Laboratory and instrumental diagnostics of chronic inflammatory demyelinating polyneuropathy: analysis of 158 cases

Introduction. Given the diversity of clinical and electrophysiological phenotypes of chronic inflammatory demyelinating polyneuropathy (CIDP) and the variability of their response to disease-modifying therapy, immunopathological mechanisms likely differ across disease forms. Identifying key laboratory and instrumental features of various clinical and pathogenetic variants within the CIDP spectrum remains an important unmet need.

The objective was to compare serum and cerebrospinal fluid (CSF) laboratory findings and instrumental study results in typical CIDP and its variants.

Methods and materials. This retrospective-prospective study analyzed clinical, laboratory, and instrumental data from 158 patients with definite CIDP meeting the 2021 European Academy of Neurology/Peripheral Nerve Society (EAN/PNS) criteria, stratified into typical CIDP and CIDP variants.

Results. Anti-ganglioside and anti-sulfatide antibodies were most frequently detected in the sensory CIDP variant, in 46.2 % (12/26) of cases. Serum paraprotein was identified in 27.2 % (36/132) of patients; among these, a substantial proportion had the sensory variant – 33 % (12/36). When analyzing the structure of clinical phenotypes among patients screened for the presence of paraprotein (n=132), patients with the distal variant prevailed – 40% (8/20) of cases. The highest protein levels in the cerebrospinal fluid (CSF) were observed in patients with disease onset at the age of 15-29 years (Kruskal–Wallis test, p=0.028), as well as in patients with a relapsing type of course and acute onset (Pearson’s Chi-Square Test, p=0.01). No significant differences in CSF protein levels were found between typical CIDP and CIDP variants. Abnormal CSF oligoclonal IgG patterns were detected in 21.7 % (20/92) of patients and were observed significantly more often in CIDP variants, comprising 60.0 % (12/20) of such cases. According to electroneuromyography (ENMG) data, an increase in distal latency according to n. tibialis was significantly more often recorded in patients with typical CIDP compared with the variants (26.5% vs 7.3%, respectively; Pearson’s Chi-Square Test, p=0.0019). The analysis of cumulative indicators (Σ indicators) for n. tibialis also revealed a higher frequency of pathological changes in patients with typical CIDP (61.2% vs 35.8%; Pearson’s Chi-Square Test, p=0.0033). On magnetic resonance imaging (MRI), accumulation of contrast agent by nerve roots and cerebrospinal nerves was detected in 57.2 % (4/7) of patients with motor CIDP variant, which was significantly more often than in other disease variants (Fisher–Freeman–Halton test, p=0.006).

Conclusion. In contemporary practice, laboratory and instrumental diagnostics in CIDP patients plays a critical role in excluding alternative causes of polyneuropathy. The identified laboratory and instrumental features across CIDP variants may be important not only for diagnosis but also for selecting optimal pathogenetic therapy.

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