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Thoracic Outlet Compression Syndromes
Thoracic outlet compression syndromes are a group of poorly defined disorders characterized by pain and paresthesias in a hand, the neck, a shoulder, or an arm. They appear to involve compression of the brachial plexus (and perhaps the subclavian vessels) as these structures traverse the thoracic outlet. Diagnostic techniques have not been established. Treatment includes physical therapy, analgesics, and, in severe cases, surgery.
Pathogenesis is often unknown but sometimes involves compression of the lower trunk of the brachial plexus (and perhaps the subclavian vessels) as these structures traverse the thoracic outlet below the scalene muscles and over the 1st rib, before they enter the axilla, but this involvement is unclear. Compression may be caused by a cervical rib, an abnormal 1st thoracic rib, abnormal insertion or position of the scalene muscles, or a malunited clavicle fracture. Thoracic outlet syndromes are more common among women and usually develop between age 35 and 55.
Pain and paresthesias usually begin in the neck or shoulder and extend to the medial aspect of the arm and hand and sometimes to the adjacent anterior chest wall. Many patients have mild to moderate sensory impairment in the C8 to T1 distribution on the painful side; a few have prominent vascular-autonomic changes in the hand (eg, cyanosis, swelling). In even fewer, the entire affected hand is weak.
Rare complications include Raynaud syndrome and distal gangrene.
Diagnosis is suggested by distribution of symptoms. Various maneuvers are alleged to demonstrate compression of vascular structures (eg, by extending the brachial plexus), but sensitivity and specificity are poor. Auscultating bruits at the clavicle or apex of the axilla or finding a cervical rib by x-ray can aid in diagnosis. Although angiography may detect kinking or partial obstruction of axillary arteries or veins, neither finding is incontrovertible evidence of disease. Electrodiagnostic testing is warranted in all patients with suggestive symptoms, and MRI (see Hereditary Motor Neuropathy With Liability to Pressure Palsies (HNPP) : Diagnosis) of the brachial plexus, cervical spine, or both is usually also necessary.
Most patients without objective neurologic deficits respond to physical therapy, NSAIDs, and low-dose tricyclic antidepressants.
If cervical ribs or subclavian artery compression is identified, an experienced specialist should decide whether surgery is necessary. With few exceptions, surgery should be reserved for patients who have significant or progressive neurovascular deficits and do not respond to conservative treatment.
Consider these syndromes if patients have unexplained pain and paresthesias that begin in the neck or shoulder and extend down the medial arm.
Do electrodiagnostic tests and usually MRI of the brachial plexus and/or cervical spine.
Treat most patients with analgesics and physical therapy.
Consider surgery if patients have a cervical rib or subclavian artery compression and neurovascular deficits that progress despite conservative treatments.
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