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 (β = 0.07, 95% CI: 0.01-0.14, p = 0.032) and F persistence (β = -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.