Introduction
Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is clinically defined as a “chronically progressive, stepwise or recurrent proximal and distal weakness and sensory dysfunction of all extremities, developing over at least 2 months, with absent or reduced tendon reflexes in all limbs and sometimes with cranial nerve involvement”1.
Chronic inflammatory demyelinating polyneuropathy (CIDP) is an acquired autoimmune disorder directed against the myelin sheath of peripheral nerves.1 It was initially characterized as chronic inflammatory polyradiculoneuropathy by Dyck et al in 1975, but cases consistent with probable CIDP were described as early as 19582,3.
CIDP is difficult to diagnose, but early diagnosis can be crucial to prevent permanent nerve damage.4
Although CIDP is the most common treatable chronic neuropathy worldwide, it is still a rare disease.5
The reported prevalence of CIDP ranges from 0.7 to 10.3 cases per 100,000 people6. There is a male predominance, with a gender rate ratio ranging from 1.5 to 4. CIDP primarily affects adults and the incidence rises with advancing age. The median age of onset is not well established. No specific predisposing risk factors for CIDP have been clearly identified6,7.
There are several clinical presentations, and sensory dysfunction is frequently present, most usually affecting joint position and vibration submodalities. Wasting is not prominent early in the disease. There are atypical forms, such as multifocal acquired demyelinating sensory and motor neuropathy (MADSAM, or Lewis– Sumner syndrome), pure sensory or pure motor CIDP and focal or distal forms (distal acquired demyelinating sensory polyneuropathy (DADS))8.
Most people with CIDP have a progressive rather than a spontaneously relapsing and remitting course, with a variable balance between motor and sensory symptoms. The American Academy of Neurology established diagnostic research criteria for CIDP in 19919 .
However, there is still no gold-standard set of diagnostic criteria for the electrophysiologic identification of demyelination, or for the clinical diagnosis of CIDP and its variants, even though multiple sets of diagnostic criteria have been published10-22.
Differences between these sets are related to definitions of the clinical picture, the requirements for nerve biopsy, electrodiagnostic criteria for demyelination, and the number of features required to make the diagnosis. The plethora of criteria sets for CIDP illustrate the difficulty of developing precise standards for problems that have multiple variations.
When independently validated in a retrospective study, the 2006 EFNS/PNS criteria had a sensitivity and specificity of 81 and 97 percent, respectively23, The most frequently used CIDP criteria in clinical practice and research are the revised European Federation of Neurological Societies/Peripheral Nerve Society 2010 criteria24.
These and other proposed criteria typically comprise a combination of clinical and electrophysiological features (there have been 15 formal sets of published electrophysiological criteria for the diagnosis of CIDP25). Cases are classified as definite, probable or possible, depending upon the number of criteria fulfilled. In most cases, finding a raised CSF protein without CSF leucocytosis26 further supports the diagnosis. Clear evidence of macrophage-associated demyelination and remyelination, with or without a T-cell inflammatory endoneurial infiltrate in a sensory nerve biopsy, remains the gold standard supportive criterion. There have been several validations of these diagnostic criteria, though none is 100% sensitive or specific1,9; for example, the EFNS/PNS criteria1 show a positive predictive value of 97% and negative predictive value of 92%,6 and different validation cohorts give widely varying sensitivities and specificities27.