The nerve affected in carpal tunnel syndrome is –
**Core Concept**
Carpal tunnel syndrome (CTS) is a condition characterized by compression of the median nerve as it passes through the carpal tunnel in the wrist. This compression leads to symptoms such as numbness, tingling, and weakness in the hand, particularly affecting the thumb, index, and middle fingers.
**Why the Correct Answer is Right**
The median nerve is responsible for innervating the thenar muscles, which include the abductor pollicis brevis, flexor pollicis brevis, and opponens pollicis. Compression of the median nerve leads to weakness and atrophy of these muscles, resulting in the characteristic symptoms of CTS. The median nerve also provides sensory innervation to the palmar surface of the thumb, index, middle finger, and the radial half of the ring finger.
**Why Each Wrong Option is Incorrect**
* **Option A:** The ulnar nerve is not affected in carpal tunnel syndrome. It is responsible for innervating the hypothenar muscles and the interosseous muscles of the hand, as well as providing sensory innervation to the little finger and the ulnar half of the ring finger.
* **Option B:** The radial nerve is not affected in carpal tunnel syndrome. It is responsible for innervating the extensor muscles of the wrist and fingers, as well as providing sensory innervation to the dorsal surface of the thumb, index, middle finger, and the radial half of the ring finger.
* **Option C:** The musculocutaneous nerve is not affected in carpal tunnel syndrome. It is responsible for innervating the biceps brachii, brachialis, and coracobrachialis muscles, and provides sensory innervation to the lateral aspect of the forearm.
**Clinical Pearl / High-Yield Fact**
The "anatomical snuffbox" test can help diagnose carpal tunnel syndrome. The test involves asking the patient to extend their wrist and rotate their thumb so that the thumb forms an "L" shape. If the median nerve is compressed, the patient will experience pain or numbness in the thumb.
**Correct Answer: C. Median nerve. Median nerve compression leads to carpal tunnel syndrome symptoms.**