Thoracic Outlet Syndrome
What is it?
Thoracic Outlet Syndrome (TOS) is characterized by upper extremity pain or paresthesia caused by occlusion, compression, injury or irritation to the neurovascular structures traversing the thoracic outlet. These structures exit the cervical spine and travel down the arm to the hands.
There are three types of TOS which include arterial, venous, and neurogenic.
Arterial TOS is caused by occlusion of the subclavian artery from stenosis, aneurysm, embolus, or compression from a cervical rib or anomalous first rib. It is the most serious cause of TOS but only accounts for 1-2% of all cases. Arterial thoracic outlet syndrome results in coldness, weakness, fatigability, and diffuse pain.
Venous TOS is caused by subclavian vein obstruction and results in symptoms such as edema, cyanosis, and venous dilation. Venous TOS is only seen in less than 5% of all cases of TOS.
The remainder of TOS patients from mechanical compression of the neurovascular bundle or Neurogenic TOS. Neurogenic TOS is by far the most common cause of TOS, accounting for well over 95% of all causes. Neurogenic thoracic outlet syndrome results from compression or irritation to the lower trunk or medial cord of the brachial plexus. Neurogenic TOS is subdivided into one of the three sites of compression which include the scalenes (neck area), pectoral (chest area), and costoclavicular (between the first rib and clavicle).
Cervical ribs are present in approximately 1% of the population and are bilateral in up to 80% of cases. Additional contributing factors include osseous overgrowth of a prior clavicle or first rib fracture and a history of trauma. Up to 23% of cervical soft tissue injuries may include a TOS component.
Poor posture, like upper cross syndrome, is a predisposing factor for all mechanical forms of TOS. Those who require static positions such as computer users, assembly line workers, and students are more likely to experience TOS. Athletes that play sports like swimming, volleyball, tennis, and baseball pitchers are subjected to stressors.
Symptoms of TOS include pain, paresthesias, and motor weakness of the neck, arm, and hand. Neck, arm, and hand pain is often gradual in onset and aggravated by elevation of the arms or excessive head and neck movement. Palpation of the supraclavicular fossa often reveals local tenderness.
The most common neurological findings include hyperesthesia in the medial forearm or ulna (pink side) digits and weakness of the abductor muscle. Motor deficits, especially diminished grip strength, are possible.
Range of motion assessment may reveal hypertonicity in the scalenes or pectoral muscles. Clinicians should also assess the mobility of the cervical spine, first rib, scapulothoracic, and glenohumeral joints.
After a clinical assessment additional diagnostic workup is dependent on what is discovered. Cervical spine radiographs can detect the presence of a cervical rib and cervical degenerative changes. MRI is the method of choice when searching for neurological compression. Diagnostic ultrasonography can play a role in diagnosis and can image the patient in a variety of positions that may cause compression of the brachial plexus.
In the absence of acute or threatening neurovascular problems, conservative care should be the treatment of choice of TOS.
Joint manipulation may be indicated for restrictions in the cervical spine, first rib, cervicothoracic junction, shoulder, elbow, hand, and wrist. Stretching and myofascial release techniques should address problems in cervical spine, scalenes, and pectoral muscles as well as distal sites. Retraining of postural faults and diaphragmatic breathing is critical. Nerve mobilization, focusing on the ulnar nerve, will likely play a role in recovery.
Lifestyle modifications may include avoidance of repetitive postural stress and workstation adjustments. Patients should avoid carrying heavy loads, especially on the shoulder. Briefcases, laptop cases or heavy shoulder bags should be lightened. Bra straps may need additional padding or consider replacing them with a sports bra.
Patients with progressive motor deficits require advanced diagnostic workup and referral. Even in the presence of a symptomatic cervical rib, studies have shown that candidates who undergo surgical resection do not have functional improvements matching those who choose conservative care. Other studies have shown good surgical outcomes for those who trail conservative care prior to surgery.