What Is Thoracic Outlet Syndrome?

  • Janell Penha Doctor of Pharmacy (Pharm.D.), Pharmacy, University of Hawaii at Hilo, United States


Thoracic Syndrome (TOS) is a medical condition that affects the upper body’s veins, which subsequently leads to various distressing symptoms.¹ Understanding TOS is crucial as it can have a significant impact on a person’s quality of life. In this comprehensive article, we will delve into the causes, symptoms, diagnosis, treatment and prognosis.

Understanding thoracic outlet syndrome²

Thoracic Outlet Syndrome (TOS) is a group of disorders that involve the compression of the nerves, arteries, or veins in the thoracic outlet. The thoracic outlet is the area between the collarbone (clavicle) and the first rib. As a result of this compression, various symptoms can arise depending on the specific structures affected.

There are three types of thoracic outlet syndrome:

  • Neurogenic thoracic outlet syndrome: the most common type of TOS. This type is characterised by the compression of a group of nerves called the brachial plexus. These nerves come from the spinal cord. The nerves control muscle movements and feeling in the shoulder, arm and hand.
  • Venous thoracic outlet syndrome: This syndrome occurs when one or more of the veins under the collarbone are compressed and damaged, which can then result in blood clots.
  • Arterial thoracic outlet syndrome: the least common type of TOS. This type is characterised by the compression of one of the arteries under the collarbone, which can result in injury to the artery, leading to the subsequent formation of a bulge, known as an aneurysm or a blood clot formation.

Causes and risk factors³,⁴

The compression of either of the vessels in the area between the neck and shoulder can be a result of many different factors, including the following:

  • Anatomical factors: thoracic outlet syndrome often occurs due to anatomical variations or abnormalities in the thoracic outlet area. These can include a cervical rib (an extra rib), a fibrous band connecting the spine and the rib, etc.
  • Trauma or injury: traumatic events, such as a car accident or a fall, can cause internal changes that then compress the vessels. Moreover, the onset of symptoms related to traumatic accidents or injuries is often delayed.
  • Repetitive movements: Occupations or activities that involve repetitive arm movements, such as throwing a ball, lifting boxes overhead, swinging a baseball bat, etc.
  • Weight: being overweight or obese would exert extra pressure on the joints.
  • Posture
  • Pregnancy

The risk of developing thoracic outlet syndrome depends on several other factors that are out of our control. These include:

  • Sex: women are more than three times more likely to be diagnosed with thoracic outlet syndrome than men. Women with larger breasts are particularly at risk due to the consequential posture of rolling their shoulders forward as a result of the weight of their breasts, causing them to have a bad posture.
  • Age: although this condition is able to be diagnosed at any age, it is most commonly found in adults between the ages of 20 and 50.


It is equally crucial to not only understand the causes but also the symptoms of thoracic outlet syndrome in order to be properly and timely diagnosed. The symptoms of thoracic outlet syndrome can vary depending on the type. 

The symptoms of neurogenic thoracic outlet syndrome include:

  • Numbness or tingling in the arm or fingers
  • Pain or aches in the neck, shoulder, arm or hand
  • Arm fatigue with activity
  • A weakening grip

The symptoms of venous thoracic outlet syndrome can include:

  • A change of colour of the hand or one or more fingers
  • Hand or arm pain and swelling

The symptoms of arterial thoracic outlet syndrome may include:

  • A pulsating lump near the collarbone
  •  Cold fingers, hands or arms
  • Hand and arm pain
  • A change in colour in one or more of the fingers or the entire hand
  • Weak or no pulse in the affected arm


Diagnosing thoracic outlet syndrome can present challenges due to the wide variation in symptoms among individuals. Cases will typically initiate with a comprehensive assessment, which may include a review of your medical history, a physical examination, and potentially several types of diagnostic tests.

The physical examination has the main aim of identifying potential signs of thoracic outlet syndrome. It may involve checking for specific indicators, such as a noticeable depression in your shoulder or the presence of a bony protrusion above your collarbone. Additionally, there might be an assessment for any swelling or changes in skin colour in the affected arm. This evaluation may also include checking the pulse and assessing the range of motion. 

The medical history is similarly important as it provides information about the life of the individual, their symptoms and any other prior medical concerns affecting the individual and/or any family member if relevant. 

To complement these and confirm the diagnosis of thoracic outlet syndrome, some tests may be requested. These include:

  • Ultrasound: An ultrasound employs sound waves to generate images of your body. It is often the initial imaging test used to assist in diagnosing thoracic outlet syndrome. Ultrasound can help determine the type of thoracic outlet syndrome present in each individual.
  • X-ray: X-rays can reveal the presence of an additional rib, known as a cervical rib. They can also help exclude other conditions that might be responsible for the symptoms presented.
  • Computerized Tomography (CT) Scan: CT scans employ X-rays to produce cross-sectional images of your body. In some cases, a dye may be injected into a vein to enhance visualization of blood vessels, a technique known as CT angiography. CT scans are valuable for identifying the location and cause of blood vessel compression.
  • Magnetic Resonance Imaging (MRI): MRIs utilize radio waves and magnetic fields to create highly detailed images of the body. MRIs can help pinpoint the location and cause of blood vessel compression. Sometimes, a contrast dye is injected to improve the visibility of blood vessels. MRIs can reveal anatomical variations, such as a fibrous band connecting the spine to the rib or the presence of a cervical rib, which, as mentioned previously, may be contributing to the symptoms present.
  • Arteriography and Venography: These tests involve the insertion of a thin, flexible tube called a catheter through a small incision, often in the groin area. During arteriography, the catheter navigates through the major arteries, while venography involves navigating through the veins. The catheter is advanced to the affected blood vessels, and a contrast dye is injected to create X-ray images of your arteries or veins. This will help assess whether the veins or arteries are compressed. Furthermore, if a clot is present, medications might be administered through the catheter to dissolve the clot.
  • Electromyography (EMG): During an EMG, a fine needle electrode is inserted through the skin into various muscles. This test evaluates the electrical activity of the muscles during contraction and at rest. It can help determine if there is any nerve damage which may be contributing to the symptoms.


For many individuals, especially those diagnosed in the early stages, a conservative approach to treatment can be highly effective. The treatment plan may encompass the following components:

  • Physical Therapy: If diagnosed with neurogenic thoracic outlet syndrome, physical therapy serves as the initial treatment strategy. Therapeutic exercises are designed to enhance the strength and flexibility of the shoulder muscles, ultimately opening up the thoracic outlet. This approach not only improves your range of motion but also enhances your posture. Over time, these exercises may alleviate pressure on the blood vessels and nerves within the thoracic outlet.
  • Medications: these may be prescribed to manage the condition. These may include anti-inflammatory drugs to reduce swelling, pain relievers to alleviate discomfort, or muscle relaxants to promote muscle relaxation. If blood clots are present, blood-thinning medications may be recommended.
  • Clot-Dissolving Medications: In cases of venous or arterial thoracic outlet syndrome accompanied by blood clots, clot-dissolving medications, known as thrombolytics, may be administered. These medications are introduced into the veins or arteries to dissolve existing blood clots. Following thrombolytic treatment, anticoagulants might be prescribed to prevent the formation of new blood clots.
  • Injections: For the management of neurogenic thoracic outlet syndrome, one of the possible courses of treatment is the use of injections as a therapeutic approach. These injections may consist of a local anaesthetic, onabotulinumtoxinA (commonly known as Botox), or steroid medication. These injections can effectively reduce pain and discomfort.

Should conservative treatments prove ineffective, surgical intervention may be recommended. Surgery is typically performed by a specialized surgeon, either a thoracic surgeon with expertise in chest surgery or a vascular surgeon specializing in blood vessel procedures.

It is crucial to be aware that thoracic outlet syndrome surgery carries potential risks and complications. These may include nerve injury, specifically damage to the brachial plexus. Additionally, surgery may not completely alleviate the symptoms or may only provide partial relief, with the possibility of symptom recurrence.

Surgical procedures to address thoracic outlet syndrome, known as thoracic outlet decompression, can be conducted through various approaches. These methods generally involve the removal of a muscle and a portion of the first rib to alleviate compression. In some cases, surgical repair of damaged blood vessels may also be necessary. In instances of venous or arterial thoracic outlet syndrome with clots, clot-dissolving medications might be administered prior to proceeding with thoracic outlet decompression. Alternatively, it may also require a separate procedure to remove or repair blood clots in the affected vein or artery, which is typically performed prior to thoracic outlet decompression. In addition, for individuals with arterial thoracic outlet syndrome, it may be necessary to replace the damaged artery, either from an artery from another part of the body or an artificial one (a graft).


Despite the distress that the individuals affected experience from this condition, they can be hopeful that following their respective treatment, they have a good prognosis, as the vast majority of patients have their symptoms alleviated completely.


To conclude, Thoracic Outlet Syndrome (TOS), presents a range of challenges for both patients and healthcare professionals. There are various triggers for TOS, including anatomical anomalies, trauma, repetitive motions, weight factors, pregnancy, and more; recognizing these factors is essential for prevention and early intervention. Symptoms of TOS, whether neurogenic, venous, or arterial, can significantly impact an individual's life, urging, therefore, for timely recognition and diagnosis are crucial for proper management. The diagnostic process involves a medical history review, physical examination, and various tests like ultrasound, X-rays, CT scans, MRI, arteriography, venography, and electromyography in order to confirm a diagnosis. Treatment options vary from conservative measures like physical therapy and medications to surgical interventions like thoracic outlet decompression and vascular procedures, which are tailored to each individual's specific needs. Despite this, the prognosis for TOS patients is generally positive, especially with prompt diagnosis and treatment. Most patients experience complete relief from their symptoms with appropriate intervention.


  1. Venous Thoracic Outlet Syndrome: Causes and Symptoms [Internet]. Cleveland Clinic. [cited 2023 Oct 7]. Available from: https://my.clevelandclinic.org/health/diseases/22317-venous-thoracic-outlet-syndrome
  2. Mayo Clinic. Thoracic outlet syndrome - Symptoms and causes [Internet]. Mayo Clinic. 2016. Available from: https://www.mayoclinic.org/diseases-conditions/thoracic-outlet-syndrome/symptoms-causes/syc-20353988
  3. ‌Venous Thoracic Outlet Syndrome: Causes and Symptoms [Internet]. Cleveland Clinic. Available from: https://my.clevelandclinic.org/health/diseases/22317-venous-thoracic-outlet-syndrome
  4. Mayo Clinic. Thoracic outlet syndrome - Symptoms and causes [Internet]. Mayo Clinic. 2016. Available from: https://www.mayoclinic.org/diseases-conditions/thoracic-outlet-syndrome/symptoms-causes/syc-20353988
  5. Thoracic outlet syndrome - Diagnosis and treatment - Mayo Clinic [Internet]. Mayoclinic.org. 2019. Available from: https://www.mayoclinic.org/diseases-conditions/thoracic-outlet-syndrome/diagnosis-treatment/drc-20353994
  6. Kaplan J, Kanwal A. Thoracic Outlet Syndrome [Internet]. PubMed. Treasure Island (FL): StatPearls Publishing; 2023 [cited 2023 Oct 7]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK557450/#:~:text=Both%20nonsurgical%20and%20surgical%20treatment
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Érica Ramos Lopes Sousa

Medical Undergraduate - MBBS / BSc , Imperial College London

Érica, a first-year medical student at Imperial College London, is already displaying a keen interest in the fields of neurosurgery and genetics. Her foundation in academic writing, acquired during her International Baccalaureate studies, serves as a strong platform for her goal of crafting informative health-related articles for the general public. As she progresses through her medical education, she harbours ambitions of further enhancing her expertise and insights, with the ultimate aim of contributing to significant advancements in the field of medicine.

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