Chronic inflammatory demyelinating polyneuropathy

The underlying cause of CIDP is unknown. There is evidence that it is related to the immune system, and that it may have multiple triggers. It is thought to be caused by the immune system mistakenly attacking and damaging the myelin sheath of the peripheral nerves. The myelin sheath is the protective covering of nerve fibers. When myelin is damaged or removed, electrical impulses are slowed or lost, and messages transmitted from the brain are disrupted.

The diagnosis of chronic inflammatory demyelinating polyneuropathy (CIDP) should be considered in people with symmetric or asymmetric polyneuropathy who have progressive or relapsing-remitting symptoms for more than two months - particularly if the symptoms include positive sensory symptoms (such as tingling), proximal weakness, or absent reflexes.

The initial diagnosis of CIDP is based on signs and symptoms, but the diagnosis can be confirmed by evidence of peripheral nerve demyelination. This may be identified by either electrodiagnostic testing or by nerve biopsy. Electrodiagnostic testing is recommended for all patients with suspected CIDP. There is general agreement among the medical community that the following criteria support the diagnosis of "classic" CIDP:

• Progression over at least two months
• Weakness more than sensory symptoms
• Symmetric involvement of arms and legs (the same symptoms on both sides)
• Proximal muscles (those closer to the trunk) involved along with distal muscles (those further from the trunk)
• Reduced deep tendon reflexes throughout (found by the clinician "tapping" the knee, outside of the elbows, crooks of the arms, wrists and ankles)
• Increased cerebrospinal fluid protein without pleocytosis (an increased cell count)
• Nerve conduction evidence of a demyelinating neuropathy
• Nerve biopsy evidence of segmental demyelination (degeneration of the myelin sheath with sparing of the axon) with or without inflammation

Additional studies that may be indicated include MRI, evaluation for inherited neuropathies, and various laboratory tests. There are no laboratory test findings that specifically point to CIDP, but they may be useful to look for other disorders that have similar symptoms.

A treatment trial may be indicated if the diagnosis remains unclear despite a thorough evaluation. A positive response to immunotherapy may add supportive evidence to the diagnosis.

CIDP is not known to be inherited and is considered an acquired disorder. No clear genetic predisposition or other predisposing factors for CIDP have been identified.

Data regarding the long-term prognosis for people with CIDP are limited, and the course of CIDP varies widely among affected people. Therefore, it is difficult to predict the future course of the condition, potential complications, and the chance to have permanent disability.

For example, if the disease becomes severe, swallowing and breathing functions can be affected, and aspiration pneumonia, atelectasis, and respiratory failure can occur. If autonomic function is involved, gastrointestinal motility and bladder function can be affected. Orthostatic hypotension and cardiac conduction defects can also occur.

A study from 2006 on long-term outcome reviewed 38 Japanese patients with CIDP who had at least five years of follow-up. The authors of this study reported that severe disability (unable to walk) or relapses related to tapering of medication were present in five of the patients (13%).

It has been suggested that those with relapsing disease have a better prognosis than those with the chronic progressive course. About 70% are said to make relatively good recovery from their relapses. However, some patients don't respond to the usual treatments and accumulate significant disability. Some patients have only a short treatment effect and become treatment dependent. According to GBS/CIDP Foundation International, early recognition and proper treatment can avoid a significant amount of disability. Left untreated, 30% of CIDP patients will progress to wheelchair dependence.

For most people with CIDP the condition is slowly progressive, but about one- third of people experience a relapsing-remitting course (relapses of symptoms with partial or complete recovery in between). With more people receiving early treatment, the course of the disease has been harder to characterize since remissions may be related to therapy, rather than to the natural course of the disease. The relapsing course is thought to be more common in younger patients (those in their 3rd or 4th decades).

Occasionally, complete remissions occur. In one review of 106 patients with CIDP and an average follow-up of 6.4 years, 11% were considered "cured" (off treatment for 5 or more years) and 20% were said to be in remission (off treatment for less than 5 years). These and other data suggest that approximately 30% of patients with CIDP will achieve cure or remission.

The long-term outlook (prognosis) for people with CIDP appears to vary, but data regarding the prognosis is limited. Post-treatment life can depend on whether the disease was caught early enough to benefit from treatment options. For example, gradual onset of CIDP can delay diagnosis by several months or even years, resulting in significant nerve damage.

Complete remission, partial remission, and severe disability have all been reported. Some people may have a "bout" of CIDP followed by spontaneous recovery, while others may have many bouts with partial recovery in between relapses. Some people are left with residual numbness or weakness that can lead to reduced quality of life and/or long-term care. Rare, severe outcomes that have been reported include quadriplegia, respiratory failure and death.

Standard treatment options for CIDP include:

• intravenous immune globulin (IVIG) - adds large numbers of antibodies to the blood plasma to reduce the effect of the antibodies that are causing the problem
• glucocorticoids - help reduce inflammation and relieve symptoms
• plasma exchange - removes harmful antibodies from the blood

The choice of treatment may depend on the preference of the patient, side effects, treatment cost, duration, and availability. There are advantages and disadvantages of each treatment option:

• IVIG and plasma exchange may lead to a more rapid improvement in CIDP than glucocorticoid therapy, but are less likely than glucocorticoids to produce a remission
• IVIG is expensive, and its supply is sometimes limited
• Glucocorticoids are inexpensive, but chronic use is limited by common and important side effects
• Plasma exchange is expensive, invasive, and available only at specialized centers

Other drugs may be used when standard treatments fail or cause significant side-effects. Physical therapy may improve muscle strength, function and mobility.