The main function of the ulnar nerve, or ulnar nerve, is the innervation of the forearm and hand.

Position. The ulnar nerve is located in the upper limb.

Structure. The ulnar nerve is one of the two terminal branches of the medial bundle of the brachial plexus and is the larger of the two branches (2). The ulnar nerve is an even and mixed nerve, that is, composed of sensory and motor nerve fibers.

Origin. The ulnar nerve originates from the medial bundle of the brachial plexus, originating from the cervical vertebra C8 and the thoracic vertebra T11.

Path. The ulnar nerve passes through the medial part of the arm towards the elbow. It passes behind the medial epicondyle, then joins and follows the ulna, bone of the forearm, in its medial part. At this level, it innervates various muscles of the forearm, before continuing its journey into the hand, where it participates in muscle and skin innervation.

Innervation. The muscular branches of the ulnar nerve supply the flexor muscles of the anterior compartment of the forearm: the flexor carpi ulnaris as well as the medial half of the flexor digitorum profundus. Its branches also innervate most of the intrinsic muscles of the hand (1). The cutaneous branches of the ulnar nerve innervate the skin of the hand at the level of its anterior and posterior surfaces, as well as at the level of its medial third (1).

Wrist and finger movements. Innervation of the ulnar nerve allows flexion as well as adduction of the wrist and fingers.

Hand feeling. The ulnar nerve allows the reception and transmission of sensitive information on the different sides of the hand.

Ulnar tunnel syndrome. This syndrome, also called cubital tunnel syndrome, corresponds to compression of the ulnar nerve at the elbow (3). The origin of this compression is generally related to a trauma such as a fracture, a hematoma or a bad posture. Compression of the ulnar nerve is sometimes associated with the development of osteoarthritis. The first symptoms are most often unusual sensations as well as numbness in the fourth and fifth fingers. This is manifested in particular by a loss of strength in the hand and wrist.

Physical treatment. Physical therapy, through specific exercise programs, may be prescribed.

Surgical treatment. Surgery is often done to free the ulnar nerve.

Physical examination. First, a clinical examination is carried out in order to identify and assess the sensory and motor signs perceived by the patient in the fingers and hand.

Medical imaging exam. An x-ray can be done to confirm or further the diagnosis.

Electrophysiological exploration. The electromyogram makes it possible to study the electrical activity of the ulnar nerve and to identify potential lesions.

In a shock to the elbow, the sensation of electric shock traveling through the forearm is due to compression of the ulnar nerve at the medial epicondyle (2).