Median nerve injury can cause numbness and weakness in which digits?

• A. Dorsal hand sensation only
• B. Thumb, index, middle finger, and part of ring finger
• C. Index finger only
• D. Pinky finger only

Answer: (C)

The key idea is the distribution of the median nerve in the hand. The median nerve provides sensation to the palmar surfaces of the thumb, index finger, middle finger, and the radial (lateral) half of the ring finger (often also described as the first three and a half digits on the palmar side). It also innervates the thenar muscles, so injury leads to weakness of thumb opposition and related fine motor tasks.

So, when a median nerve injury occurs, numbness is felt in the thumb, index, middle, and part of the ring finger, rather than in only a single finger or in the pinky. The dorsal aspect of the hand may have some sensation preserved or variably affected, but the hallmark distribution is the palmar surface of those four digits.