Focal Chronic Inflammatory Demyelinating Polyneuropathy – Clinical application and validation of 2021 EAN/PNS criteria

Abstract

Abstract Background The updated 2021 criteria of the European Academy of Neurology/Peripheral Nerve Society (EAN/PNS) for chronic inflammatory demyelinating polyneuropathy (CIDP) has excellent diagnostic sensitivity and specificity for typical and variants CIDP. For focal monomelic CIDP, applications of this criteria may be different compared to typical or multifocal CIDP due to limited peripheral nerves involvement. Case presentation We illustrate using a rare case of focal right lower limb sensori-motor CIDP on the applicability of the 2021 EAN/PNS criteria and demonstrate the practical limitations of clinical, electrodiagnostic and supporting criteria in the diagnosis of focal CIDP. Unlike typical CIDP, diagnostic hallmark of classical proximal and distal weakness is frequently absent in focal CIDP. Therefore, accuracy of clinical diagnosis is less reliable. For a confirmed diagnosis, electrodiagnostic findings require fulfilment of at least 2 demyelinating features in two different motor nerves with sensory conduction abnormalities in at least 2 nerves in the affected limb. This is difficult to achieve as all the motor nerves in the affected limb are required to meet demyelination criteria. In addition, individual nerves in the affected limbs, especially the lower limbs come with specific misdiagnosis pitfalls, making misinterpretation of demyelinating features difficult. The role of demyelination of sensory nerves is limited in improving diagnosis but additional supportive criteria improved diagnostic certainty. Conclusion The updated EAN/PNS diagnostic criteria for focal CIDP has its own limitations on both clinical and electrodiagnostic grounds. The inclusion of supportive criteria improves diagnostic certainty, but the reliability and accuracy require future study.