Motor unit number index correlates with disability in Charcot-Marie-Tooth disease

Abstract : Objective: The aim of this study was to assess the usefulness of motor unit number index (MUNIX) tech-nique in Charcot-Marie-Tooth disease and test the correlation between MUNIX and clinical impairment. Methods: MUNIX technique was performed in the abductor pollicis brevis (APB), the abductor digiti min-imi (ADM) and the tibialis anterior (TA) muscles in the nondominant side. A MUNIX sum score was cal-culated by adding the MUNIX of these 3 muscles. Muscle strength was measured using the MRC (medical research council) scale. Disability was evaluated using several functional scales, including CMT neuropa-thy score version 2 (CMTNSv2) and overall neuropathy limitation scale (ONLS). Results: A total of 56 CMT patients were enrolled. The MUNIX scores of the ADM, APB and TA muscles correlated with the MRC score of the corresponding muscle (p < 0.01). The MUNIX sum score correlated with the clinical scales CMTNSv2 (r = -0.65, p < 0.01) and ONLS (r = -0.57, p < 0.01). Conclusion: MUNIX correlates with muscle strength and clinical measurements of disability in patients with CMT disease. Significance: The MUNIX technique evaluates motor axonal loss and correlates with disability. The MUNIX sum score may be a useful outcome measure of disease progression in CMT. (C) 2018 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.