Definition

Thoracic outlet syndrome (TOS) is a condition characterized by the compression of neurovascular structures — specifically nerves, veins, or arteries in the confined space between the collarbone (clavicle) and the first rib, commonly referred to as the thoracic outlet.

Description

Thoracic Outlet Syndrome (TOS) is classified into three principal types based on the impinged structure within the thoracic outlet, each with separate pathophysiology and clinical features:

• Neurogenic Thoracic Outlet Syndrome (nTOS):
  • This is the most common form, estimated to be 90-95% of all TOS cases. It includes compression of the brachial plexus, a complex web of nerves that originates in the neck and regulates muscle movements and sensation in the shoulder, arm, and hand
  • Symptoms: Prime neurological symptoms such as pain, aching, or weakness in the neck, shoulder, arm, tingling, or "pins and needles" sensation in the arm or fingers
  • Muscle wasting (atrophy) in the hand
  • Symptoms often intensify with overhead or repetitive arm movement activities
• Venous Thoracic Outlet Syndrome (vTOS):
  • The compression of the subclavian vein causes it. It comprises about 4 to 5% TOS cases. Frequently accompanied by an arm swelling, prominent superficial vein, and cyanosis. It may also lead to Paget-Schroetter syndrome
• Arterial Thoracic Outlet Syndrome (aTOS):
  • This is the rarest form; it includes compression of the subclavian artery.
  • Symptoms include coldness, limb ischemia, pallor, or a weak pulse in the affected arm.

Epidemiology

Incidence/Prevalence

• Approximate incidence ranges from 3 to 80 cases per 100,000 people, subject to the diagnostic definitions and demographics studied
• The projected prevalence of symptomatic TOS is around 10 per 100,000 people
• Neurogenic TOS (nTOS): This is the most common type, comprising 90-97% of all TOS cases
• Venous TOS (vTOS): Accounts for roughly 3-5% of cases
• Arterial TOS (aTOS): The rarest, generally less than 1% of cases

Age

• TOS primarily affects adults between 20 and 50 years of age
• Neurogenic TOS is more prominent in the 30s–50s. Venous TOS is often seen in individuals in their 20s and 30s

Gender

• TOS is more common in females. The study's assessment is a female-to-male ratio anywhere from 2:1 to 4:1

Race

• Insufficient race-based data is available

Risk factors

• General
  • Posture
  • Trauma
  • Heavy shoulder loads
  • Pregnancy
  • Mental stress
  • Family history
  • Athletic activity
• Physiological
  • Cervical rib: Present in ~0.2–0.7% of Americans, multiplying the risk of arterial and neurogenic TOS.
  • Fibrous bands: Congenital fibrous tissue constricts neurovascular structures.
  • Elongated C7 transverse process: Structural abnormality contributing to compression.
  • Hypertrophied scalene or pectoralis minor muscles: Seen in athletes and muscular people.
  • Obesity: Enhances mechanical load and vascular congestion.
  • Muscle imbalance: Weakness or overutilization of shoulder girdle muscles.
  • Anomalous first rib or clavicle: modify thoracic outlet dimensions.
  • Tumors or space-occupying lesions: Rare but remarkable contributors.
  • Tight thoracic fascia may restrict neurovascular mobility.
  • Congenital dysplasia: Regional musculoskeletal abnormality affecting outlet geometry.

Etiology

• A range of anatomical factors, repetitive activities, or traumatic incidents generally influences the cause of TOS.
• Congenital/Anatomical Factors:
  • Cervical rib: It is an extra rib above the first rib. Present in 0.5– 1% of the U.S. population; enhances the risk of arterial and neurogenic TOS.
  • Hypertrophied scalene muscles: It is commonly found in athletes and weightlifters.
  • C7 transverse process elongation or abnormalities of the clavicle.
• Acquired/Functional factors:
  • Poor Posture: Slouching, rounded shoulders, or forward head posture can narrow the space in the thoracic outlet by adjusting the alignment of the clavicle, first rib, and neck muscles.
  • Excess body weight: An Overweight condition or muscle bulk in the shoulder or neck area can lead to compression.
  • Occupational strain: Recurring overhead work
  • Lesion causing compression: Tumors or bone callus resulting from fractures.
• Trauma-induced factor:
  • Whiplash Injuries: Typically seen in automobile crashes, a neck sprain can cause soft tissue damage, muscle spasms, and changes in movement patterns in the neck and shoulder region, leading to compression.
• Fractures: Fractures of the clavicle or first rib can heal in a manner that malforms the thoracic outlet, leading to compression.
• Pathophysiology
  • Neurogenic TOS (nTOS)
  • Chronic compression causes:
  • Nerve ischemia (primarily affecting lower trunk: C8-T1).
  • Demyelination in advanced cases.
  • Symptoms: Paresthesia, pain in the neck, shoulder, weakness, and muscle atrophy.
  • Venous TOS (vTOS):
  • Intermittent obstruction of venous outflow leads to:
  • Venous stasis and thrombosis.
  • Symptoms: Swelling, or heaviness of the arm, cyanosis
  • Arterial TOS (aTOS):
  • Persistent compression of an artery results in:
  • Endothelial injury, aneurysm, and thrombus formation
  • Symptoms: pallor, coldness, or claudication.

History

• Look for symptoms like numbness or tingling in the arms when lifting or carrying weight.
• It is essential to investigate the history of the present illness:
  • Onset is gradual in most cases
  • Sudden onset may arise after trauma such as a clavicle fracture or whiplash
  • Symptoms like Pain, paresthesia in the ulnar nerve distribution, swelling, weakness, discoloration, or symptoms worsen with carrying heavy loads or prolonged incorrect postures.
• Past medical history should be sought, such as repetitive strain, trauma, or any congenital risk.
• Social history, such as a sedentary lifestyle, occupational strain, or athletic involvement.

Physical findings on examination

• General Inspection:
  • Postural imbalance: Forward head posture, Rounded shoulders,
  • Muscle loss in the thenar or hypothenar
  • Atrophy of the Intrinsic hand muscle
• Palpation:
  • Tenderness or stiffness in:
    • Scalene muscles
    • Pectoralis minor
    • Supraclavicular fossa
    • cervical rib (if present)
• Neurologic Findings:
  • Numbness in the ulnar nerve distribution (ring and little fingers)
  • Reduced grip strength or finger abduction/adduction
  • Reflexes may be decreased in severe cases
• Vascular Findings Venous TOS:
  • Swelling, bulging superficial veins, cyanosis
  • Heaviness or stiffness in the arm
• Arterial TOS:
  • Pallor, hypothermic limb
  • Lowered or absent radial pulse
  • Distal embolic signs

Laboratory Tests

• Complete Blood Count (CBC) – To rule out infection or anemia.
• Erythrocyte Sedimentation Rate (ESR) and C-Reactive Protein (CRP) – To evaluate systemic inflammation or autoimmune conditions.
• Basic Metabolic Panel (BMP) – To assess electrolyte balance and kidney function.
• Thyroid-Stimulating Hormone (TSH) – To exclude metabolic causes of neuropathy.
• Rheumatologic Panel (e.g., ANA, RF) – If autoimmune causes are suspected in the differential diagnosis.
• D-dimer – May be utilized if venous thrombosis is suspected in venous TOS.

Diagnostic Tests

• Provocative maneuvers
  • Adson test
  • Roos/EAST test
  • Wright test
  • Costoclavicular maneuver
• Electrodiagnostic Studies
  • EMG
  • Nerve conduction studies (NCS)
• Imaging
  • X-ray (cervical spine, chest)
  • CT scan / CTA
  • MRI / MRA
  • Doppler ultrasound
  • Venography
  • Arteriography

Differential Diagnosis

• Cervical Radiculopathy
• Carpal Tunnel Syndrome (CTS)
• Ulnar Neuropathy at the Elbow
• Rotator Cuff Pathology or Shoulder Impingement
• Brachial Plexopathy
• Subclavian Artery Aneurysm or Stenosis
• Paget-Schroetter Syndrome
• Peripheral Arterial Disease (PAD)
• Pancoast Tumor
• Cervical Rib or First Rib Anomalies
• Poor Posture or Muscle Imbalance

General treatment items

• Conservative management is generally the first-line approach, especially for neurogenic TOS.
• Restorative Therapy: This is a foundation of conservative treatment. It emphasizes postural correction and reconditioning.
• Stretching exercises: Focusing on tight muscles like the scalenes, pectoralis minor, and levator scapulae.
• Strengthening exercises: Strengthening the shoulder girdle muscles (e.g., rhomboids, lower trapezius, cervical erectors) to increase the stability and reduce the compression in the thoracic outlet.
• Neural mobilization exercises: To alleviate irritation and enhance the mobility of the brachial plexus.
• Medications:
  • NSAIDs (e.g., ibuprofen, naproxen) for pain/inflammation
  • Muscle relaxants or low-dose antidepressants for neuropathic pain
  • Botulinum toxin injections: Into the scalene or pectoralis minor muscles to decrease spasm and compression
  • Corticosteroid injections: To relieve localized inflammation

Surgical Interventions

• First Rib Resection: This is a standard surgical procedure involving partial or complete resection of the first rib.
• Approaches: The surgeons may use multiple operative approaches, such as Transaxillary, supraclavicular, or infraclavicular.
• Robotic-Assisted: Newer techniques are being evaluated for first rib resection, offering the potential for smaller incisions and improved surgical visibility.
• Scalenectomy: Excision of the anterior and/or middle scalene muscles, which can put pressure on nerves and blood vessels.
• Neurolysis/Venolysis/Arteriolysis: It releases the constricted tissues around the nerves (neurolysis), veins (venolysis), or arteries (arteriolysis).
• Pectoralis Minor Tenectomy: It is a minimally invasive and outpatient procedure.
• Vascular Repair: For arterial or venous TOS.
• Thromboembolectomy: Surgical removal of blood clots.
• Angioplasty and stenting: To open constricted veins.
• Vein graft or synthetic prosthesis: To restore or bypass a compromised blood vessel.

Adjunctive Therapies

• Myofascial release: Targets tight fascia near the scalene and pectoralis minor muscles.
• Trigger point therapy: Relieves muscle knots contributing to compression.
• First rib mobilization: Enhances mobility of the first rib to reduce brachial plexus impingement.
• Thoracic spine mobilization: Improves posture and shoulder mechanics
• Cervical spine control: Focuses on deep neck flexor activation to decrease forward head posture.
• Heat or ice therapy: Decreases muscle tightness and swelling.
• Diaphragmatic breathing: Decrease the use of accessory muscles.

Medications indicated with specific doses

Toxoids

• Not applicable

Immunoglobulins

• Not applicable

Vasodilators

• Not applicable

Thrombolytic agents

• Thrombolytic agents are primarily used in venous TOS when patients present with acute venous thrombosis, also known as Paget-Schroetter syndrome. The goal is to dissolve the clot and prepare the patient for definitive surgical decompression.
• Commonly used thrombolytic agents: Alteplase (tPA), Tenecteplase, and Reteplase.

Dietary or Activity restrictions

• A balanced anti-inflammatory diet may support neuromuscular health
• Avoid repetitive overhead activities such as painting, lifting, and swimming
• Limit carrying heavy shoulder loads like backpacks or shoulder bags
• Modify posture to avoid prolonged forward head or rounded shoulder positions
• During post-surgical recovery for (first 2–4 weeks)
• Avoid lifting >5–10 lb
• No overhead reaching or repetitive arm motions
• Minimize driving until cleared by the surgeon
• After 4–6 weeks, there should be a gradual return to activity under therapy supervision.

Disposition

Admission Criteria

Patients with TOS are typically managed on an outpatient basis, but hospital admission is warranted under the following conditions:

• Acute upper extremity deep vein thrombosis (DVT) or Paget-Schroetter syndrome
• Pulmonary embolism
• Acute limb ischemia
• Need for urgent thrombolysis or vascular surgery
• Postoperative monitoring
• Intractable pain nonresponsive to outpatient management
• Diagnostic uncertainty requiring inpatient workup such as EMG, imaging, and scalene block.

Discharge criteria

• Stable vital signs and no signs of acute neurovascular issue
• Control pain with oral medications
• No signs of surgical site infection
• Enduring oral intake and able to perform basic self-care
• Clear discharge instructions provided, including activity restrictions and follow-up plan
• Completion of the initial therapy phase with documented improvement
• Patient education on posture and a home exercise program
• Outpatient follow-up organized with physical therapy
• Physiologically stable with no bleeding or respiratory complications
• Pain is manageable with oral analgesics
• Patient understands wound care and activity restrictions
• Follow-up scheduled with thoracic surgery within 1–2 weeks.

Monitoring

• Symptom tracking: Regular assessment of pain, weakness, or vascular changes using standardized scales
• Functional assessment: Monitoring grip strength, range of movement, and tolerance during physical therapy sessions
• Nerve conduction studies (NCS) and electromyography (EMG) to eliminate cervical radiculopathy
• D-dimer and coagulation panels: Used in acute thrombosis to monitor anticoagulation therapy
• Pulse volume recordings
• Wound and neurovascular checks: Within 24–48 hours post-op and at follow-up visits
• Physical therapy progress: Monitored every week with reassessment every 4–6 weeks
• Annual clinical assessment: Especially for vascular TOS

Patient Education

• Goals: Improve understanding of Thoracic Outlet Syndrome, covering its causes, symptoms, and available treatments.
• Promote compliance with physical therapy, lifestyle changes, and ongoing medical visits.
• Prevent symptoms from recurring or worsening by applying proper ergonomic and posture practices.
• General education: Assist in making sure the patient attends all physical therapy sessions consistently.
• Keep an eye out for changes in symptoms, like increased pain or new weakness.
• Activity modification involves avoiding repetitive overhead motions and heavy lifting.
• Action Plan for Patients and Families:
  • Assist the patient in attending follow-up appointments whenever possible.
  • Oversee or help with exercises.
  • Keep in contact with your healthcare team, including primary care, orthopedics, physical therapy, or vascular specialists.

Complications

• General
  • Pain
  • Disability
  • Fatigue
  • Depression
  • Anxiety
  • Dysfunction
• Neurogenic TOS
  • Neuropathy
  • Paresthesia
  • Atrophy
  • Weakness
  • Dysesthesia
  • CRPS
• Venous TOS
  • Thrombosis
  • Cyanosis
  • Embolism
  • Edema
  • Congestion
  • Insufficiency
• Arterial TOS
  • Aneurysm
  • Embolization
  • Ischemia
  • Gangrene
  • Ulceration
  • Hypoperfusion
• Surgical
  • Hemorrhage
  • Neuropraxia
  • Infection
  • Readmission
  • Reoperation
  • Scarring

Prevention

• Maintain a balanced posture: Prevent forward head and rounded shoulder positions
• Ergonomic workstations: Utilize flexible and comfortable chairs and armrests to minimize shoulder strain.
• Avoid extended overhead activity: Limit monotonous arm elevation (e.g., painting, lifting).
• Load balancing: Use backpacks with both straps to avoid unilateral contraction.
• Stabilization exercises: Strengthen mid/lower trap muscles and serratus anterior to support the shoulder girdle.
• Stretch stiff muscles: Concentrate on pectoralis minor, scalenes, and sternocleidomastoid.
• Diaphragmatic breathing: Diminish the use of accessory muscles, such as scalenes.
• Do not sleep with arms overhead: This can aggravate neurovascular compression during rest.
• Athletes: Incorporate shoulder motility and postural training into routines, especially for swimmers and weightlifters.
• Heavy breast support: Broad bra strap garments may reduce clavicular compression in large-breasted women.
• Quick rehab after neck/shoulder trauma: Early intervention post-clavicle fracture can prevent recurrent compression.
• Lifestyle modification: Weight loss can reduce mechanical load on thoracic structures.
• Cutting down stress: Persistent tension can worsen muscle tightness and posture.
• Health literacy: Teaching body mechanics and symptom awareness.

Prognosis

• Normally found to be favorable in most cases, especially with early diagnosis and appropriate treatment.
• Neurogenic TOS (NTOS), the most common form, often responds well to general therapy.
• Vascular TOS (VTOS and ATOS) may need surgical intervention, but outcomes are generally excellent
• 70–90% of patients improve with physical therapy and activity development and alteration.
• Delayed treatment may lead to post-thrombotic syndrome or chronic venous insufficiency.
• Prognosis depends on the extent of arterial damage, such as an aneurysm or embolism.
• Early surgical procedure can prevent limb-threatening ischemia.

Associated conditions

• Cervical radiculopathy
• Brachial plexopathy
• Rotator cuff pathology
• Scapular dyskinesis
• Cervical rib
• Fibrous bands or hypertrophied scalene muscles
• Clavicular or first rib fractures
• Paget-Schroetter syndrome
• Subclavian artery aneurysm or stenosis
• Pulmonary embolism

Synonyms

• Neurovascular compression syndrome
• Thoracic outlet compression syndrome
• Costoclavicular syndrome
• Scalene triangle syndrome

ICD-10-CM

• G54.0 – Brachial plexus disorders
• I72.3 – Aneurysm of the artery of the upper extremity
• I77.1 – Stricture of artery
• I87.1 – Compression of vein

• Jones, M. R., Prabhakar, A., Viswanath, O., Urits, I., Green, J. B., Kendrick, J. B., et al. (2019). Thoracic outlet syndrome: A comprehensive review of pathophysiology, diagnosis, and treatment. Pain and Therapy, 8, 5–18.
• Rosa, J. M., Sousa, A., Fonte, H., Pereira, E., Sapage, R., & Trigueiros, M. (2020). Difficult diagnosis of a neurogenic thoracic outlet syndrome and review of the current literature. International Journal of Research in Orthopaedics, 6(5), 1087–1089.
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• Hopkins Medicine. (n.d.). Thoracic outlet syndrome. Johns Hopkins Medicine.
• Mayo Clinic. (n.d.). Thoracic outlet syndrome – Diagnosis & treatment. Mayo Clinic.
• National Center for Biotechnology Information. (2018). Thoracic outlet syndrome. In StatPearls. StatPearls Publishing.
• Society for Vascular Surgery. (n.d.). Thoracic outlet syndrome. Vascular.org.
• Washington University Center for Thoracic Outlet Syndrome. (n.d.). Neurogenic thoracic outlet syndrome (TOS). Washington University School of Medicine.