• CIDP is a neurological disorder characterized by progressive weakness and impaired sensory function, including loss of reflexes.
• CIDP is considered an autoimmune disorder, in which the immune system begins to attack the peripheral nerves, although the exact mechanisms by which this happens are still not clearly defined.
• The antigenic target is unknown in the majority of CIDP, and no reliable biologic markers have been identified, adding to the complexity of managing this disorder.
• The incidence of CIDP is approximately 0.33 per 100,000 individuals per year and prevalence is approximately 2.81 per 100,000 individuals however may be as high as 9 per 100,000.
• CIDP most commonly occurs between ages 40 and 60 and is more common in men than in women.
• CIDP is one of a spectrum of acquired demyelinating neuropathies that differ in their time course and clinical features. CIDP has a similar presentation to that of Guillain-Barre Syndrome (GBS), except that GBS is acute and usually peaks within 4 weeks, whereas CIDP is chronic (8 weeks or more) and may be progressive or relapsing.
  • Part of the difficulty in CIDP is getting an accurate diagnosis due to many variants of CIDP as there are both typical and atypical forms. The existence of several phenotypes within CIDP suggests that it may be a spectrum of related conditions rather than a discrete disease.

The classic clinical symptoms of CIDP include:

• progressive, symmetric weakness of the arms and legs, especially in proximal muscles
• loss of sensation (numbness); abnormal sensations (tingling, buzzing)
• progressive or relapsing loss of reflexes (areflexia)
• unsteady gait (usually resulting from sensory loss and weakness)

Diagnostic tests typically find:

• electrophysiological features of demyelination (e.g., reduced conduction velocities)
• high protein levels in spinal fluid analysis
• inflammation and demyelination observed in nerve biopsy samples

The symptoms of CIDP are caused by damage to the myelin sheath of peripheral nerves, but the particular nerves affected can vary from one patient to another.

The course of CIDP varies widely. Some may have a monophasic course of CIDP followed by recovery, while others may have progressive or relapsing-remitting courses.

The primary goals of treatment for CIDP are to:

• reduce symptoms (weakness, sensory loss, imbalance, pain)
• improve functional status (reduce disability and handicap)
• maintain long-term remission, if possible

Standard treatments for CIDP include:

• Intravenous immunoglobulin (IVIg) therapy at high doses
• Subcutaneous immunoglobulin 20% is also approved for maintenance regimens in patients stabilized on IVIg
• Corticosteroids, which are similar to naturally occurring anti-inflammatory hormones made by the body. Corticosteroids often improve strength, can be taken by mouth, and are inexpensive, but side effects can limit long-term use.
• Plasma exchange (PE) or plasmapheresis (PLEX), which may help remove harmful substances in the plasma.

Despite the proven benefits of IVIg in patients with CIDP, such treatment may be associated with certain limitations and drawbacks, including poor venous access in some patients, treatment-limiting systemic adverse reactions, and the requirement for regular visits to infusion centers or home visits.

Without treatment, about 30% of CIDP patients will progress to wheelchair dependence. Early recognition and proper treatment can prevent loss of nerve function and avoid a significant amount of disability.

Background

The Inflammatory Neuropathy Cause And Treatment (INCAT) disability score was developed in 2001 and used for the first time in a clinical study comparing the efficacy and safety of intravenous immunoglobulin with oral prednisone in patients with CIDP. It has subsequently been used in several CIDP clinical trials, although its use in day-to-day clinical practice is uncommon.

Scoring

The INCAT comprises two parts, the arm score and the leg score. Based on a patient’s level of impairment in their arms and legs, each part is scored between 0 and 5 points, resulting in an INCAT total score between 0 and 10. The adjusted INCAT score, which is used in clinical trials, excludes changes of 0 to 1 or 1 to 0 in upper limb function as regulatory agencies do not considered this clinically significant.

Note: INCAT score is inversely related to function, with 0 representing no functional impairment and 10 representing inability to make any purposeful movement with either arms or legs.

Background

The Inflammatory Rasch-built Overall Disability Scale (I-RODS) was developed in 2011 and is intended to specifically assess activity and social participation limitations in patients with inflammatory neuropathies. It is a patient-reported outcome measure, meaning the assessment is dependent on a patient’s own assessment about his or her disability.

Scoring

I-RODS is a 24-item scale, with each item representing a common, daily activity. I-RODS captures clinically meaningful changes over time and is scored from 0-100 (0 is the most severe limitation in activities and social participation, 100 is no limitation in activities and social participation).

The items range in difficulty from very easy (“reading a newspaper/book” and “eating”) to very difficult (“standing for hours” and “running”) The patient assigns a score between 0 and 2 to each item as follows:

• 0 = impossible to perform
• 1 = performed with difficulty
• 2 = easily performed

Background

The Medical Research Council (MRC) system for testing and grading of muscle function aims to provide a standardized and objective way to assess muscle function.

It was originally introduced in 1943 and has a long history of use in neurology, rehabilitation and general medicine examinations.

Scoring

In the MRC grading system, each tested muscle is assigned one of the following scores based on its function. Scores range from 0-80; 0 being paralysis and 80 being normal strength.

• 0 = paralysis
• 1 = only a trace or flicker of muscle contraction
• 2 = muscle movement is possible with gravity eliminated
• 3 = muscle movement is possible against gravity
• 4 = muscle strength is reduced, but movement against resistance is possible
• 5 = normal strength

Assessments of muscles are done bilaterally, meaning that for each muscle tested, the same muscle on the opposite side of the body is also tested. The MRC sum score is finally calculated by adding the score of each individually assessed muscle.

Background

Grip strength assessments have been recommended to be used in clinical practice because they can be done with relatively simple tools and provide near instantaneous results.

A variety of tools are available to assess grip strength; two commonly used instruments are the Martin Vigorimeter and Jamar Dynamometer.

Scoring

With the Martin Vigorimeter, the patient squeezes a rubber ball that is connected to a manometer with rubber tubing.

• The patient’s grip strength is expressed in kilopascal (kPa), with a range of0–160 kPa

With the Jamar Dynamometer, the patient squeezes the handle of a hand-held device inwards against increasing resistance.

• The patient’s grip strength is expressed in kg or lb, with a range of 0–90 kg or 0–200 lb