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Nerve Conduction Abnormalities Beyond Conduction Block in Multifocal Motor Neuropathy. Impact on Diagnostic Criteria
Pietro Emiliano Doneddu1,2, Chiara Gallo1, Yuri Falzone3
1Neuromuscular and Neuroimmunology Unit, IRCCS Humanitas Research Hospital, Milano, Italy.
European Journal of Neurology
|September 23, 2025
Summary
Diagnosing multifocal motor neuropathy (MMN) can be improved by including additional nerve conduction abnormalities beyond motor conduction block. This enhances sensitivity for MMN diagnosis while maintaining specificity.
Area of Science:
- Neurology
- Neurophysiology
Background:
- Multifocal motor neuropathy (MMN) is a rare condition often diagnosed by motor conduction block (CB), which can be absent or transient.
- This diagnostic challenge necessitates exploring additional electrophysiological markers.
Purpose of the Study:
- To evaluate nerve conduction abnormalities beyond motor conduction block in MMN.
- To assess the diagnostic value of these additional parameters.
Main Methods:
- Retrospective analysis of 70 MMN patients and 359 controls.
- Electrophysiological studies assessed parameters like temporal dispersion, F-wave abnormalities, and distal CMAP duration.
- Compared standard EFNS/PNS criteria with an extended set including additional parameters.
Main Results:
- 71% of MMN patients showed abnormalities beyond CB, significantly more than controls.
- Abnormal temporal dispersion and distal CMAP duration were most frequent.
- Extended criteria increased MMN diagnostic sensitivity by 26% with minimal specificity loss.
Conclusions:
- Incorporating additional electrophysiological parameters enhances MMN diagnostic sensitivity.
- This approach maintains diagnostic specificity, improving upon existing criteria.
- MMN exhibits a broader electrophysiological profile than previously recognized.
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