A patient presented with numbness of little and ring finger, atrophy of hypothenar muscles. The nerve damaged will be:
**Core Concept**
The patient's symptoms suggest damage to the ulnar nerve, which is responsible for innervating the muscles of the hypothenar eminence and providing sensory innervation to the little and ring fingers. The ulnar nerve is a branch of the brachial plexus that runs down the arm and forearm, passing through the cubital tunnel at the elbow.
**Why the Correct Answer is Right**
The symptoms described are classic for ulnar nerve damage, which can occur due to compression or injury at the elbow (cubital tunnel syndrome) or at the wrist (Guyon's canal syndrome). The ulnar nerve innervates the interosseous muscles and the hypothenar muscles, leading to atrophy in these areas. The sensory branch of the ulnar nerve provides sensation to the little and ring fingers, explaining the numbness in these areas.
**Why Each Wrong Option is Incorrect**
* **Option A:** The median nerve, which runs through the carpal tunnel, is responsible for innervating the thenar muscles and providing sensation to the thumb, index, and middle fingers. Damage to the median nerve would not explain the patient's symptoms.
* **Option B:** The radial nerve, which runs down the back of the arm and forearm, is responsible for innervating the extensor muscles of the wrist and fingers. Damage to the radial nerve would lead to symptoms such as wrist drop, not numbness of the little and ring fingers.
* **Option D:** The musculocutaneous nerve, which runs through the arm, is responsible for innervating the biceps and brachialis muscles. Damage to the musculocutaneous nerve would lead to weakness of elbow flexion, not numbness of the little and ring fingers.
**Clinical Pearl / High-Yield Fact**
The ulnar nerve is often compressed at the elbow, leading to symptoms such as numbness and tingling in the little and ring fingers. This condition is known as cubital tunnel syndrome and can be exacerbated by activities that involve bending the elbow, such as playing musical instruments or using a computer mouse.
**Correct Answer: C. Ulnar nerve**