Claw hand is caused by lesion of
**Core Concept**
Claw hand, also known as intrinsic spastic paralysis or spastic claw hand, is a condition characterized by flexion deformities of the fingers and wrist. This condition is typically caused by an upper motor neuron lesion affecting the corticospinal tract, leading to spasticity and weakness in the intrinsic muscles of the hand.
**Why the Correct Answer is Right**
The correct answer is related to the anatomy and function of the corticospinal tract and the intrinsic muscles of the hand. The corticospinal tract is responsible for motor control of the upper limb, and lesions affecting this tract can lead to spasticity and weakness in the intrinsic muscles of the hand. The intrinsic muscles of the hand, including the thenar and hypothenar muscles, are responsible for fine motor movements and are affected by upper motor neuron lesions. The ulnar nerve, which innervates the intrinsic muscles of the hand, is often implicated in claw hand deformity due to its anatomical course and vulnerability to injury.
**Why Each Wrong Option is Incorrect**
* **Option A:** Lesion of the radial nerve would more likely result in wrist drop, a condition characterized by weakness or paralysis of the extensor muscles of the wrist.
* **Option B:** Lesion of the median nerve would more likely result in weakness or paralysis of the thenar muscles, leading to a "claw" hand deformity but with a different distribution of weakness.
* **Option D:** Lesion of the brachial plexus would more likely result in weakness or paralysis of the muscles of the upper limb, including the muscles of the shoulder and elbow.
**Clinical Pearl / High-Yield Fact**
Claw hand is often associated with spinal cord injuries, cerebral palsy, and other conditions that affect the corticospinal tract. It is essential to perform a thorough neurological examination to identify the underlying cause of claw hand deformity.
**Correct Answer:** C.