Thoracic Outlet Syndrome

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[edit] Thoracic Outlet Syndrome

In this condition the pain in the shoulder could be radiating pain from muscles in spasm in the lower neck area. The thoracic outlet is the area in the upper thoracic cage and below the clavicle where the neurovascular bundle passes through to the arm. There are differences of the angle of the upper opening of the thoracic cage between various persons, some are born with additional ribs and some with abnormalities of the scalene muscles that can form a sling.

All of this can put pressure onto the brachial plexus, which in turn can cause neck and shoulder pain with associated arm numbness, arm weakness, shooting pains into the arm and numbness in fingers. The nerve roots that paticipate in the formation of the brachial plexus originate from the lower cervical spine and are numbered C5, C6, C7 and C8. When the C6 nerve root is irritated the thumb would experience numbness and C6 innervated muscles such as the shoulder and arm muscles would ache and get weak. When C8 gets irritated there would be a mimicking of an ulnar nerve entrapment with numbness of the 4th and 5th fingers and weakness of the small hand muscles, making it difficult for the person making a fist and grasping items.

In people who are born with additional ribs attached to the lower cervical spine vertebral bodies (a cervical rib)direct pressure is put onto the brachial plexus, particulalarly with the arm elevated. There is a lot af variation with the anatomy in the thoracic outlet from person to person and in some people the space where the subclavian artery travels into the arm can by more narrow than usual. This can be because of the angle of the rib cage, but can also be because of a cervical rib that compresses the artery and the brachial plexus or because of fibrous bands in association with the anterior scalene muscle. This muscle can be located behind the subclavian artery or it can be divided into two parts and squeeze the subclavian artery in the middle of it.

Diagnostic tests: Imaging studies (ultrasonic studies and MRI scan) and clinical examination can pinpoint the particular cause. The Adson test consists of testing the radial pulse and elevating the arm at the same time.

When you picture an abnormality of the thoracic outlet as indicated above where the subclavian artery gets hooked, the link shows how with the Adson test the pressure on the the sublavian artery will clamp down the blood supply to the arm and the radial pulse disappears. This is called a positive Adson test and is indicative for the presence of a thoracic outlet syndrome.

Thoracic outlet syndrome treatment: Milder cases may respond to physiotherapy, posture training and chiropractic corrections. Occasionally a rib resection has to be done by a chest surgeon, but this will not always lead to a resolution of this problem. Sometimes the nerve damage is permanent leading to a chronic pain syndrome, which can be very frustrating for patient and physician alike.

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References:

1. ABC of rheumatology, second edition, edited by Michael L. Snaith , M.D., BMJ Books, 1999.

2. The Merck Manual, 7^th edition, by M. H. Beers et al., Whitehouse Station, N.J., 1999.

3. Goldman: Cecil Textbook of Medicine, 21st ed.(©2000)W.B.Saunders

4. Ferri: Ferri's Clinical Advisor: Instant Diagnosis and Treatment, 2004 ed., Copyright © 2004 Mosby, Inc.

5. Rakel: Conn's Current Therapy 2004, 56th ed., Copyright © 2004 Elsevier

6. Wheeless' Textbook of Orthopaedics: http://www.wheelessonline.com/ Several topics can be found under this link by entering the term you search for.