Ulnar nerve dysfunction is a common form of peripheral neuropathy. It occurs when there is damage to the ulnar nerve, which travels down the arm, supplying flexion (bending movement) to the wrist and aiding movement and sensation of the wrist and hand.
Dysfunction of a single nerve group (such as the ulnar nerve) is classed as mononeuropathy. Mononeuropathy implies a local cause of the nerve damage, although systemic disorders may occasionally cause isolated nerve damage such as occurs with mononeuritis multiplex. The usual causes are direct trauma, prolonged external pressure on the nerve, or compression of the nerve caused by swelling or injury of nearby body structures. Entrapment involves pressure on the nerve where it passes through a narrow structure. The damage involves destruction of the myelin sheath of the nerve, or destruction of part of the nerve cell (the axon). 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. The mechanical factors may be complicated by ischemia (lack of oxygen related to decreased blood flow) in the area.
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