It occurs when there is damage to the ulnar nerve, which travels down the arm and supplies flexion to the wrist, and aids in movement and sensation of the wrist and hand. Ulnar nerve dysfunction is a common form of peripheral neuropathy. Dysfunction of a single nerve group, such as the ulnar nerve, is classed as mononeuropathy . The usual causes are direct trauma, prolonged external pressure on the nerve, and compression of the nerve from nearby body structures.
Entrapment involves pressure on the nerve where it passes through a narrow structure.
This damage slows or prevents conduction of impulses through the nerve. The ulnar nerve is commonly injured at the elbow because of elbow fracture or dislocation . The ulnar nerve is near the surface of the body where it crosses the elbow, so prolonged pressure on the elbow or entrapment of the nerve may cause damage. Prolonged pressure on the base of the palm may also cause damage to part of the Ulnar nerve, resulting in symptoms that are localized to the small hand muscles. In some cases, no detectable cause can be identified.