70 CAROTID DISEASE
Rao Gutta M.D., B. Timothy Baxter M.D.

1. What diseases affect the carotid arteries?

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Atherosclerosis is by far the most common (accounting for 90% of lesions in the Western world). The carotid also can be affected by fibromuscular dysplasia, inflammatory arteriopathies (e.g., Takayasu’s arteritis), extrinsic compression (e.g., neoplasm), and trauma.

2. What are the most common symptoms of carotid artery disease?

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* Transient ischemic attack (TIA)
* Reversible ischemic neurologic deficit (RIND)
* Cerebrovascular accident (CVA)
* Amaurosis fugax

3. Define TIA, RIND, and CVA.

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These clinical terms describe a spectrum of cerebral ischemic syndromes. A TIA is a neurologic deficit that lasts < 24 hours. Most TIAs last only 15-30 seconds. RIND lasts longer than 24 hours and completely resolves within 1 week (usually within 3 days). CVA, or acute stroke, is a stable neurologic deficit that may show gradual improvement over a long period.

4. Define amaurosis fugax.

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It is an episode of transient (minutes to hours) monocular blindness, often likened to a window shade pulled across the eye. It is caused by decreased blood flow through or embolization into the ophthalmic artery.

5. What are Hollenhorst plaques?

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They are bright yellow plaques of cholesterol, usually at a branch point in the retinal vessels, that have embolized from the carotid bifurcation. Clinically, this finding indicates that the atheromatous plaque in the carotid is quite friable. Further embolization may occur with manipulation at the time of surgery.

6. What mechanisms produce neurologic deficits?

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* Embolization from atherosclerotic arteries or the heart
* Reduced blood flow
* Occlusive disease with thrombosis
* Intracranial hemorrhage

7. What is the natural history of a TIA?

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The natural history of a TIA is defined by the pathology of the ipsilateral carotid artery. In patients with severe stenosis (> 70%), the risk of ipsilateral stroke within 24 months is 26%. For those with moderate disease (50-69%), the risk is 22% at 5 years. With minimal stenosis (< 30%), the risk is 1% at 3 years (see Required Reading in Chapter 1).

8. What is the effect of aspirin on TIAs?

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Acetylsalicylic acid is a cyclooxygenase inhibitor that decreases platelet stickiness and lowers the incidence of both TIAs and stroke.

9. What does a carotid bruit signify?

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Unfortunately, a carotid bruit is a general marker for atherosclerosis and is specific for very little; it is more predictive of a cardiac event than a neurologic event. Although a carotid bruit indicates increased risk of neurologic events, it is just as likely to occur on the contralateral side as on the side of the bruit.

10. Does the sound of a bruit correlate with the degree of stenosis?

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No. As a stenosis progresses, the bruit should actually diminish and disappear as flow decreases.

11. What test should be ordered to evaluate a cervical bruit?

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Duplex scanning.

12. When is surgery indicated for symptomatic carotid artery disease?

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Surgery is strongly indicated for symptomatic carotid artery disease associated with > 70% stenosis. The absolute risk reduction of stroke is 17% at 2 years. Recent data also suggest a smaller benefit in patients with symptomatic stenoses of 50-69% (6.5% risk reduction at 5 years). Patients with stenosis of < 50% do not benefit from surgery.
KEY POINTS: CAROTID DISEASE

1. The symptoms of carotid disease include transient ischemic attack, reversible ischemic neurologic deficit, cerebrovascular accident, and amaurosis fugax.
2. A carotid bruit is a general marker for atherosclerosis and is specific for very little; it is more predictive of a cardiac event than a neurologic event.
3. Surgery is strongly indicated for symptomatic carotid artery disease associated with > 70% stenosis.

13. Should a patient with asymptomatic stenosis undergo surgery?

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The absolute reduction in risk of stroke is 6% over a 5-year period in asymptomatic patients with > 60% stenosis who undergo carotid endarterectomy (CEA) plus aspirin versus patients treated with aspirin alone (5.1% versus 11%). Thus, CEA should be performed for asymptomatic carotid disease when the patient is expected to live at least 3 years and when the CEA can be performed with a combined stroke and mortality rate of < 3%.

14. What are the complications of carotid endarterectomy?

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* TIA or stroke (approximately 2%)
* Hematoma
* Cranial nerve injury
* Hypertension
* Hypotension

15. Which cranial nerves (CNs) may be injured during CEA? What are the clinical signs of injury?

* Facial nerve (CN VII): injury to the marginal mandibular branch may cause droop of the ipsilateral corner of the mouth
* Glossopharyngeal nerve (CN IX): difficulty in swallowing both solids and liquids
* Vagus nerve (CN X): hoarseness, loss of effective cough
* Superior laryngeal nerve (branch of the vagus): voice fatigue, loss of high-pitch phonation
* Hypoglossal nerve (CN XII): deviation of the tongue to the ipsilateral side, difficulty with speech and chewing

16. What is the danger of wound hematoma after surgery?

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The main danger is airway compromise, which may necessitate emergent decompression by opening of the wound. Whether vacuum drains prevent this complication is not clear.

17. What are the possible causes of postoperative hypertension?

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* Denervation of the carotid sinus
* Cerebral rennin, norepinephrine production, or both
* Preexisting hypertension
* Central neurologic deficit

18. When do neurologic events occur during CEA?

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* Dissection: dislodgement of material from the arterial wall with embolization
* Clamping: ischemic infarct
* Postoperatively: intimal flap, reperfusion, external carotid artery clot

19. What is a shunt? When is it used?

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A shunt is a small plastic tube that diverts blood flow around the surgically opened carotid artery while endarterectomy is performed. A shunt is used to ensure adequate cerebral blood flow and to avoid intraoperative cerebral ischemia. Many surgeons routinely use shunts, but others use them selectively, if at all. The decision to use a shunt is based on intraoperative assessment, including temporary clamping of the carotid under local anesthesia, measurement of stump pressure, intraoperative electroencephalography, or transcranial Doppler. None of these methods is 100% accurate.

20. What is stump pressure?

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Stump pressure is the back pressure of the internal carotid artery after clamping. It is used to assess the adequacy of cerebral perfusion. The “safe” pressure varies from author to author, but is probably around 40 mmHg.

21. Does stenosis recur after carotid endarterectomy?

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Yes. The reported incidence has been quite variable and ranges from < 2% to as much as 36%. During the first 24 months after operation, restenosis is thought to be secondary to myointimal hyperplasia. Beyond this time, it is caused by progression of disease (atherosclerosis). The incidence is lower when the arteriotomy is closed with a vein patch angioplasty.

22. What is the most common complication associated with reoperation endarterectomy?

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Cranial nerve injury (reported incidence = 2-20%). Most injuries are transient, however.
23. In which layer of the artery is the carotid endarterectomy performed? Show answer
The outer layers of the tunica media.

24. What anatomic landmark is useful in identifying the level of the carotid artery bifurcation?

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The facial vein.

25. How many branches of the internal carotid artery are located in the neck?

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None.

26. When the internal carotid artery is occluded, which branches of the external carotid artery form collaterals and reestablish circulation in the circle of Willis?

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The periorbital branches of the external carotid artery form communications with the ophthalmic artery, a branch of the internal carotid.

27. What are the functions of the carotid sinus and the carotid body?

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Both are located at the carotid bifurcation and are innervated by the glossopharyngeal and vagus nerves, respectively. The function of the carotid sinus is regulation of blood pressure. Hypertension stimulates efferent impulses to the vasomotor center in the medulla, inhibiting sympathetic tone and increasing vagal tone. The carotid body regulates respiratory drive and acid-base status via chemoreceptors. It also induces bradycardia when manipulated (this is your target during carotid massage for cardiac dysrhythmias).

28. When was the first successful surgical procedure of the extracranial carotid artery performed? Who is credited with it?

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In 1954 by Eastcott.