Also called: TOS
Important: This page is general information, not medical advice. It does not recommend or prescribe any treatment. Always consult your doctor or pharmacist before starting, stopping or changing any medicine.
About Thoracic Outlet Syndrome
Thoracic outlet syndrome (TOS) causes pain in the shoulder, arm, and neck. It happens when the nerves or blood vessels just below your neck are compressed, or squeezed. The compression can happen between the muscles of your neck and shoulder or between the first rib and collarbone. You may feel burning, tingling, and numbness along your arm, hand, and fingers. If a nerve is compressed, you may also feel weakness in your hand. If a vein is compressed, your hand might be sensitive to cold, or turn pale or bluish. Your arm might swell and tire easily.
TOS is more common in women. It usually starts between 20 and 50 years of age. Doctors do nerve and imaging studies to diagnose it.
There are many causes of TOS, including:
- Injury
- Anatomical defects
- Tumors that press on nerves
- Poor posture that causes nerve compression
- Pregnancy
- Repetitive arm and shoulder movements and activity, such as from playing certain sports
Treatment depends on what caused your TOS. Medicines, physical therapy, and relaxation might help. Surgery may also be an option. Most people recover.
It sits within Brain and Nerves.
The lead U.S. institute for this subject is the National Institute of Neurological Disorders and Stroke.
When to speak to someone. Reading about a topic cannot tell you whether it applies to you. Speak to a doctor or pharmacist if symptoms are severe, sudden, getting worse, or simply not going away — and seek emergency care immediately for chest pain, breathing difficulty, sudden weakness or confusion, or a serious allergic reaction.
Research on Thoracic Outlet Syndrome
39 studies areregistered for this condition on ClinicalTrials.gov, the U.S. National Library of Medicine's public registry. A selection is below — the links go straight to the registry entry, not to a summary of ours.
What a registered study does and does not mean. Registration means a study exists and has been declared publicly. It says nothing about whether the treatment being tested works, is safe, or is available to you. Many studies find no benefit — that is what research is for. Never seek out an experimental treatment on the strength of a registry entry alone.
Research currently under way
- Motivational Interviewing in Thoracic Outlet SyndromeHacettepe University
- Effect of Low-Power Laser Therapy on Pain and Functional Outcomes in Patients With Thoracic Outlet SyndromeCairo University
- Vascular Lab Resource (VLR) BiorepositoryThe Cleveland Clinic
- A Study of Paravertebral Block in Thoracic Outlet SyndromeMayo Clinic
- Study Assessing The "Best of" Radiotherapy vs the "Best of" Surgery in Patients With Oropharyngeal CarcinomaEuropean Organisation for Research and Treatment of Cancer - EORTC
- Dysfunctional Breathing in Individuals With Thoracic Outlet SyndromeHacettepe University
Research already completed
- Assessment of the Impact of Thoracic Outlet Syndromes on the Performance at WorkUniversity Hospital, Lille
- DEFILE-QoL5 - Evaluation of the Long-term Surgical Management of the Thoraco-brachial Displacement SyndromeUniversity Hospital, Angers
- Outpatient Office Based Endovascular ProceduresMethodist Health System
- CHAO Tos: Codeina, HederA Helix, LevOdropropizina Para la TOSPontificia Universidad Catolica de Chile
- Cali Sin Tos Aim 2Yale University
- Differences in Quality of Life After Thoracic Outlet Syndrome SurgeryUniversity Hospital, Angers
Study data from ClinicalTrials.gov, a service of the U.S. National Library of Medicine. Retrieved 2026-07-30. Registry entries are supplied by study sponsors and investigators; ClinicalTrials.gov does not verify their scientific validity. PocketsInfo is not affiliated with, and not endorsed by, the NLM or the NIH.
Where to read more
Rather than paraphrase, we point you to the primary sources. Every link below is to a government health agency, a national institute or a recognised medical body — grouped by what you are trying to find out.
Learn More
- Electromyography (EMG) and Nerve Conduction StudiesNational Library of Medicine
- Musculoskeletal UltrasoundRadiological Society of North America
- National Institute of Neurological Disorders and StrokeNational Institute of Neurological Disorders and Stroke
- Thoracic Outlet SyndromeJohns Hopkins Medicine
Clinical Trials
- ClinicalTrials.gov: Thoracic Outlet SyndromeNational Institutes of Health
Medical subject headings
Clinicians and researchers index this subject under Thoracic Outlet Syndrome. These are the terms to use when searching medical literature.
This page is built from the MedlinePlus health topic record for Thoracic Outlet Syndrome, a service of the U.S. National Library of Medicine (NLM), National Institutes of Health. Information is from MedlinePlus.gov. PocketsInfo is not affiliated with, and is not endorsed by, the NLM or the NIH. Retrieved 30 July 2026.