Ulnar nerve entrapment classic distribution?

• A. Pain and numbness in little finger and ulnar half of ring finger
• B. Numbness in the thumb and index finger
• C. Numbness in the forehead
• D. Pain in the great toe

Answer: (A)

The key concept is the sensory distribution of the ulnar nerve in the hand. The ulnar nerve provides sensation to the medial one and a half digits—the little finger and the ulnar half of the ring finger—on both the palm and the back of the hand. When the nerve is entrapped, this area is where numbness or paresthesias occur most commonly, which distinguishes it from other nerve distributions. Numbness in the thumb and index finger points to the median nerve, numbness in the forehead involves the trigeminal distribution, and pain in the great toe involves lower limb nerves. So the classic distribution for ulnar nerve entrapment is numbness in the little finger and the ulnar half of the ring finger.