Venous thoracic outlet syndrome

The venous thoracic outlet syndrome (vTOS) is the second commonest form of thoracic outlet syndrome (with neurogenic thoracic outlet syndrome being the commonest and the arterial thoracic outlet syndrome being the least common).

Clinical presentation

It may develop suddenly, often after unusual and tiring exercise of the arms with (subclavian vein compression causes upper limb swelling and pain with resultant venous thrombosis (Paget-Schroetter syndrome).

Some can present with intermittent venous compression in the absence of thrombosis (McCleery syndrome). Patients may have swelling of the hands, fingers and arms, as well as heaviness and weakness of the neck and arms. Veins in the anterior chest wall may appear dilated.

Pathology

The typical site of subclavian vein compression is at the level of the costoclavicular space between the 1^st rib, subclavius muscle, and clavicle. 

Radiographic assessment

Imaging aims to assess three separate facets of this condition: 

1. confirm the presence of stenosis/compression/obstruction

2. identify underlying anatomical abnormalities or variants that cause compression

3. characterize the vessel and identify the presence of thrombus

Plain radiograph

Chest radiography is typically performed to exclude an underlying bony abnormality.

Ultrasound

Ultrasound can both directly visualize the subclavian vein and assess flow using duplex Doppler scanning. Additionally, it is ideally suited to dynamic maneuvers (i.e. abducting the arm) and assessing for the impact that this has on flow. 

CT and MRI

Both CT and MRI are able to assess regional anatomy and vascular anatomy. It is possible to also perform neutral and abducted views although this not as straightforward as with ultrasound and, in the case of CT, requires additional radiation exposure. 

Features to assess include ⁴:

• bone and soft-tissue abnormalities

  • cervical rib 

  • hypertrophic C7 transverse process

  • first rib callus, exostosis or osseous lesion

  • fibrous band

  • muscle insertional variation

  • supernumerary muscles (e.g. scalenus)

• subclavian and/or axillary vein

  • thrombosis

  • fixed venous stenosis

  • dynamic narrowing of the vein with abduction

• enlarged collaterals

Digital subtraction venography

Digital subtraction venography is excellent at visualizing the lumen of the veins and imaging can be performed in various arm positions to demonstrate dynamic narrowing. It can also allow balloon venoplasty.