Benediction Sign · What Is It, Causes, and More

Benediction sign and ulnar claw are both abnormal hand positions caused by peripheral nerve damage; however, they result from different nerve injuries and give rise to different clinical manifestations.  

Classically, benediction sign has been attributed to injuries of the median nerve, particularly those at the level of the elbow or forearm. The median nerve originates from the brachial plexus and travels down the forearm to supply motor function to the flexor digitorum superficialis (FDS) and the lateral half of the flexor digitorum profundus (FDP), allowing flexion of the thumb, index, and middle fingers. Since the other half of the flexor digitorum profundus (FDP) is innervated by the ulnar nerve, flexion of the ring and little fingers remains intact. With median nerve damage, when a person is asked to make a fist, they will only be able to flex the ring and little fingers, leading to benediction sign.  

On the other hand, ulnar claw is caused by damage to the ulnar nerve, typically at the level of the wrist. It’s caused by weakness in small hand muscles called the lumbricals. The lumbricals act on the metacarpophalangeal (MCP) joints to help bend the fingers at their base, while keeping the rest of the finger straight. When there’s damage to the ulnar nerve, the muscles that flex the interphalangeal joints take over the lumbricals, causing the ring and little fingers to curl up, especially at rest. Additionally, the muscles that extend the metacarpophalangeal joints function normally, so the knuckles of the ring and little fingers get pulled back too far, which leads to the characteristic claw-like appearance of the hand. 

Benediction sign is caused by damage to the median nerve at the level of the elbow or forearm. A common cause is a fracture of the distal humerus, often due to falling on an outstretched hand, which can damage the median nerve as it passes near the supracondylar region. The median nerve can also become trapped between the two heads of the pronator teres muscle in the forearm, usually due to inflammation from repetitive forearm movements (e.g., in athletes, mechanics, or manual laborers). Other causes of proximal median nerve damage include penetrating trauma, elbow dislocation, or surgeries involving the cubital fossa.   

Distal median nerve injuries, such as in carpal tunnel syndrome, generally don’t result in benediction sign because the forearm flexor muscles are supplied by the median nerve before it reaches the carpal tunnel. Carpal tunnel syndrome can cause thenar muscle weakness, leading to thumb weakness, loss of grip strength, and sensory loss, but not the inability to flex the fingers like in proximal median nerve injuries. 

Treatment for benediction sign involves managing and treating the cause of median nerve damage. In cases of mild compression or injury, this often involves activity modification (e.g., avoiding repetitive forearm movements that worsen the symptoms), as well as the use of non-steroidal anti-inflammatory drugs (NSAIDs), such as aspirin or ibuprofen, to prevent worsening of symptoms and help control pain. In some cases, the use of an elbow or wrist brace may be helpful to reduce nerve strain.  

Nerve decompression surgery may be performed in severe injuries or if conservative measures are not effective. The goal of decompression surgery is to release pressure on the nerve by removing fibrous bands, releasing tight muscles (e.g., pronator teres), or widening the nerve passage. In cases of traumatic nerve injuries, surgery may involve repairing severed nerves, which may be done by connecting both ends of the nerve directly or using a graft if the gap is too large to be repaired. 

In addition, individuals may benefit from physical or occupational therapy to help to strengthen and stretch the forearm and hand muscles. Depending on the severity of the injury, muscle strength and sensation may not be completely recovered with therapy. Even with appropriate treatment, nerve injuries can take months to heal completely, whereas severe trauma can result in permanent dysfunction if not repaired early.