Neurovascular Imaging
By David Rubinstein, MD

The vessels of the Central Nervous System can be studied by multiple modalities.These modalities range from noninvasive (ultrasound and MRA) to minimally invasive (CTA) to invasive (intraarterial angiography). In all cases, these studies should only be ordered when the test result will affect the management of the patient and the risk of the study is less than the proposed treatment.

Intraarterial angiography has the best spacial resolution. It is the study of choice for identifying aneurysms in patients with subarachnoid hemorrhage. Angiography, is emergently indicated for infarcts, only if intraarterial thrombolysis is being considered for therapy. Intraarterial angiography is the best imaging study to identify changes from vaculitis but has poor sensitivity and specificity in this situation. It may also be helpful for treatment planning for arteriovenous malformations, although the diagnosis can usually be made by MRI. Angiography is the gold standard for determining the degree of carotid stenosis and is useful in determining candidates for carotid endarterectomy.

Computed tomography angiograms are most helpful for evaluating the dural venous sinuses. Because they don’t have artifacts from flow as magnetic resonance venograms do or artifacts from dilution as intrarterial angiograms do, computed tomography venograms usually depict dural venous sinuses better than any other study. The diagnosis of dural venous thrombosis is most commonly made on an unehanced CT scan at Unviversity Hospital, but is best demonstrated by CTV.

Ultrasound and magnetic resonance angiography are useful screening studies for evaluation of carotid stenosis, with ultrasound being more widely recognised as the indicated screening study. MRA is also useful as a screening study for aneurysms and has been helpful when intraarterial angiograms have been negative in patients with subarachnoid hemorhhage.

While the straight forward indications for neurovascular imaging have been outlined above, the choice of imaging studies for the CNS vessels can be complex, especially when patients have contraindications to the study of choice. In those more complicated situations, or for those needing more information please contact the Neuroradaiology section.