Thoracic outlet syndrome encompasses several diseases. It occurs by compression of nervous or vascular structures in the thoracic outlet region.
Among the most common compressed structures responsible for the symptoms of this syndrome are the brachial plexus and the subclavian artery and vein.
Diagnosis is based on complex signs and symptoms resulting from the compression of neurovascular structures. In most cases, the lack of confirmatory tests with adequate specificity makes diagnosing thoracic outlet syndrome a challenge.
Epidemiology
The incidence of thoracic outlet syndrome is challenging due to the lack of a reliable and objective confirmatory test.
It occurs more frequently in patients between 20 and 50 years and is three times more common in females.
Etiopathogenesis
Several factors can predispose the patient to thoracic outlet syndrome, such as scalene medius abnormalities, scalene minimus, tumors, first rib abnormalities, elongated transverse process of C7, fibrous bands, and cervical rib.
The thoracic outlet is limited anteriorly by the manubrium-clavicular complex, laterally by the first rib, and posteriorly by the vertebral column. This space contains the brachial plexus and the subclavian artery and vein.
This region can be divided into three zones. The most proximal is the interscalene triangle, the most common site of brachial plexus compression. Its boundaries are formed by the scalenus anterior, scalenus medius, and the medial surface of the first rib. The dimension of the interscalene triangle can be reduced with provocative maneuvers. Some anomalous structures, such as the presence of a cervical rib, abnormal muscles, or fibrous bands, can further narrow this site.
The second region is called the costoclavicular space. It is formed by the middle third of the clavicle, the upper border of the scapula and the first rib.
The most distal region, called the subcoracoid space, is formed by the coracoid process, the pectoralis minor, and the ribs. It is a rare place of compression.
Classification
Thoracic outlet syndrome can be divided according to the compressed structures responsible for the patient’s symptoms.
The most common neurogenic form occurs in approximately 98% of cases. It is caused by compression of the brachial plexus. It can be subdivided into a true form, or Gilliatt-Sumner hand syndrome, in which there are objective signs such as atrophy of the hand musculature, or a more frequent form in which there are no objective signs.
The vascular form is rarer and can be subdivided into the arterial form, when the subclavian artery is involved, or the venous form if the subclavian vein is involved.
Clinical condition
The clinical diagnosis of the neurogenic form can be difficult in its most frequent presentation due to the variety of symptoms, the predominance of subjective symptoms, and the lack of objective signs. In the evaluation, excluding other potential causes of pain radiating to the upper limbs is essential.
Symptoms are often bilateral but predominantly in the dominant upper limb. In the neurogenic form, symptoms are usually insidious. The most common complaint of patients is neck pain or shoulder pain radiating to the upper limb. Occasionally, there is a history of traumatic, repetitive, or sustained strain in the upper limb.
The area of pain irradiation will depend on the location of the compressed brachial plexus. In most cases, the lower trunk is involved and causes symptoms of hypoesthesia or paresthesia in the medial border of the forearm and in the 4th and 5th fingers. If there is an involvement of the upper trunk, the patient may complain of pain and paresthesia in the lateral border of the forearm and in the radial fingers of the hand.
Complaints of hand weakness and fatigue are common and are more associated with repetitive or sustained activities with the upper limb above the head.
The atrophy of the hand musculature is not common but can be found in the neurogenic form called true or Gilliatt-Sumner hand syndrome.
Symptoms may suggest a peripheral nerve compression syndrome or a cervical hernia, and the differential diagnosis can be difficult. Thoracic outlet syndrome should be considered when symptoms do not follow a typical distribution of a specific root or nerve or if there is no agreement between physical examination tests or subsidiary tests with the clinical complaint.
Detailed evaluation of peripheral nerves is essential to exclude compressive syndromes. Particular attention should be paid to carpal tunnel syndrome, cubital tunnel syndrome from ulnar nerve compression, and radial nerve compression.
Occasionally, peripheral nerve compression can co-exist with a thoracic outlet syndrome and cause a double compression phenomenon, in which proximal compression can make the distal region more predisposed to producing compressive symptoms.
The cervical region should be examined with greater attention to the possibility that the symptoms radiating to the upper limb are due to radicular pain due to cervical disc herniation. Cervical traction can be used to assist in the differential diagnosis as it improves the symptoms caused by a herniated disc but does not change those caused by the thoracic outlet syndrome. Spurling’s maneuver may be positive in cervical herniated cervical disc hernia and negative in thoracic outlet syndrome. Lateral flexion of the patient’s head to the side of pain and axial compression is performed. In this test, a narrowing of the intervertebral foramen is provoked by the worsening of the symptoms of root compression.
In the vascular form, which is rarer, patients often present with more objective signs and symptoms, which helps in the diagnosis of the disease. In the presence of arterial compression, the patient may experience pallor and cold in the hands. The venous form can cause edema, cyanosis, and superficial venous distension in the affected upper limb.
The vascular form can also cause neurogenic symptoms by ischemia of the distal nerves. Imaging studies usually allow the evaluation of the site of involvement of the vascular system.
Physical examination maneuvers
There are several maneuvers described for the diagnosis of thoracic outlet syndrome. However, they all have low specificity. Therefore, several maneuvers must be combined to improve the quality of diagnosis.
Most of the described maneuvers assess the vascular form of the thoracic outlet syndrome. In the Adson test, the radial artery pulse is palpated with the patient’s arm in abduction and the elbow extended. The patient is then asked to take a deep breath and turn their head to the symptomatic side. If there is compression of the subclavian artery, a reduction in the pulse amplitude of the radial artery can be identified. A positive Adson test does not necessarily indicate the presence of thoracic outlet syndrome, as there is a high frequency of asymptomatic people who present abnormal radial artery pulses during the maneuver.
In the raised arm stress test, the patient is positioned with the shoulder abducted to 180º and the elbow extended. The patient is then asked to open and close the hand quickly for 3 minutes. The patient with a positive test will present symptoms consistent with the clinical complaint.
In patients with a long course of the disease, a supraclavicular Tinel’s sign can be found in the presence of paresthesia radiating through the arm to percussion in the supraclavicular region.
Subsidiary exams
Subsidiary tests help in the differential diagnosis or identification of potential compression sites.
Plain radiography of the cervical spine should be taken in front and side. One should look for first rib abnormalities, a long transverse process at C7, a pseudarthrosis of a clavicle fracture, or a cervical rib. Cervical rib, although associated with thoracic outlet syndrome, is present in approximately 0.5-1.0% of individuals and occurs bilaterally in 50-80% of the time. In less than 10% of cases, compressive symptoms are associated with their presence.
Computed tomography and magnetic resonance imaging may allow the identification of compression of a cervical root by a herniated disc and aid in the differential diagnosis. It may also demonstrate deviation or distortion of nerves and vessels and assess for local anatomic abnormalities in the thoracic outlet that may be responsible for the symptoms.
In patients with signs of vascular compromise, non-invasive tests such as magnetic resonance angiography or Doppler ultrasound can identify the site of compression.
Electrophysiological assessment allows the identification of up to 70% of patients with thoracic outlet syndrome. However, electroneuromyography is not an adequate test to exclude thoracic outlet syndrome, as it can be normal, even in patients with significant symptoms. It may also be helpful for differential diagnosis with peripheral nerve compression syndromes.
Treatment
Occasionally, thoracic outlet syndrome in the vascular form may require urgent treatment. However, in most cases, thoracic outlet syndrome can be treated on an outpatient basis.
In the neurogenic form, conservative treatment should be indicated first, especially if there are no objective findings on physical examination associated with the clinical complaint.
Conservative treatment is done with the recommendation that the patient avoids activities that cause or exacerbate symptoms. Therefore, it may be necessary to change the work environment or role. The myofascial pain syndrome that is usually associated with it should be treated. Exercises are oriented to correct posture, to gain cervical and shoulder range of motion and stretching and strengthening exercises. A study showed that more than 50% of patients reported improvement in the relief of global symptoms and 90% reported improvement in symptoms in the shoulder and cervical region.
Analgesic medications such as nonsteroidal anti-inflammatory drugs and trigger point injections can be helpful in symptomatic control.
Surgical treatment is indicated for cases in which there was no success with conservative treatment appropriately performed for 6 to 12 months and with the maintenance of intense symptoms. Its objective is to promote decompression of the portion of the plexus or compressed vessels.
Several modalities of surgical treatment can be performed by different access routes, such as the transaxillary, supraclavicular, infraclavicular, transthoracic or posterior routes. The choice of the ideal access route or surgical procedure should consider where decompression will be necessary and which structures will need to be resected.
Exercises for Thoracic Outlet Syndrome
In this section, we will discuss several stretches and exercises to help alleviate the symptoms of TOS and improve overall posture.
These techniques focus on stretching the pectoral muscles, performing nerve glides, and mobilizing the first rib.
- Pec Stretches:
Stretching the pectoral muscles is essential for correcting posture and relieving pressure on the nerves and blood vessels in the thoracic outlet. One simple way to stretch the pec muscles is by clasping your hands behind your back and pushing your chest outwards. Hold this stretch for about 30 seconds, relax, and repeat three times.
- First Rib Mobilization:
To perform first rib mobilization, use a firm ball (e.g., massage ball, lacrosse ball) and place it in the small pocket underneath your collar bone where the first rib is located. Relax your arm and tilt your neck to the side. Take a deep breath in, and as you exhale, apply pressure to the ball. Repeat this process four to five times, taking care not to cause pain.
- Pec Stretches with a Foam Roller:
Using a foam roller is another effective way to stretch the pec muscles. Place the foam roller vertically on the ground and lie down with your head resting on the roller. Extend your arms out to the sides, allowing them to drop towards the ground. Hold this position for about 30 seconds, relax, and repeat three times.
- Scapular Squeezes:
Scapular squeezes help improve posture by opening up the chest and strengthening the muscles between the shoulder blades. To perform scapular squeezes, imagine there is a hand in the middle of your back, and try to squeeze that hand with your shoulder blades. Hold the squeeze for 3-5 seconds and then relax. Perform 5-10 repetitions.
- Nerve Glides:
Nerve glides, or nerve flossing, help to loosen the nerves and reduce irritation in the thoracic outlet area. Start with your elbow bent and your head up, then extend your arm while tilting your head to the side. Repeat this motion 10 times. Be cautious not to overdo nerve glides, as they can further irritate the nerve if done excessively.
- Stretching the Scalene Muscles:
The scalene muscles attach to the first rib, and if tight, can pull up on the rib, causing TOS symptoms. To stretch these muscles, place your hands behind your back, turn your head to one side at an angle, and bend your neck to the side. Hold this stretch for 30 seconds and then relax. Perform three repetitions.
Conclusion:
By incorporating these stretches and exercises into your routine, you can help alleviate the symptoms of Thoracic Outlet Syndrome and improve your posture.
Remember to always consult with a healthcare professional before beginning any new exercise regimen.
MD. Physiatrist at University of São Paulo