In the early 1970's, Dr Peter Dyck and colleagues at the Mayo Clinic published their experience of a large number of patients with chronic inflammatory demyelinating polyneuropathy (Dyck PJ et al, Mayo Clinic Proc 197550 621). Dr Dyck's group suggested guidelines for diagnoses for this important treatable peripheral neuropathy. They pointed out that patients usually have symmetric weakness affecting both proximal and distal limb muscles. In the initial Mayo report, it was recommend that the time of progression of the illness that was required to diagnose CIDP should be 6 months. The Mayo Clinic also emphasized that laboratory studies which supportive diagnoses of CIDP included an elevation of spinal fluid (CSF) protein and nerve conduction studies (NCS) and sural nerve biopsy which showed changes of demyelination.

In the 1980’s, Dr Jerry Mendell's neuromuscular group at Ohio State University (of which I was fortunate enough to be associated with) relooked at that center's large experience with CIDP and an attempters made to fashion more definitive diagnostic criteria. In the criteria published in 1989 (Barohn RJ et al, Arch Neurol 1989; 46: 878), we set forth mandatory clinical features that included symmetric proximal and distal weakness with a progression of at least 2 months. We felt that the initial 6 months progression guideline suggested by the Mayo group was too long and could cause physicians to delay an appropriate diagnosis and treatment. The 2 month time course served to distinguish patients from most Guillain Barré Syndrome cases in which nearly all patients have stopped progressing by 4 weeks.

Therefore, in our original proposed CIDP criteria, the mandatory inclusion criteria consisted of the presence of proximal and distal weakness with progression longer than 2 months. Using the laboratory parameters of elevated CSF protean and evidence of demyelination on electrodiagnosis and sural nerve biopsy, diagnostic levels of confidence were proposed: definite CIDP - all 3 laboratory parameters abnormal, probable CIDP - 2 of 3 laboratory parameters abnormal, possible CIDP - 1 of 3 laboratory parameters abnormal (see Table). These Initial criteria were developed primarily to assist clinicians in making the diagnoses of CIDP particularly in patients who did not fall in the ''definite'' group, so that treatment would not be delayed.

Subsequently, an Ad Hoc Subcommittee of the AAN (Cornblath D et al' Neurology 1991, 41:617) elaborated and modified the diagnostic criteria for CIDP. In the AAN criteria, the electrophyslologic parameters for demyelination were outlined in much greater detail in the Ohio State group's original criteria, we took a minimalistic approach for demyelinating nerve conduction study one motor nerve conduction study with a velocity reduced below 70% of the lower limit of normal. The AAN subcommittee greatly expanded and refined the electrodiagnostic criteria to include distal latency and F wave latency values and to take into account low amplitude motor responses. On the other hand, while more emphases was given to the electrodiagnostic criteria, the requirement for an elevated CSF protein was de-emphasized in the probable and possible groups and considered to be ''supportive'' if present. Interestingly, the presence of symmetrical proximal weakness was also deemphasized as a mandatory clinical feature. The authors of the AAN subcommittee stated that the criteria were to be used unmanly as a research tool. Indeed, it has been demonstrated that only about two-thirds of patients diagnosed by a neuromuscular specialist with CIDP will be able to meet the electrophyslologic criteria for demyelination proposed by either the Ohio State group, the AAN subcommittee, or the Michigan group (Bromberg MB, Muscle & Nerve 1991, 14 968).

The Table outlines our new proposed CIDP Y2K diagnostic criteria which we believe are more reflective of the current practice. In most neuromuscular centers the primary modification in the Y2K criteria is that we have deemphasized the need for obtaining a sural nerve biopsy. In order to find evidence for a demyelination and inflammation it has been shown that histological evidence for demyelination is present in only about one-half of CIDP patients and inflammation is rare (10%), and the nerve appears normal. In about 20% most neuromuscular specialists now feel confident in making a definite diagnoses of CIDP without obtaining a nerve biopsy and the present criteria reflect this change. In practice we feel that a neurologist skilled in diagnosing CIDP can make a ''definite'' diagnoses. If the patient fulfills mandatory clinical features (proximal and distal weakness with progression for at least 2 months), has an elevated CSF protein, and has electrophyslologic features that meet demyelinating criteria. A sural nerve biopsy should be reserved for patients in whom either the electrodiagnostic criteria or the CSF studies are not supportive of the diagnosis or if one is looking for histologic evidence of an alternate diagnosis. In our Y2K criteria, we have adopted most of the electrophyslologic demyelinating features suggested by the AAN subcommittee, with modifications to the definition of conduction block and temporal dispersion to conform to currently accepted concepts.

Therefore, in our CIDP Y2K criteria, we re-emphasized the presence for both proximal and distal weakness as well as for CSF protein elevation; we have incorporated most of the AAN committee's electrodiagnostic criteria; and we have de-emphasized the need for sural nerve biopsy. We believe that a diagnosis of probable CIDP can be made with either abnormal electrodiagnostic criteria or an abnormal biopsy, or an abnormal CSF and an abnormal biopsy. Possible CIDP would be reserved for patients who have the clinical features but only 1 of the 3 laboratory criteria.

We believe that these criteria will be useful in the day-to-day diagnosis and approach to patients with chronic inflammatory demyelinating polyneuropathy. Whether or not they will be of use for clinical research trials awaits further validation.

These criteria were developed as a group effort with Drs. David S. Saperstein (San Antonio), Jonathan S Katz (Palo Alto), Anthony A. Amato (Boston), and Richard J. Barohn (Dallas). If you would like a complete table with all of the details concerning the CIDP Y2K criteria this group has developed, contact Dr. Barohn (214-648-6419).

Evolution of Diagnostic Criteria for CIDP

Clin – Clinical => Symmetric distal and proximal weakness for at least 2 months with areflexia or hyporeflexia
CSF – Cell count < 10 mm3 (<50 if HIV), inc protein supportive, not mandatory
CSF – Mandatory protein > 45 mg/dl