Median nerve injury at the wrist causes-
**Core Concept**
The median nerve, a branch of the brachial plexus, runs through the carpal tunnel at the wrist, supplying motor and sensory innervation to the hand. Damage to this nerve at the wrist level can lead to specific clinical manifestations due to the distribution of its branches.
**Why the Correct Answer is Right**
Median nerve injury at the wrist, also known as carpal tunnel syndrome, typically presents with symptoms of thenar muscle weakness, particularly affecting the thumb opposition and abduction. 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. The injury leads to decreased sensation and pain in these areas.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because ulnar nerve injury typically affects the intrinsic muscles of the hand, leading to claw hand deformity and sensory changes over the little finger and ulnar half of the ring finger.
**Option B:** This option is incorrect because radial nerve injury at the wrist would affect the extensor muscles of the wrist and fingers, leading to wrist drop and difficulty in extending the wrist and fingers.
**Option C:** This option is incorrect because radial nerve injury typically presents with symptoms of wrist drop, weakness in extension of the wrist and fingers, and sensory changes over the back of the hand.
**Clinical Pearl / High-Yield Fact**
Carpal tunnel syndrome is a common condition that can be caused by repetitive motion, trauma, or compression of the median nerve at the wrist. It's essential to recognize the symptoms and signs of median nerve injury, such as thenar muscle weakness, to provide appropriate treatment and prevent long-term damage.
**Correct Answer:** C.