Table 18.1 Nomenclature of bone tumors

Carotid sinus syndrome

BASIC INFORMATION
DEFINITION
Dizziness, presyncope, or syncope in a patient with carotid sinus hypersensitivity is defined as carotid sinus syndrome. Carotid sinus hypersensitivity is the exaggerated response to carotid stimulation resulting in bradycardia, hypotension, or both.
Cardiac and vasomotor factors are also involved in carotid sinus syndrome. Under physiologic conditions, unilateral compression of the carotid sinus leads to a drop in blood pressure and heart rate. In cases of disease (particularly arteriosclerosis) this reflex can be so increased that symptoms such as dizziness, confusion, and even unconsciousness occur.
Clinically, a distinction is made between the cardioinhibitory type (with bradycardia and consequent drop in blood pressure), the vasodepressor type (with a fall in blood pressure without significant bradycardia), and mixed forms of the two types.
SYNONYMS
Carotid sinus syncope
CSS
EPIDEMIOLOGY & DEMOGRAPHICS
• The incidence of carotid sinus hypersensitivity is 15% in the adult population.
• The incidence increases with age.
• Men are affected more often than women (2:1).
• Carotid sinus syndrome is rarely found before the age of 50 years.
PHYSICAL FINDINGS & CLINICAL PRESENTATION
Properly performed carotid sinus massage at the bedside is diagnostic. This maneuver can elicit three types of responses in the appropriate patient (see “Diagnosis”).
1. Carotid sinus massage (CSM) should be done in the supine position while monitoring the patient’s blood pressure by cuff and heart rate by ECG.
2. CSM should not be performed on patients with carotid bruits or recent TIA/CVA.
3. CSM should be performed on only one artery at a time.
4. CSM should be applied for approximately 5-8 sec.
ETIOLOGY
• Idiopathic
• Head and neck tumors (e.g., thyroid)
• Significant lymphadenopathy
• Carotid body tumors
• Prior neck surgery

DIAGNOSIS
• The diagnosis of CSS is made when carotid sinus hypersensitivity is diagnosed by CSM and no other cause of syncope is identified.
• CSM can elicit three types of responses that are diagnostic of carotid sinus hypersensitivity:
1. Cardioinhibitory type: CSM producing asystole for at least 3-5 sec
2. Vasodepressor type: CSM producing a decrease in systolic blood pressure of 50 mm Hg or 30 mm Hg in the presence of neurologic symptoms
3. Mixed type: CSM producing both types of responses
• It is not absolutely necessary to produce symptoms with CSM to diagnose CSS.
DIFFERENTIAL DIAGNOSIS
All causes of syncope, e.g., cardiac tachyarrhythmias and bradyarrhythmias, cardiac valvular disease and obstructive cardiomyopathy, cerebrovascular events, seizures, drug-induced, autonomic dysfunction, orthostasis/hypovolemia, cough, micturition, hypoxemia, and hypoglycemia
WORKUP
The workup must exclude other causes of syncope as guided by the history and the physical examination. Blood tests, cardiac noninvasive studies (Holter, echocardiograms, ECG, tilt test, treadmill testing), cardiac invasive testing (electrophysiologic studies), EEG, and CT scan should be ordered in the appropriate clinical setting.
TREATMENT
NONPHARMACOLOGIC THERAPY
Avoidance of triggering factors such as straining or applying neck pressure from tight collars, shaving, or rapid head turning.
ACUTE GENERAL Rx
Treatment will vary according to the type of carotid hypersensitivity response (e.g., cardioinhibitory, vasodepressor, or mixed) and symptoms present (see “Chronic Rx”). Acute treatment is usually not needed, because most patients at presentation are hemodynamically stable but present with either a fall resulting in an injury (e.g., hip fracture, laceration) or a complaint of true syncope with no injury.
CHRONIC Rx
For asymptomatic carotid sinus hypersensitivity of either the cardioinhibitory or vasodepressor type, it is generally agreed that pacemaker implantation is not necessary.
For patients with CSS with a cardioinhibitory response to CSM:
• Dual-chamber permanent pacemaker is indicated.
• Controversy exists as to whether to implant the pacemaker after the first syncopal episode or after a recurrent episode.
For patients with CSS with a vasodepressor response to CSM:
• Measures to maintain systolic blood pressure are tried:
1. Sympathomimetics (ephedrine has been tried with success but has significant side effects, e.g., palpitations, tremors.)
2. Fludrocortisone with its mineralocorticoid effect also has been tried with limited success.
3. Dual-chamber pacemaker is not indicated in the patient with pure vasodepressor response.
4. Elastic knee-high or thigh-high stockings help to maintain systolic blood pressure.
5. Carotid sinus denervation is reserved for those patients refractory to the above mentioned treatment.
For patients with CSS with a mixed response to CSM:
• Dual-chamber permanent pacemaker and atropine can effectively treat the bradycardic response but have no major effect on the hypotensive response. The vasodepressor response should be treated as mentioned above.
DISPOSITION
CSS occurs in the elderly population and presents with falls or syncope often resulting in injury. Up to 55% of the patients who present with symptoms will have recurrent symptoms. This is reduced in the group of patients for whom a pacemaker is indicated. There is no difference in survival in this group of patients when compared with the general population.