Thoracic Outlet Syndrome

Thoracic Outlet Syndrome (TOS) describes a collection of symptoms caused by compression of particular nerves and blood vessels as they pass from the neck down into the arm. Symptoms vary depending on which structures are being compressed, but often they are felt concurrently.

How does compression occur?

The thoracic outlet itself is formed by the borders of the first rib (medially), posterior clavicle (anteriorly) and anterior scapula (laterally/posteriorly).  A raised first rib or cervical rib (C7) can cause symptoms on that side. Structures can also be compressed as they pass between the anterior and middle scalene and within the subcoracoid space, beneath pectoralis minor.

An apical tumour of the lung (Pancoast Tumour) can also be a cause, albeit a rare one.

Which structures are compressed?

The neurovascular bundle consists of the brachial plexus (nerve roots C5-T1), subclavian artery and vein.

What are the symptoms?

Depending on whether arteries, veins or nerves are compressed, the symptoms vary, but include:

  • parasthesia (pins & needles) or numbness in the hand or forearm, often in the little and ring fingers and medial border of the forearm (neurological compression)
  • heaviness, altered sensation in whole hand (arterial)
  • cold or whitened hand/arm (arterial)
  • reduced radial pulse patency (arterial)
  • acutely swollen, cyanosed and painful hand/arm (venous)

How is it tested?

There are a number of standard tests for TOS, including Adson’s, Allen’s and Roo’s tests. Each is designed to test the integrity of various structures and stress them accordingly, to diagnose what type of TOS is presenting and what is the best way to treat.

How is it treated?

Treatment is dependant on the cause of the TOS and should be focussed on that presentation, which includes:

  • mobilisation of first rib combined with breathing exercises
  • stretching of anterior/middle scalenes and/or pectoralis minor along with postural and occupational advice
  • surgical decompression to first rib and/or scalenes (scalenectomy) in extreme cases
  • a cervical rib can also be removed surgically if appropriate
  • in cases of acute venous TOS, subclavian venous thrombectomy can also be used

References
Abdul-Jabar etal (2008) Thoracic Outlet Syndrome
Drake et al (2005) Gray’s Anatomy for Students
Vizniak & Carnes (2009) Conditions Manual

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