The carotid artery is one of the main sites affected by atherosclerotic disease. Plaque deposition tends to occur at sites of turbulent blood flow, in this case along the bifurcation of the common carotid artery. As the disease progresses, the enlarging plaque impinges upon the vessel lumen, causing stenosis of the carotid artery. While most patients with carotid stenosis will remain asymptomatic, some will experience a neurologic event due to low cerebral blood flow or embolization of plaque material. A stroke or transient ischemic attack (TIA) is the most common symptom of carotid stenosis, and typically manifests as a contralateral motor defect, sensory loss, or abnormal speech. Another sign of carotid disease is amaurosis fugax, an ipsilateral transient monocular blindness caused by a small embolus to the ophthalmic artery.

Patients suspected of having carotid artery disease should undergo evaluation with a carotid duplex ultrasound. CT or MR angiography may also be used in certain cases (Fig. 28.1). The method used to determine the degree of stenosis varies somewhat, but is typically calculated as the diameter of the most stenotic portion of the vessel compared to the diameter of the normal vessel just distal to the stenosis. A narrowing of the carotid artery lumen greater than 50 % is generally considered clinically significant.

The treatment of carotid artery disease begins with lifestyle modifications such as smoking cessation, and pharmacologic therapy with aspirin and cholesterol lowering agents. Multiple randomized controlled trials have been performed to assess the efficacy of surgical carotid endarterectomy (CEA) in preventing future strokes over this pharmacologic therapy alone. The results of these studies indicate that the greatest benefit of endarterectomy is seen in patients who have experienced neurologic symptoms attributable to carotid disease. Patients are considered to have symptomatic carotid stenosis if a stroke, TIA, or amaurosis fugax has occurred within the prior 6 months. Symptomatic patients with carotid stenosis greater than 70 % have been shown to have lower future stroke rates with CEA than with medical therapy alone. In addition, CEA may have benefit in carefully selected symptomatic patients with even lower degrees of stenosis, from 50 to 70 %.

The optimal management of patients with asymptomatic carotid stenosis is not as clear. Earlier studies suggested that even asymptomatic patients could benefit from CEA, although the advantage was more modest than seen for symptomatic patients. However, the quality of pharmacologic therapy has improved substantially in the years since these trials were performed, thereby lowering the potential benefit margin of surgery. In addition, female patients were found to have derived less benefit than their male counterparts. As a result, recommendations for asymptomatic patients vary considerably with some surgeons recommending medical management only, and others reserving CEA for selected male patients with stenosis of greater than 60 %.

The benefit of endarterectomy assumes that the procedure itself can be performed with minimal morbidity. During clamping of the carotid artery it is imperative to ensure that the cerebral hemisphere continues to receive adequate perfusion. The vast majority of individuals will obtain sufficient cerebral blood flow from the contralateral circulation via the Circle of Willis. If endarterectomy is being performed under local anesthesia, the adequacy of this perfusion can be monitored in real time with ongoing assessments of the patient’s mental status, speech, and extremity function. If general anesthesia is used, adequate brain perfusion can be assessed using continuous EEG monitoring. If signs of neurologic compromise are seen, an emergent carotid shunt is placed in order to restore blood flow to the cerebral hemisphere. Some surgeons prefer to use carotid shunting routinely in all patients as a method of ensuring continuous blood flow. However critics of universal shunting point out that shunts are associated with their own set of complications.

Carotid endarterectomy is considered the standard treatment for patients requiring intervention for carotid stenosis. However, symptomatic patients who have significant comorbidities and are considered to be of unacceptably high medical risk for surgery can be evaluated for carotid artery stenting as an alternative to CEA (Fig. 28.2). Endovascular stenting may also be preferable in patients who develop restenosis after prior surgical endarterectomy.