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A 29-year-old man presents with a chief complaint of difficulty with fine motor contr
Clinical VignetteA clinical vignette is a concise presentation of an interesting or challenging patient encounter that stimulated an interesting learning issue.
A 29-year-old man presents with a chief complaint of difficulty with fine motor control in his hand. Physical examination reveals a deficit in his ability to abduct and adduct his digits, and inability to oppose his thumb on his right hand. The patient reports that a few weeks ago he had been on a ladder trimming the branches of a tree outside his home. The ladder slid out from under him, and as he was falling he reached out and grabbed onto a limb of the tree to break his fall. Which of the following neural structures was most likely injured?
A. Lower trunk of the brachial plexus
B. Median nerve
C. Musculocutaneous nerve
D. Upper trunk of the brachial plexus
E. Ulnar nerve
I Love Clinical Vignette a concise presentation of an interesting & challenging patient encounter that stimulates an inquisitive learning session.
The correct answer is A. The lower trunk of the brachial plexus contains nerve fibers from the eighth cervical and first thoracic spinal nerves. These nerve fibers innervate the intrinsic muscles of the hand, including the interosseous muscles, responsible for abduction and adduction of the digits, and the opponens muscle, responsible for opposition of the thumb. The lower trunk ascends from the lower neck and upper thorax to reach the axilla. Upward traction on the upper limb, such as that which occurred in grabbing onto the tree limb to break the fall, may stretch the lower trunk and injure these nerve fibers.
The median nerve (choice B) innervates many muscles of the anterior compartment of the forearm and some muscles in the hand, including the opponens muscle. The median nerve, however, does not innervate the interosseous muscles, responsible for abduction and adduction of the digits.
The musculocutaneous nerve (choice C) innervates the muscle of the anterior compartment of the arm. It does not innervate any muscles in the hand.
The upper trunk of the brachial plexus (choice D) contains nerve fibers from the fifth and sixth cervical spinal nerves. The nerve fibers innervate muscles in the proximal part of the upper limb, including muscles around the shoulder and axilla. No muscles in the hand are innervated by these nerve fibers.
The ulnar nerve (choice E) innervates many muscles in the hand, including the interosseous muscles, which are responsible for abduction and adduction of the digits. However, it does not innervate the opponens muscle, which is responsible for opposition of the thumb.
I Love Clinical Vignette a concise presentation of an interesting & challenging patient encounter that stimulates an inquisitive learning session.
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