Thoracic Outlet Syndrome
Neurovascular compression between the clavicle and first rib
ICD-10: G54.0 · thoracic condition
Thoracic outlet syndrome (TOS) is a group of conditions caused by compression of the brachial plexus, subclavian artery, or subclavian vein as these structures pass through the narrow space between the clavicle and first rib — the thoracic outlet. Three subtypes exist: neurogenic TOS (95% of cases), involving brachial plexus compression; venous TOS (Paget-Schroetter syndrome, 4%), with subclavian vein thrombosis; and arterial TOS (1%), with subclavian artery compression or aneurysm. Neurogenic TOS predominantly affects young women and is strongly associated with poor posture, repetitive overhead work, and anatomical variations such as a cervical rib or anomalous scalene muscles. Patients typically describe aching shoulder and neck pain with paresthesias radiating down the arm — often into the ulnar digits — that worsen with overhead arm use or carrying heavy objects. Electrodiagnostic studies are often normal, making this a clinical diagnosis. Conservative treatment — physical therapy with scalene stretching, postural correction, and activity modification — resolves symptoms in 50–70% of neurogenic TOS patients. Vascular TOS (venous or arterial) more often requires urgent surgical intervention including thrombolysis, first rib resection, and vascular reconstruction to prevent chronic venous insufficiency or limb-threatening ischemia.
Anatomy & Pathology
The thoracic outlet is a triangular space bounded by the clavicle (collarbone) anteriorly, the first rib inferiorly, and the scalene muscles laterally. The brachial plexus (C5–T1 nerve roots), subclavian artery, and subclavian vein all pass through this tight corridor on their way to the arm. Anatomical variants such as a cervical rib (an extra rib arising from C7) or fibromuscular bands can significantly reduce the available space and predispose individuals to compression.
Symptoms
- Shoulder, neck, and arm pain worsened by overhead activity
- Paresthesias and numbness in the arm, forearm, or hand (ulnar distribution)
- Hand weakness and grip fatigue
- Arm swelling, cyanosis, or prominent veins (venous TOS)
- Pale, cold hand with loss of radial pulse on arm elevation (arterial TOS)
- Positive provocative tests: Adson, Wright hyperabduction, Roos stress test
- Wasting of intrinsic hand muscles in chronic severe cases
Causes & Risk Factors
- Anatomical narrowing from cervical rib, anomalous first rib, or fibrous bands
- Hypertrophied or anomalous anterior and middle scalene muscles
- Poor posture with dropped shoulders and forward head position
- Repetitive overhead work or throwing athletes (swimmers, baseball pitchers)
- Trauma: clavicle fracture malunion, neck injury causing scalene scarring
Treatment Options
Conservative
- Physical therapy: scalene and pectoralis minor stretching, postural strengthening, shoulder girdle exercises
- Botulinum toxin injection into the anterior scalene muscle to relieve brachial plexus compression
- Activity modification, ergonomic optimization, and weight loss to reduce mechanical load
Surgical
- First rib resection (transaxillary or supraclavicular approach) — gold standard for refractory neurogenic and vascular TOS
- Scalenectomy combined with rib resection for persistent brachial plexus compression
- Catheter-directed thrombolysis followed by first rib resection for acute subclavian vein thrombosis (Paget-Schroetter)
When to see a spine specialist
Seek urgent vascular evaluation for sudden arm swelling with bluish discoloration (venous TOS) or sudden cold, pale, pulseless arm (arterial TOS) — both are emergencies. For neurogenic symptoms, see a specialist experienced in TOS if arm pain, paresthesias, and weakness persist beyond 4–6 weeks or interfere with work and daily activities.
Specialists Who Treat Thoracic Outlet Syndrome
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Search spine specialists →Frequently Asked Questions
Why is neurogenic thoracic outlet syndrome so difficult to diagnose?
True neurogenic TOS has abnormal electromyography and nerve conduction studies — but this affects fewer than 1% of TOS patients. The majority have "disputed" neurogenic TOS where electrodiagnostic studies are normal and diagnosis relies entirely on clinical history, physical exam, provocative tests, and exclusion of other diagnoses. This leads to significant diagnostic delay, averaging 3–4 years in most series.
Is thoracic outlet syndrome the same as a pinched nerve in the neck?
No. Cervical radiculopathy compresses a nerve root in the foramen of the neck and produces dermatomal symptoms corresponding to that cervical level. TOS compresses the brachial plexus below the neck between the scalene muscles and first rib. MRI of the cervical spine is typically normal in TOS, and cervical nerve root tension signs (Spurling) are negative.
What is the success rate for first rib resection?
In well-selected patients, first rib resection for neurogenic TOS improves symptoms in 70–85% of patients, with complete relief in 40–50%. Venous TOS treated with thrombolysis and first rib resection achieves excellent long-term patency in 85–95% of cases. Arterial TOS has similarly high surgical success rates. Outcomes are best when surgery is performed by high-volume thoracic outlet specialists.