Which sensory distribution is affected early in median nerve compression at the wrist?

• A. Dorsal surfaces of the hand
• B. Palmar surface of the thumb, index, middle, and radial half of ring finger
• C. Palmar surface of little finger
• D. Dorsal surface of the index finger

Answer: (B)

When median nerve compression occurs at the wrist, the earliest sensory changes appear in the palmar skin of the lateral three and a half digits—the thumb, index, middle, and the radial half of the ring finger. This happens because the carpal tunnel houses the median nerve’s sensory fibers that supply those digits. Pressure within the tunnel disrupts those digital sensory branches first, producing numbness or tingling in those palmar surfaces. The dorsal surfaces and areas supplied by other nerves (like the little finger, or much of the dorsal hand) are less affected early, since they’re not primarily served by the median nerve within the carpal tunnel.