Atypical chronic inflammatory demyelinating polyradiculoneuropathy: recent advances on classification, diagnosis, and pathogenesis

Unclassified clinical presentations of chronic inflammatory demyelinating polyradiculoneuropathy

BACKGROUND

To assess the ability of the 2021 European Academy of Neurology/Peripheral Nerve Society (EAN/PNS) clinical criteria for chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) to include within their classification the whole spectrum of clinical heterogeneity of the disease and to define the clinical characteristics of the unclassifiable clinical forms.

METHODS

The 2021 EAN/PNS clinical criteria for CIDP were applied to 329 patients fulfilling the electrodiagnostic (and in some cases also the supportive) criteria for the diagnosis of CIDP. Clinical characteristics were reviewed for each patient not strictly fulfilling the clinical criteria ('unclassifiable').

RESULTS

At study inclusion, 124 (37.5%) patients had an unclassifiable clinical presentation, including 110 (89%) with a typical CIDP-like clinical phenotype in whom some segments of the four limbs were unaffected by weakness ('incomplete typical CIDP'), 10 (8%) with a mild distal, symmetric, sensory or sensorimotor polyneuropathy confined to the lower limbs with cranial nerve involvement ('cranial nerve predominant CIDP') and 4 (1%) with a symmetric sensorimotor polyneuropathy limited to the proximal and distal areas of the lower limbs ('paraparetic CIDP'). Eighty-one (65%) patients maintained an unclassifiable presentation during the entire disease follow-up while 13 patients progressed to typical CIDP. Patients with the unclassifiable clinical forms compared with patients with typical CIDP had a milder form of CIDP, while there was no difference in the distribution patterns of demyelination.

CONCLUSIONS

A proportion of patients with CIDP do not strictly fulfil the 2021 EAN/PNS clinical criteria for diagnosis. These unclassifiable clinical phenotypes may pose diagnostic challenges and thus deserve more attention in clinical practice and research.

What Is in the Literature

What is in the Literature focuses on chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), a neuropathy with challenges in diagnosis and treatment. A recent revision of diagnostic criteria (EFN/PNS criteria) has helped define clinical features of typical and atypical variants and what is not considered CIDP. Initiating pathologic factors is not known for typical CIDP or variants. New treatment approaches are based on immunologic mechanisms. Rare patients with a CIDP-like clinical pattern are found to have antibodies to proteins at and around the node of Ranvier and are not considered to be CIDP but a nodal-paranodopathy. Although occurring mainly in adults, CIDP also occurs in children. CIDP may have clinical and electrodiagnostic features that overlap with hereditary neuropathies, and the latter might show some response to treatment. Articles published in the past year that address these issues are discussed in this review.

Nerve Ultrasound Distinguishes Non-Inflammatory Axonal Polyneuropathy From Inflammatory Polyneuropathy With Secondary Axonal Damage

Introduction

Chronic inflammatory demyelinating polyneuropathy (CIDP) may have a similar clinical and electrophysiological presentation to non-inflammatory axonal polyneuropathies (NIAPs) when secondary axonal damage occurs. We aimed to investigate if nerve ultrasound can help to differentiate CIDP with additional secondary axonal damage from NIAP.

Methods

In a retrospective analysis, the cross-sectional area (CSA) of the peripheral nerves measured by ultrasound at six suitable nerve sites was compared in 95 patients with CIDP and 82 patients with NIAP. We developed the adjusted Bochum ultrasound score (aBUS) ranging from 0 to 6 resulting from the number of sites with enlarged CSA (median, ulnar, radial, and sural nerve).

Results

The mean CSA of patients with CIDP was enlarged at all six nerve sites compared with the mean CSA of patients with NIAP. A total of 21 patients with CIDP did not meet 2010 electrophysiological diagnostic criteria (European Academy of Neurology/Peripheral Nerve Society Guideline, EFNS/PNS criteria) for CIDP at examination timepoint but only in further follow-up, while 25 patients with NIAP fulfilled electrophysiological EFNS/PNS criteria for CIDP as “possible” or “probable” CIDP. To increase diagnostic power, we included aBUS measured by ultrasound in patients classified as “possible” or “probable” resulting in an improved specificity of 94% and a sensitivity of 59%, compared to a specificity of the EFNS/PNS criteria alone of 60% and sensitivity of 78%.

Conclusion

Using nerve ultrasound and the aBUS as a complementary method to distinguish CIDP from NIAP in case of secondary axonal damage can facilitate the diagnosis of CIDP.