Thoracic Outlet Syndrome · TOS Specialist · First Rib Resection · London
Arm pain, numbness, and tingling that no one has been able to explain.
Thoracic outlet syndrome is one of the most consistently misdiagnosed conditions in medicine. Symptoms that affect the arm, hand, shoulder, and neck — but originate in the space between your collarbone and first rib. If you’ve been through neurology, orthopaedics, and physiotherapy without a clear answer, you may be in the right place.
For Patients Who Have Been Through the Diagnostic System Without Answers
You’ve been told it isn’t carpal tunnel. It isn’t your rotator cuff. Your MRI is “normal.” And you’re still in pain.
The journey to a thoracic outlet syndrome diagnosis is, for most patients, a long and frustrating one. Tingling in the arm leads to nerve conduction studies — normal. Shoulder pain leads to an orthopaedic review — no significant rotator cuff pathology. Neck pain leads to a cervical spine MRI — mild degenerative changes, nothing that explains the symptoms. You are reassured that nothing serious is wrong. The symptoms persist.
The reason TOS is missed is straightforward: the problem is not in the arm, the shoulder, or the cervical spine. It is in the thoracic outlet — the space between your collarbone and first rib — where the nerves and blood vessels supplying your arm pass through a narrow passage. When this passage is compressed, the consequences are felt entirely in the arm and hand. The source, however, is in the chest. And most specialists who examine the arm never look at the thoracic outlet.
“The average time between the onset of TOS symptoms and a correct diagnosis is around 18 months. Most patients have seen at least two or three other specialists before reaching a thoracic surgeon. The diagnosis is not difficult to make — but it requires knowing what to look for, and knowing where to look.”
This page explains what thoracic outlet syndrome is, why it is so consistently missed, how it is properly diagnosed, what treatment looks like, and when surgery is the right decision.
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Key facts about TOS
“I had been told it was carpal tunnel, then a rotator cuff problem, then a cervical disc. After two operations that made no difference, I came to Mr Scarci. He diagnosed neurogenic TOS within the first appointment and confirmed it with a scalene block. Surgery followed three months later — and for the first time in four years, my arm doesn’t tingle constantly. I wish someone had looked at the thoracic outlet years earlier.”
What is the thoracic outlet — and what goes wrong?
A narrow passage with no room for error
The thoracic outlet is the space between the collarbone (clavicle) and the first rib at the top of your chest. Through this narrow passage run three vital structures: the brachial plexus (the network of nerves supplying the arm), the subclavian artery (carrying oxygenated blood to the arm), and the subclavian vein (returning blood from the arm).
In thoracic outlet syndrome, one or more of these structures is compressed — either dynamically (in certain positions) or constantly. The compression can result from anatomical variations (an extra cervical rib, an abnormally wide first rib, or tight scalene muscles), from trauma that changes the anatomy of the area, or from repetitive overhead strain that gradually tightens the structures in the outlet.
Because the nerves and vessels being compressed supply the entire arm and hand, the symptoms appear far from where the compression is occurring. This is the fundamental reason TOS is so often misdiagnosed — doctors investigate the arm rather than the outlet.
Thoracic Outlet Syndrome: Symptoms, Diagnosis and Treatment
The three types of thoracic outlet syndrome
TOS is not one condition but three, depending on which structure is being compressed. Understanding which type you have determines the urgency and the treatment approach.
Neurogenic TOS (NTOS)
Compression of the brachial plexus — the network of nerves controlling movement and sensation in the shoulder, arm, and hand. The most common form by far, and typically the one that causes the longest diagnostic odyssey because symptoms are diffuse and variable.
- →Aching or burning pain in the arm, shoulder, or neck
- →Tingling or numbness — especially in ring and little finger
- →Weakness or fatigue with overhead use
- →Symptoms worse with arm raised or sustained overhead work
- →Headache at the base of the skull (occipital)
Venous TOS (VTOS) — Paget-Schroetter
Compression of the subclavian vein causes blood clot formation (effort thrombosis). Classically occurs in young, athletic patients after sudden intense upper arm exertion. Requires prompt treatment to prevent chronic venous damage.
- →Sudden arm swelling — often the whole arm
- →Heaviness and fatigue in the arm
- →Blue or purple discolouration of the arm
- →Visible distended veins across the shoulder and chest
Arterial TOS (ATOS)
The rarest and most serious type. Compression of the subclavian artery can cause arterial damage — aneurysm formation, blood clot, or distal embolisation — potentially threatening the viability of the hand and fingers. Almost always associated with a cervical rib.
- →Cold, pale, or white fingers or hand
- →Fingertip pain, ulceration, or gangrene (if emboli present)
- →Arm fatigue with exertion (claudication)
- →Pulsatile mass above the clavicle
The cervical rib — an anatomical cause of TOS
Approximately 1% of the population has a cervical rib — an extra rib that grows from the seventh cervical vertebra (C7) in the neck. When present, it narrows the thoracic outlet and dramatically increases the risk of TOS, particularly arterial TOS. If you have a cervical rib on imaging and arm symptoms, specialist assessment is strongly advised — even if symptoms are currently mild. Surgical removal of the cervical rib, combined with first rib resection, is highly effective.
Risk Factors For Thoracic Outlet Syndrome — And Why Certain Groups Are Particularly Susceptible
TOS is not random. Certain anatomical, occupational, and lifestyle factors significantly increase the risk of developing compression in the thoracic outlet.
Overhead athletes
Swimmers, overhead throwers (baseball, volleyball), gymnasts, rowers, and weightlifters develop TOS through repetitive overhead motion that progressively tightens the scalene muscles and narrows the outlet. Young competitive athletes are particularly affected — venous TOS (Paget-Schroetter) most commonly presents in this group.
Manual workers
Jobs requiring sustained overhead work — painters, electricians, assembly workers, mechanics — cause cumulative tightening of the scalene muscles and can trigger neurogenic TOS. The symptoms often correlate directly with work activity and improve on rest.
Neck trauma / whiplash
Road traffic accidents causing whiplash can injure the scalene muscles, leading to scarring, spasm, and subsequent compression of the brachial plexus. TOS following trauma may develop weeks or months after the accident — making the causative link non-obvious.
Anatomical variations
A cervical rib (extra rib at C7), an abnormally long C7 transverse process, or congenital fibromuscular bands in the outlet can all narrow the space through which the neurovascular structures pass. These variations are present from birth but may only become symptomatic after a triggering injury or accumulation of muscle bulk.
Desk workers with poor posture
Prolonged forward head posture and rounded shoulders — characteristic of sustained desk or computer work — tightens the scalenes and pectoralis minor muscle, contributing to outlet narrowing. May trigger or exacerbate neurogenic symptoms.
Musicians
Instrumentalists — particularly violinists, viola players, and guitarists — sustain awkward arm and shoulder positions for hours daily. This repetitive asymmetrical loading progressively tightens the thoracic outlet structures and is a recognised cause of occupational neurogenic TOS.
Why it takes so long to get a TOS diagnosis
What TOS gets confused with — and why the difference matters
Thoracic outlet syndrome mimics several common conditions. Each is investigated and excluded in turn, while TOS itself remains uninvestigated — because the thoracic outlet is rarely examined.
Carpal tunnel syndrome
Carpal tunnel compresses the median nerve at the wrist, causing numbness in the thumb, index, and middle finger. TOS affects the ulnar distribution (ring and little finger) and the whole arm, is worse with overhead activities, and normal nerve conduction studies are common with TOS. Many TOS patients undergo carpal tunnel surgery without benefit before the correct diagnosis is made.
→ Key distinction: carpal tunnel is wrist-level; TOS is outlet-level. Distribution of numbness differs.
Cervical radiculopathy
A pinched nerve in the neck also causes radiating arm pain and tingling. However, cervical radiculopathy follows a strict dermatomal pattern; TOS symptoms are more diffuse, affect the whole arm, and are often worsened by overhead position. Both may exist simultaneously (double crush syndrome), complicating diagnosis further.
→ Key distinction: positional pattern (overhead worsens TOS). MRI neck is often normal in TOS.
Rotator cuff injury
Shoulder pain, weakness, and difficulty with overhead activities are features of both TOS and rotator cuff pathology. Patients with TOS may have a normal shoulder MRI, or incidental low-grade rotator cuff changes deemed the cause. Treating the wrong condition produces no improvement in TOS symptoms.
→ Key distinction: rotator cuff pain is localised to shoulder; TOS pain radiates into the arm and hand.
Fibromyalgia / chronic pain syndrome
When all standard investigations return normal and symptoms are diffuse, TOS may be attributed to fibromyalgia or central sensitisation. These conditions are real, but should only be diagnosed after specific conditions — including TOS — have been properly assessed and excluded. A positive scalene block confirms TOS as the source.
→ Key distinction: TOS symptoms are provoked by specific positions. A diagnostic scalene block is definitive.
Raynaud’s phenomenon
Cold, colour-changing fingers in response to cold or stress is characteristic of Raynaud’s. Arterial TOS also causes cold, pale, or blue fingers — but typically affects the whole arm, is asymmetric, and is associated with exertion rather than cold exposure. TOS with vascular compromise must be excluded before attributing hand colour changes to primary Raynaud’s.
→ Key distinction: Raynaud’s is bilateral and cold-triggered; arterial TOS is unilateral and exertion-related.
Multiple sclerosis / neurological disease
Diffuse arm numbness, fatigue, and neurological symptoms in a young person can raise MS concerns. TOS patients occasionally undergo brain and spinal MRI for this reason. A thorough neurological examination distinguishes TOS (no upper motor neurone signs) from MS, and a positive scalene block confirms the peripheral compressive cause.
→ Key distinction: TOS has no upper motor neurone signs. Positional provocation is characteristic of TOS.
Diagnosing thoracic outlet syndrome — the tests that actually matter
There is no single definitive test for TOS. The diagnosis is made through clinical history, physical examination, and a combination of targeted tests. Expert interpretation is essential.
Clinical History & Physical Examination
A detailed history identifying symptom pattern, triggering positions, occupational and sporting risk factors, and prior investigations. The physical examination assesses muscle tenderness (particularly the scalene muscles), neck range of motion, and performs provocation tests to reproduce symptoms in specific positions.
The diagnosis of TOS is primarily clinical — made by an experienced examiner
Adson’s Test
The patient rotates their head toward the affected side, extends the neck, and takes a deep breath. A positive test — reduction in the radial pulse or reproduction of symptoms — indicates compression of the subclavian artery or brachial plexus. A positive test in the context of characteristic symptoms is highly significant.
Assesses arterial compression; positive = clinical indicator of TOS
Roos Test (Elevated Arm Stress Test, EAST)
The patient holds both arms abducted to 90° with elbows bent and repeatedly opens and closes the fists for 3 minutes. In TOS, symptoms are reproduced within 3 minutes — heaviness, fatigue, numbness, or inability to complete the test. This is the most sensitive clinical test for neurogenic TOS.
Most sensitive test for neurogenic TOS; reproduces the positional trigger
Scalene Muscle Block (Diagnostic Nerve Block)
Local anaesthetic is injected into the anterior scalene muscle under imaging guidance. If this produces significant, temporary relief of symptoms, it confirms that the scalene muscles are responsible for the compression. A positive scalene block is the most reliable single test for neurogenic TOS and predicts response to surgical scalenectomy.
Confirms diagnosis AND predicts surgical outcome — the most important test in TOS
X-Ray / CT of the Cervical Spine and Chest
Identifies cervical ribs, an abnormally long C7 transverse process, first rib abnormalities, or other bony structures contributing to outlet narrowing. Essential for surgical planning. CT angiography shows the precise relationship between the vessels and compressive structures — critical for arterial and venous TOS.
Identifies anatomical cause; guides surgical approach
MRI of the Thoracic Outlet
Dedicated MRI (including dynamic sequences with the arm in provocative positions) can directly visualise brachial plexus compression, scalene muscle abnormalities, and vascular involvement. More useful than standard MRI of the cervical spine or shoulder, which assesses the wrong anatomical location.
Shows soft tissue compression; identifies brachial plexus abnormalities
EMG and Nerve Conduction Studies
Electromyography and nerve conduction studies assess nerve function in the arm. In neurogenic TOS, these are frequently normal — which is a diagnostic pitfall. A normal nerve conduction study does not exclude TOS; it simply means nerve damage is not yet detectable.
Often normal in TOS — a normal result does NOT exclude the diagnosis
Treatment — from physiotherapy to thoracic outlet decompression surgery
Treatment follows a logical progression from conservative measures through to surgery. For most neurogenic TOS patients, a structured period of physiotherapy is the appropriate first step — but surgery should not be delayed indefinitely when conservative treatment has genuinely failed.
Physiotherapy — directed at the thoracic outlet
Targeted physiotherapy for TOS focuses on stretching the scalene and pectoralis minor muscles, strengthening the muscles that depress and stabilise the shoulder girdle, postural retraining to open the outlet, and nerve mobilisation exercises. It is important that this is TOS-specific physiotherapy — generic shoulder or neck physiotherapy without this focus is far less effective. Many patients with mild to moderate neurogenic TOS achieve adequate symptom control with physiotherapy alone. The typical course is 3–6 months before reassessing.
Medications and lifestyle modifications
Anti-inflammatory medications, muscle relaxants, and neuropathic pain agents (gabapentin, pregabalin) manage symptoms during the physiotherapy phase. Identifying and modifying the occupational or sporting activity that is driving the compression is essential. Ergonomic changes at work, modified training programmes, and postural strategies all contribute to symptom management.
Scalene muscle injection — Botulinum toxin or local anaesthetic/steroid
When physiotherapy provides insufficient relief, injection of the scalene muscles offers both diagnostic value and therapeutic benefit. Botulinum toxin (Botox) injections into the anterior and middle scalene muscles chemically relax these muscles for 3–4 months, temporarily opening the outlet and relieving neurogenic compression. A positive response also helps confirm surgical candidacy and guides the approach.
Thoracic outlet decompression surgery
Surgery is recommended when conservative treatment has not produced sufficient relief after 3–6 months; when symptoms are severe enough to significantly impair daily activities, work, or sport; or when vascular TOS (arterial or venous) is present. Published long-term data show 80–90% of appropriately selected patients report significant or complete symptom resolution after surgery.
Thoracic outlet decompression surgery — what the operation involves
The fundamental surgical goal is to decompress the structures passing through the thoracic outlet. This is achieved by removing the anatomical bottleneck — which may be the first rib, the scalene muscles, a cervical rib, or abnormal fibromuscular bands. The specific procedure depends on which type of TOS is present, the anatomical cause, and the patient’s circumstances.
First Rib Resection + Scalenectomy
Removal of part or all of the first rib combined with excision of the anterior and middle scalene muscles. First rib resection eliminates the rigid lower boundary of the outlet, while scalenectomy removes the muscular compression. The gold standard surgical approach for most TOS, performed via a transaxillary (through the armpit) or supraclavicular (above the clavicle) incision.
✓ 80–90% long-term symptom improvement in published series
Scalenectomy (Without Rib Resection)
Removal of the anterior and middle scalene muscles without excising the first rib. A less extensive procedure with a lower complication rate, supported by evidence showing comparable outcomes in selected patients — particularly those with a history of neck trauma where scalene scarring is the primary cause.
✓ Lower complication rate; suitable for trauma-related neurogenic TOS
Cervical Rib Resection
When a cervical rib is the primary anatomical cause of TOS — particularly in arterial TOS — its surgical removal is essential. Typically combined with first rib resection to fully decompress the outlet. Particularly important for arterial TOS where the rib has caused subclavian artery damage, requiring vascular reconstruction alongside bony decompression.
✓ Essential for cervical rib-associated arterial and neurogenic TOS
First Rib Resection + Thrombolysis/Venoplasty
Venous TOS requires first rib resection to eliminate the structural compression, combined with catheter-directed thrombolysis to dissolve the clot and balloon venoplasty to reopen the subclavian vein if narrowed. Timing matters — prompt treatment produces better venous outcomes.
✓ Most effective when performed within 2 weeks of clot formation
Frequently asked questions about thoracic outlet syndrome
Your arm symptoms deserve more than another normal MRI.
A specialist TOS consultation examines the thoracic outlet directly — the structure that has never been properly assessed. Most patients leave knowing more about their condition in one appointment than in years of prior investigation.
