Numbness or paresthesias in the first three and a half digits with weakness in grip is due to entrapment of which nerve?

• A. Ulnar nerve
• B. Radial nerve
• C. Median nerve
• D. Axillary nerve

Answer: (C)

Compression of the median nerve in the hand, such as at the carpal tunnel, produces numbness and tingling in the lateral three and a half digits (thumb through the radial half of the ring finger) because those digits are supplied by the median nerve. At the same time, the median nerve innervates the thenar muscles (the thumb’s key movers for opposition and abduction) and the lateral two lumbricals. When the nerve is compressed, these muscles lose function, leading to weakness in grip and pinch. That combination—sensory loss in the thumb, index, middle, and half of the ring finger with reduced thumb opposition and grip strength—is classic for median nerve entrapment.

If the ulnar nerve were involved, you’d expect numbness in the little finger and the medial half of the ring finger with weakness in intrinsics of the hand. Radial nerve entrapment or injury would more commonly show extension weakness and sensory changes on the dorsum of the hand. Axillary nerve issues affect shoulder movements, not hand sensation or grip.