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# Thoracic outlet syndrome

Thoracic outlet syndrome is pressure on the nerves or vessels to the arm as they pass between the neck and armpit; it causes arm pain, tingling or swelling.

Updated 2026-10-29

## Structures involved

Tap one to see what it is and open it in 3D.

- [Plexus trunks](https://durgical.com/en/anatomy/brachial-plexus-trunks/)
- [Subclavian artery](https://durgical.com/en/anatomy/right-subclavian-artery/)
- [Subclavian vein](https://durgical.com/en/anatomy/subclavian-veins/)
- [Scalenes](https://durgical.com/en/anatomy/scalenus-anterior-muscle/)
- [First rib](https://durgical.com/en/anatomy/first-rib/)
- [Clavicle](https://durgical.com/en/anatomy/clavicle/)
- [Pectoralis minor](https://durgical.com/en/anatomy/pectoralis-minor-muscle/)
- [Subclavius](https://durgical.com/en/anatomy/subclavius/)
- [Brachial plexus roots](https://durgical.com/en/anatomy/roots-of-brachial-plexus/)
- [Axillary vein](https://durgical.com/en/anatomy/axillary-vein/)

## What it is

A group of disorders caused by compression of the [brachial plexus](https://durgical.com/en/anatomy/roots-of-brachial-plexus/), [subclavian artery](https://durgical.com/en/anatomy/right-subclavian-artery/) or [subclavian vein](https://durgical.com/en/anatomy/subclavian-veins/) as they pass between the neck and the axilla, through the scalene triangle, costoclavicular space and under [pectoralis minor](https://durgical.com/en/anatomy/pectoralis-minor-muscle/).

## Who gets it

Uncommon and debated, since diagnostic criteria vary. Neurogenic forms are by far the most frequent; venous and arterial forms are rare. It often affects young adults, more women in the neurogenic form.

## Causes

- Bony anomalies: cervical rib, long C7 transverse process or abnormal first rib
- Scalene muscle hypertrophy or fibrous bands
- Neck trauma such as whiplash
- Repetitive overhead activity (venous form: effort thrombosis, Paget-Schroetter syndrome)
- Malunited [clavicle](https://durgical.com/en/anatomy/clavicle/) or first rib fracture

## Risk factors

- Cervical rib or other congenital anomalies
- Repetitive overhead work or sport (swimming, volleyball, baseball)
- Poor posture with drooping shoulders
- Previous neck trauma

## Pathophysiology

The plexus and subclavian artery pass through the interscalene triangle and then the costoclavicular space; the subclavian vein passes in front of the anterior scalene. Narrowing of these spaces, especially with arm elevation, compresses the lower trunk (C8–T1) or the vessels. Repeated arterial compression can cause stenosis, aneurysm and emboli; venous compression can cause thrombosis.

## Classification

- Neurogenic (most cases): compression of the brachial plexus
- Venous: subclavian vein compression or effort thrombosis
- Arterial: subclavian artery stenosis or aneurysm, often with a cervical rib

## Symptoms and signs

- Neurogenic: pain in the neck, shoulder and arm; tingling on the ulnar side of the forearm and hand; weakness or clumsiness, worse with the arms raised
- Gilliatt-Sumner hand: wasting of thenar and intrinsic muscles in advanced neurogenic cases
- Venous: swelling, heaviness and bluish colour of the arm with visible chest wall veins
- Arterial: cold, pale hand, pain with use, finger ulcers or Raynaud-like attacks

## Red flags

- Sudden arm swelling and bluish colour (subclavian vein thrombosis)
- Cold, pale or pulseless hand, or fingertip ulcers (arterial emboli)
- Progressive muscle wasting of the hand
- Chest pain or breathlessness with an arm thrombosis (pulmonary embolism)

## Diagnosis

**Clinical**
Provocative tests such as the elevated arm stress test (Roos), Adson and Wright tests; many healthy people test positive, so results are interpreted with the whole picture. Diagnosis of neurogenic forms is largely clinical and of exclusion.

**Tests**
Nerve conduction studies and electromyography for neurogenic forms and to exclude other neuropathies. Response to a scalene muscle block is used in some centres.

**Imaging**
[Chest](https://durgical.com/en/anatomy/region/chest/) and cervical [spine](https://durgical.com/en/anatomy/region/spine/) X-ray for a cervical rib. Duplex ultrasound with arm positions for arterial or venous compression; CT or MR angiography, or venography, for vascular forms.

## Differential diagnosis

- Cervical radiculopathy
- [Carpal tunnel](https://durgical.com/en/anatomy/carpal-tunnel/) or cubital tunnel syndrome
- Rotator cuff disease
- Pancoast tumour
- Raynaud phenomenon or vasculitis

## Goal of treatment

Relieve compression, restore nerve function and blood flow, and prevent thrombosis, emboli and permanent hand damage.

## Treatment

**Conservative**
First line for neurogenic TOS: posture correction and modification of overhead activities.

**Rehabilitation**
Physiotherapy focused on scapular stabilisation, scalene and pectoral stretching and nerve gliding.

**Medical**
Analgesics, NSAIDs or neuropathic pain medications; botulinum toxin injections into the [scalenes](https://durgical.com/en/anatomy/scalenus-anterior-muscle/) are used in some centres.

**Surgical**
Venous thrombosis is treated with anticoagulants and sometimes catheter-directed thrombolysis, often followed by surgical decompression.

**Acute**
Surgical decompression ([first rib](https://durgical.com/en/anatomy/first-rib/) resection, scalenectomy, cervical rib removal) for vascular forms and for neurogenic cases that fail therapy; arterial aneurysms need vascular repair.

## Complications

- Chronic pain and disability
- Subclavian vein thrombosis and pulmonary embolism
- Subclavian artery aneurysm, thrombosis or emboli to the hand
- Muscle wasting of the hand
- Surgical complications: brachial plexus injury, pneumothorax, phrenic or [long thoracic nerve](https://durgical.com/en/anatomy/long-thoracic-nerve/) injury

## Prognosis

Many neurogenic cases improve with therapy. Vascular forms treated promptly usually have good outcomes; results of surgery in neurogenic TOS vary between series.

## Test yourself

Think of the answer, then tap the question to see it.

## What are the three types of thoracic outlet syndrome, and which is most common?

Neurogenic, venous and arterial. Neurogenic is by far the most common.

## Which bony anomaly is classically associated with arterial thoracic outlet syndrome?

A cervical rib (or an elongated C7 transverse process).

## Which part of the brachial plexus is most often compressed, and where are the symptoms?

The lower trunk (C8–T1); symptoms affect the ulnar side of the forearm and hand.

## What is Paget-Schroetter syndrome?

Effort thrombosis of the subclavian vein from compression at the thoracic outlet, often in young people doing repeated overhead activity.

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## Related conditions

- [Cervical radiculopathy](https://durgical.com/en/conditions/cervical-radiculopathy/)
- [Cubital tunnel syndrome (ulnar neuropathy at the elbow)](https://durgical.com/en/conditions/cubital-tunnel-syndrome/)
- [Carpal tunnel syndrome](https://durgical.com/en/conditions/carpal-tunnel-syndrome/)
- [Brachial plexus injury](https://durgical.com/en/conditions/brachial-plexus-injury/)
- [Deep vein thrombosis](https://durgical.com/en/conditions/deep-vein-thrombosis/)
- [Pulmonary embolism](https://durgical.com/en/conditions/pulmonary-embolism/)
- [Raynaud phenomenon](https://durgical.com/en/conditions/raynaud-phenomenon/)
- [Lung cancer](https://durgical.com/en/conditions/lung-cancer/)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Thoracic Outlet Syndrome](https://www.ncbi.nlm.nih.gov/books/NBK557450/) (StatPearls (NCBI Bookshelf), 2023).

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Source: https://durgical.com/en/conditions/thoracic-outlet-syndrome/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/thoracic-outlet-syndrome/