Ulnar Neuropathy
Definition
Ulnar neuropathy is an inflammation or compression of the ulnar nerve, resulting in paresthesia (numbness, tingling, and pain) in the outer side of the arm and hand near the little finger.
Description
The ulnar nerve transmits impulses to muscles in the forearm and hand. The nerve is responsible for the proper sensing of touch, texture, and temperature throughout the fourth and fifth digits of the hand, the palm, and the underside of the forearm. Ulnar neuropathy arises most commonly because of damage to the nerve as it passes through the wrist. The elbow is also a frequent site of nerve damage. Ulnar neuropathy is variously known as bicycler's neuropathy, cubital tunnel syndrome, Guyon or Guyon's canal syndrome, and tardy ulnar palsy.
Demographics
Ulnar neuropathy that originates at the elbow is very common. Estimates are that 40% of Americans experience some form of this neuropathy at some point in their lives. While the ulnar nerve is structurally identical in men and women, men tend to develop ulnar neuropathy more than women. This is because men generally do not have as much fat overlaying the elbow, and so the underlying nerve can be more susceptible to irritation and damage.
The onset of ulnar neuropathy can occur slowly. As a result, many of those who are affected are middle-aged or older adults. Demographic risk factors include a family history of diabetes, alcoholism, and presence of human immunodeficiency virus. Because leaning on the elbows can trigger ulnar neuropathy, people such as telephone operators, receptionists, and those who operate computers for extended periods of time are at risk for developing the disorder.
Causes and symptoms
Ulnar neuropathy is caused by nerve damage. The nature of the nerve damage is varied, and can result from inflammation or compression. Nerve damage at the elbow can result from compression of the nerve when sensation is obliterated during general anesthesia. As well, a blow to the elbow or even too much leaning on the elbow can be damaging, as can diseases (rheumatoid arthritis) and metabolic disturbances (diabetes). Even malnutrition can be a factor, as protective fatty deposits and muscle mass waste away. Damage to the nerve at the wrist can be caused by a blow, tumors, and impinging of an artery.
The nerve damage that results in ulnar neuropathy can involve the main body of the nerve, the branching region at the end of the nerve known as the axon (which is involved in the movement of the nerve impulse to the adjacent nerve), and the protective myelin coating around the nerve. When the main body of the nerve is involved, the problem is usually a block in the passage of the impulse down the nerve. Axon damage typically decreases the movement of the nerve impulse away from the nerve or the wavelength of the impulse. As a result, the impulse may not reach the adjacent nerve, or may not be recognized by the receptors of that adjacent nerve. Finally, damage to the myelin sheath (demyelination) also impedes the movement of signal down the body of the nerve.
Depending on the site of the neuropathy and whether the neuropathy arises suddenly (acute) or has been present for a long time (chronic), various symptoms can arise. Acute and chronic ulnar neuropathy of the elbow is always associated with numbness and weakness. Pain is present almost 40% of the time in the acute form of the disorder and almost 80% of the time in the chronic disorder. When the ulnar neuropathy involves the wrist, weakness is ever-present in a main muscle controlling wrist movement,
Other physical signs include the adoption of a clawed shape by the hand and the inability of the entire thumb to move to the forefinger in a single motion.
