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ESSENTIALS OF DIAGNOSIS
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ESSENTIALS OF DIAGNOSIS
Sudden onset of weakness and numbness of an extremity or the face, aphasia, dysarthria, or unilateral blindness (amaurosis fugax).
Bruit heard loudest in the mid neck.
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GENERAL CONSIDERATIONS
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Unlike the other vascular territories, symptoms of ischemic cerebrovascular disease are predominantly due to emboli. When collateral flow reestablishes perfusion, ischemia reverses (transient ischemic attacks [TIAs]) but signals a high risk for additional emboli and stroke. The origins of emboli that cause ischemic strokes are the heart (most commonly) and an arterial source (25% of ischemic strokes). Approximately 90% of emboli from an arterial source originate from the proximal internal carotid artery, an area uniquely prone to the development of atherosclerosis. The aortic arch may also be an atheroembolic source. Intracranial atherosclerotic lesions are uncommon in western populations but are the most frequent location of cerebrovascular disease in Asian populations.
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A. Symptoms and Signs
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Generally, the symptoms of a TIA last only a few seconds to minutes (but may continue up to 24 hours) while a stroke is defined as persistent symptoms beyond 24 hours. The most common lesions associated with carotid disease involve the anterior circulation in the cortex with both motor and sensory involvement. Emboli to the retinal artery cause unilateral blindness; transient monocular blindness is termed “amaurosis fugax.” Posterior circulation symptoms referable to the brainstem, cerebellum, and visual regions of the brain may be due to atherosclerosis of the vertebral basilar systems and are much less common.
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Signs of cerebrovascular disease may include carotid artery bruits. However, there is poor correlation between the degree of stenosis and the presence of the bruit. Furthermore, the presence of a bruit does not correlate with stroke risk. Nonfocal symptoms, such as dizziness and unsteadiness, seldom are related to cerebrovascular atherosclerosis.
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Duplex ultrasonography is the imaging modality of choice with high specificity and sensitivity for detecting and grading the degree of stenosis at the carotid bifurcation (see Chapter 26).
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Excellent depiction of the full anatomy of the cerebrovascular circulation from aortic arch to cranium can be obtained with MRA or CTA (Figure 14–1) (eFigure 14–5). Each of the modalities may have false-positive or false-negative findings. Since the decision to intervene in cases of carotid stenosis depends on an accurate assessment of the degree of stenosis, it is recommended that at least two modalities be used to confirm the degree of stenosis. Diagnostic cerebral angiography is reserved when carotid artery stenting is planned or other imaging modalities are contraindicated.
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