Anatomy Exam Brachial Plexus Structures 4

Question 1

A 'waiter's tip' deformity results from injury to which brachial plexus component?

Accepted Answer

Upper trunk (C5–C6)

Answer

Upper trunk injury (Erb's palsy) causes the arm to hang in adduction, medial rotation, and forearm pronation — the waiter's tip position.

Question 2

Injury to the posterior cord of the brachial plexus would spare which movement?

Accepted Answer

Elbow flexion

Answer

Elbow flexion (primarily musculocutaneous nerve) arises from the lateral cord, not the posterior cord.

Question 3

The nerve to the subclavius arises from which part of the brachial plexus?

Accepted Answer

Upper trunk

Answer

The nerve to subclavius (C5–C6) branches from the upper trunk of the brachial plexus.

Question 4

Which cord of the brachial plexus splits into the musculocutaneous nerve and the lateral root of the median nerve?

Accepted Answer

Lateral cord

Answer

The lateral cord divides into the musculocutaneous nerve and contributes the lateral root to the median nerve.

Question 5

A crutch placed too high in the axilla compresses which nerve structure, typically injuring which nerve first?

Accepted Answer

Posterior cord / Radial nerve

Answer

Crutch palsy most often affects the radial nerve via compression of the posterior cord in the axilla.

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