Thoracic outlet syndrome

Thoracic outlet syndrome is defined as a set of variable clinical signs and symptoms resulting from compression of the brachial plexus, subclavian artery, or vein as they pass through the anatomical passages that carry these structures from the neck to the upper extremity. This often underdiagnosed clinical entity has an incidence of 10 cases per 100,000 inhabitants. However, anatomical studies in cadavers suggest that up to 90% of the population have anatomical variants that may determine the presence of this syndrome. The condition is more common in women, with a 4:1 ratio.

The narrowing of this passage can be acquired or congenital in three specific anatomical areas:

1. The interscalene triangle, the most medial of the compartments, contains the superior, middle, and inferior trunks of the brachial plexus and the subclavian artery. Anteriorly, the anterior scalene, posteriorly, the middle and posterior scalenes, and inferiorly, the first rib. This is the most common site of neurological compression.
2. The costoclavicular space, the middle compartment, is the most common site of vascular compression. It is bordered superiorly by the clavicle, anteriorly by the subclavius ​​muscle, and posteriorly by the first rib and the middle scalene muscle.
3. The lesser retropectoral space, the more lateral compartment, is bordered anteriorly by the pectoralis minor muscle, the subscapularis muscle superiorly, and the anterior thoracic wall inferiorly. In this compartment, we find the divisions of the brachial plexus and the axillary vascular bundle.

The anatomical abnormalities that can affect these compartments are:

• Scalene muscle hypertrophy or their insertional variability.
• Presence of the minimal accessory scalene muscle.
• Soft tissue tumors.
• Congenital fibrous bands.
• Anomalous muscle bands.
• Cervical rib.
• Prominent C7 transverse processes, bone callus, or displacement of the first rib.
• Bone tumors.
• Sternoclavicular joint injuries.

Classification of Thoracic Outlet Syndrome
Depending on the affected component, we have:

1.-Neurogenic thoracic outlet syndrome, due to compression of the brachial plexus. It has two types:

• True or classic, rare, 1 case per million inhabitants. Also known as Gilliat-Summer syndrome, it is characterized by atrophy of the abductor pollicis brevis muscle and the hypothenar and interosseous muscles of the hand.
• Disputed (non-neurogenic), the most common form of thoracic outlet syndrome (accounting for 90-95% of all cases with a prevalence of up to 80 cases per 1,000 inhabitants).

2.-Arterial thoracic outlet syndrome represents between 1 and 5% of all cases, occurring in patients who perform repetitive upper extremity movements with arms raised above the shoulders.

3.-Venous thoracic outlet syndrome represents 2 to 3% of cases.

Thoracic outlet syndrome symptoms
The variability of clinical manifestations and the lack of specific data make the diagnosis of this syndrome a real challenge.

Within the neurogenic origin, the symptoms will vary depending on the location of the compression. The most common is in the lower part of the brachial plexus, affecting the C8-T1 roots, which will cause clinical involvement of the ulnar area of ​​the forearm, hand, axillary region, and anterior shoulder. Upper brachial plexus compression will affect the C5-C7 roots, with clinical presentation of insidious supraclavicular pain radiating to the same side of the face, head, scapula, or distal involvement of the radial nerve on the back of the second and third fingers.

It is important to perform a differential diagnosis with peripheral compression neuropathies (carpal tunnel syndrome, Fröhse's arcade syndrome, etc.) and cervical radiculopathies. Remember that thoracic outlet syndrome typically presents with a broad anatomical distribution of symptoms that do not follow a specific radicular pattern.
In venous thoracic outlet syndrome, we find significant pain and edema in the upper extremity with a sensation of heaviness and cyanosis that worsens after physical activity. In arterial syndrome, pain, numbness, coldness, and pallor worsen at low temperatures.

Diagnosis of thoracic outlet syndrome

A physical examination of the cervical spine, shoulders, and upper extremities is essential, assessing the patient's head-neck-shoulder position and general posture.

Comparison of the affected extremity with the contralateral extremity will provide information on temperature, color, muscle atrophy, and trophic changes in the nails. Palpation of the supraclavicular region may reveal tenderness in this area, palpable masses, etc.

There are several exploratory maneuvers that allow us to suspect neurovascular compression and approximate the diagnosis:

• Wright's test: Patient seated with arm in hyperabduction and external rotation. Head turned to the side opposite the extremity being examined. A decrease in the radial pulse is assessed (this can occur in up to 7% of the healthy population).
• Adson test: The patient sits with the arm abducted at 30° with the head turned to the side being examined. Forced and sustained inspiration is requested, which causes elevation of the first rib (floor of the interscalene triangle) and increased tone of the anterior scalene muscle. The radial pulse is simultaneously palpated and its reduction or elimination is assessed.
• Roos test: described as the most reliable test for diagnosing thoracic outlet syndrome, especially the neurogenic type. The patient sits with the arms abducted at 90° and the elbows also flexed at 90°. In this position, the patient is asked to open and close their hands for a period of 3 minutes. Patients with thoracic outlet syndrome will report symptoms such as paresthesia, heaviness in the arms, or exacerbation of their usual pain, and may fail to perform the test.

Additional Tests

• Plain X-ray: A cervical X-ray and chest X-ray are a first diagnostic approach that allows us to rule out cervical ribs, prominent transverse processes, bone callus in fractures, degenerative processes of the cervical spine, or neoplasia (Pancoast tumor).
• Electromyography: In many cases, electromyography can be negative, but it helps us rule out cervical root involvement, brachial plexus injuries, or peripheral compression neuropathies.
• Ultrasonography: useful in the evaluation of syndromes with venous and arterial involvement, demonstrating alterations in flow velocity in the presence of stenosis or aneurysms, the presence of venous thrombi, and the ability to correlate the patient's symptoms with the dynamic ultrasound findings.
• Arteriography and CT venography: provide vascular images of great diagnostic aid in cases of arterial or venous syndrome.
• Magnetic Resonance Imaging: the examination of choice for evaluating brachial plexus compression in neurogenic syndrome.

Treatment
Treatment of thoracic outlet syndrome is usually conservative. Physical therapy is primarily indicated in cases of neurogenic involvement, while surgical treatment is reserved for vascular and neurogenic cases that do not respond to conservative treatment.
Correction of predisposing factors: In the early stages of the neurogenic form, symptoms may be caused by traction of the lower trunk of the brachial plexus, a condition that is exacerbated by obesity, poor postural hygiene, or occupational factors.

Conservative treatment aims to improve:

• The normal arthrokinetics of the surrounding joints.
• Correction of muscle weaknesses and imbalances.
• Improving the mobility of nerve structures to avoid compression or tension in the gorge.

Physical therapy aims to reduce pressure on neurovascular structures through:

• Relaxation of the scalene muscles.
• Strengthening the muscles of the shoulders and shoulder girdle (trapezius, levator scapulae, SCM, pectorals, and suboccipital muscles).
• Performing postural exercises to correct poor posture.

Physical therapy is often combined with treatments such as hydrotherapy, massage, or pharmacological treatment (NSAIDs and muscle relaxants). Anesthetic blocks of the stellate ganglion or the scalene muscles have also been used.

Make an appointment with Dr. Jordi Jiménez. He will see you in the center of Palma and help you regain your quality of life.