Abstract
Background: The definition of conduction block (CB) is variable in multifocal motor neuropathy (MMN). In current criteria, excessive temporal dispersion (TD) may preclude the recognition of CB and the diagnosis of MMN.
Methods: We retrospectively studied the electrophysiological data of 47 consecutive subjects with MMN and of 69 consecutive controls with upper limb-onset motor neuron disease, from three neuromuscular centres in the United Kingdom and Korea.
Results: Compared to CB defined by compound muscle action potential (CMAP) area reduction (CB-Area) > 30%, CB defined by CMAP amplitude reduction (CB-amp) > 30% was more sensitive (78.7% vs. 63.8%; McNemar's Test: p = 0.008), but less specific versus controls (90.1% vs. 96.7%; McNemar's Test: p = 0.001). CB-amp > 30% offered greater diagnostic accuracy than CB-Area > 30% (Youden's Index: 0.688 vs. 0.606). TD showed a sensitivity of 59.6% and specificity of 94.3%. F-wave
prolongation or absence showed a sensitivity of 42.6% and specificity of 96.9%. Considering CB-amp > 30% or TD or F-wave prolongation or absence, as independent electrodiagnostic markers of MMN, improved diagnostic sensitivity from 78.7% to 91.5% compared to CB-amp > 30% alone (McNemar's Test: p = 0.031), also offering optimal accuracy (Youden's Index: 0.816). Within this three-parameter combination, CB defined by CMAP amplitude reduction > 30% offered similar sensitivity, specificity and accuracy to when defined by CMAP amplitude reduction > 50%.
Conclusions: CB-amp has higher sensitivity and accuracy than CB-Area for the electrodiagnosis of MMN. Consideration of TD or F-wave prolongation or absence, as independently diagnostic of MMN, in addition to CB-amp > 30% alone, may improve electrophysiological sensitivity as well as accuracy.
Methods: We retrospectively studied the electrophysiological data of 47 consecutive subjects with MMN and of 69 consecutive controls with upper limb-onset motor neuron disease, from three neuromuscular centres in the United Kingdom and Korea.
Results: Compared to CB defined by compound muscle action potential (CMAP) area reduction (CB-Area) > 30%, CB defined by CMAP amplitude reduction (CB-amp) > 30% was more sensitive (78.7% vs. 63.8%; McNemar's Test: p = 0.008), but less specific versus controls (90.1% vs. 96.7%; McNemar's Test: p = 0.001). CB-amp > 30% offered greater diagnostic accuracy than CB-Area > 30% (Youden's Index: 0.688 vs. 0.606). TD showed a sensitivity of 59.6% and specificity of 94.3%. F-wave
prolongation or absence showed a sensitivity of 42.6% and specificity of 96.9%. Considering CB-amp > 30% or TD or F-wave prolongation or absence, as independent electrodiagnostic markers of MMN, improved diagnostic sensitivity from 78.7% to 91.5% compared to CB-amp > 30% alone (McNemar's Test: p = 0.031), also offering optimal accuracy (Youden's Index: 0.816). Within this three-parameter combination, CB defined by CMAP amplitude reduction > 30% offered similar sensitivity, specificity and accuracy to when defined by CMAP amplitude reduction > 50%.
Conclusions: CB-amp has higher sensitivity and accuracy than CB-Area for the electrodiagnosis of MMN. Consideration of TD or F-wave prolongation or absence, as independently diagnostic of MMN, in addition to CB-amp > 30% alone, may improve electrophysiological sensitivity as well as accuracy.
| Original language | English |
|---|---|
| Article number | e70361 |
| Number of pages | 8 |
| Journal | European Journal of Neurology |
| Volume | 32 |
| Issue number | 10 |
| Early online date | 2 Oct 2025 |
| DOIs | |
| Publication status | Published - 2 Oct 2025 |
Bibliographical note
Copyright © 2025 The Author(s). European Journal of Neurology published by John Wiley & Sons Ltd on behalf of European Academy of Neurology. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.Keywords
- conduction block
- demyelination
- diagnosis
- electrophysiology
- F-wave
- multifocal motor neuropathy
- temporal dispersion