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Thoracic Outlet Syndrome


KEY FACTS

Terminology

  • Thoracic outlet syndrome (TOS)

  • Neural, venous, &/or arterial compressive syndrome at thoracic outlet (TO)

  • Diagnosis made by 1 of 3 methods (by event, affected structure, or compression cause)

Imaging

  • ± cervical rib, elongated C7 transverse process

  • ± brachial plexus compression or distortion, scalene muscle inflammation or fibrosis, abnormal vascular flow voids within TO

  • Positional occlusion or narrowing of subclavian artery (SCA) with arm hyperabduction, external rotation

Top Differential Diagnoses

  • Primary and secondary plexus tumors

  • Radiation plexopathy

  • Trauma

Pathology

  • Cervical ribs, abnormal transverse processes, fibrous bands, scalene compression of TO contents

  • Neural injury with fibrosis, axonal loss

Clinical Issues

  • “True” neurological TOS: Intermittent arm pain, numbness, and weakness with hyperabduction, external rotation

    • Pain in shoulder, proximal upper extremity → neck

    • Paresthesias, numbness in forearm/hand

  • Vascular TOS: Paresthesias secondary to arterial or venous ischemia

    • Obliteration of brachial, radial pulses with arm hyperabduction and elevation

Diagnostic Checklist

  • SCA aneurysm or subclavian vein thrombosis, brachial plexus compression with abnormal T2 hyperintensity at TO strongly suggest TOS

Coronal graphic of the thoracic outlet (TO) demonstrates brachial plexus compression and a subclavian artery (SCA) aneurysm
arising secondary to the C7 cervical rib
and anterior scalene muscle
compression.

Anteroposterior radiograph demonstrates bilateral rudimentary C7 cervical ribs
. The right cervical rib articulates with the 1st thoracic rib.

Sagittal oblique STIR MR shows normal anatomy of the interscalene triangle: Brachial plexus trunks
, anterior
and middle scalene muscles, SCA
, subclavian vein
, and 1st thoracic rib
.

Axial STIR MR demonstrates normal axial thoracic outlet anatomy. The brachial plexus
passes between the anterior
and middle/posterior scalene muscles and over the 1st thoracic rib
.

TERMINOLOGY

Abbreviations

  • Thoracic outlet syndrome (TOS)

Definitions

  • Neural, venous, &/or arterial compressive syndrome at thoracic outlet (TO)

  • Diagnosis made by 1 of 3 methods (by event, affected structure, or compression cause)

IMAGING

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