Thoracic Outlet

Pathogenesis

• Compression of the neurovascular bundle as it transverses the thoracic outlet

• 200 patients undergoing surgery for thoracic surgery

  • 8% had a cervical rib

  • 10% had supernumerary scalene muscles

  • 43% had variations in scalene muscle attachments

• Extra ribs

  • More present in TOS than no symptoms

    • 28% versus 1%

  • Can be bilateral

  • 70% are women

  • Predisposes to develops TOS after whiplash

• Muscular anomalies

  • Narrows the space between anterior and middle scalenes

  • Muscle insertions are variable and can narrow the space through which brachial plexus and subclavian artery pass

• Injury

  • Chronic inflammation after whiplash

Clinical

• Compression tests may demonstrate a decrease in the radial or ulnar pulse with abduction of the upper extermity overhead

  • Adson test

    • Hold radial pulse

    • Extend head and rotate toward affected side

    • Inhale

    • Monitor pulse

• Neurogenic TOS

  • Symptoms

    • Pain

    • Dysthesia

    • Numbness

    • Weakness

  • Most common at 96%

  • Symptoms are reproducible by elevation or sustained use of the arms and hands

    • Brushing hair, holding telephone to ear, getting objects from cabinet, prolonged computer work, driving

    • Provocative movements including neck rotation, head tilting, arm abduction, external rotation

• Venous TOS

  • Venous is the second most common

  • 3% of cases

  • Occur in those who perform vigorous upper body exercises

• Arterial TOS

  • Least common at 1%

  • Symptoms are spontaneous unrelated to work or trauma

  • Always related to cervical rib or anomalous rib

  • Symptoms

    • Hand ischaemia with symptoms of pain, pallow paraesthesia and coldness

    • Due to thromboembolism from mural thrombus from the subclavian artery or a subclavian aneurysm

  • Needs differentiation from Raynaud’s phenomenom

  • Lower BP in affected arm

  • Diminished pulses in affected arm

  • Bruit on subclavian artery

Diagnosis

• For arterial and venous, diagnosis is supported by demonstration of stenosis or occlusion of the corresponding subclavian vessel

• Electrophysiological testings for neurogenic TOS

• Scalene muscle test injection

  • Local anaesthetic into scalene

    • Signs of pathology occurring at thoracic outlet

    • Signs of nerve compression

    • Absence of other pathology

    • Positive response to scalene injeciton

• Physiological vascular studies

• Imaging

  • Ultrasound is the initial test to evaluate aTOS and vTOS because it’s inexpensive and noninvasive

  • Duplex ultrasound is a highly sensitive and specific test for venous stenosis

  • for aTOS, duplex U/S may demonstrate an increased flow velocity in the subclavian artery

  • CT shows the relationship of vascular structures to surrounding bone and muscle

  • CT angiography produce high-quality images of the central vasculature and extremity vessels

  • MRI

Management

• Only for symptomatic patients

• Physical therapy for at least 4 to 6 weeks for NTOS

  • Exercises strengthen the msucles surrounding the shoulder and postural exercises help the patient to sit and stand straighter

  • Other measures include passage of time and weight reduction

• Medical therapy

  • Interscalene injection of anaesthetic agents, steroids or Botox have all been used in patients with nTOS

• Anticoagulation

  • vTOS

• Ischemia

  • Urgent review

• Thoracic outlet decompression

  • Anterior scalenectomy

nTOS

• Conservative approach

aTOS

• Decompression

vTOS

• Thombolysis