Like GBS, CIDP is an autoimmune disease but little is known about what may trigger the abnormal immune response.  In fact, a trigger is suspected in only about 20% of cases and is difficult to prove, probably in part because the slower onset of the disease makes any antecedent event more difficult to recall.  Infections and vaccinations may exacerbate CIDP once it has developed.  Unlike most autoimmune diseases, men are twice as likely to develop it than women.  It is primarily a disease of adults but rarely develops after 70 years of age.

Once CIDP is suspected, the diagnosis is relatively easy to establish.  Because it is not as dramatic as GBS the diagnosis is often delayed; symptoms of neuropathy are often attributed to other causes and appropriate testing may be delayed or not done at all.  However, most neuropathies such as those that accompany diabetes, excessive alcohol use or other toxins are predominantly sensory and evolve very slowly, over years, whereas CIDP is predominantly motor and usually evolves over months.  As in GBS, the reflexes are usually absent in CIDP whereas most reflexes are present in most other neuropathies.

Once the diagnosis is suspected it can usually be confirmed by performing nerve conduction studies.  Lumbar puncture to perform spinal fluid (CSF) analysis can also be helpful but is not usually necessary; if the diagnosis is in doubt, a CSF protein level greater than 100 can add to the confidence of the diagnosis.  Rarely, a nerve biopsy is done to show the inflammation and demyelination characteristic of the disease.  Occasionally CIDP is associated with abnormal antibodies in the blood and these should be tested for since it may indicate a bone marrow disorder that might need to be treated differently.

Three treatments for CIDP that have been studied in a careful scientific manner and have been shown to be effective.

Corticosteroids (“Steroids”):  There are many different steroid formulations the most common of which is Prednisone which is also the most widely studied.  However, there are probably no differences in efficacy, safety or tolerability.  When given as a daily oral dose of 80-100 mg the treatment is highly effective but long term treatment lasting months or even years is often needed and the duration of dosing is limited by adverse effects (AE’s) such as weight gain, fluid retention, hypertension, diabetes, skin bruising and breakdown, stomach problems and many others.  Several small studies have been done using different dosing schedules and it  appears that administering a very high dose once a week is just as effective but has many fewer AE’s.  The treatment is convenient and inexpensive and is the only treatment that has been proven to be effective and also may induce remission so that treatment can be stopped, perhaps permanently.  Most doctors in NZ use steroids first before trying other treatments.

Plasmapheresis (PLEX):  PLEX works by removing the antibodies in the blood that are thought to be attacking the myelin sheath.  PLEX has been proven to be beneficial but is expensive and cumbersome and can be done only at a few major centre in NZ.  PLEX does not induce remission, providing only a short term benefit requiring repeated treatment every few weeks so for a long term condition such as CIDP it is not an ongoing solution.

High Dose Intravenous Immunoglobulin (IVIg):  IVIg is a blood product that is effective and can be used for long-term treatment of CIDP.  It is usually given intravenously but has recently been shown to be effective in some patients given subcutaneously (under the skin).  If given intravenously it does require that the patient come to an infusion centre which is often inconvenient.  The product is extremely expensive and needs to be given on a regular schedule, typically every 3-4 weeks.  It is generally well tolerated but headache and allergic reactions can occur during the infusions and rarely it can cause blood clots leading to stroke, heart attack and pulmonary embolism (blood clots in the lungs) and can also cause kidney failure.  It does not induce remission so long term or life long treatment may be necessary.

In addition to these three proven effective treatments there are other immune suppressant drugs such as azathioprine and cyclophosphamide that are widely used but have not been proved to be of benefit.  They may be tried in combination with one of the proven therapies to try to reduce dependence on much more expensive and sometimes poorly tolerated proven therapies.  They have many potential AE’s and should be used under careful supervision and with great caution.

CIDP is a chronic disease that usually requires long term therapy.  Without medication it is usually steadily progressive (about 80% of patients) or may run a relapsing course with intermittent attacks.  Spontaneous remission is probably rare, occurring in about 5% of patients but steroids may induce remission.  Several studies have suggested a remission rate of about 30%  but one small study found 60% of patients remitted and were able to withdraw treatment for long periods.  The risk of future relapse always remains.  Even if remission does occur patients may be left with residual effects of variable severity but very few patients die and about three quarters are able to continue to work and function independently with minimal limitations.

Symptomatic treatment of pain and fatigue is important and patients will benefit from physiotherapy immediately after diagnosis and during times of deterioration.  Occupational therapists have an important role to play in helping patients maintain function and independence through the use of assistive devices.

There are several other immune-mediated demyelinating neuropathies that are often classified as CIDP variants but which have several important differences in clinical appearance, response to treatment and prognosis.

1. 1. Paraproteinemic neuropathies:In typical CIDP it is assumed that there are antibodies in the blood that are attacking the nerve but in the majority of cases none have been identified.  In all CIDP patients a blood test called serum protein electrophoresis is done to look for abnormal levels of certain proteins called immunogobulins, the protein part of serum that contains antibodies.  Sometimes a single family of proteins is found, called monoclonal proteins which are antibodies, and this indicates that cells in the bone marrow are proliferating and producing the proteins.  These are collectively called the paraproteinemic neuropathies.  Usually these are benign condition known as monoclonal antibodies of undetermined significance (MGUS) but occasionally there is a bone marrow cancer so it is obviously important to identify this.  Most of the paraproteinemic neuropathies look just like typical CIDP and although a monoclonal protein is identified a specific antibody to nerves is not identified.
   2. Recently a whole suite of specific “nodal” antibodies have been identified.  The nodes of Ranvier are a series of tiny gaps in the myelin sheath and antibodies against proteins at these nodes can damage the myelin and cause CIDP.  These patients have tremor and major problems with balance more than weakness but otherwise look like CIDP.  They may respond to treatment with steroids but do not seem to respond to IVIg.  Probably the best treatment is a drug called rituximab but it is difficult to get Pharmac to approve that.
   3. Occasionally there are specific antibodies against a protein in the myelin sheath called “myelin-associated glycoprotein (MAG)”.  These patients are generally older, usually over 70, and have a predominantly sensory disorder with numbness in the feet and sometimes the hands and severe balance problems.  They may have distal weakness (the muscles farthest form the spine) causing foot drop but they don’t have widespread weakness like CIDP patients.  MAG neuropathy patients are amongst the hardest to treat.  They do not respond to steroids, IVIg or PLEX.  They may respond to drugs such as cyclophosphamide or rituximab but the responses are not very good.
   4. Multifocal motor neuropathy (MMN) is a very rare disease in which there are often antibodies against a molecule called GM1 ganglioside.  MMN looks very different from CIDP.  It is a pure motor disorder causing weakness and muscle atrophy but not numbness or other sensory symptoms.  It is extremely restricted in its distribution, affecting a few individual nerves in a seemingly random fashion so it might affect one nerve in one hand and  different nerve in the opposite hand and yet another in one leg.  Because it causes weakness and muscle atrophy without sensory involvement it is often mistaken for motor neuron disease (MND), a critical mistake since MND is invariably fatal but MMN is treatable and is not fatal.  The only treatment that is effective is IVIg and it controls but does not cure so treatment needs to be very long term, perhaps life-long.  Steroids and PLEX can make MMN worse and chemotherapy probably doesn’t help although some doctors dispute that.
   5. Focal CIDP, also called Lewis-Sumner syndrome or multifocal acquired demyelinating sensory and motor (MADSAM) neuropathy looks very much like MMN but has unequivocal sensory involvement.  It responds to the same treatments as CIDP but responses are not very satisfactory, probably because it is very slowly progressive so diagnosis and treatment are delayed.
   6. CANOMAD (it doesn’t matter what the letters stand for) is an extremely rare neuropathy with probably only 2 or 3 cases in all of NZ.  It can be thought of as a chronic form of Miller Fisher syndrome (discussed in the GBS section) with severe balance problems (ataxia) and involvement of eye muscles causing double vision.  There can be some weakness.  It is very difficult to treat but has a partial response to IVIg and rituximab.