Diagnosis of Thoracic Outlet Syndrome

Diagnostic Evaluation of Thoracic Outlet Syndrome

Part of the challenge of diagnosing thoracic outlet syndrome is distinguishing which symptoms are related to vascular involvement, to neurologic involvement, to both, or to neither and the patient must be tested for all of the above (e.g., arterial TOS is often overlooked if symptoms of neurogenic TOS are prominent). Thoracic outlet syndrome remains a controversial diagnosis and is based entirely on the clinical picture, with attention to:

  • Detailed medical history
  • Physical examination
  • Testing with provocative maneuvers
  • Other selective tests

Medical History

A thorough medical history is an essential component of the diagnostic evaluation for thoracic outlet syndrome. Important information to obtain includes:

  • What activities initiate symptoms
  • Types of symptoms (e.g., numbness, tingling, paresthesia, pain)
  • Review of signs and symptoms and description of the pain (exact location, extent, severity, and duration)
  • Pattern of pain (e.g., how or if it radiates down the arm)
  • Quality of the pain (e.g., shooting pain or aching pain)
  • History of previous trauma or injury and extent of injury (e.g., a hand injury which may have indirectly involved the shoulder)
  • Progression of symptoms since the injury
  • Work history (risk factors for TOS)

Typically, the intensity and frequency of pain and paresthesia increase as the interval of time since the initial injury increases.

Physical Examination

Because the diagnosis of thoracic outlet syndrome is so difficult to pinpoint, the physical examination must focus on all symptoms and not just evaluate symptoms that confirm TOS. Before starting the examination, it is important for the physician to observe the posture of the patient and to notice relevant details such as position of the shoulders (rolled forward, hunched up), and position of the head (forward placement or erect and straight). The focus of the physical exam is on the head, neck, shoulders and arms.

Overall, the following parameters should be evaluated:

  • Thorough musculoskeletal and neurologic evaluation
  • Evaluation of posture and muscle function in the cervical, thoracic, scapular (upper back muscles) and shoulder areas
  • Passive range of motion of the neck, shoulder, elbow, wrist
  • Evaluation of reflexes (biceps and triceps muscles)
  • Manual muscle strength test
  • Sensory response to light touch and warm/cold stimuli
  • Vascular examination to detect acute or chronic blood flow problems (arterial insufficiency; venous thrombosis)
Arms
  • Check for blood pressure differences between the two arms. A difference greater than 20 mm Hg is significant and may be indicative of involvement of the subclavian artery.
  • Compare both arms and hands for temperature, color, edema, skin moisture, nail growth, and other physical characteristics.
  • Evaluate and compare muscle strength in muscle groups of each arm. Strong biceps and weak triceps may be indicative of TOS.

  • Test for carpal tunnel syndrome (CTS) by looking at the Tinel sign and Phalen's test.

    • Tinel sign - a test to detect nerve irritation. The target nerve is lightly tapped (percussed) to elicit a sensation of pins and needles (tingling) in the path of the nerve distribution. This test is positive in carpal tunnel syndrome but not in TOS.

    • Phalen's maneuver - the patient keeps their wrist flexed to the maximum for 30 seconds which compresses the carpal tunnel. If the test is positive for CTS, the patient experiences burning and tingling in the fingers, but not for TOS.

Head and Neck
  • Muscle spasm in head/neck/shoulder region
  • Range of motion
  • Try to reproduce symptoms that appear from brachial plexus compression by tilting the head away from the affected side. Radiating pain is indicative of TOS but does not typically present in CTS or other shoulder-related conditions.
  • Applying pressure with a finger over the brachial plexus of the affected side will typically evoke symptoms of TOS but not CTS or cervical disk disease.
Cervicoscapular Region

The cervicoscapular region is the muscular area of the upper chest and neck. The areas of observation and evaluation include:

  • Observation of posture during sitting and standing. It is most common to see the head placed forward of the thorax (chest) with rounded shoulders turned inward. When this position is maintained over a long term period, it causes changes in the length and strength of muscles in this region.
  • The extent of cervical range of motion and any pain associated with movement
  • Evaluation of individual chest/neck muscles for tightness, weakness, or tenderness
  • Range of motion of the shoulders and the degree of discomfort. Rotator cuff tendonitis (irritation of the rotator cuff which are the 4 muscles that elevate and move the shoulder) is a common finding.

Provocative Maneuvers

In addition to the physical examination, an important aspect in the diagnosis of thoracic outlet syndrome is to verify the effects of the compression of the brachial plexus by attempting to reproduce the patient's symptoms. A variety of provocative thoracic outlet compression maneuvers may be used to reproduce the patient's symptoms, however, none of these tests are considered either highly sensitive or specific for the diagnosis of TOS. Some of the maneuvers are used to evaluate vascular symptoms and some to evaluate nerve compression. Nevertheless, these provocative maneuvers, along with a careful medical history and physical examination, improve the doctor's likelihood of arriving at an accurate diagnosis. Some of the more common provocative maneuvers include:

  • Wright Hyperabduction Test - the radial and ulnar pulses of each wrist are measured at rest and then the radial pulse is measured when the arm is raised 90 degrees. The test is positive if the radial pulse weakens during the maneuver. However, the pulse changes are not definitively diagnostic for TOS since the same changes occur in approximately 7% of the normal population.

  • EAST (Elevated Arm Stress Test) - also called the Roos Maneuver. This is considered one of the more reliable tests for the diagnosis of TOS. The patient stands with arms out and elbow bent at 90 degrees (surrender position) and opens and closes their hands slowly for 3 minutes. Usually, the only sensation is muscle fatigue but if a patient has TOS, the symptoms can be reproduced up to the point that the patient may not even be able to complete the test. Symptoms evoked by the test include:

    • gradual increase of pain in the neck and shoulder region
    • changes of sensation in the fingers
    • pain which radiates down the arm
    • arm pallor when the arm is elevated and hyperemia (abnormally high level of blood) when lowered (if there is arterial TOS)
    • cyanosis and swelling (if there is venous involvement)

  • Halstead Maneuver - the patient stands with shoulders back and arms down. The test is positive if the radial pulse is obliterated while standing in this position.

  • Adson Maneuver - the patient keeps their arms down, turns their head towards the affected side, and breathes deeply. The test is positive if the radial pulse disappears while standing in this position or is weakened during deep inspiration.

There is no consensus regarding provocative maneuvering of the arms as a diagnostic tool for TOS since it has been found that in many individuals without TOS, the same degree of arterial compression occurs when their arms are maneuvered in a similar fashion.

Patients with other neurological conditions, (e.g., CTS or cervical disk disease) may develop various symptoms as a result of individual provocative maneuvers but the patterns are markedly different than those for thoracic outlet syndrome. It is not clear whether the severity of TOS is indicated by how long the patient can tolerate the test. The symptoms which the patient describes following the EAST maneuver are strong indicators for the presence of TOS.

Other Diagnostic Tests

A variety of other diagnostic tests may be used in assessing patients with signs and symptoms of TOS. None of these tests are specific for TOS but are used primarily to rule-out other possible causes of the signs and symptoms that the patient is experiencing. Testing should be done selectively based on the patient's history and physical exam. The tests may include:

  • Nerve Testing - there is no specific test to directly measure nerve compression, necessitating indirect measurements to help in the diagnosis of TOS including:

    • provocative tests at compression sites
    • direct pressure on the nerve
    • combination of these two procedures. The combination of tests is considered positive if the symptoms are reproduced along the expected neural pathways
    • palpation of the scalene muscle for tenderness
    • Tinel sign - physician taps each entrapment site a few times. If the test is positive, a tingling feeling is elicited. This test is usually positive at later stages of nerve compression.

    Caution must be taken to test only one entrapment site at a time (e.g., wrist, elbow, or shoulder) since it is important to isolate the site of compression. It is also important to identify multiple compression or entrapment sites. Research has shown that more than 50% of patients with TOS have clinical evidence of carpal or cubital tunnel syndrome. Provocative maneuvers at nerve entrapment sites in the early stage of TOS may elicit symptoms but electrodiagnostic tests and sensory nerve tests will be negative.

  • Sensory Testing - there are two types of sensory receptors that relay the message of touch to the brain.

    • quickly adapting receptors respond to moving touch. These receptors are tested by threshold vibration, which is the lowest level of vibration needed to evoke a response from these cells.

    • slowly adapting receptors respond to constant touch and are evaluated by cutaneous pressure threshold (i.e., how much pressure must be exerted before the receptors respond.

    The density of the sensory receptors (called innervation density) is assessed by two-point discrimination where two points on the skin, typically a few millimeters apart, are stimulated simultaneously. The threshold is the distance at which the patient perceives 2 separate stimuli. In thoracic outlet syndrome, vibration and pressure thresholds will typically be abnormal during provocation maneuvers but normal at rest.

  • X-ray of cervical spine - to identify any bony abnormalities that may be the cause of pain, including:

    • degenerative cervical spine disease
    • spinal disk abnormalities (e.g., narrowing of the disk space)
    • abnormal C7 transverse processes
    • arthritic changes

  • CT/MRI of the brachial plexus - there is a lack of consensus regarding the efficacy of traditional CT/MRI. Hi-speed multidetector CT is being studied since its resolution is very clear and new computer techniques offer novel ways of imaging layers of tissue. CT may reveal other conditions that may cause symptoms of TOS.

  • Electrophysiologic tests - tests used to measure muscle response to stimulation of nerves. These tests remain controversial and have not generally gained acceptance since they're subject to inaccuracy. Sometimes they are employed for diagnosis of late stages of TOS. Some clinicians also feel that since electrodiagnostic testing is helpful in the diagnosis of carpal and cubital tunnel syndrome, both of which are frequently found with TOS, there is some value of these tests for confirming TOS in an indirect manner.

  • Anterior scalene block - the anterior scalene muscle is injected with a nerve block and if the symptoms abate, it may indicate that the pain is due to muscle spasm, not TOS.