What is the median nerve?

The median nerve is located in the middle of the three major nerves of the hand (median nerve, ulnar nerve, and radial nerve). It is the only nerve that passes through the carpal tunnel at the center of the wrist, controlling the rough movements of the hand and is known as the "laborer's nerve."
Common conditions like "mouse hand" or "mommy wrist" are caused by median nerve damage.

Which department should you visit for median nerve issues?

English name: median nerve
Alias: Laborer's nerve
Departments to visit: Neurology, Orthopedics, Hand Surgery

What is the distribution and function of the median nerve?

The median nerve originates from the C6 to T1 nerve roots, descends along the medial side of the biceps brachii, runs through the entire arm, reaches the carpal tunnel, and finally extends to the palm. As shown in Figures 1 and 2.

Figure 1 source: Reference [2]

It gives off almost no branches in the upper arm. In the forearm, its first branch innervates the pronator teres, which functions to pronate the forearm. It then innervates the flexor carpi radialis (responsible for radial flexion of the hand and wrist flexion), palmaris longus (responsible for wrist flexion), and flexor digitorum superficialis (responsible for flexion of the finger phalanges).
Further down, it splits into a pure motor branch called the anterior interosseous nerve, which innervates the flexor pollicis longus (flexes the distal phalanx of the thumb), the flexor digitorum profundus of the 2nd and 3rd fingers (flexes the distal phalanges of the index and middle fingers), and the pronator quadratus (pronates the forearm).

Figure 2 source: Reference [2]

Near the carpal tunnel but before entering it, the median nerve gives off a palmar sensory branch, which provides sensation to the skin over the thenar eminence. It then enters the carpal tunnel and divides into motor and sensory branches in the palm.
The median nerve innervates nearly all the flexor muscles of the forearm and the thenar muscles, as well as the sensation of the thumb, index finger, middle finger, and the radial half of the ring finger (3.5 fingers). Damage at different locations can lead to varying motor and sensory deficits.
Damage above the elbow can affect all branches of the median nerve, resulting in an inability to pronate the forearm and a "simian hand" deformity characterized by a flat palm and atrophy of the thenar muscles.
The most common site of damage is the carpal tunnel, known as "carpal tunnel syndrome." Lightly tapping the midpoint between the two wrist creases may cause numbness in the fingers due to compression of the median nerve as it passes through this area.