Thoracic outlet syndrome (TOS) is a group of disorders caused by compression of nerves or blood vessels as they pass from the neck and chest into the arm. Depending on which structures are affected, TOS can cause pain, numbness, weakness, swelling, color changes, or problems with circulation in the arm and hand.
At Saint John’s Health Center, thoracic outlet syndrome is evaluated according to the pattern of symptoms, the structures involved, underlying anatomy, and the effect on nerve function or blood flow. Because TOS can resemble other conditions involving the neck, shoulder, arm, or hand, an accurate diagnosis is an important first step in determining appropriate treatment.
What Is the Thoracic Outlet?
The thoracic outlet is the area between the lower neck, collarbone, and upper chest where important nerves and blood vessels travel into the arm. These structures include the brachial plexus, which carries nerve signals between the spinal cord and upper extremity, as well as the subclavian artery and vein.
The available space in this region can be affected by bones, muscles, scar tissue, posture, injury, or congenital anatomy. When a nerve or blood vessel becomes compressed, symptoms can develop along the shoulder, arm, hand, or fingers.
Types of Thoracic Outlet Syndrome
Thoracic outlet syndrome is classified according to whether compression primarily affects the nerves, veins, or arteries. The type of TOS influences the symptoms a patient experiences, how urgently the condition needs to be evaluated, and which treatments may be appropriate.
Neurogenic Thoracic Outlet Syndrome
Neurogenic thoracic outlet syndrome occurs when the brachial plexus nerves are compressed as they travel through the thoracic outlet. It is the most common form of TOS and can cause pain, numbness, tingling, weakness, or fatigue in the shoulder, arm, or hand.
Symptoms often become more noticeable with repetitive arm movement or when the arms are held overhead. Because similar symptoms can result from cervical spine disorders, carpal tunnel syndrome, shoulder conditions, or other nerve problems, neurogenic TOS can require careful evaluation before the diagnosis is established.
Venous Thoracic Outlet Syndrome
Venous thoracic outlet syndrome occurs when the subclavian vein is compressed, interfering with normal blood flow from the arm back toward the heart. Patients may develop arm swelling, heaviness, aching, bluish discoloration, or prominent veins across the shoulder or chest.
Compression can sometimes contribute to formation of a blood clot in the vein. When thrombosis develops in association with repeated or strenuous upper-extremity activity, the condition is often called Paget-Schroetter syndrome or effort thrombosis.
Arterial Thoracic Outlet Syndrome
Arterial thoracic outlet syndrome occurs when the subclavian artery is compressed. Although less common than neurogenic or venous TOS, arterial compression can interfere with blood supply to the arm and hand and may damage the artery over time.
Symptoms may include hand or arm pain, coldness, pale or bluish skin, weakness, diminished pulses, or other signs of reduced circulation. Blood clots or arterial injury can make arterial TOS a more urgent vascular problem requiring prompt evaluation.
Symptoms of Thoracic Outlet Syndrome
Symptoms vary depending on which nerves or blood vessels are being compressed and may range from intermittent discomfort to significant neurologic or vascular problems. They most often affect one arm, although thoracic outlet abnormalities can occasionally occur on both sides.
Symptoms of Neurogenic TOS
- Neck, shoulder, arm, or hand pain
- Numbness or tingling in the arm or fingers
- Weakness of the arm or hand
- Arm heaviness or fatigue
- Symptoms that worsen with overhead activity
- Reduced endurance during repetitive arm movement
Symptoms of Venous TOS
- Swelling of the arm or hand
- Arm heaviness or aching
- Bluish or dusky discoloration
- Prominent veins across the shoulder, upper chest, or arm
- Symptoms that develop after strenuous or repetitive arm activity
Symptoms of Arterial TOS
- Coldness of the hand or arm
- Pale or bluish discoloration
- Pain or fatigue with arm use
- Weak or diminished pulse
- Numbness or weakness associated with reduced circulation
Sudden arm swelling, significant discoloration, a cold or unusually pale hand, severe pain, or signs of impaired circulation should be evaluated promptly because they may indicate a blood clot or compromised blood flow.
What Causes Thoracic Outlet Syndrome?
Thoracic outlet syndrome develops when the space available for nerves or blood vessels becomes narrowed or when surrounding structures place abnormal pressure on them. In some patients, the cause is primarily anatomical, while in others symptoms develop following injury, repetitive movement, muscle changes, or a combination of factors.
Repetitive or Overhead Activity
Repeated overhead movement can place stress on the thoracic outlet and surrounding muscles. Athletes, musicians, construction workers, hairstylists, and others whose activities require repetitive arm elevation may develop symptoms related to compression or irritation of the nerves or blood vessels.
In some individuals, increased muscle development around the shoulder and upper chest can also reduce available space within the thoracic outlet.
Posture and Shoulder Mechanics
Posture and movement patterns can influence the relationship among the collarbone, ribs, shoulder girdle, and surrounding muscles. Rounded shoulders, muscle imbalance, or poor mechanics may contribute to compression in susceptible patients.
For neurogenic TOS in particular, correcting posture and shoulder mechanics can become an important part of conservative treatment.
Injury and Scar Tissue
Trauma involving the neck, shoulder, collarbone, or upper chest can alter the anatomy of the thoracic outlet. Fractures, soft-tissue injuries, or scar formation may narrow the available space or change how the nerves and blood vessels move through it.
Symptoms may begin soon after an injury or develop gradually as inflammation, muscle tightness, or scar tissue progresses.
Cervical Rib and Other Anatomical Differences
Some people are born with an extra rib arising from the cervical spine, known as a cervical rib, or with other skeletal differences that reduce space within the thoracic outlet. Variations involving the first rib, collarbone, muscles, or connective tissues may also contribute to nerve or vascular compression.
These anatomical differences do not always cause symptoms, but they can increase susceptibility to TOS when combined with repetitive activity, trauma, or other changes in the surrounding tissues.
How Thoracic Outlet Syndrome Is Diagnosed
Thoracic outlet syndrome can be challenging to diagnose because symptoms overlap with a number of neck, shoulder, nerve, and vascular disorders. Diagnosis is based on the clinical history, physical examination, pattern of symptoms, and selected imaging or functional studies rather than a single test in every patient.
The evaluation also differs depending on whether neurogenic, venous, or arterial TOS is suspected. Vascular forms often require studies that directly assess blood flow or identify thrombosis, while neurogenic TOS may require a broader evaluation to rule out other causes of arm pain, numbness, or weakness.
Medical History and Physical Examination
The physician will ask when symptoms occur, which activities make them better or worse, whether the arms are frequently used overhead, and whether there has been a previous neck, shoulder, or collarbone injury. Work activities, athletic participation, previous treatments, and the presence of swelling or color changes can provide important diagnostic clues.
During the physical examination, the physician may assess posture, shoulder movement, muscle strength, sensation, tenderness, pulses, swelling, and changes that occur when the arm is placed in certain positions.
X-Ray
Chest, neck, or shoulder X-rays may help identify a cervical rib, abnormal first rib, previous clavicle fracture, or other skeletal features that could contribute to compression.
X-rays do not diagnose every form of TOS but can provide useful information about the anatomy of the thoracic outlet.
Ultrasound and Vascular Imaging
Duplex ultrasound can evaluate blood flow through the arteries and veins and may identify vascular compression or thrombosis. In some cases, imaging is performed with the arm in different positions to determine whether blood flow changes with movement.
CT angiography, MR angiography, venography, or other vascular studies may be used when more detailed information is needed about the subclavian artery or vein.
MRI and Advanced Imaging
MRI may be used to evaluate soft tissues, nerves, muscles, and surrounding anatomy or to investigate other conditions involving the cervical spine or shoulder that may produce similar symptoms.
The type of imaging selected depends on the suspected form of TOS and what the clinical team needs to clarify before determining treatment.
Electromyography and Nerve Conduction Studies
Electromyography (EMG) and nerve conduction studies evaluate how well nerves communicate with muscles. These studies may help identify other nerve disorders or neurologic conditions that can mimic neurogenic TOS.
Because patients with neurogenic TOS may have normal electrodiagnostic studies, results are interpreted as part of the broader clinical evaluation rather than as a stand-alone test.
Scalene Muscle Block
In selected patients with suspected neurogenic TOS, a local anesthetic may be injected into the anterior scalene muscle. Temporary improvement in symptoms after the injection can provide additional support that compression within the thoracic outlet is contributing to the patient’s symptoms.
A scalene block is not required for every patient, but it may be useful when the diagnosis remains uncertain or when surgery is being considered.
Conditions That Can Mimic Thoracic Outlet Syndrome
Many disorders can produce symptoms similar to thoracic outlet syndrome, particularly pain, numbness, tingling, or weakness in the arm and hand. Identifying competing diagnoses is an important part of evaluating suspected neurogenic TOS.
- Cervical disc disease or cervical radiculopathy
- Carpal tunnel syndrome
- Ulnar nerve compression
- Shoulder disorders, including rotator cuff disease or bursitis
- Peripheral nerve injuries
- Other neurologic or vascular conditions affecting the arm
Some patients can have more than one condition at the same time, which is another reason treatment should be based on a careful clinical evaluation rather than symptoms alone.
Treatment for Thoracic Outlet Syndrome
Treatment depends on the type of thoracic outlet syndrome, severity of symptoms, underlying anatomy, and whether nerves or blood vessels are being affected. Neurogenic TOS is often treated initially with conservative measures, while venous and arterial TOS may require more direct vascular treatment or surgical decompression.
The goal is not simply to reduce discomfort but to relieve compression, protect nerve or vascular function, restore normal use of the arm, and reduce the risk of complications or recurrence.
Treatment for Neurogenic Thoracic Outlet Syndrome
Physical therapy is commonly the first treatment for neurogenic TOS. Therapy may focus on posture, shoulder positioning, flexibility, breathing mechanics, muscle balance, and movement patterns that increase pressure within the thoracic outlet.
Activity modification, anti-inflammatory or pain-relieving medications, and selected injections may also be considered. When symptoms remain significant despite appropriate conservative treatment, thoracic outlet decompression surgery may be discussed.
Treatment for Venous Thoracic Outlet Syndrome
Venous TOS requires attention to both the compression and any associated blood clot. Treatment may include anticoagulation, catheter-based treatment of thrombosis in selected patients, and surgical decompression of the thoracic outlet.
The treatment sequence depends on how recently the clot developed, the degree of venous obstruction, and whether the vein has been damaged by chronic compression.
Treatment for Arterial Thoracic Outlet Syndrome
Arterial TOS generally requires specialist vascular evaluation because reduced blood flow, thrombosis, aneurysm formation, or embolization can threaten circulation to the arm or hand. Treatment may include medication, removal of arterial clot when necessary, and surgical decompression.
If the subclavian artery has been damaged, surgical repair or reconstruction may also be required.
Thoracic Outlet Decompression Surgery
Surgery is designed to create more space for the compressed nerves or blood vessels. Depending on the patient’s anatomy and the type of TOS, this may involve removal of the first rib or a cervical rib, division or removal of scalene muscles, removal of scar tissue, or treatment of affected blood vessels.
The surgical approach is individualized to the structures causing compression. Patients being considered for surgery undergo careful evaluation to confirm the diagnosis and determine whether decompression is likely to improve symptoms or protect vascular function.
Learn more about treatment and surgery for thoracic outlet syndrome.
Recovery and Long-Term Outlook
Recovery depends on the type and duration of thoracic outlet syndrome, the structures involved, and whether treatment is conservative or surgical. Many patients with neurogenic TOS improve with physical therapy and changes in posture or activity, while vascular TOS may require more intensive treatment to restore normal blood flow and prevent future complications.
Following surgery, rehabilitation often focuses on restoring shoulder mobility, rebuilding strength, and gradually returning to normal activities. Long-standing nerve compression may take longer to improve, and some patients require continued therapy after the initial treatment period.
Preventing Recurrent Symptoms
Long-term management may include maintaining good shoulder mechanics, continuing prescribed exercises, modifying repetitive activities, and avoiding positions that consistently provoke symptoms. Patients whose TOS developed in association with work or sports may benefit from changes in technique or ergonomics.
Patients treated for venous or arterial TOS may also require vascular follow-up to confirm that circulation remains adequate and to monitor for recurrent narrowing or thrombosis.
Frequently Asked Questions About Thoracic Outlet Syndrome
What does thoracic outlet syndrome feel like?
Thoracic outlet syndrome can cause pain, numbness, tingling, weakness, heaviness, swelling, or changes in temperature or skin color in the arm or hand. The exact symptoms depend on whether nerves, veins, or arteries are being compressed.
Symptoms of neurogenic TOS are often triggered or worsened by overhead activity, while vascular TOS may cause more noticeable swelling, discoloration, coldness, or circulation changes.
Is thoracic outlet syndrome serious?
Neurogenic TOS can cause persistent pain and functional limitations but is not usually an emergency. Venous and arterial TOS can be more serious because compression may lead to blood clots or impaired circulation.
Sudden swelling, significant discoloration, severe pain, or a cold or pale hand should be evaluated promptly.
Can thoracic outlet syndrome be treated without surgery?
Yes. Many patients with neurogenic TOS are initially treated with physical therapy, posture correction, activity modification, and other non-surgical measures. Some improve sufficiently without requiring an operation.
Venous or arterial TOS is managed differently because blood clots or vascular injury may require more immediate intervention and surgical decompression.
What is a cervical rib?
A cervical rib is an extra rib that develops above the normal first rib and arises from the cervical spine. Most people with a cervical rib never develop symptoms, but in some patients it can reduce space within the thoracic outlet and contribute to nerve or blood vessel compression.
Why is thoracic outlet syndrome difficult to diagnose?
Symptoms of TOS overlap with many common disorders involving the neck, shoulder, arm, and hand. Neurogenic TOS in particular does not always produce an abnormal result on a single diagnostic test.
Diagnosis therefore depends on the pattern of symptoms, physical examination, exclusion of competing conditions, and selected imaging or nerve studies interpreted together.
What is Paget-Schroetter syndrome?
Paget-Schroetter syndrome is a form of venous thoracic outlet syndrome in which compression of the subclavian vein contributes to development of a blood clot, often following strenuous or repetitive upper-extremity activity. It is sometimes referred to as effort thrombosis.
Because a venous blood clot can cause significant swelling and other complications, sudden symptoms should receive prompt medical evaluation.
Thoracic outlet syndrome care is part of the broader Pulmonary and Thoracic Center of Excellence at Saint John’s Health Center. Our specialists evaluate the anatomy and functional effects of thoracic outlet compression to distinguish neurologic symptoms from venous or arterial disease and determine an appropriate treatment pathway.
Care may involve physical therapy, advanced imaging, vascular evaluation, minimally invasive procedures, and thoracic surgery when needed. The goal is to address the source of compression while protecting nerve and vascular function and helping patients return safely to work, exercise, and normal daily activities.
If you have questions regarding Thoracic Outlet Syndrome, diagnosis, treatment, or of other thoracic conditions, please call today. Click here to request an appointment.
