Thoracic Outlet Syndrome

Introduction and prevalence

Thoracic outlet syndrome (TOS) represents a group of conditions that result in the compression of the neurovascular structures that pass through the thoracic outlet. TOS is most common in women, those between 20-40 years age, and with poor posture. TOS can be neurogenic, arterial, or venous; 95% of TOS cases are neurogenic in nature, and therefore the focus of this section will be on neurogenic TOS.

Etiology and Pathophysiology

Most cases of TOS are due to acute trauma causing cervical rib impingement or repeat injuries to the scalene muscles leading to muscle fibrosis and thoracic outlet narrowing. With a trapezius muscle deficiency, the shoulder usually depresses and causes the outlet to diminish, thus increasing the pressure. Clavicle fracture is another cause of increased pressure on the thoracic outlet. The compression on the vasculature and nerves in the thoracic outlet gives rise to the sensation of pain, numbness, and tingling in the shoulder and upper extremities.

Clinical presentation

Arterial TOS most often presents with symptoms of intermittent ischemia of the hand including pain, pallor, claudication, numbness, and coldness. Venous TOS is associated with arm swelling and cyanosis. Patients with neurogenic TOS experience neck pain, trapezius pain, supraclavicular pain, shoulder pain, arm pain, paresthesias, hand weakness, arm weakness, and/or shoulder weakness.

Physical examination

A focused cervical spine and shoulder exam is necessary. Special tests for TOS include Adson's test, Elevated Arm Stress test, and Upper Limb Tension test.

  • In the Adson’s Test, the arm is extended in 30° abduction, while the clinician feels for pulse disappearance, pain, and numbness .

  • In the Elevated Arm Stress Test, while the patient abducts arms to 90° with shoulders in full external rotation and elbows flexed to 90°, he/she opens and closes hands for 30 seconds; pain, numbness, or tingling in the affected extremity is a positive result.

  • In the Upper Limb Tension Test, the patient abducts shoulders to 90° with elbows extended and wrists in full flexion while laterally flexing the head away from affected limb; a positive result is if the pain, tingling, and numbness is reproduced.

Investigations

Cervical spine x-ray can be helpful in providing information about the bony anatomy of the cervical spine, which often can be the culprit. US has 92% specificity and 95% sensitivity in diagnosing venous TOS. Angiography is controversial but can be helpful in diagnosing arterial TOS. Electrodiagnostic studies (EMS) are the gold standard diagnostic mode to diagnose neurogenic TOS.

Management

Conservative management begins with postural correction, sleep positioning correction, and using preventative splints and pads during work. Physical therapy is the mainstay treatment and aims to strengthen the muscles around the thoracic outlet to relieve pressure on the impaired structures. Analgesics and NSAIDs can be used for neuropathic pain, as well as muscle relaxants, anticonvulsants, and/or antidepressants as adjuvants. Some of the newer treatment modalities include injection of local anesthetic, steroids, or botulinum toxin type A into the anterior scalene and pectoralis muscles, however no long-term data regarding efficacy is available. Surgical intervention is controversial but should be considered for patients with severe symptoms; the preferred surgery is a first rib resection aimed at brachial plexus decompression, typically performed by vascular surgeons.