Phalen's test is positive when paresthesias occur along which nerve distribution?

• A. Median nerve distally
• B. Ulnar nerve distally
• C. Radial nerve distally
• D. Musculocutaneous nerve distally

Answer: (A)

Phalen's test stresses the median nerve as it passes through the carpal tunnel. When the wrists are held in full flexion, the pressure inside the tunnel increases, and if the median nerve is compressed, paresthesias are produced along its sensory area in the hand. This distribution includes the palmar surface and fingertips of the lateral 3.5 digits (thumb, index, middle, and the radial half of the ring finger). So a positive test indicates symptoms in the median nerve distribution distally. The other nerves have distinct distributions (ulnar to the little finger and ulnar half of the ring finger; radial to the dorsum of the hand and dorsal aspects of the lateral digits; musculocutaneous to the lateral forearm), which is why they don’t fit the test’s result.