Saturday, July 28, 2012

Quiz: Why is my right hand weak?

This is a chest x-ray of 35 year old man. He complained that his right hand grip is not as good as his left hand. On examination, thenar eminence on the right is smaller than the left. What do you think is the cause of his problem?

This is a magnified view of this right apex.

There is a large right cervical rib.
No wonder his right hand is weak.

A cervical rib is a supernumerary or extra rib which arises from the seventh cervical vertebra. It is a congenital abnormality located above the normal first rib. A cervical rib is present in only about 1 in 500 (0.2%) of people; in even rarer cases, an individual may have two cervical ribs. Cervical ribs are sometimes known as "neck ribs".
The presence of a cervical rib can cause a form of thoracic outlet syndrome due to compression of the lower trunk of the brachial plexus or subclavian artery. These structures are entrapped between the cervical rib and scalenus muscle.
Compression of the brachial plexus may be identified by weakness of the muscles around the muscles in the hand, near the base of the thumb. Compression of the subclavian artery is often diagnosed by finding a positive Adson's sign on examination, where the radial pulse in the arm is lost during abduction and external rotation of the shoulder (Wikipedia)

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