Thoracic Outlet Syndrome
Expert guidance from Mr Ashley Simpson, Consultant Peripheral Nerve Surgeon. Understanding symptoms, diagnosis, investigations, physiotherapy, surgery and referral routes for neurogenic and vascular thoracic outlet syndrome.
What Is Thoracic Outlet Syndrome?
Thoracic outlet syndrome, often shortened to TOS, is a group of conditions caused by compression of important nerves or blood vessels as they pass from the neck and chest into the arm.
The "thoracic outlet" is the narrow passage around the lower neck, collarbone, first rib and upper chest. Through this space pass the brachial plexus — the network of nerves supplying the arm and hand — as well as the subclavian artery and subclavian vein.
When these structures are compressed, irritated or stretched, patients can develop pain, heaviness, pins and needles, numbness, weakness, swelling, colour change or vascular symptoms in the arm.
TOS is often difficult to diagnose because symptoms may overlap with more common conditions such as cervical radiculopathy, carpal tunnel syndrome, cubital tunnel syndrome, shoulder pathology, complex regional pain syndrome or chronic neck and shoulder pain.
The Three Main Types of Thoracic Outlet Syndrome
TOS is not a single condition. It is a group of related disorders, each involving a different structure and requiring a different management pathway.
Neurogenic TOS
Caused by compression or irritation of the brachial plexus. The most common form, accounting for the great majority of cases.
Patients often describe arm pain, heaviness, fatigue, tingling, numbness or weakness. Symptoms are often worse with the arms elevated, during overhead activity, driving, carrying, lifting, typing or sustained postures.
The symptoms may not follow a single dermatome or one named peripheral nerve distribution. This non-dermatomal pattern is one reason neurogenic TOS is frequently missed.
Venous TOS
Involves compression of the subclavian vein. May present with sudden arm swelling, heaviness, cyanosis or visible veins around the shoulder and chest wall.
Can occur after strenuous or repetitive upper limb activity. This may represent effort thrombosis, also called Paget-Schroetter syndrome.
Suspected venous TOS requires urgent vascular assessment.
Arterial TOS
Rare but important. Involves compression or damage to the subclavian artery, often associated with a cervical rib, anomalous first rib or fibrous band.
Patients may develop a cold, pale hand, weak pulses, digital colour change, pain with exertion, embolic symptoms or signs of limb ischaemia.
Suspected arterial TOS requires urgent vascular referral.
Why Neurogenic TOS Is So Often Missed
Neurogenic TOS is one of the more challenging diagnoses in upper limb nerve practice. Many patients have persistent symptoms but normal routine scans and normal standard nerve conduction tests.
This does not mean the symptoms are imaginary. It means that the compression may be dynamic, positional, intermittent, or affecting the brachial plexus in a way that is not captured by routine tests.
Patients with neurogenic TOS may spend months or years moving between specialties before receiving a clear explanation. During that time, symptoms may affect work, sleep, exercise, mental health and confidence.
"Normal tests do not always exclude neurogenic thoracic outlet syndrome. The diagnosis is built from the clinical story, the pattern of symptoms, examination findings, exclusion of mimics and careful specialist judgement."— Mr Ashley Simpson
Mr Simpson's Published Work on TOS
Mr Ashley Simpson has authored a British Journal of General Practice clinical practice article entitled "Recognising and managing thoracic outlet syndrome in primary care."
The article was written to help GPs and primary care clinicians recognise TOS, identify red flags, avoid unnecessary investigations, start sensible conservative treatment and refer patients to the right specialist pathway.
Published Article
Sivathasan N, Simpson AI. Recognising and managing thoracic outlet syndrome in primary care. British Journal of General Practice. 2026.
Common Symptoms of Neurogenic TOS
The key diagnostic clue is often the pattern. Neurogenic TOS symptoms are typically position-dependent and may not fit neatly into one nerve or one spinal root distribution.
Pain
Neck, shoulder, trapezius, chest wall or upper back pain, often radiating into the arm or hand.
Sensory Symptoms
Pins and needles, tingling or numbness — often affecting the whole hand or the ulnar side of the hand.
Heaviness and Fatigue
A feeling of heaviness, fatigue or weakness in the arm, particularly with sustained use.
Activity-Related Worsening
Symptoms worse with overhead activity, driving, carrying, lifting, exercise or sustained posture.
Hand Function
Difficulty using the hand for fine tasks. A sense that the arm "does not feel right" even when routine tests are normal.
Sleep Disturbance
Sleep disturbance because of arm discomfort, particularly when lying on the affected side.
Non-Dermatomal Pattern
Symptoms that do not follow a single nerve root or peripheral nerve distribution — a hallmark of brachial plexus involvement.
Positional Dependence
Symptoms that change with arm or neck position, particularly worsening with elevation or sustained overhead use.
Red Flags That Need Urgent Assessment
Most neurogenic TOS is not an emergency, but some presentations should be assessed urgently. Recognising these warning signs is essential for all clinicians and patients.
Anatomy: Where Compression Happens
Thoracic outlet compression can occur at three main anatomical sites. Understanding these locations helps explain why symptoms vary between patients and why targeted treatment is important.
1. Interscalene Triangle
Lies between the anterior scalene muscle, middle scalene muscle and first rib. The brachial plexus and subclavian artery pass through this region. A common site of compression in neurogenic TOS.
2. Costoclavicular Space
The space between the clavicle and first rib. Narrowing here can affect the neurovascular bundle and is particularly important in venous TOS.
3. Subpectoral Space
Lies beneath the pectoralis minor tendon near the coracoid. Compression here can produce symptoms similar to neurogenic TOS and is sometimes described as pectoralis minor syndrome.
How TOS Is Diagnosed
There is no single test that proves or excludes neurogenic TOS in every patient. Diagnosis is based on a careful combination of history, examination, exclusion of other conditions and, where appropriate, targeted investigations.
A specialist assessment will usually consider the following:
Symptom Pattern
Whether symptoms are provoked by arm position and whether they are localised to the thoracic outlet, shoulder girdle or brachial plexus.
Differential Diagnosis
Whether the symptoms fit a cervical root, peripheral nerve or shoulder diagnosis instead, and whether there are vascular signs.
Objective Findings
Whether there are objective neurological deficits and whether the patient has tried appropriate physiotherapy.
Investigation Review
Whether investigations support or contradict the clinical diagnosis, and whether further targeted tests are needed.
Physical Examination
During examination, Mr Simpson will assess the neck, shoulder, scapula, brachial plexus, arm and hand. The examination looks for both TOS and alternative diagnoses.
Examination Components
- Posture and shoulder girdle position
- Neck movement and cervical nerve root signs
- Shoulder examination
- Motor testing of the upper limb and hand
- Sensory testing and reflexes where relevant
- Tinel signs over peripheral nerves
- Palpation of the supraclavicular fossa and pectoralis minor region
- Provocative manoeuvres such as the Elevated Arm Stress Test (Roos test)
- Upper limb tension testing
- Vascular examination where indicated
Important
Provocative tests can support the diagnosis, but they are not definitive on their own. They must be interpreted in the context of the whole clinical picture.
A thorough examination also actively seeks alternative diagnoses — the goal is to find the correct cause of symptoms, not simply to confirm TOS.
Investigations
Investigations are used to support the diagnosis, identify structural risk factors, exclude mimics, and detect vascular TOS where suspected. A normal standard investigation does not necessarily exclude neurogenic TOS.
Cervicothoracic Radiograph
Can show a cervical rib, elongated C7 transverse process, anomalous first rib or other bony abnormality that may contribute to compression.
MRI Cervical Spine
May be used to exclude cervical disc prolapse, foraminal stenosis or other cervical causes of arm symptoms.
MRI Shoulder
Helpful when symptoms suggest rotator cuff disease, instability, labral pathology or other local shoulder conditions.
MRI Neurography or Brachial Plexus Imaging
Specialist imaging may help in selected cases but is not required for every patient.
Nerve Conduction Studies and EMG
Can help exclude carpal tunnel syndrome, cubital tunnel syndrome, cervical radiculopathy and other nerve disorders. In true neurogenic TOS, detailed testing may include medial antebrachial cutaneous sensory studies and assessment of lower brachial plexus muscles. A normal test does not necessarily exclude neurogenic TOS.
Vascular Imaging
Duplex ultrasound, CT angiography, MR angiography or venography are particularly important when venous or arterial TOS is suspected, especially where there is swelling, colour change, vascular compromise or thrombosis.
Conditions That Can Mimic TOS
Many conditions can resemble thoracic outlet syndrome. A good assessment actively looks for these, rather than assuming all arm symptoms are TOS.
Nerve Conditions
- Cervical radiculopathy
- Carpal tunnel syndrome
- Cubital tunnel syndrome
- Ulnar neuropathy
- Brachial neuritis
- Peripheral nerve tumour
- Peripheral neuropathy
Shoulder and Musculoskeletal
- Rotator cuff disease
- Shoulder instability
- Frozen shoulder
- Chronic neck and shoulder pain
Other Conditions
- Complex regional pain syndrome
- Vascular disease
- Chronic pain syndromes
Initial Management: Conservative Treatment
Most patients with suspected neurogenic TOS should start with conservative treatment unless there are urgent vascular signs or progressive neurological deficits.
Physiotherapy Focus Areas
The cornerstone of treatment is structured physiotherapy, ideally delivered by a therapist familiar with thoracic outlet syndrome.
Posture and Scapular Control
Addressing shoulder girdle position and movement patterns that contribute to compression.
Strengthening and Flexibility
Shoulder girdle strengthening, scalene and pectoralis minor flexibility, and breathing mechanics.
Neural Mobility and Graded Return
Neural mobilisation techniques and graded return to activity, with ergonomic changes and avoidance of sustained provocative positions early in rehabilitation.
Adjunctive Treatment
Adjunctive treatment may include:
- Simple analgesia
- Anti-inflammatory medication where appropriate
- Neuropathic pain medication
- Pacing strategies
- Support for sleep, work and activity modification
When to See a Specialist
Specialist assessment is appropriate when symptoms are persistent, severe, diagnostically unclear, progressive or function-limiting.
1
Persistent Symptoms
Symptoms have not improved despite appropriate physiotherapy, or the diagnosis remains uncertain after initial assessment.
2
Progressive Neurology
Progressive weakness or muscle wasting, or significant impact on work, sleep or daily function.
3
Normal Tests, Convincing Pattern
The patient has had multiple normal tests but a convincing clinical pattern consistent with neurogenic TOS.
4
Structural Abnormality
There is a cervical rib or structural abnormality identified on imaging.
5
Vascular Features
There are suspected vascular features, or the patient is being considered for injection, specialist imaging or surgery.
Surgery for Thoracic Outlet Syndrome
Surgery is not required for every patient with neurogenic TOS. It is usually considered only after careful specialist assessment and after appropriate conservative management has failed, unless there are urgent vascular or progressive neurological features.
Surgical Procedures
The aim of surgery is to decompress the thoracic outlet and reduce pressure or irritation on the brachial plexus or blood vessels. Depending on the individual case, surgery may include:
- First rib resection
- Anterior scalenectomy
- Middle scalene release or excision
- Release of fibrous bands
- Brachial plexus neurolysis
- Pectoralis minor tenotomy
- Vascular reconstruction or venous treatment in selected vascular cases
The exact operation depends on the type of TOS, the compression site, the anatomy, the symptom pattern and whether the nerves, vein or artery are primarily involved.
What Patients Should Know
In carefully selected patients, thoracic outlet decompression can significantly improve pain, function and quality of life. However, it is not a guaranteed cure and complete symptom relief is not achieved in every case.
- The aim is improvement, not a promise of total symptom abolition
- Recovery requires rehabilitation
- Long-standing symptoms may take longer to settle
- Some residual discomfort, altered sensation or fatigue can persist
- Outcomes are better when the diagnosis is sound and the patient is carefully selected
- Surgery should be performed by clinicians experienced in thoracic outlet and brachial plexus pathology
Work, Sport and Daily Life
Thoracic outlet syndrome can have a major impact on work and daily life, especially when diagnosis is delayed. A key part of treatment is understanding the patient's goals — management should be tailored to the demands of work, sport, hobbies and home life.
Patients may struggle with:
Work Activities
Computer work, driving, overhead work, manual labour and carrying bags can all provoke or worsen symptoms.
Sport and Exercise
Gym training, swimming, throwing sports and musical instruments may be significantly affected by TOS symptoms.
Daily Life and Sleep
Housework, childcare and sleep can all be disrupted. Sleep disturbance is a common and underappreciated consequence of persistent TOS.
Frequently Asked Questions
Is thoracic outlet syndrome a nerve problem?
Often, yes. The most common form is neurogenic TOS, where the brachial plexus is compressed or irritated. However, TOS can also affect the subclavian vein or subclavian artery, which require different treatment pathways.
Can TOS cause symptoms if my MRI and nerve tests are normal?
Yes. Routine investigations can be normal in neurogenic TOS, particularly where the compression is dynamic or positional. Normal tests should not automatically invalidate a patient's symptoms.
What does neurogenic TOS feel like?
Patients often describe pain, heaviness, fatigue, numbness, tingling or weakness in the arm or hand. Symptoms are commonly worse with overhead activity, driving, lifting, carrying or sustained posture.
How is TOS different from a trapped nerve in the neck?
A cervical nerve root problem often follows a more recognisable root distribution and may be associated with neck movement, reflex changes or MRI findings. TOS symptoms are often more diffuse, posture-dependent and provoked by arm position. The two can overlap, which is why careful assessment is important.
Is TOS dangerous?
Neurogenic TOS is usually not dangerous but can be very disabling. Venous or arterial TOS can be urgent, particularly if there is sudden swelling, blue discolouration, coldness, pallor, weak pulses or signs of thrombosis or ischaemia.
What should I try before surgery?
Most patients should try structured TOS-focused physiotherapy, posture and activity modification, ergonomic changes, pacing and appropriate pain control. This should usually be continued for several months unless there are urgent vascular or progressive neurological features.
When is surgery considered?
Surgery may be considered when symptoms are severe, persistent, function-limiting and have not responded to appropriate conservative treatment, or where there is objective neurological deterioration or significant vascular compression.
What operation is performed for TOS?
The operation depends on the subtype and compression site. Procedures may include first rib resection, scalenectomy, fibrous band release, brachial plexus neurolysis, pectoralis minor tenotomy or vascular reconstruction in selected cases.
Will surgery cure all my symptoms?
Not always. Many carefully selected patients improve significantly, but complete relief is not guaranteed. Long-standing pain, central sensitisation, coexisting diagnoses and delayed treatment can affect recovery.
Who should I see for suspected TOS?
For persistent neurogenic symptoms, assessment by a clinician experienced in brachial plexus and peripheral nerve disorders is appropriate. For sudden arm swelling, cyanosis, coldness, pallor, weak pulses or suspected thrombosis, urgent vascular assessment is required.
"Thoracic outlet syndrome should not be a diagnostic dead end. The right approach is to listen carefully, recognise the pattern, exclude mimics, identify vascular red flags, and guide patients through a rational stepwise treatment plan."— Mr Ashley Simpson, Consultant Peripheral Nerve Surgeon
If your symptoms have not been explained by standard tests, or if you have been told everything is normal despite persistent arm pain, numbness, heaviness or weakness, a specialist peripheral nerve assessment may help.
