Repetitive F-waves and f-WAVE motor unit number estimation in cases with diabetes mellitus

Introduction: Motor unit estimation using F-waves (F-MUNE) is a rarely used electrophysiologic method. In this study, it was aimed to evaluate the amount of axon loss by repeater F wave parameters and F-MUNE analysis in patients with Type 2 Diabetes Mellitus (DM). Methods: In twenty-four healthy controls and 51 DM patients with complaints of peripheral neuropathy, 90 F-waves elicited with supramaximal and 300 F-waves with submaximal stimulation of the ulnar nerve at the wrist were recorded from the abductor digiti minimi muscle. F-MUNE values were calculated using repeater F wave parameters for the recordings elicited with the automatic software for those recorded with submaximal stimulation. Calculated F-wave parameters were statistically compared between the patient and control groups. Results: Ulnar repeater F-wave index and repeater neuron index were found to be significantly higher in DM patients compared to the control group. On the other hand, ulnar F-MUNE numbers were similar in the two groups. The sural/radial and sural/medial femoral cutaneous sensory nerve action potential ratios and repeater F wave indices were able to distinguish DM and control groups with moderate-to-good sensitivity and specificities. Conclusion: Repeater F-wave parameters recorded from the upper extremity may indicate the presence of axon loss in DM related polyneuropathy. However, F-MUNE method did not provide information useful for discriminating the patient and control groups in this length-dependent neuropathy. Keywords: motor unit number estimation, neuropathy, F-wave, repeater F-wave, diabetes