Thoracic Outlet Syndrome: A Common Cause of Neck, Shoulder, Arm and Hand Symptoms

Thoracic Outlet Syndrome (TOS) is a group of disorders arising from compression of the neurovascular structures that pass through the thoracic outlet — the space between the collarbone, first rib, and surrounding muscles at the base of the neck. It’s a condition that is frequently underdiagnosed, often misattributed to carpal tunnel syndrome or cervical disc disease, and can cause years of unnecessary suffering before it is correctly identified and managed.

Understanding the Thoracic Outlet

The thoracic outlet is not a single space but a series of anatomical passages through which the brachial plexus (the network of nerves supplying the arm and hand), the subclavian artery, and the subclavian vein must travel from the neck into the upper limb. Compression can occur at any of three key sites, each producing a slightly different clinical picture.

The Scalene Triangle

Bordered by the anterior scalene muscle medially, the middle scalene laterally, and the first rib inferiorly, this is the most common site of brachial plexus compression. The scalene muscles attach to the first and second ribs and are primarily respiratory muscles, but in people with poor posture or chronic upper chest breathing patterns they become chronically overloaded and hypertrophied. Anomalous fibromuscular bands — congenital structures that develop between the scalenes and the first rib — can also traverse this space and are found in a significant minority of TOS patients.

The Costoclavicular Space

Between the clavicle superiorly and the first rib inferiorly, the costoclavicular space carries the neurovascular bundle from the scalene triangle toward the arm. This space narrows with shoulder depression (poor posture, heavy bag carrying), clavicular depression after fracture, or first rib elevation. Prolonged working positions with the arms forward and shoulders rounded — as seen at desks, on assembly lines, and in some surgical roles — chronically narrow this space.

The Retropectoralis Minor (Subcoracoid) Space

The third and most distal compression site lies beneath the pectoralis minor tendon as it runs from the anterior chest wall to the coracoid process of the scapula. A hypertrophied or shortened pectoralis minor — very common in people with rounded shoulder posture and in overhead athletes — can compress the brachial plexus and subclavian vessels directly beneath it, particularly when the arm is in elevation and abduction.

Types of TOS

There are three recognised types of TOS, based on which structure is primarily compressed. Understanding which type is present is essential for appropriate management.

Neurogenic TOS (nTOS) — Approximately 95% of Cases

Compression of the brachial plexus is by far the most common presentation. Symptoms include aching pain in the neck, shoulder, and arm; numbness and tingling in the hand and fingers (classically in the ulnar distribution — the medial forearm, ring finger, and little finger, reflecting lower trunk brachial plexus involvement); hand weakness and clumsiness; and difficulty sustaining overhead activities. Symptoms are often worse at night, with prolonged arm use, and in positions that narrow the outlet.

Neurogenic TOS is further subdivided into true neurogenic TOS, a rare but objective condition associated with a cervical rib and demonstrable neurological deficit (muscle wasting, reduced nerve conduction), and disputed neurogenic TOS, which accounts for the overwhelming majority of clinical presentations and involves symptoms without objective neurological changes. The word “disputed” reflects historical debate rather than any suggestion that the condition is not real — these patients have genuine and often severe symptoms.

Arterial TOS (aTOS) — Less Than 1% of Cases

Compression of the subclavian artery is uncommon and almost always associated with a structural anomaly — typically an anomalous cervical rib or abnormal first rib. Symptoms include arm fatigue and claudication with exertion, pallor or coldness of the hand, and in severe cases, distal embolism causing ischaemia of the fingers. Arterial TOS requires urgent referral to a vascular surgeon — conservative management is not appropriate, and definitive surgical decompression is usually required.

Venous TOS (vTOS) — Approximately 4% of Cases

Also known as Paget-Schroetter syndrome or “effort thrombosis,” venous TOS involves compression and thrombosis of the subclavian vein, typically triggered by sustained overhead effort. It is particularly seen in throwing athletes, competitive swimmers, manual overhead workers, and military personnel. The classic presentation is acute swelling of the entire arm, cyanotic discolouration, pain, and distension of superficial chest and shoulder veins. Venous TOS is a medical emergency — it requires immediate anticoagulation and urgent vascular assessment, often followed by catheter-directed thrombolysis and surgical decompression.

In clinical practice, the vast majority of presentations to osteopathic and manual therapy clinics are neurogenic TOS — and this is the type that responds well to conservative management.

Who Gets TOS?

Neurogenic TOS is more common in women between the ages of 20 and 50 (approximately 3:1 female to male ratio), though it affects people of all ages and backgrounds. Risk factors include:

• Forward head posture and rounded shoulders, which compress the costoclavicular space and load the scalenes
• Repetitive overhead work: painters, hairdressers, welders, teachers, and healthcare workers who sustain arm elevation
• Prolonged desk work with the neck forward and shoulders rounded
• Musicians — particularly violinists, guitarists, and pianists who sustain asymmetric upper limb loads
• Swimmers, particularly butterfly and freestyle specialists, and throwing athletes (baseball, cricket, volleyball)
• History of whiplash injury, clavicle fracture, or first rib fracture — all of which can alter the mechanics of the thoracic outlet
• Cervical rib — an anomalous extra rib arising from the C7 vertebra, present in approximately 0.5% of the population, which directly narrows the scalene triangle
• Elongated C7 transverse process or fibromuscular bands — anatomical variants that mimic the effect of a cervical rib

Symptoms and Presentations

The symptom profile of neurogenic TOS is highly variable, which is the primary reason it is so frequently missed or misdiagnosed. Symptoms can fluctuate significantly day to day, often correlating with activity levels, posture, and sleep position. Common presentations include:

Pain

A dull, aching pain in the neck, shoulder, and upper arm is the most common complaint. Some patients describe a burning or electric quality, particularly with neural irritation. Pain typically radiates down the arm and into the hand, and can involve the anterior chest and interscapular region. The distribution can closely mimic cervical radiculopathy, rotator cuff pathology, or even cardiac pain — all of which must be considered and excluded in the assessment.

Neurological Symptoms

Paraesthesia (pins and needles), numbness, and tingling are extremely common. In classical lower trunk brachial plexus compression, these follow the ulnar distribution — the medial forearm, ring finger, and little finger. However, symptoms can be diffuse and poorly localised, involving the entire hand, or shifting between sessions. Some patients report “electric shock” sensations with certain movements. Symptoms are typically reproduced or worsened by arm elevation, prolonged computer use, driving, and lying on the affected side.

Hand Weakness and Clumsiness

Difficulty gripping objects, dropping things unexpectedly, and weakness with fine motor tasks (typing, writing, doing up buttons) are frequently reported. In true neurogenic TOS — a rare subset with objective neurological change — visible wasting of the intrinsic hand muscles (particularly the thenar eminence, producing a characteristic “wasted hand” appearance) may be present. In disputed neurogenic TOS, strength testing may be subjectively reduced but formal neurological examination is typically normal.

Positional Exacerbation

One of the most characteristic features of TOS is how strongly symptoms are influenced by arm and neck position. Activities that narrow the thoracic outlet — reaching overhead to shelves, hanging washing, blow-drying hair, overhead sport, carrying heavy bags on the affected shoulder — reliably worsen symptoms. Many patients find they can’t sustain arm elevation for more than a few minutes. Military posture (chest out, shoulders back) can paradoxically worsen symptoms in some patients by narrowing the costoclavicular space.

Nocturnal Symptoms

Many TOS patients are woken at night with arm numbness and tingling, particularly if they sleep with the arm overhead or tucked under their body. This nocturnal presentation can mimic carpal tunnel syndrome, which is another reason TOS is frequently misdiagnosed. A key clinical differentiator is the distribution of symptoms — TOS characteristically affects the ulnar nerve territory, while carpal tunnel syndrome affects the median nerve (thumb, index, and middle finger).

Vascular Symptoms in Neurogenic TOS

Even in cases without primary vascular compression, some patients with neurogenic TOS report colour changes in the hand (intermittent pallor or bluish discolouration), a sensation of coolness, and mild swelling — particularly after prolonged use. These symptoms are thought to result from involvement of sympathetic nerve fibres within the brachial plexus, which carry autonomic signals to the hand’s vasculature. Their presence can occasionally cause concern about arterial involvement, making thorough assessment important.

Differential Diagnosis: What Else Could It Be?

TOS mimics several other common conditions, and distinguishing between them requires careful clinical assessment rather than pattern-matching. The most important differentials include:

Cervical disc disease and radiculopathy: Compression of cervical nerve roots — particularly C8 and T1 — can produce very similar symptoms to lower trunk brachial plexus compression in TOS. Key differentiators include reproduction of symptoms with cervical compression testing (Spurling’s test), restricted and painful cervical range of motion, and MRI findings of disc pathology. It is worth noting that cervical disc disease and TOS frequently coexist — the “double crush” phenomenon.

Carpal tunnel syndrome: Median nerve compression at the wrist produces symptoms in the thumb, index, middle finger, and radial half of the ring finger — distinct from the ulnar distribution typical of TOS. Phalen’s test and Tinel’s sign at the wrist are positive in carpal tunnel but not TOS. Again, double crush syndrome (compression at both the thoracic outlet and the wrist) is common and explains why some patients have a partial response to carpal tunnel release.

Cubital tunnel syndrome: Ulnar nerve compression at the elbow also produces ring and little finger symptoms, but is typically reproduced by sustained elbow flexion (the elbow flexion test) rather than by thoracic outlet provocation manoeuvres. Tingling over the elbow (Tinel’s at the cubital tunnel) helps localise the lesion.

Rotator cuff pathology: Shoulder pain and arm weakness can mimic TOS symptoms and are far more common. Careful shoulder examination, arc testing, and, where needed, ultrasound or MRI will differentiate shoulder pathology from TOS — though both can coexist.

Pancoast tumour: An apical lung tumour involving the T1 nerve root can produce TOS-like symptoms including shoulder pain, arm weakness, and Horner’s syndrome (ptosis, miosis, anhidrosis). While rare, this diagnosis must not be missed. A chest X-ray is an important component of any TOS assessment where this is not already excluded.

Clinical Assessment and Special Tests

Thorough assessment for TOS begins with a detailed history — paying attention to occupation, sporting activities, mechanism of onset, symptom distribution, positional factors, and nocturnal symptoms. This is followed by postural assessment, cervical and shoulder range of motion testing, a complete upper limb neurological examination, and specific provocation testing.

Adson’s Test

The patient rotates the head toward the affected side, extends and slightly elevates the chin, takes a deep breath, and holds. The examiner simultaneously monitors the radial pulse at the wrist. Obliteration or significant reduction of the pulse, combined with reproduction of the patient’s familiar symptoms, suggests involvement at the scalene triangle. Sensitivity and specificity of this test in isolation are moderate — a positive Adson’s is useful in clinical context but not definitive on its own.

Wright’s Test (Hyperabduction Test)

The examiner passively abducts the patient’s arm to 90° with external rotation while monitoring the radial pulse. A positive test — pulse reduction and symptom reproduction — suggests compression at the costoclavicular space or beneath the pectoralis minor. Some clinicians extend the arm further into full abduction to increase the provocation.

Roos Test (EAST — Elevated Arm Stress Test)

The patient holds both arms in the “hold-up” position — 90° shoulder abduction, 90° elbow flexion — and slowly opens and closes both hands for 3 minutes. Reproduction of the patient’s familiar symptoms (pain, numbness, tingling, heaviness) within 3 minutes is a positive test. The Roos Test is considered the most sensitive and clinically useful provocation test for neurogenic TOS, and is often positive even when pulse tests are equivocal. A key observation is whether the patient needs to lower the arm before the 3 minutes are complete — this is almost invariably positive in TOS and often helps distinguish TOS from other conditions.

Costoclavicular Compression Test

The patient is instructed to assume a military posture — shoulders drawn back and downward, chest forward. This manoeuvre narrows the costoclavicular space. Reproduction of arm symptoms suggests involvement at this level.

It is important to note that none of these vascular tests are sufficiently sensitive or specific to diagnose TOS in isolation. Pulse obliteration with arm elevation occurs in a significant proportion of asymptomatic individuals. The diagnostic value lies in the combination of positive provocation tests with reproduction of the patient’s familiar symptoms — and this must always be interpreted within the full clinical picture.

Imaging and Investigations

For most neurogenic TOS presentations, imaging plays a supportive rather than diagnostic role. Relevant investigations may include:

• Cervical and chest X-ray: To identify a cervical rib, elongated C7 transverse process, clavicle deformity, or apical lung pathology. This is a recommended baseline in TOS assessment.
• MRI of the cervical spine: To exclude cervical disc disease or cord compression that may account for some or all symptoms.
• MRI of the brachial plexus: High-resolution brachial plexus MRI can, in experienced hands, identify fibromuscular bands, assess brachial plexus anatomy, and occasionally demonstrate neural oedema at the compression site. Availability and interpretation expertise vary.
• Nerve conduction studies and EMG: Often normal in disputed neurogenic TOS. In true neurogenic TOS, reduced ulnar sensory nerve action potential amplitude may be present. Abnormal NCS findings can help confirm the diagnosis but normal findings do not rule it out.
• Vascular Doppler ultrasound or CT/MR angiography: Essential when arterial or venous TOS is suspected — not routinely required for neurogenic TOS.
• Diagnostic scalene muscle block: Injection of local anaesthetic into the anterior scalene muscle, performed under ultrasound guidance, can serve as both a diagnostic test and a predictor of surgical outcome. Significant symptom relief following the block supports the diagnosis of TOS and the scalene triangle as the primary compression site.

Conservative Management: What Works?

The good news for people with neurogenic TOS is that the vast majority of cases — estimated between 70 and 90% in the literature — can be successfully managed conservatively, without surgery. This is important context, because the surgical options (first rib resection, scalenectomy, or a combination) are significant procedures that carry meaningful risks including brachial plexus injury, pneumothorax, and vascular injury. Surgery is generally reserved for cases that have failed a sustained and properly executed course of conservative treatment, or where vascular involvement is confirmed.

Postural Retraining

This is the foundation of conservative TOS management. The goal is to restore optimal thoracic spine extension, scapular position, and cervical alignment — all of which directly increase the dimensions of the thoracic outlet. Forward head posture elongates and tensions the brachial plexus against the first rib and scalenes. Rounded shoulders depress the clavicle, narrowing the costoclavicular space. Thoracic kyphosis reduces scapular upward rotation, loading the pectoralis minor and narrowing the subcoracoid space. Correcting these postural drivers reduces compression on the neurovascular structures at every level.

Scalene and Pectoralis Minor Stretching

Tight, shortened scalene muscles are a primary driver of neurogenic TOS via the scalene triangle. Targeted stretching of the anterior and middle scalenes — typically performed with the head laterally flexed away from the affected side and rotated slightly toward it, with the ipsilateral shoulder depressed — must be taught carefully and progressed gradually. Aggressive stretching of an irritated brachial plexus can worsen symptoms temporarily. Pectoralis minor stretching, addressing the subcoracoid compression site, is equally important — corner stretches, doorway stretches, and lying supine over a rolled towel are commonly used.

Thoracic Spine Mobilisation

Thoracic hypomobility — stiffness in the mid-back — is almost universal in desk workers and directly contributes to TOS through altered rib cage mechanics and scapular kinematics. When the thoracic spine cannot extend normally, the shoulders round to compensate. Restoring thoracic extension and rotation is a key component of conservative TOS management and is well within the scope of osteopathic and manual therapy treatment.

Scapular Stabilisation Exercises

Strengthening the lower and middle trapezius, serratus anterior, and rhomboids helps lift and retract the shoulder girdle, increasing the costoclavicular space, improving scapular upward rotation during arm elevation, and reducing pectoralis minor tension. These exercises are typically introduced progressively — beginning with low-load, body-weight movements and advancing to resistance work as tolerance builds. Wall slides, prone Y and T exercises, face pulls, and serratus anterior activation exercises are commonly used.

Neural Mobilisation

Gentle mobilisation of the brachial plexus and its individual divisions — using upper limb neurodynamic techniques — can reduce neural sensitisation, improve nerve mobility, and enhance symptom tolerance over time. These techniques must be progressed slowly and carefully: an irritated neural tissue responds badly to aggressive or prolonged tensioning. The initial goal is simply to restore normal neural gliding through the affected spaces, not to stretch the nerve.

Breathing Retraining

Upper chest breathing — with the scalenes acting as primary respiratory muscles rather than the diaphragm — is an often-overlooked contributor to TOS. Every breath that elevates the clavicle and first rib rather than expanding the lower chest and abdomen increases resting scalene tension and dynamically compresses the scalene triangle with each breath cycle. Diaphragmatic breathing retraining directly reduces this scalene overactivation and is particularly valuable in patients with high breath rates, anxiety, or a history of prolonged respiratory illness.

Activity Modification and Ergonomics

During the symptomatic phase, modifying aggravating activities allows neural irritation to settle while active treatment progresses. Practical measures include avoiding heavy bag carrying on the affected shoulder, adjusting monitor height and keyboard position to reduce neck and shoulder strain, modifying sleep position (avoiding arm overhead or under the body), using a supportive pillow that maintains cervical alignment, and taking regular breaks during sustained desk work or overhead tasks.

The Role of Osteopathy in TOS Management

Osteopathy is well-placed to address the multiple contributing factors in neurogenic TOS within a single treatment framework. Unlike approaches that focus on only one structure or one level, osteopathic assessment considers the entire kinetic chain — from breathing mechanics and cervical alignment through to shoulder function and thoracic mobility.

First rib and cervicothoracic junction: Elevated first rib position is one of the most clinically significant drivers of scalene triangle compression. Osteopathic techniques targeting first rib mobility — muscle energy techniques, articulation, and gentle high-velocity techniques where appropriate — can produce rapid symptomatic relief and are a core component of TOS treatment.

Thoracic spine: Restoring segmental mobility in the thoracic spine, particularly at T1–T6, directly improves scapular kinematics and reduces the forward-rounded posture that perpetuates TOS. Thoracic manipulation and articulation are among the most effective tools available for this.

Scalene and pectoralis minor soft tissue treatment: Direct myofascial release and inhibition of the scalene muscles, subclavius, and pectoralis minor can rapidly reduce resting muscle tension and increase the available space within the outlet. This is most effective when combined with active stretching and postural correction.

Cervical spine assessment: Joint dysfunction at C5–T1 can directly influence nerve root tension and brachial plexus irritability. Cervical assessment and treatment — with appropriate caution where vascular screening indicates the need for it — is part of a complete TOS approach.

Sternoclavicular and acromioclavicular joints: Restricted clavicular mechanics — either at the sternoclavicular or acromioclavicular joint — affect the clavicle’s ability to elevate and retract, maintaining compression in the costoclavicular space. These joints are easily overlooked but can be highly relevant in TOS presentations with a prior clavicle injury.

Patient education: Understanding posture, identifying aggravating positions, implementing breathing changes, and committing to a home exercise program are as important as anything done in the treatment room. TOS is a condition where the patient’s active participation is essential to a good outcome.

Treatment must be graduated and respectful of neural irritability. An irritable brachial plexus can be exacerbated by heavy-handed treatment, particularly in the early phases. Starting conservatively and progressing as symptoms settle is the safest approach.

When to Refer

The following presentations warrant prompt referral and should not be managed conservatively without specialist input:

• Any signs of arterial TOS — ischaemic hand, absent radial pulse, pallor: urgent vascular surgery referral
• Venous TOS — arm swelling, cyanosis, venous distension: emergency presentation to hospital
• Progressive neurological deficit — objective muscle wasting, progressive weakness on formal testing
• Suspected Pancoast tumour — any apical mass or unexplained weight loss accompanying TOS-like symptoms
• Confirmed cervical rib with symptoms: vascular surgery opinion recommended even if currently neurogenic, given risk of arterial complication
• Failure to improve after 8–12 weeks of well-executed conservative management: consider referral to a vascular surgeon experienced in TOS, a neurologist, or a pain specialist for further investigation and consideration of scalene muscle block or surgical options

Prognosis

For patients with neurogenic TOS who engage with a structured, evidence-informed conservative management program, the prognosis is generally good. Neural sensitisation takes time to resolve, and postural retraining is a slow process — but meaningful improvement over 8 to 12 weeks of consistent treatment is a reasonable expectation, with continued gains over 6 months. The key predictors of good outcome are early diagnosis, patient adherence to a home program, and addressing the underlying postural and occupational drivers rather than simply treating symptoms.

For the minority of patients who do not respond adequately to conservative treatment, surgical outcomes for appropriately selected cases are generally positive — with symptom improvement reported in 70 to 85% of cases in experienced hands. The decision to pursue surgery should always be made collaboratively and with realistic expectations about recovery time and residual symptoms.

If you are experiencing persistent neck, shoulder, arm, or hand symptoms and have not had TOS considered in your assessment, we encourage you to book in for an evaluation. TOS is a condition that rewards careful, thorough diagnosis — and one where the right conservative approach can make a profound difference.

Disclaimer: The information in this article is for educational purposes only and is not a substitute for professional medical assessment. If you have symptoms consistent with arterial or venous TOS, please seek emergency medical attention immediately.