What are the symptoms of median nerve injury

The symptoms of median nerve injury mainly refer to loss of sensation in the hands. Some symptoms may seriously affect the function of the hands, such as the tendency to drop objects easily when picking them up. Some may also experience bone atrophy or fingertip deformation.

1. Median nerve injury at the wrist

1. Movement: The three thenar muscles, namely the opponens pollicis, abductor pollicis brevis and superficial head of flexor pollicis brevis, are paralyzed. Therefore, the thumb cannot oppose the palm, cannot form a 90° angle with the palm plane, and cannot touch other fingertips with the pad of the finger. The thenar atrophy and thumb adduction form ape hand deformity. The flexor pollicis brevis is sometimes supplied by an abnormal ulnar nerve.

2. Sensation: The loss of sensation in the hand is most severely affected by injury to the median nerve. After the injury, the radial semi-palmar surface of the thumb, index finger, middle finger, ring finger and the dorsal surface of the corresponding distal knuckles lose sensation, which seriously affects the function of the hand. Objects held are easily dropped and there is no sense of reality. The hand is easily injured and burned.

3. Nutritional changes: There are significant nutritional changes in the skin and nails of the fingers, the phalanges atrophy, and the fingertips become smaller and pointed.

(ii) Median nerve injury at the elbow

1. Movement: In addition to the above, the pronator teres, radial flexor carpi, pronator quadratus, palmaris longus, superficial flexor digitorum, radial half of flexor digitorum profundus and flexor pollicis longus are paralyzed. Therefore, the thumb and index finger cannot be flexed. When making a fist, these two fingers are still straight. Some middle fingers can be partially flexed. The metacarpophalangeal joints of the index and middle fingers can be partially flexed, but the interphalangeal joints are still straight.

2. Changes in sensation and nutrition remain the same as before.

3. Symptoms

The injury site is usually in the wrist or forearm, and injuries to the upper arm or armpit are less common. If the injury is in the wrist or forearm (distal to the origin of the muscle branch), the main manifestation is the inability to abduct the thumb and oppose the palm and fingers. The radial half of the palm is sensory impaired, but the sensory loss is limited to the skin of the distal palmar and dorsal surfaces of the index and middle fingers. In the late stage, the thenar muscles atrophy and form an ape-like hand deformity. If the injury is at the elbow or above, in addition to the above symptoms, the superficial flexor muscles of the fingers and the radial half-digitorum profundus muscles are paralyzed. Therefore, the thumb and index finger are in an extended position and cannot be flexed, while the middle finger can be flexed to a certain extent because it is connected to the deep flexor tendon of the ring finger by a tendon bundle. Due to paralysis of the radial flexor carpi and palmaris longus, the wrist can flex, but due to compensation by the ulnar flexor carpi, it deviates to the ulnar side when flexing. The forearm pronation movement is also significantly affected or impossible due to paralysis of the pronator teres and pronator quadratus muscles. In the late stage, the forearm flexor muscles atrophy.