Master Nerve Palsies: Median Claw Hand

The distal median nerve courses through the carpal tunnel to innervate the the first and second lumbricals, opponens pollicis, abductor pollicis brevis, and flexor pollicis brevis.

This syndrome is caused by compression of the median nerve, which runs with nine tendons through the tight the carpal tunnel. Median nerve compression causes numbness, tingling, and pain over the palmar side of the thumb and second, third, and half of the fourth digits. It commonly occurs in patients who sleep with pressure on the wrist, pregnancy due to the state of fluid overload, hypothyroidism due to GAG accumulation, and rheumatoid arthritis due to tendon inflammation.

The distal median nerve innervates the first and second lumbricals, which allow flexion at the metacarpophalangeal joint and extension at the proximal and distal interphalangeal joint. With distal median nerve compression and unopposed flexion by the flexor digitorum profundus, the pointer and middle finger are unable to fully extend at the proximal and distal interphalangeal joints. Therefore, the pointer and middle finger appear flexed, or clawed, on extension.

The distal median nerve innervates the first and second lumbricals, which allow flexion at the metacarpophalangeal joint and extension at the proximal and distal interphalangeal joint. With distal median nerve compression and unopposed flexion by the flexor digitorum profundus, the pointer and middle finger are unable to fully extend at the proximal and distal interphalangeal joints. Therefore, the pointer and middle finger appear flexed, or clawed, on extension.

When tapping on the median nerve, patients with a positive Tinel’s sign experience numbness and tingling over the sensory distribution of the median nerve, which encompasses the palmar side of the thumb and second, third, and half of the fourth digits.

Phalen test involves having a patient forcefully press the dorsal side of both hands together and flex at the wrist for 30 seconds; this maneuver causes the lumbrical tendons to slide further into the carpal tunnel and compress the median nerve. Patients with a positive Phalen's sign experience numbness and tingling over the sensory distribution of the median nerve, which encompasses the palmar side of the thumb and second, third, and half of the fourth digits. This sign may indicate that the patient has distal median nerve compression.

Because the proximal median nerve innervates the muscles of the thenar eminence, median nerve damage may result in muscle atrophy. These muscles include opponens pollicis, abductor pollicis brevis, and flexor pollicis brevis.