Ulnar nerve

Of the Ulnar nerve belongs to the nerves of the arm plexus (Brachial plexus) and is responsible for important motor and sensitive functions of the hand. It is a long nerve that extends over the entire arm to the hand. Damage to the ulnar nerve can lead to abnormal sensations in the hand and functional failures with symptoms of paralysis.

What is the ulnar nerve?

Inside the brachial plexus is the Ulnar nerve connected to the spinal cord by nerve fibers. These fibers originate in the 8th segment (C8) of the spinal cord, which lies between the seventh cervical and first thoracic vertebrae. Sensitive signals are sent via the ulnar nerve from the skin via the spinal cord to the brain and, conversely, impulses from the brain to the supplying muscles.

The ulnar nerve, too Ulnar nerve called, ensures the transmission of stimuli to special muscle groups of the arm] and hand muscles, which are responsible for the flexion and fine motor skills of the hand and fingers. The previous sensible impulse signals to the brain which muscle groups should be activated. In extreme cases, damage to the ulnar nerve can lead to paralysis and muscle breakdown in the hand area.

Anatomy & structure

The ulnar nerve runs through the entire arm from the upper arm over the elbow to the forearm and splits even further in the hand. It is part of the arm braid. The arm plexus (plexus brachialis) is a nerve cord that is formed by the aggregation of the spinal cord nerves from the cervical cord of the spinal cord. The brachial plexus is the source of all the nerves that supply the arm. It contains short and long branches.

The ulnar nerve is one of the long branches of the Brachial plexus. First, the ulnar nerve runs from the armpit over the inside of the upper arm to the elbow. There it breaks through the muscular skin on the medial side of the upper arm and pulls behind the bony protrusion of the elbow onto the front inside of the forearm. In the area of ​​the humerus, the ulnar nerve is unprotected and can lead to severe pain when impacted. This pain reaction is also known colloquially as the musician's bones. In the forearm, the nerve is protected by a forearm muscle. Above the carpal tunnel, it then runs to the palm of the hand. In front of the wrist, the ulnar nerve splits into the motor Ramus profundus and the sensitive Ramus superficialis on.

Function & tasks

The ulnar nerve supplies the muscles that are involved in flexing the wrist and flexing and spreading the fingers. The nerve forms motor and sensitive branches. This includes the motor ramus profundus and the sensitive ramus superficialis. The motor branches transmit impulses from the brain to the corresponding muscles. The characteristic movements are triggered.

There are different motor branches in both the forearm and the hand. In the forearm, three muscles are innervated, which are necessary for hand and finger flexion. In the hand area, muscles are stimulated which regulate the flexion and splaying of the little and ring fingers. Overall, the ulnar nerve controls the tightening and flexion of the thumb, the spreading, stretching and flexing of the little finger, the flexion of the fingers in the metatarsophalangeal joint and the extension of the fingers in the end joint, the spreading of the fingers and the flexing of the wrist.

These movements are coordinated through the interaction of the brachial plexus, spinal cord and brain. This is also ensured by the sensitive branches of the ulnar nerve, among other things. They transmit the sensitive impressions of the skin to the brain via the spinal cord. The ulnar nerve is responsible for the sensitive areas of the edge of the hand with the little finger, the back of the hand up to half of the middle finger and the palm up to the middle of the ring finger.

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Illnesses & ailments

Damage or irritation of the ulnar nerve can lead to paralysis or paralysis in the hand. It also plays a role at which point the nerve is disturbed. Common ulnar nerve disorders are ulnar channel syndrome and Loge de Guyon syndrome.

Ulnar channel syndrome is caused by irritation of the nerve on the elbow. There the ulnar nerve is unprotected and can be strongly irritated by impact or pressure. Symptoms are tingling and numbness on the little finger, the ring finger and the adjacent palm area. Motor disorders follow, whereby the little finger can no longer be spread apart.

The muscles are no longer optimally supplied, so that in the worst case, muscle loss can also occur. This limits the overall mobility of the hand. Without treatment, complete paralysis of the hand with the development of a so-called claw hand is possible. The causes of this disease are many.

At the elbow, the nerve is often irritated by impact or constant pressure. A protruding bone or fracture can also be responsible. Other causes are signs of wear and tear or congenital anatomical changes in the elbow joint. It should also be noted that the pressure damage develops over the long term. Only permanent irritation leads to the disease.

Another condition called Guyon-Lodge syndrome can lead to similar symptoms. This causes irritation of the ulnar nerve on the wrist. In contrast to the ulnar groove syndrome, however, the reduction in sensitivity on the back of the hand on the elbow side is missing here. In order to treat ulnar nerve diseases, it is necessary to clarify the respective cause through a thorough medical history and imaging tests.