ABSTRACT
The hemodynamic changes associated with internal carotid artery stenosis and occlusion have provided the basis for a wide range of noninvasive diagnostic techniques. The cerebrovascular or periorbital Doppler examination (CDE), supraorbital photoplethysmography, oculoplethysmography, and ocular pneumoplethysmography (OPG) were sensitive to alterations in collateral circulation, ocular pulse delay, or decreased end-ophthalmic (distal internal carotid) artery pressure. They provided indirect evidence of hemodynamically significant carotid artery stenosis or occlusion. These indirect techniques, however, were unable to quantify the degree of stenosis, distinguish between stenosis and occlusion, or detect nonstenotic ulcerative disease. Techniques that directly assess the cervical carotid artery, such as real-time B-mode imaging and spectral analysis, provide additional information relative to the morphology of the plaque and the degree of obstruction. More recently, these techniques have also been employed to obtain information regarding the flow profile and its relationship to atherogenesis; the composition and morphology of atherosclerotic plaques and their relationship to symptomatic cerebrovascular disease; and the natural history of carotid atherosclerosis and atherogenesis.
