Unusual Carotid Artery Conditions

Introduction

While cerebrovascular atherosclerotic disease is the most common pathology encountered by vascular surgeons, there are several other distinct entities that can result in cerebral ischemia, bleeding and death. This chapter discusses the rare clinical presentations and treatments for carotid body tumors, carotid sinus syndrome, intracranial carotid aneurysms, intracranial vascular lesions, carotid kinks and coils, and moyamoya disease.

Carotid Body Tumors

Carotid body tumors are described in Chapter 98 (Carotid Body Tumors), and will only be briefly summarized here. The carotid body, also known as the carotid glomus or glomus caroticum, consists of neural crest-derived chemoreceptors and associated cells found in the medial portion of the carotid bifurcation. There are two types of cells in the carotid body, glomus type I chief cells and glomus type II/sustentacular cells. The glomus type I cells are derived from the neural crest and when tumors develop, they are referred to as extra-adrenal neuroendocrine neoplasms. These rare but highly vascularized neoplasms are called carotid body tumors (CBT) when seen in the neck and head, although they can occur throughout the body. Head and neck paragangliomas occur with an incidence of 1 in 30,000 or 1 in 100,000. Prevalence is higher in women, up to 25% are bilateral, and familial incidence ranges from 30% to 40%. Early detection may prevent late diagnoses and extended resections. The incidence of malignancy is low (5%); however, due to the possibility of undetected micrometastasis, any associated or large lymph nodes should be removed for histological review. ^, CBTs have an increasing incidence in inhabitants of high altitude and are predominantly female in distribution. CBTs present as asymptomatic painless masses or focal cervical fullness. When larger, cranial nerve palsy can occur, 10%–20% with pain, hoarseness, odynophagia, stridor and dysphagia. Other symptoms include cough, tinnitus, tenderness, and dysphonia. Cervical bruits and thrills are atypical. The mass is typically located at the level of the hyoid bone. Nerves involved can include the glossopharyngeal, vagus and hypoglossal. Patients may have Horner syndrome, vocal cord paralysis or other nerve involvement. The vertical fixation and horizontal mobility known as Fontaine’s sign has been described in slender patients. Sympathetic hyperactivity such as headache, tachycardia, hypertension and palpitations are symptoms of the rare presentation of a functional CBT. ^,

While CBTs are typically benign, there is a potential to evolve into malignant tumor in 3%. Surgical treatment is guided by Shamblin classification. Preoperative embolization (PAE) can be performed to decrease tumor size and vascularity in large Shamblin 2 or 3 tumors. The use of PAE varies, with considerable debate on its merits. CBT resections can be performed safely and with acceptable morbidity, although cranial nerve injury has been reported in 1%–30% of cases. Some centers report a lymph node resection rate of up to 54% of concomitant excisions. Early series by Hallet and colleagues reported improvement in perioperative stroke and morbidity from 23% to 2.7% and 65% to 0%, respectively, over a 50-year experience.

Carotid Sinus Syndrome

The carotid sinus (CS) is a baroreceptor in the adventitia of the carotid bulb, often described as a dilated region at the bifurcation containing wall pressure receptors. The CS nerve, the nerve of Hering, is a branch of the glossopharyngeal (cranial nerve IX). The CS provides baroreceptor responses to changes in stretch or pressure in the vessel wall from manipulation or blood pressure. When stimulated, parasympathetic fibers are activated, while sympathetic fibers are inhibited, resulting in decreased systemic blood pressure and heart rate. Carotid sinus hypersensitivity (CSH) or syndrome (CSS) is an important but frequently unrecognized cause of recurrent syncope and falls in elderly patients. Aging and instability of the carotid sinus baroreceptors contribute to CSS in the elderly population.

Epidemiology

The prevalence of CSS is as high as 45% in individuals 35 to 60 years of age, occurring more often in men (4:1 ratio). With CS massage, CSH is seen in 20% of elderly presenting with syncope. CSH increases with age, cardiovascular, neurogenic and cerebrovascular degeneration. The prevalence is increased in neurodegenerative disorders such as Parkinson disease, Alzheimer dementia and dementia with Lewy bodies. This is attributed to the degeneration of the medullary autonomic nuclei, which senses the baroreceptor signals and leads to a stimulated response resulting in hypotension and bradycardia.

Classification

There are three subtypes of CSH. Cardioinhibitory carotid sinus hyperactivity (CICSH) is the most common, representing 70%–75% of cases, characterized by ventricular pauses greater than or equal to 3 seconds (asystole). Vasodepressor carotid sinus hyperactivity (VDCSH) represents 5%–10% of CSH, and displays blood pressure drops of at least 50 mm Hg (hypotension) without concomitant bradycardia. The mixed CSH type, 20%–25% of cases, shows both ventricular pauses and a decrease in systolic blood pressure. It is important to differentiate these classifications clinically as they dictate the approach to treatment; CICSH is a class 1 indication for cardiac pacing, whereas VDCSH typically requires pharmacologic treatment. ^,

Physiology and Pathophysiology

Baroreceptors activate the autonomic system, balancing blood pressure and heart rate. The message is sent via the vagus and glossopharyngeal nerves to the solitary nucleus of the medulla. The nucleus then sends signals via the efferent limb. With increases in blood pressure and vessel wall stretch, the parasympathetic system is activated causing hypotension and bradycardia, while decreased blood pressure and wall stretch activate the sympathetic system causing hypertension and tachycardia. The hypersensitivity seen in CSH is not well understood but the exaggerated signal response results in dramatic physiologic changes in these patients.

There are two proposed theories of CSS pathophysiology, one based on central disease and the other on peripheral origins. The central theory attributes CSS to deterioration or lesions of the nucleus tractus solitarii. The peripheral theory focuses on disease at the CS baroreceptor and the sternocleidomastoid (SCM). The chronic loss of innervation of the SCM results in an exaggerated sensitivity of the baroreceptor pathway.

Presentation and Risk Factors

Common symptoms include dizziness or syncope of sudden onset, short duration, and quick recovery; this can be more prolonged if hypotension is severe. Complications are most serious in the elderly, who have falls (typically without loss of consciousness) and sustain resulting trauma. In patients with loss of consciousness, there may be a prodrome of visual loss or darkening of the visual field. Neurologic symptoms, which are rare and transient, include abnormal sensorium, vision changes, paresthesia, paresis, and cognitive dysfunction. Spontaneous CSS can be caused by manipulation of the CS by tight collars, neck wear, shaving, neck movement, or cervical massages. Other causes include compression from adjacent masses such as tumors and lymph nodes. Neck irradiation and previous neck surgery increase the susceptibility to CSS. However, most CSS is induced without a predisposing maneuver or trigger.

Diagnosis and Workup

The diagnosis involves assessing for common causes of syncope and hypotension, including dehydration, hypoglycemia, and cardiovascular disease such as aortic stenosis and hypertrophic cardiomyopathy. Serum chemistries, complete blood count, and electrocardiogram should be obtained as baseline. Holter monitor and electrophysiologic testing can also be used.

Monitored carotid sinus massage (CSM) is the most effective method for confirming CSH. The technique reproduces spontaneously occurring symptoms during 10-second sequential right and left massage, performed both supine and erect under continuous heart rate and blood pressure monitoring. Typically, massage of the right CS is performed first, as it contains more receptors. If there is no response, similar massage for several seconds on the left is performed. The test is positive if there is asystole for greater than 3 seconds (CICSH) or greater than 50 mm Hg drop in blood pressure (VDCHS). Current guidelines from the European Society of Cardiology state that the upright position is preferred, and this is supported by Morillo (diagnostic accuracy of CSM increased by 38%). If the test is positive, atropine is administered, and repeat massage performed to determine the degree of hypersensitivity. The mixed subtype is diagnosed when CSM produces asystole for 3 seconds and after atropine administration, greater than 30 mm Hg drop. The differential diagnosis should include vasovagal syncope, given the potential for the coexistence in elderly patients.

Contraindications to CSM include stroke, transient ischemic attack and myocardial infarction in the previous three months. While the presence of carotid bruit is not a contraindication, documented greater than 70% stenosis on carotid duplex is a relative contraindication.

Treatment

In asymptomatic patients, no further treatment other than trigger avoidance is needed. Treatment includes adequate fluid and salt intake and avoidance of physical manipulation and compressive clothing. If the patient is not responsive to conservative measures, medical or surgical management should be considered based on the subtype.

For VDCSH, appropriate salt intake (6 g/day) and hydration will suffice to control symptoms. These therapies are contraindicated in patients with congestive heart failure and hypertension. The addition of alpha-adrenergic agonist agents such as midodrine or mineralocorticoid such as cortisone can be used, albeit carefully for patients with hypertension.

In CICSH and mixed subtypes, a dual-chamber pacemaker is recommended for atrial and ventricular stimulation. DDD pacing is accepted as better for symptom reduction. The guidelines from the European Society of Cardiology (ESC) reflect this by noting that dual-chamber pacing is better than single-chamber pacing. ^, As there is an association between sick sinus syndrome (SSS) and CSH, pacemaker insertion is indicated for both.

Nonpharmacologic therapies include CS nerve denervation, glossopharyngeal nerve or CS transection and CS irradiation. Nerve transections can be morbid and ineffective. CS transection can be difficult and lead to incomplete sinus denervation. Glossopharyngeal nerve and upper rootlets of the vagus nerve transections at the level of the brain stem involves craniotomy and are typically reserved for patients unresponsive to lesser invasive therapies. Complications of glossopharyngeal transection include loss of taste, impaired gag reflex and dry mouth.

Another surgical option is adventitial stripping of the CS ( Fig. 99.1 ). ^, Toorop and colleagues reported a review of 110 CSS patients with adventitial stripping and clinical results were encouraging. The procedure is performed under general anesthesia. The nervous tissue attached to the adventitia of the bifurcation is removed circumferentially over a 3-cm segment. Topical lidocaine application along the ICA or intravenous atropine and norepinephrine were used to treat severe bradycardia or hypotension. Concomitant carotid endarterectomy can be performed. Complications with stripping include cervical hematoma and nerve injury. At 1-month follow-up, 93% of patients were symptom free, but long-term data has not been established.

Figure 99.1, Operative Photographs Depicting Adventitial Stripping of the Left Carotid Artery.

Carotid irradiation has been utilized in the past but is limited currently. The mechanism of action is based on depression of nerve endings. The benefits are not consistent, often delayed and associated with development of CSH in patients with neck tumors.

Moyamoya Disease

You're Reading a Preview

Become a Clinical Tree membership for Full access and enjoy Unlimited articles

Become membership

If you are a member. Log in here