Median nerve lesion at the wrist causes all of the following.except ?
**Core Concept**
Median nerve lesions at the wrist, also known as carpal tunnel syndrome, result from compression of the median nerve as it passes through the carpal tunnel. This compression leads to damage to the nerve, causing symptoms such as numbness, tingling, and weakness in the hand.
**Why the Correct Answer is Right**
The median nerve innervates the thenar muscles (thumb muscles), including the abductor pollicis brevis, flexor pollicis brevis, and opponens pollicis. When the median nerve is compressed at the wrist, it can cause weakness or paralysis of these muscles, leading to difficulty in thumb movements.
**Why Each Wrong Option is Incorrect**
**Option A:** Atrophy of the thenar muscles is a common consequence of median nerve compression at the wrist, making this option incorrect.
**Option B:** Wasting of the first dorsal interosseous muscle is not a direct consequence of median nerve compression at the wrist, as this muscle is primarily innervated by the ulnar nerve. Therefore, this option is incorrect.
**Option C:** Claw hand deformity is typically associated with ulnar nerve lesions, not median nerve lesions, making this option incorrect.
**Option D:** Hyperextension of the wrist is not a direct consequence of median nerve compression at the wrist, but rather a possible compensatory mechanism for weakness in wrist flexion.
**Clinical Pearl / High-Yield Fact**
It's essential to distinguish between median and ulnar nerve lesions, as the symptoms and signs can be quite different. A thorough examination, including tests for thenar muscle weakness and ulnar nerve function, is crucial in diagnosing carpal tunnel syndrome.
**Correct Answer: C. Claw hand deformity is typically associated with ulnar nerve lesions, not median nerve lesions.**