Physical Medicine and Rehabilitation for Thoracic Outlet Syndrome Clinical Presentation

Pain, numbness and/or tingling, and heaviness of the involved upper extremity are common complaints reported by a patient with thoracic outlet syndrome (TOS). Often, the symptoms are vague and generalized. The entire extremity may be involved; additionally, neck pain and headaches are reported concomitantly. A retrospective study by Kim et al of 13 patients with true neurogenic TOS reported a more specific pattern of findings, determining that hypesthesia in the medial forearm or ulnar digits was among the condition’s most common neurologic symptoms. ^[10]

Symptoms may begin insidiously after repetitive or stressful activity, such as prolonged computer keyboard use or mechanical and overhead work. Trauma, such as an automobile accident with occurrence of a whiplash injury, also has been associated with onset of TOS with a frequency of up to 23%. Sports activities, especially throwing and swimming, have been implicated as well; symptoms may be similar to those of a clavicular fracture, with a delayed onset from hours to weeks.

Autonomic phenomena (eg, cold hands, blanching, swelling) also may be reported. The proximity of the stellate ganglion to the first rib articulation, which is often dysfunctional or restricted in TOS, has been postulated as a cause.

According to the Society for Vascular Surgery, neurogenic TOS can be diagnosed when three of the following four criteria exist ^[15] :

• Pathologic signs and symptoms (pain and/or tenderness) at the thoracic outlet
• Signs and symptoms of nerve compression (distal neurologic changes, frequently more severe when the arms are overhead or dangling)
• Absence of other pathology that might cause the symptoms
• A positive response to a correctly executed scalene muscle test injection

A careful neurologic and musculoskeletal examination is essential to diagnose thoracic outlet syndrome (TOS) adequately. Often, the most important aspect of the physical examination is to diagnose or rule out other problems of the neck and arm. ^{[16, 17]}  Typically, there are no objective findings such as loss of a reflex or strength, but specific weakness of the abductor pollicis brevis has been noted in cases of true neurogenic TOS. ^[10]

The mainstay of the physical examination diagnosis of TOS involves the so-called stress tests (or provocative maneuvers) (see the images below). The sensitivity and specificity of these tests have been low in the studies on TOS completed to date. Different techniques for performing and interpreting these tests are discussed in the literature and vary even more in the bedside clinical situation.

Scalene focal (left) and regional (right) stress tests for thoracic outlet syndrome. Both tests can be easily combined to enhance the stress effect (may be helpful in mild cases).

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Pectoral focal (left) and regional (right) stress tests for thoracic outlet syndrome.

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The most common tests are the Adson maneuvers, where the head is placed in extension and side bending while the patient takes a deep breath and holds it, followed by rotation to stretch or tether the plexus and/or artery by the anterior and middle scalenes. The maneuver is held for 15-30 seconds while the clinician observes for onset of symptoms and obliteration of the pulse. Symptoms have been reported to the side of bending and, more commonly, to the side away from bending. If the symptoms are reported on the side of bending, then this finding overlaps with the Spurling sign, commonly used to assist in the diagnosis of cervical radiculopathy. Some examiners ask the patient to pull the head forward while maintaining the test position, causing the anterior scalene to contract against the plexus to enhance the stress effect.

Hyperabduction of the involved arm also can be used to stress the outlet; however, this maneuver often causes symptoms and loss of pulse even in normal individuals and may be misleading. The area of compression with this maneuver is considered more distal and frequently located at the anterior humeral head and plexus, with tethering under the pectoralis minor muscle.

Costoclavicular bracing (military maneuver) closes the space between the clavicle and first rib and may reproduce symptoms.

Focal stress tests involve applying pressure directly to the anterior scalene or upper segment of the pectoralis minor. These tests are considered positive if symptoms are reproduced within 15-30 seconds. In addition, some authors have noted a positive Tinel sign (percussing over the plexus) as diagnostic for TOS.

The elevated arm stress test has been noted to be highly sensitive for TOS. The upper extremity is held in the "stick-'em-up" position with the arms abducted and elbows flexed (both at 90°) for 3 minutes, while the patient simultaneously and vigorously flexes and extends the fingers (grasp and release). This test is considered positive if the patient cannot complete the full 3 minutes. Unfortunately, this test is challenging even for individuals without neurovascular symptoms to complete; thus, it may have limited practical usefulness in most clinical situations. In one study, over 80% of patients with carpal tunnel syndrome presenting to an electrodiagnostic medicine laboratory had a positive elevated arm stress test results.

Careful observation for asymmetry of the upper chest wall may reveal clavicular irregularity consistent with prior fracture. A nontender hard mass over the middle third of the clavicle often is noted. Deformity from displaced fracture (with or without nonunion) or exuberant callus could be responsible for direct compression of the plexus. Pressure on the clavicle can reproduce or aggravate symptoms, especially when nonunion is present; motion can be detected between the fragments.

Thoracic outlet syndrome (TOS) most likely has multiple causes. The primary cause is believed to be mechanical or postural. Stress, depression, overuse, and habit all can lead to the forward head, droopy shoulder, and collapsed chest posture that allows the thoracic outlet to narrow and compress the neurovascular structures (see the image below). ^[14] Accessory ribs or fibrous bands also may be present, predisposing the site to narrowing and compression. Large breasts have been implicated as a contributing cause by pulling the chest wall forward (anterior and inferior); this theory has been supported by relief of discomfort following reduction mammoplasty. TOS has also been associated with breast implants, which may increase tension under the chest wall muscles and irritate the neurovascular tissue.

Progressive postural decompensation with neurovascular compression. A: Normal resting posture. B: Shoulder protraction beginning; the sternomastoid muscles are shortening, drawing the head anteriorly and inferiorly. C: Advanced deformity with adaptive shortening of scalene and pectoralis minor muscles. Also note narrowed costoclavicular space (ribs 1-5 have been relatively elevated). Neurovascular compression is evident at all 3 sites.

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Trauma can lead to decompensation or shifting of structures in the shoulder and chest wall, leading to symptom onset. Additionally, trauma with fracture of the clavicle can result directly in compression of the plexus from bone fragments, exuberant callus, hematoma, or pseudoaneurysm. Following median sternotomy, brachial plexus injury can occur from displacement of the ribs, which usually involves the C8 fibers, distinguished from the typical pattern that primarily involves T1.

Primary vascular lesions, such as thrombus or aneurysm, may be present as well as secondary problems such as emboli. Tumors, such as upper lobe lung lesions (Pancoast tumor), are also possible causes.

Many other problems may predispose an individual to TOS, some of which are classic perpetuators of myofascial pain syndrome, including the following:

• Sleep disorder

• Hormonal imbalance (estrogen, thyroid)

• Inflammatory disorder (rheumatoid arthritis)

• Fibromyalgia

• Nutritional insufficiency (B vitamins, folate, vitamin C)

• Anemia

• Infection

• Masses, tumors, axillary lymph nodes

• Mechanical disorders (short leg, hyperlordosis, hypolordosis)

• Psychologic (stress, depression)

• Nerve entrapment/impingement (other sites)