Cerebrovascular Disease, Occlusive

Essentials of Diagnosis

• Sudden onset

  • Weakness and numbness of an extremity

  • Aphasia

  • Dysarthria

  • Unilateral blindness (amaurosis fugax)

• Bruit heard loudest in the mid neck

General Considerations

• Unlike the other vascular territories, symptoms of occlusive cerebrovascular disease are predominantly due to emboli

• The ischemia is reversible (transient ischemic attacks [TIAs]) when collateral flow reestablishes perfusion but is a sign that the risk of additional emboli and stroke is high

• Most ischemic strokes are due to emboli from the heart

• One-quarter of all ischemic strokes may be due to emboli from an arterial source; approximately 90% of these emboli originate from the proximal internal carotid artery

• Intracranial atherosclerotic lesions are less uncommon in western populations but are the most common location of cerebrovascular disease in Asian populations

Symptoms and Signs

• Ischemic symptoms of TIAs

  • Generally last only a few seconds to minutes

  • May continue for up to 24 hours

• Most common lesions associated with carotid disease are in the cortex with both motor and sensory involvement

• Emboli to the retinal artery cause unilateral blindness which, when transient, is called amaurosis fugax

• Posterior circulation symptoms referable to the brainstem, cerebellum, and visual regions of the brain are

  • Due to atherosclerosis of the vertebral basilar systems

  • Much less common than carotid disease

• Carotid artery bruits

  • Correlation between the degree of stenosis and the presence of the bruit is poor

  • Absence of a bruit does not exclude the possibility of carotid stenosis

• Nonfocal symptoms, such as dizziness and unsteadiness, seldom are related to cerebrovascular atherosclerosis

Differential Diagnosis

• Transient ischemic attack

• Ischemic stroke

• Intracerebral hemorrhage

• Subdural or epidural hematoma

• Space-occupying lesion, eg, brain tumor

• Seizure (Todd paralysis)

• Migraine

• Peripheral causes of vertigo, eg, Ménière disease

• Hypoglycemia

• Guillain-Barré syndrome

• Multiple sclerosis

• Aortic dissection

Imaging Studies

• Duplex ultrasonography

  • Imaging modality of choice

  • Has high specificity and sensitivity for detecting and grading degree of stenosis at the carotid bifurcation

  • Prospective screening valuable in timing intervention in asymptomatic patients since about 10% will have evidence of plaque progression in a given year

• Magnetic resonance angiography or CT angiography

  • Provides excellent depiction of full anatomy of the cerebrovascular circulation from aortic arch to cranium

  • Each of these modalities may have false-positive or false-negative findings

• Use at least two modalities to confirm degree of stenosis

• Cerebral angiography is reserved for cases that cannot be resolved by magnetic resonance or CT angiography

Asymptomatic patients

• Carotid intervention is likely beneficial in those

  • With no neurologic symptoms but with carotid stenosis on imaging

  • Who are considered to be at low risk and whose expected survival is > 5 years

• The CREST2 study is examining whether aggressive risk factor modification including high potency statins may be as valuable an intervention as carotid intervention

• Recommendation for intervention also presumes that the stroke rate at the treating institution is acceptable (< 3%)

• Large studies indicate a reduction in stroke rate from 11.5% to 5.0% over 5 years with surgical treatment of asymptomatic carotid stenoses > 60%

• However, the usual practice is to only treat those patients who have > 80% stenosis

• Patients whose carotid stenosis suddenly increases in severity are thought to have an unstable plaque and are at particularly high risk for embolic stroke

Symptomatic patients

• Patients who have completely or nearly completely recovered from TIAs or stroke

  • Will benefit from carotid intervention if ipsilateral carotid artery has a stenosis ≥ 70%

  • Are likely to derive benefit if stenosis is 50–69%

• In these situations, carotid endarterectomy has been shown to have a durable effect in preventing further events

Complications

• Cutaneous sensory or cranial nerve injury

• Stroke due to embolization of plaque material during the procedure

• Transient cranial nerve injury (usually vagus or hypoglossal nerve)

• Permanent deficits

• Postoperative neck hematoma, which can compromise the airway

• Myocardial infarction

• Upper limits of acceptable combined morbidity and mortality

  • 3% for asymptomatic

  • 5% for those with TIAs

  • 7% for patients with previous stroke

• Risk of second event is increased in symptomatic patients when intervention is delayed

Prognosis

• Poor for patients with carotid stenosis who have had a TIA or small stroke and no treatment

• 25% of these patients will have a stroke, most occurring within the first 6 months

• Patients with carotid stenosis without symptoms have an annual stroke rate of just over 2%

• Concomitant coronary artery disease is common and is an important factor in these patients both for perioperative risk and long-term prognosis

Prevention

• Risk factor modification with antiplatelet agents is not nearly as effective in preventing stroke as removing the stenosis

When to Refer

• Asymptomatic or symptomatic patients with a carotid stenosis of > 70% and patients with carotid stenosis of < 70% stenosis with symptoms of a TIA or stroke should be referred to a vascular specialist