Conventional Angiography

When performing conventional catheter angiography, one should obtain views of the arch, the vessels in the neck and the intracranial circulation. When interpreting the angiogram, one should first assess the degree of stenosis of the carotid artery. A stenosis needs to be greater than 80% (1-2 ml residual lumen) for it to be a hemodynamically significant lesion. The term "hemodynamically significant" means that it sufficiently obstructs flow through the carotid artery to decrease flow to the brain or to set up collateral circulatory patterns within the cerebral circulation. Any ulcerations or irregularity of a carotid plaque should also be noted. A long segment narrowing or a tapered occlusion of the cervical internal carotid artery suggests arterial dissection.

When evaluating the intracranial circulation, one should look for: 1) atheromatous disease of the intracranial vessels, 2) vessel occlusion, 3) transit time, 4) collateral circulation, 5) mass effect, and 6) integrity of the major venous sinuses. Atheromatous disease of the carotid siphon or vessels about the circle of Willis is commonly associated with atheromatous disease in the neck. It is important to note any significant stenosis of the intracranial vessels as well. In patients with suspected embolic stroke, it is particularly important to look for any occluded vessels to document the diagnosis. The normal cerebral transit time from the first opacification of the carotid siphon to maximum opacification of the cortical veins is normally six seconds. If the transit time is longer than seven seconds, one should suspect a proximal obstruction. Delayed transit time can also be caused by increased intracranial pressure, but then it should be seen bilaterally. In patients with severe carotid stenosis or occlusion, collateral patterns develop to supply the low flow areas of the brain. The major source of collateral is via the circle of Willis, namely the anterior communicating and posterior communicating arteries. Another common collateral pathway in patients with internal carotid disease is via the external carotid-ophthalmic route. Leptomeningeal collateral pathways generally also develop between the three major vascular territories. When slowly progressive arterial occlusion occurs in younger patients, prominent collaterals may develop in the basal ganglia regions, giving the appearance of a "puff of smoke" on the angiogram (Moya Moya disease). Intracranial mass effect is usually evident by displacement of the anterior cerebral arteries or internal cerebral veins to one side or displacement of the Sylvian triangle.

The middle cerebral territory is the most common location for cerebral infarctions for two reasons. First, emboli more commonly go to the middle cerebral territory because the majority of carotid flow goes to this area. In addition, when the embolus lodges at the major bifurcation or trifurcation of the middle cerebral artery, the territory is isolated from the circle of Willis. The middle cerebral territory is also the more common location for thrombotic strokes because it is further away from the major collateral at the base of the brain. The anterior cerebral arteries are directly connected by the anterior communicating artery, and the posterior communicating arteries connect the internal carotids to the posterior cerebral arteries. 

{To return to cases, use the "Back " button on the Toolbar}