Abstract
Thoracic outlet syndrome consists of a constellation of signs and symptoms, including paresthesias and aching pain of the neck, shoulder, and arm. The cause is thought to be compression of the brachial plexus and subclavian artery and vein as they traverse the interscalene triangle, the costoclavicular space, and the subpectoral (subcoracoid) tunnel. Compression or entrapment of the neurovascular structures may be caused by congenitally abnormal structures such as cervical ribs, aberrant scalene muscles, fibrous bands, and/or abnormal pectoralis minor and subscapularis muscles as the plexus cords, subclavian/axillary artery, and the terminal branches of the brachial plexus traverse the subpectoral space. Cervicothoracic tumors and aneurysms must also be considered when evaluating a patient with thoracic outlet syndrome. One or all of the structures may be compressed, thus giving the syndrome a varied clinical expression. Thoracic outlet syndrome is seen most commonly in women between 25 and 50 years of age.
Keywords
thoracic outlet syndrome, brachial plexopathy, cervical radiculopathy, brachial plexus block, cervical rib, Pancoast’s tumor, Adson test, subclavian artery aneurysm
ICD-10 CODE G54.0
The Clinical Syndrome
Thoracic outlet syndrome consists of a constellation of signs and symptoms, including paresthesias and aching pain of the neck, shoulder, and arm. The cause is thought to be compression of the brachial plexus and subclavian artery and vein as they traverse the interscalene triangle, the costoclavicular space, and the subpectoral (subcoracoid) tunnel ( Fig. 24.1 ). Compression or entrapment of the neurovascular structures may be caused by congenitally abnormal structures such as cervical ribs, aberrant scalene muscles, fibrous bands, and/or abnormal pectoralis minor and subscapularis muscles as the plexus cords, subclavian/axillary artery, and the terminal branches of the brachial plexus traverse the subpectoral space ( Fig. 24.2 ). Cervicothoracic tumors and aneurysms must also be considered when evaluating a patient with thoracic outlet syndrome. One or all the structures may be compressed, thus giving the syndrome a varied clinical expression. Thoracic outlet syndrome is seen most commonly in women between 25 and 50 years of age. It has been the subject of significant debate, and the diagnosis and treatment of thoracic outlet syndrome remain controversial.
Signs and Symptoms
Although the symptoms of thoracic outlet syndrome vary, compression of neural structures accounts for most of them. Paresthesias of the upper extremity radiating into the distribution of the ulnar nerve may be misdiagnosed as tardy ulnar palsy. Aching and incoordination of the affected extremity are also common findings. If the pain persists, abnormal position of the shoulder girdle to relieve compression or entrapment of the neurovascular structures may be observed. If vascular compression exists, edema or discoloration of the arm may be noted; in rare instances, venous or arterial thrombosis may occur. Rarely, the symptoms of thoracic outlet syndrome are caused by arterial aneurysm, and auscultation of the supraclavicular region reveals a bruit.
The symptoms of thoracic outlet syndrome may be elicited by various maneuvers, including the Adson test, the costoclavicular test, and the Roo elevated arm stress test, which is also known as the hyperabduction test. The Adson test is carried out by palpating the radial pulse on the affected side with the patient’s neck extended and the head turned toward the affected side ( Fig. 24.3 ). A diminished pulse suggests thoracic outlet syndrome. The elevated arm stress test is performed by having the patient hold his or her arms over the head and open and close the hands. Normally, patients without thoracic outlet syndrome can perform this maneuver for approximately 3 minutes, whereas those suffering from thoracic outlet syndrome experience the onset of symptoms within 30 seconds.
Testing
Plain radiographs of the cervical spine should be obtained in all patients suspected of having thoracic outlet syndrome. These films should be carefully reviewed for congenital abnormalities such as cervical ribs or overly elongated transverse processes. Patients should also undergo chest radiography with apical lordotic views to rule out Pancoast’s tumor. Magnetic resonance imaging (MRI) of the cervical spine is indicated to identify lesions of the cervical spinal cord and exiting nerve roots, as well as cervical ribs and fibrous adhesions ( Fig. 24.4 ). If the diagnosis is still in doubt, MRI of the brachial plexus is indicated to search for an occult pathologic process, including primary tumors of the plexus and aberrant scalene muscles which may cause compression or entrapment ( Fig. 24.5 ). Ultrasonography may also help clarify the diagnosis ( Fig. 24.6 ). Screening laboratory tests consisting of a complete blood count, erythrocyte sedimentation rate, antinuclear antibody testing, and automated blood chemistry may be performed to exclude other causes of the patient’s pain.
