The Median Nerve - Anatomy, Functions, and Disorders

Introduction

The median nerve is one of the significant nerves in the human body that arises from the brachial plexus, a network of nerves in the upper arm. The median nerve provides both sensory and motor innervation to the muscles and skin of the hand, wrist, and forearm. The median nerve passes through a narrow passage in the wrist called the carpal tunnel, along with tendons and other structures. Compression or injury to the median nerve in the carpal tunnel can result in a condition called carpal tunnel syndrome, which causes pain, numbness, and weakness in the hand and fingers. The median nerve also plays an important role in hand function, as it controls the movements of certain muscles that enable the fingers and thumb to move and grip objects. Damage to the median nerve can result in weakness, numbness, or even paralysis of the affected muscles, leading to difficulty with fine motor skills and decreased grip strength.

What Are the Functions of the Median Nerve?

The median nerve has both motor and sensory functions, and it plays an important role in the movement and sensation of the forearm, wrist, and hand.

Motor Functions:

• Controls the muscles of the forearm that flex the wrist and fingers, and pronates the forearm.

• Controls the muscles that oppose the thumb (opponens pollicis) and allows for the opposition of the thumb to the other fingers.

Sensory Functions:

• The median nerve is responsible for providing sensory input to the palmar side of the thumb, index, middle, and half of the ring finger, as well as the skin over the base of the palm, palm side of the hand, and tips of the fingers on the palmar side.

Damage or injury to the median nerve can result in a variety of symptoms, depending on the extent and location of the injury. These symptoms can include weakness or paralysis of the muscles controlled by the nerve, as well as numbness, tingling, or pain in the areas supplied by the nerve.

What Is the Anatomy of the Median Nerve?

Derived from the medial and lateral cords of the brachial plexus, the median nerve is one of the principal nerves of the upper extremity. The median nerve travels down the arm and forearm, passing through the cubital fossa (the area in front of the elbow) and entering the anterior compartment of the forearm. It then passes through the carpal tunnel, a narrow passageway in the wrist, where it is accompanied by several tendons and blood vessels.

It is divided into three main branches:

• The muscular branch, which innervates the muscles in the forearm.

• The anterior interosseous nerve, which innervates the deep muscles of the forearm.

• The palmar digital nerves, which supply the fingers.

In the hand, the median nerve gives off several branches that supply the muscles that control the thumb and fingers, and the skin on the palmar side of the hand and fingers. The median nerve is closely associated with the ulnar and radial nerves, which also supply the hand and fingers.

What Are the Disorders That Can Affect the Median Nerve?

The disorders that can affect the median nerve include:

• Carpal Tunnel Syndrome: Carpal tunnel syndrome is a prevalent condition that arises when the median nerve gets compressed as it travels through the wrist's carpal tunnel. This compression can result in various symptoms, including weakness, numbness, and pain in the hand and fingers.

• Pronator Syndrome: This rare disease arises when the median nerve becomes compressed as it traverses through the pronator teres muscle located in the forearm. The symptoms include weakness, numbness, and pain in the hand and fingers.

• Median Nerve Injury: This can occur as a result of trauma, such as a fracture or dislocation of the wrist or elbow, or from repetitive use or overuse of the hand and wrist. Symptoms can include weakness or paralysis of the muscles controlled by the median nerve, as well as numbness, tingling, or pain in the areas supplied by the nerve.

• Radiculopathy: This is a condition that occurs when the spinal nerve roots that give rise to the median nerve are compressed or damaged, resulting in symptoms such as pain, weakness, or numbness in the arm, forearm, and hand.

• Tumors: Tumors or growths that develop along the path of the median nerve can cause compression and damage to the nerve, resulting in symptoms such as pain, numbness, and weakness in the hand and fingers.

What Are the Signs of Median Nerve Compression?

Compression of the median nerve can cause a variety of signs and symptoms, including:

• Pain: Compression of the median nerve can cause pain in the wrist, hand, and fingers. The pain may be sharp, dull, or aching, and may be felt in the palm of the hand, thumb, index, middle, and half of the ring finger.

• Numbness and Tingling: Compression of the median nerve can cause numbness and tingling in the thumb, index, middle, and half of the ring finger. This sensation may be described as "pins and needles" or a feeling of electric shock.

• Weakness: Compression of the median nerve can cause weakness in the muscles of the hand and forearm that are controlled by the nerve. This may result in difficulty gripping or holding objects, as well as difficulty with fine motor tasks such as buttoning clothes or writing.

• Muscle Atrophy: In severe cases of median nerve compression, the muscles of the hand and forearm may begin to shrink or atrophy. This may be visible as a loss of muscle bulk or a hollowing of the space between the thumb and index finger.

• Sensitivity to Cold: Some people with median nerve compression may experience increased sensitivity to cold temperatures in the affected hand and fingers.

What Is the Diagnosis and Treatment of Median Nerve Compression?

Diagnosis of median nerve compression typically involves a thorough medical history and physical examination by a healthcare professional. The doctor may recommend diagnostic tests such as nerve conduction studies or electromyography (EMG) to evaluate the function of the median nerve and the muscles it controls.

Treatment for median nerve compression depends on the underlying cause and severity of the condition. Some common treatment options include:

• Rest and Immobilization: Resting the affected hand and wrist and using a splint or brace to immobilize the area can help relieve pressure on the median nerve and reduce symptoms.

• Medications: Nonsteroidal anti-inflammatory drugs (NSAIDs) or other pain relievers may be prescribed to help manage pain and inflammation associated with median nerve compression.

• Physical Therapy: Exercises to stretch and strengthen the muscles of the hand and wrist can help improve the range of motion and relieve pressure on the median nerve.

• Corticosteroid Injections: Injections of corticosteroids into the wrist can help reduce inflammation and relieve pressure on the median nerve.

• Surgery: If the compression of the median nerve is severe, surgery may be required to alleviate the pressure on the nerve. This may involve cutting the ligament that forms the roof of the carpal tunnel (known as a carpal tunnel release) or other procedures to remove pressure on the nerve.

Conclusion

The median nerve supplies motor and sensory innervation to the muscles and skin of the forearm, wrist, and hand. Damage or injury to the median nerve can result in a variety of symptoms, depending on the extent and location of the injury. These symptoms can include weakness or paralysis of the muscles controlled by the nerve, as well as numbness, tingling, or pain in the areas supplied by the nerve. If there are any signs or symptoms, it is important to seek medical attention. Early treatment can help prevent further damage to the nerve and improve outcomes.