A case control study of the relationship between persistent serum creatine kinase elevation and polyneuropathy

Creatine kinase (CK) has been associated with neuropathy, but the mechanisms are uncertain. We hypothesized that peripheral nerve function is impaired in subjects with persistent CK elevation (hyperCKemia) compared to age- and sex matched controls in a general population. The participants were recruited from the population based Tromsø study in Norway. Neuropathy impairment score (NIS), nerve conduction studies (NCS) and electromyography (EMG) in subjects with persistent hyperCKemia (n = 113; 51 men, 62 women) and controls (n = 128; 61 men, 67 women) were performed. The hyperCKemia group had higher NIS score than the controls (p = 0.050). NCS of the tibial nerve showed decreased compound motor action potential amplitude (p < 0.001), decreased motor conduction velocity (p < 0.001) and increased F-wave latency (p = 0.044). Also, reduced sensory amplitudes of the median, ulnar, and sural nerves were found. EMG showed significantly increased average motor unit potential amplitude in all examined muscles. CK correlated positively with glycated hemoglobin and non-fasting glucose in the hyperCKemia group, although not when controlled for covariates. The length dependent polyneuropathy demonstrated in the hyperCKemia group is unexplained, but CK leakage and involvement of glucose metabolism are speculated on.