A patient with thoracic outlet syndrome can have pain in the shoulder, which is radiating from muscles that are 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.
Nerve root irritation
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 participate in the formation of the brachial plexus originate from the lower cervical spine and have the designation 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.
Some people are born with additional ribs attached to the lower cervical spine vertebral bodies (a cervical rib). This puts direct pressure onto the brachial plexus, particularly with the arm elevated. There is a lot of 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 be 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. The location of the muscle may be behind the subclavian artery or there may be a division into two parts and squeeze the subclavian artery in the middle of it.
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. Here is a YouTube video demonstrating the Adson test.
When a patient has a thoracic outlet syndrome, the subclavian artery can experience compression with certain arm movements. Thee video link demonstrates this. The physiotherapist moved the arm backwards with her finger on the radial artery.With the Adson test the pressure on the the subclavian artery will clamp down the blood supply to the arm and the radial pulse disappears. A positive Adson test indicates a possible thoracic outlet syndrome.
Thoracic outlet syndrome treatment
Milder cases may respond to physiotherapy, posture training and chiropractic corrections. Occasionally the chest surgeon needs to do a rib resection. However, this will not always lead to a resolution of this problem. Sometimes the nerve damage is permanent leading to a chronic pain syndrome. This can be very frustrating for patient and physician alike.
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