resonance Angiography (MRA). MRA capitalizes on velocity-dependent phase contrast to image blood flow and vasculature. Three-dimensional time-of-flight (MRA) can provide information about irregular AVM shape that cannot be seen with DSA.MRA is superior to MRI for defining the dimensions of an AVM, but it is susceptible to the same image artifacts as MRI (surgical clip artifacts and embolizing glue), whereas arteriography remains unaffected.
View a movie of a 3D MRA.Download it from here or
from the Harvard Whole Brain Website (they’ve got other cool stuff).
Scinitgraphy uses a radiographic tracer injected into the blood stream to detect breaks in the blood brain barrier. It is mainly used to diagnose disorders that rupture the blood-brain barrier (e.g. tumors, abscesses, or hemorrhage). Scintigraphy is useful in differentiating between hemangiomas and unruptured AVMs.
Sometimes a clinician can tell an AVM from another disorder without resorting to radiographic procedures. AVMs can be differentiated from saccular aneurysms by the presence of bruit, a history of seizures or unilateral headaches, and previous “mild” subarachnoid hemorrhages. The final diagnosis, however, should always be backed up with imaging techniques for certainty’s sake. Back to top.