What are the electrodiagnostic criteria for chronic inflammatory demyelinating polyneuropathy (CIDP)?

Electrodiagnostic Criteria for CIDP

The diagnosis of CIDP requires electrodiagnostic evidence of demyelination using the European Federation of Neurological Societies/Peripheral Nerve Society (EFNS/PNS) criteria, which offer 81.3% sensitivity and 96.2% specificity for "definite/probable" CIDP when applied to standard four-nerve studies. 1

Core Demyelinating Features Required

The electrodiagnostic criteria focus on identifying the following demyelinating abnormalities across multiple nerves 2:

• Reduced conduction velocities - slowing of nerve conduction across tested segments 2
• Prolonged distal motor latencies - delayed response at distal nerve terminals 2
• Abnormal temporal dispersion - non-uniform slowing reflecting different conduction velocities across nerve fibers, a hallmark of demyelination 2
• Partial motor conduction blocks - reduction in amplitude between proximal and distal stimulation sites 2
• Prolonged or absent F-waves - indicating proximal nerve root involvement 2

Critical Pattern Recognition

The key distinguishing feature is that these demyelinating abnormalities must be relatively uniform across multiple tested nerves, differentiating generalized polyneuropathy from multifocal processes. 2

• Multiple nerves are affected symmetrically, with both upper and lower extremities showing similar patterns of involvement 2
• Both sensory and motor fibers are typically involved, though motor-predominant variants exist 3
• The distribution reflects diffuse abnormalities rather than focal lesions 2

Specific EFNS/PNS Electrodiagnostic Criteria

Using standard unilateral, right-sided, forearm/foreleg, four-nerve studies, the EFNS/PNS criteria provide the highest diagnostic sensitivity (81.3%) while maintaining excellent specificity (96.2%) for "definite/probable" CIDP 1. These criteria outperform other established criteria, including the American Academy of Neurology criteria (sensitivity 45.7%, specificity 100%) and Koski criteria (sensitivity 63%, specificity 99.3%) 1.

Important caveat: The "possible" EFNS/PNS electrodiagnostic category has poor specificity (69.2%) and should not be used alone to establish the diagnosis. 1

Timing Considerations and Common Pitfalls

• Do not perform electrodiagnostic studies too early - studies within the first week of symptom onset may be normal in 30-34% of patients with active demyelinating disease 2
• Repeat testing 2-3 weeks later is essential when initial studies are normal or equivocal but clinical suspicion remains high 2
• Symptoms must evolve over at least 8 weeks to distinguish CIDP from Guillain-Barré syndrome 4

Extent of Testing

More extensive nerve conduction studies (beyond the standard four-nerve protocol) can increase diagnostic sensitivity to 96.7%, but this comes at the cost of reduced specificity (79.3%) 1. The practical approach is to start with standard four-nerve studies and expand testing only when initial results are equivocal. 1

Sensitivity Limitations

Even with optimal criteria, electrodiagnostic sensitivity for CIDP has practical limits of approximately 66%, as demonstrated across multiple validation studies 5. This occurs because nerve conduction abnormalities in different neuropathic disorders have overlapping distributions 5. Therefore, clinical judgment combined with CSF analysis (elevated protein with normal cell count) and MRI findings (nerve root enhancement) remain essential when electrodiagnostic studies are inconclusive. 6, 4

Pediatric Considerations

In children with demyelinating neuropathies, specific parameters help differentiate CIDP from hereditary conditions 7:

• Distal compound muscle action potential (dCMAP) duration >9 ms is observed in CIDP but not in hereditary neuropathy with pressure palsy 7
• Abnormal median/normal sural SNAP pattern and ≥10 m/s difference between conduction velocities of corresponding nerves are not seen in CMT1a patients 7