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.
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.
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, generalized weakness in the absence of pain in 50% of those afflicted, and finger numbness occurs in about 25% of cases.
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.
Typically, the development of weakness in the elbow or wrist is the sign that alerts a clinician to the possibility of ulnar neuropathy. Follow-up tests can include ultrasound or magnetic resonance imaging to visualize cysts or structural abnormalities. The functioning of the nerve can be assessed in a nerve conduction test. Laboratory analyses of blood can be done to detect the presence of diabetes or infections that can damage nerves (such as Lyme disease , human immunodeficiency virus, or hepatitis viruses).
Treatment can involve the family physician, family members, neurosurgeons, hand surgeon, pain specialist, and physical and occupational therapists. Therapists can often provide exercises that assist in maximizing muscular strength and orthotic devices to maintain proper positioning during repetitive or stressful movements, thereby reducing inflammation.
Treatment can consist of the use of nonsteroidal anti-inflammatory drugs to control swelling around the nerve. The use of splints or cushions can ease the discomfort and the stress on the ulnar nerve. For some, surgery is a useful option, when relief can be gained by removal of a cyst or correction of damage caused by a blow.
Recovery and rehabilitation
Sports and other normal activity can be resumed when the person is able to perform normal hand-gripping tasks such as opening a jar, forcefully grip a tennis racquet or bicycle handlebars, or work at a keyboard without pain or tingling in the elbow or hand. Braces and other orthotic devices, if worn consistently, often prevent reoccurrence of ulnar neuropathy.
If nerve damage has been caused by a blow or by trauma such as putting too much pressure on the elbow or wrist, recovery can be complete.
Hochman, M. G., and J. L. Zilberfarb. "Nerves in a pinch: imaging of nerve compression syndromes." Radiology Clinics of North America (January 2004): 221–245.
Kern, R. Z. "The electrodiagnosis of ulnar nerve entrapment at the elbow." Canadian Journal of Neurological Science (November 2003): 314–319.
"Ulnar Neuropathy." emedicine.com. <http://www.emedicine.com/neuro/topic387.htm> (May 5, 2004).
National Institute for Neurological Diseases and Stroke. P.O. Box 5801, Bethesda, MD 20824. (301) 496-5751 or (800) 352-9424. <http://www.ninds/nih.gov>.
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS). 31 Centre Dr., Rm. 4Co 2 MSC 2350, Bethesda, MD 20892-2350. (301) 496-8190 or (877) 226-4267. [email protected] <http://www.niams.nih.gov>.
Brian Douglas Hoyle, PhD