Thoracic Outlet Syndrome (TOS)

Anatomy of the thoracic outlet

The brachial plexus (the network of nerves to the arm) and the subclavian artery and vein pass from the neck and chest to the arm through three tight spaces:

1. The scalene triangle: between two neck muscles (anterior and middle scalenes) and the first rib. Nerves and the artery pass here.
2. The costoclavicular space: between the collarbone (clavicle) and the first rib. The vein is especially vulnerable here.
3. The pectoralis minor space: under a chest muscle near the shoulder.

Anything that narrows these spaces, such as an extra rib, tight or enlarged muscles, scar tissue or drooping shoulders, can compress the structures inside.

Types of thoracic outlet syndrome

Causes and risk factors

• Anatomical variations: an extra rib from the lowest neck vertebra (cervical rib, in less than 1% of people), a long transverse process, or fibrous bands.
• Trauma: car crashes and whiplash, falls, and collarbone fractures.
• Repetitive overhead activity: swimming, baseball pitching, volleyball, weightlifting, painting, stocking shelves.
• Posture: drooping shoulders, forward head posture, heavy backpacks.
• Muscle bulk: enlarged scalene or pectoral muscles in athletes.
• Weight gain and large breasts in some people.

Symptoms in detail

Neurogenic TOS

• Aching pain in the neck, shoulder, chest and arm
• Pins and needles or numbness, often along the inner forearm and in the ring and little fingers
• Weakness and clumsiness of the hand
• Arm fatigue and heaviness when lifting the arms
• Headaches at the back of the head
• Symptoms worse with arms overhead, carrying, typing or driving
• In rare true neurogenic TOS, wasting of the muscles at the base of the thumb (Gilliatt-Sumner hand)

Venous TOS

• Rapid swelling of the whole arm, often after strenuous activity
• Heaviness, aching and bluish discoloration
• Visible distended veins on the shoulder, chest and arm
• Clot in the subclavian vein, a form of deep vein thrombosis

Arterial TOS

• Coldness, pallor and pain in the hand and fingers, especially with use
• Color changes that resemble Raynaud's phenomenon, usually in one hand
• Small clots traveling to the fingers, causing ulcers or gangrene

How TOS is diagnosed

TOS, especially the neurogenic type, is hard to diagnose because no single test confirms it, and many conditions cause similar symptoms.

Examination

• Elevated arm stress test (EAST or Roos test): raising both arms in a "hands up" position and opening and closing the hands for 3 minutes reproduces symptoms.
• Upper limb tension test: stretching the nerves reproduces arm symptoms.
• Tenderness over the scalene muscles and pain reproduction with pressure.
• Adson's test: checking whether the wrist pulse disappears with certain neck and arm positions. Many healthy people have a positive result, so it is not diagnostic by itself.

Tests

• X-ray of the neck and chest to look for a cervical rib or abnormal first rib.
• Duplex ultrasound of the subclavian vein and artery with arms in different positions.
• CT or MR angiography/venography for suspected vascular TOS.
• Nerve conduction studies and EMG: often normal in neurogenic TOS but help rule out carpal tunnel syndrome, cubital tunnel syndrome and cervical radiculopathy.
• Scalene muscle block: a local anesthetic injection into the anterior scalene. Temporary relief supports the diagnosis and predicts a good response to surgery.

Treatment

Neurogenic TOS

Physical therapy is the first treatment for most people, usually for at least 3 to 6 months:

• posture correction and shoulder blade (scapular) strengthening
• stretching of the scalene and pectoral muscles
• nerve gliding exercises
• breathing techniques to reduce overuse of neck muscles
• workplace changes: avoiding sustained overhead work, adjusting desk setup, and lighter bags

Other measures include pain relief, weight management and, sometimes, botulinum toxin injections into the scalene muscles.

Surgery is considered when symptoms are severe and persist despite good therapy. The operation, thoracic outlet decompression, removes the first rib (and any cervical rib) and releases the scalene muscles. Many patients improve, though recovery takes months and ongoing therapy is needed.

Venous TOS

• Anticoagulation (blood thinners) for the clot.
• Catheter-directed thrombolysis to dissolve a recent clot.
• Surgical decompression (first rib resection) is usually recommended to prevent the clot from coming back, often followed by a vein balloon procedure if narrowing persists.

Arterial TOS

Surgery to remove the cervical rib or abnormal first rib and repair or bypass the damaged artery, plus removal of any clots. Aneurysms and clots in the hand may need additional procedures.

Outlook

Most people with neurogenic TOS improve with therapy and activity changes. Those who need surgery usually improve, though some keep mild symptoms. Venous and arterial TOS have good outcomes when treated promptly. Delayed treatment can lead to chronic arm swelling, recurrent clots or hand damage.

Frequently asked questions

What are the symptoms of thoracic outlet syndrome?

Neurogenic TOS causes neck, shoulder and arm pain with tingling and numbness, often in the ring and little fingers, plus weakness and arm fatigue when the arms are raised. Venous TOS causes sudden arm swelling and bluish color. Arterial TOS causes a cold, pale, painful hand.

How do doctors test for thoracic outlet syndrome?

They use the history and provocative tests, such as the elevated arm stress test, plus X-rays for an extra rib, ultrasound or CT and MR angiography for vascular types, and nerve studies to rule out other conditions. A scalene muscle injection can support the diagnosis.

What exercises help thoracic outlet syndrome?

Physical therapy programs include posture correction, shoulder blade strengthening, stretching of the scalene and chest muscles, nerve gliding and breathing exercises. They should be guided by a therapist, because some exercises can worsen symptoms if done incorrectly.

Is thoracic outlet syndrome serious?

Neurogenic TOS is painful and can limit work and daily life but is not life-threatening. Venous and arterial TOS are more serious because they can cause blood clots, lung clots or loss of blood flow to the hand, and need urgent treatment.

When is surgery needed for thoracic outlet syndrome?

Surgery is usually recommended for venous and arterial TOS, and for neurogenic TOS when severe symptoms persist after several months of good physical therapy. The operation typically removes the first rib and releases the scalene muscles to decompress the outlet.