Creatine kinase level and its relationship with quantitative electromyographic characteristics in amyotrophic lateral sclerosis

Objective: To explore the relationship between serum creatine kinase (CK) level and electromyographic characteristics in patients with amyotrophic lateral sclerosis (ALS). Methods: Two hundred thirty-eight consecutive ALS patients were enrolled. All patients underwent electrophysiological study with a consistent approach. We calculated a compound muscle action potential (CMAP) sum score, and spontaneous potentials were graded from 0 to 4 depending on their density and distribution. We tested for any independent correlation of the CK levels with CMAP sum score, mean spontaneous potential (MSP) score, F wave persistence or conduction velocity. Results: The median serum CK level was 151 U/L. Log CK was independently correlated with MSP score (beta = 0.07, 95% CI: 0.01-0.14, p = 0.032) and F persistence (beta = -0.0013, 95% CI: -0.00251 to -0.0002, p = 0.02) but not with CMAP sum score or F wave conduction velocity. When stratified by sex, the correlation of log CK with MSP score and F persistence was significant in male but not female patients. Conclusions: The results support that lower motor neuron loss and muscle denervation are associated with elevated CK levels of ALS patients. Significance: The severity of lower motor neuron loss and denervation might be involved in pathophysiological mechanisms of CK elevation in ALS patients. (C) 2018 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.