Radiographic Assessment

Cerebral Angiography

The major clinical trials that identified which patients with cerebrovascular disease should undergo CEA relied on measurement of vessel stenosis based on angiography; hence, this invasive imaging modality is an essential component of the pre-operative evaluation.

Cerebral angiography should include visualization of both carotid bifurcations and the intracranial carotid circulation; this is because there can be tandem lesions situated in the same arterial tree as the carotid bifurcation stenosis. Because it can affect surgical therapy, visualization of the carotid siphon is also important. Angiography is not only useful in determining the percentage of cervical carotid stenosis, but also in assessing plaque ulceration and identifying areas of thrombosis. Assessment of anatomic variants and collateral flow patterns can also be accomplished with angiography.

Most carotid arteries harboring a high-grade stenotic area return to normal caliber distal to the stenotic segment. A high-grade ICA lesion with a tapering post-stenotic segment with a reduced caliber is usually referred to as the "string sign". This substantiated the concept that narrowing of the distal vessel past the stenotic segment occurs as a result of decreased perfusion pressure, because the diameter of the lumen always returns to normal after removal of the obstructing lesion. Conditions that can present with an angiographic "string sign" include radiation vasculopathy, moyamoya disease, FMD and congenital hypoplasia. The post-angiography stroke rate has been reported to be less than 1%. Cerebral angiogra-phy remains the "gold standard" for evaluating stenosis in patients with symptomatology suggestive of ischemic stroke. Recent data have shown that non-invasive evaluations may provide sufficient and accurate information regarding the degree of carotid stenosis [23].

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