Chronic Inflammatory Demyelinating Polyneuropathy
Chronic inflammatory demyelinating polyneuropathy (CIDP) is a disorder that affects the nerves outside of the brain and spinal cord (peripheral nerves). Specifically, the fatty covering, or sheath, that is wrapped around the out-side of a nerve cell is damaged. The covering is called myelin, and the damage is called demyelination. The nerve damage becomes apparent as weakness in the legs and arms increases in severity with time.
The demyelination of peripheral nerves causes a weakness in the legs and arms that grows progressively more severe over time. The ability of the limbs to feel sensory impulses such as touch, pain, and temperature can also be impaired. Typically, the malady is first apparent as a tingling or numbness in the toes and the fingers. The symptoms can both spread and become more severe with time.
The symptoms, treatment, and prognosis of CIDP is very similar to another nerve disease known as Guillain-Barré syndrome. In fact, CIDP has been historically known as "chronic Guillain-Barré syndrome" (Guillain-Barré syndrome is an acute malady whose symptoms appear and clear up more rapidly). Despite their similarities, however, CIDP and Guillain-Barré are two distinct conditions. CIDP is also known as chronic relapsing polyneuropathy.
CIDP can occur at any age. However, the malady is more common in young adults, and in men more than in women. The disorder is rare in the general population.
Causes and symptoms
CIDP is an immune system disorder. Specifically, the immune system mistakenly recognizes the myelin sheath of the peripheral nerve cells as foreign. Damage to the sheath occurs when the immune system attempts to rid the body of the invader. There is no evidence to support a genetic basis for the disease, such as a family history of CIDP or other, similar disorders. CIDP cannot be inherited.
As with Guillain-Barré syndrome, it is strongly suspected that CIDP is at least triggered by a recent viral infection. For example, critical immune cells can be damaged in viral infection such as occurs in acquired immunodeficiency syndrome (AIDS), leading to malfunction of the immune system. Whether viral or other microbial infections are the direct cause of CIDP is not clear.
CIDP is different from Guillain-Barré syndrome in that the viral infection often does not occur within several months of the first appearance of the symptoms. In Guillain-Barré syndrome, a viral or bacterial infection typically immediately precedes the appearance of the symptoms.
CIDP typically begins with a tingling or prickling sensation, or numbness in the fingers and toes. This can spread to the arms and legs (an ascending pattern of spread). Both sides of the body can be affected; this is described as a symmetrical pattern. Other symptoms that can develop over time include the loss of reflexes in some tendons (a condition referred to as areflexia), extreme tiredness, and muscle ache. In some people, these symptoms develop slowly, reach a peak over several weeks or months, and then resolve themselves over time. However, for the majority of people with CIDP, the symptoms do not improve without treatment, and the symptoms can persist for many months to years.
An important part of the diagnosis of CIDP is the detection of muscle weakness by a neurological examination. One relevant neurological test is nerve conduction velocity. In this test, a patch that is attached to the skin's surface over the target muscle is stimulated. A very mild electrical current stimulates the nerves in the muscle. A measurement called the nerve conduction velocity is then calculated as the time it takes for the impulses to travel the known distance between electrodes.
In demyelinating diseases such as CIDP, the nerves are not capable of transmitting electrical impulses as speedily as normal, myelinated nerves. Thus, the damaged nerves will display a greater conduction velocity than that displayed by an unaffected person.
Another test called electromyography (EMG) is used to measure muscle response to electrical stimulation. In EMG, an electrode contained within a needle is pushed through the skin into the muscle; several electrodes may need to be inserted throughout a muscle to accurately measure the muscle's behavior. Stimulation of a muscle causes a visual or audio pattern. The pattern of wavelengths carries information about the muscle's response. The characteristic pattern of wavelengths produced by a healthy muscle, which is called the action potential, can be compared to a muscle in someone suspected of having CIDP. For a nerve-damaged muscle, the action potential's wavelengths are smaller in height and less numerous than displayed by a normal muscle.
An electrocardiogram can be used to record the electrical activity of the heart when paralysis of the heart muscle is suspected. Nerve damage will alter the normal pattern of the heartbeat.
Finally, an examination of the cerebrospinal fluid by alumbar puncture (also known as a spinal tap) may detect a higher than normal level of protein in the absence of an increase in the number of white blood cells (WBCs). An increase in WBCs occurs when there is a microbial infection.
The treatments for CIDP and Guillain-Barré syndrome are similar. The use of corticosteroids such as prednisone, which lessen the response of the immune system, can reduce the amount of demyelination that occurs. Corticosteroids can be prescribed alone or in combination with other immunosupressant drugs.
The medical procedure known as plasmapheresis, or plasma exchange, can be another useful treatment. In plasmapheresis, the liquid portion of the blood that is known as plasma is removed from the body. The red blood cells are retrieved from the plasma and added back to the body with antibody-free plasma or intravenous fluid. Although plasmapheresis can lessen the symptoms of CIDP, it is not known exactly why plasmapheresis works. Because the blood plasma withdrawn from the body of a CIDP patient can contain antibodies to the nerve myelin sheath, the subsequent removal of these antibodies may lessen the effects of the body's immune attack on the nerve cells.
Another procedure that produces similar results involves the administration of intravenous immunoglobulin (IVIG). IVIG is a general all-purpose treatment for immune system-related neuropathies. As with plasmapheresis, immunoglobulin may help reduce the amount of anti-myelin antibodies, and so suppress the immune response. As well, IVIG contains healthy antibodies from the donated blood. These antibodies can help neutralize the defective antibodies that are causing the demyelination. When more standard approaches fail, alternative forms of immunosuppressive therapies are sometimes considered, including the drugs azathioprine, cyclophosphamide, and cyclosporine.
Physical therapy is helpful. Caregivers can move a patient's arms and legs to help improve the strength and flexibility of the muscles, and minimize the shrinkage of muscles and tendons that are not being actively used.
Recovery and rehabilitation
Recovery from CIDP varies from person to person. Some people recover completely without a great deal of medical intervention, while others may relapse again and again. Because some people can display permanent muscle weakness or numbness, physical therapy can be a useful part of a rehabilitation regimen.
The National Institutes of Health (NIH) sponsored four clinical trials for the study and treatment of CIDP, all completed by 2001. The National Institute of Neurological Disorders and Stroke supports continued broad research for demyelinating diseases, although no further clinical trials are ongoing as of March 2004.
A patient's prognosis can range from complete recovery to a pattern of a periodic reappearance of the symptoms and residual muscle weakness or numbness.
The potential exists that IVIG will increase the risk of kidney damage in older or diabetic patients. Enoxaparin, a drug that can be prescribed to reduce the risk of blood clotting in patients with high blood pressure, can make a patient more prone to bleeding. This risk can be greater when enoxaparin is given at the same time as aspirin or anti-inflammatory drugs. The use of corticosteroids can restrict the efficiency of the immune system, which can increase the risk that other microorganisms will establish a secondary, or opportunistic, infection. Medical staff regularly monitor people receiving these treatments for signs of complication.
Comi, G., A. Quattrini, R. Fazio, and L. Roveri. "Immunoglobulins in Chronic Inflammatory Demyelinating Polyneuropathy." Neurological Science (October 2003): S246–S250.
Fee, D. B., and J. O. Flemming. "Resolution of Chronic Inflammatory Demyelinating Polyneuropathy-associated Central Nervous System Lesions after Treatment with Intravenous Immunoglobulin." Journal of the Peripheral Nervous System (September 2003): 155–158.
Katz, J. S., and D. S. Saperstein. "Chronic Inflammatory Demyelinating Polyneuropathy." Current Treatment Options in Neurology (September 2003): 357–364.
NINDS Chronic Inflammatory Demyelinating Polyneuropathy (CIDP) Information Page. National Institute of Neurological Disorders and Stroke. December 22, 2003 (March 30, 2004). <http://www.ninds.nih.gov/health_and_medical/disorders/cidp.htm>.
American Autoimmune Related Diseases Association. 22100 Gratiot Avenue, Eastpointe, MI 48201-2227. (586) 776-3900 or (800) 598-4668; Fax: (586) 776-3903. email@example.com. <http://www.aarda.com>.
Guillain-Barre Syndrome Foundation International. P.O. Box 262, Wynnewood, PA 19096. (610) 667-0131; Fax: (610) 667-7036. firstname.lastname@example.org. <http://www.aarda.org>.
National Organization for Rare Disorders. P.O. Box 1968, Danbury, CT 06813-1968. (203) 744-0100. email@example.com. <http://www.rarediseases.org>.
Neuropathy Association. 60 East 42nd Street, New York, NY 10165-0999. (212) 692-0662 or (800) 247-6968; Fax: (212) 696-0668. firstname.lastname@example.org. <http://www.neuropathy.org>.
Brian Douglas Hoyle, PhD