A-waves increase the risk of developing neuropathy

Introduction A-waves, which are observed following the M-wave during motor nerve conduction studies (NCS), are late responses that are frequently found in many types of neurogenic disorders. However, A-waves are also common in healthy individuals, where their significance remains unclear. The aim of this study was to examine whether the occurrence of A-waves does in fact represent an increased risk for the future development of changes upon NCS or needle electromyography (EMG) in the corresponding nerve. Methods Nerve conduction studies/needle electromyography findings at control examination were evaluated in relation to the occurrence of initial A-waves in 327 individuals who had undergone repeated NCS/EMG examination and exhibited normal initial findings, with or without the occurrence of A-waves as the only acceptable abnormality. Results The odds ratio, which reflects the predictive power of the occurrence of A-waves at the initial testing for the development of an abnormality (neuropathy or radiculopathy) at the follow-up examination, ranged from 2.7 (p = .041) in the tibial nerve and 3.9 (p = .034) in peroneal one, to 30.0 (p = .002) in the ulnar nerve. Conclusions A-waves constitute an initial abnormality in all nerves, and they may be predictive for the future development of broader NCS/EMG abnormalities in the corresponding nerve.