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.