Application of CMAP scan for the evaluation of patients with chronic inflammatory demyelinating polyneuropathy: a prospective study

Aims: We aimed to assess the compound muscle action potential (CMAP) scan in the follow-up of chronic inflammatory demyelinating polyneuropathy (CIDP) patients and investigate the correlation of CMAP scan parameters with functional and standard electrodiagnostic tests. Methods: We evaluated four parameters of abductor pollicis brevis (APB) CMAP scan (i.e., step numbers, step percentage, S10, S90), functional measures (e.g., Medical Research Council Sum Scores), and electrodiagnostic tests, including nerve conduction study (NCS) and motor NCS of the median nerve in the baseline and after six months of treatment. Results: Twenty patients completed baseline clinical and electrodiagnostic studies. However, sixteen patients completed the follow-up study. The median of step numbers at baseline was 3.5 (2�4.2), which decreased to 2.5 (0�3) (p = 0.005). After the treatment, step percentage reduced from 28.6 (23.9�38.7) to 13.4 (0�23.6) (p = 0.001). The scores obtained from the clinical scales showed significant recovery of most of the functions, while the alterations of NCSS and NCS of the median nerve were not significant. Conclusions: We found a significant reduction in step number and step percentage after follow-up. This alteration was not reflected in standard electrodiagnostic values. The improvement of functional scales alongside the CMAP scan parameters suggests that the CMAP scan could be considered an appropriate outcome measurement in research and clinical fields. © 2020 Elsevier Masson SA