A 40-year-old male patient presented to the ER with pain and deformity in the left arm after having a fall 2 hours ago. The doctor ordered an x-ray of the affected area. The nerve most likely involved in the above condition supplies which of the following marked muscles: –
**Core Concept**
The patient's symptoms suggest a possible fracture or dislocation in the left arm, which may have injured a nerve that innervates nearby muscles. The nerve most likely involved in this condition is a branch of the brachial plexus, a complex network of nerves that arise from the spinal cord and supply the arm.
**Why the Correct Answer is Right**
The correct answer is likely the radial nerve, which is a branch of the brachial plexus that arises from the posterior cord. The radial nerve supplies the extensor muscles of the forearm, including the extensor carpi radialis brevis, which is responsible for wrist extension. The radial nerve also innervates the triceps brachii, which is responsible for elbow extension. In the context of a fall, it is possible that the radial nerve was injured, leading to weakness or paralysis of these muscles.
**Why Each Wrong Option is Incorrect**
**Option A:** The median nerve is another branch of the brachial plexus that supplies the muscles of the anterior forearm, including the flexor carpi radialis and the flexor digitorum profundus. However, it does not supply the extensor muscles of the forearm.
**Option B:** The ulnar nerve is a branch of the brachial plexus that supplies the muscles of the medial forearm, including the flexor carpi ulnaris and the flexor digitorum profundus. However, it does not supply the extensor muscles of the forearm.
**Option C:** The axillary nerve is a branch of the brachial plexus that supplies the deltoid and teres minor muscles, which are responsible for shoulder abduction and rotation. However, it does not supply the extensor muscles of the forearm.
**Clinical Pearl / High-Yield Fact**
In the context of a fall, the radial nerve is at risk of injury due to its location in the radial groove of the humerus. This is known as a "radial nerve palsy" and can result in weakness or paralysis of the extensor muscles of the forearm, leading to a characteristic "wrist drop".
**Correct Answer: C.**