Malady Wise

View Original

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