Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3860_Библиотеки_им_академика_М_И_Перельмана

The thoracic outlet is anatomically defined as a region bounded by the first rib inferiorly, the clavicle superiorly, the scalenus muscles posteriorly, and the costoclavicular ligament anteriorly. compromise is most often compression of the subclavian artery between a cervicle rib and the clavicle. Other sites of compression may be between the scalenus anticus and the scalenus medius tendons or at the costoclavicular space due to a prominent subclavius muscle. The axillary

Although the diagnosis of axillosubclavian venous thrombosis is much easier to make than neurologic tho­racic outlet syndrome, the decisions regarding treatment are more complex. Catheter-directed intravenous throm­bolysis may be effective in patients who have acute symp­toms of axillosubclavian venous thrombosis. With less acute or chronic occlusions, the incidence of complete lysis is of little or no benefit because rethrombosis is virtually inevitable. Some investigators advocate balloon angioplasty for underlying residual venous stenoses after thrombolysis.

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can include changes in mentation, and laryngeal edema with upper airway obstruction. Symptoms may be sub­acute and slowly progressive, or they may have an acute

The SVC is a relatively thin-walled vessel lying within a nondistensible space in the mediastinum, making it sus­ceptible to extrinsic compression by primary tumors or lymphadenopathy.

The SVC syndrome most commonly is secondary to an underlying malignancy of the mediastinum and has been shown to be responsible for 85 to 97% of all cases.

Furthermore, SVC syndrome may occur in up to 10% of all patients with a right-sided intrathoracic mass lesion. Prior to the onset of antibiotic therapy, infectious etiolo­gies of the chest and mediastinum were commonly the source of SVC obstruction. Nevertheless, with the in­crease in the number of immunosuppressed patients sec­ondary to human immunodeficiency virus (HIV) infec­tion with an associated increased incidence of tuberculosis, histoplasmosis, and syphilis, infectious proc­esses remain in the differential diagnosis of SVC syn­drome.

Radionuclide imaging using technetium-99m (Tc99m)­labeled sulfur colloid is a valuable screening tool for suspected SVC obstruction. Serial radionuclide examina­tions can be obtained to evaluate for possible recanali-

zation ofthe central veins orthe restoration of flowfollow­ing therapy.

tion with endovascular stent placement has been shown to be a safe and effective treatment for SVC syndrome.

Within the superior mediastinum, the aortic arch nor­mally gives rise to three major arteries that supply the upper extremities, head, and neck. The first branch is the brachiocephalic trunk, also called the innominate artery. This vessel courses superiorly for a short distance before bifurcating into the right subclavian and right common carotid arteries (Fig. 18-1). The right sub­clavian artery (RSCA) courses superiorly, gives off the right vertebral artery, and then turns laterally to supply the right upper extremity. The right common carotid artery (RCCA) courses superiorly to bifurcate into the right internal and external carotid arteries The second vessel off the aortic arch is the left common carotid ar­tery, which travels cephalad and bifurcates into the left internal and external carotid arteries. The left subclavian artery is normally the final arch vessel. It courses supe­riorly before turning sharply laterally to supply the left upper extremity. The common carotid arteries are paired vessels located anteriorly within the neck. Each common carotid artery courses superiorly, along with the

The ECA is the smaller of the two branches of the common carotid artery. At its origin, the ECA is antero­medial to the ICA. The branches of the ECA are the superior thyroid, ascending pharyngeal, lingual, facial, occipital, and posterior auricular arteries. The ECA then bifurcates into the internal maxillary and superficial tem­poral arteries. Certain branches of the ECA may serve as important collaterals to the intracranial circulation in the setting of ICA stenosis or occlusion. These include the distal branches of the internal maxillary artery and the facial artery, both of which may fill the supraclinoid ICA by anastomosing with the ophthalmic artery. Less com­monly, the ascending pharyngeal artery and the middle

Fibromuscular dysplasia (FMD) is an idiopathic process that leads to stenoses of medium to small arteries as a result of segmental overgrowth of fibrous and muscular elements of the arterial media and, to a lesser extent, the adventitia (Fig. 18-7). Originally described in renal arter­ies, FMD most commonly affects the cervical ICA, but it may involve any of the major arteries of the neck. is often bilateral and is associated with spontaneous arte­rial dissection as well as intracranial aneurysms. It is more common in women and tends to occur in patients younger than the expected age distribution for athero­sclerosis. Radiographically, FMD usually appears as alter­nating segments of stenosis and dilatation, producing a so-called “string of beads” appearance.

In some cases, collateral pathways are already present but do not manifest until normal hemodynamics are altered, as in the case of subclavian steal syndrome. Subclavian steal syndrome occurs when the subclavian artery, most commonly the left, becomes occluded proximal to the ori­gin of the vertebral artery. In this setting, the distal sub­clavian artery “steals”blood from the posterior circulation of the brain by means of retrograde flow through the ipsi­lateral vertebral artery (Fig. 18-9). The decreased blood flow to the posterior circulation of the brain may result in ischemia, from which patients often become symptomatic when exercising the affected upper extremity.