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. 2025 Sep;32(9):e70300.
doi: 10.1111/ene.70300.

Nerve Conduction Abnormalities Beyond Conduction Block in Multifocal Motor Neuropathy. Impact on Diagnostic Criteria Accuracy

Pietro Emiliano Doneddu  1   2 , Chiara Gallo  1 , Yuri Falzone  3 , Sabrina Matà  4 , Giuseppe Cosentino  5 , Vincenzo Di Stefano  6 , Massimiliano Filosto  7 , Luca Leonardi  8 , Dario Ricciardi  9   10 , Anna Mazzeo  11 , Luana Benedetti  12 , Marco Luigetti  13   14 , Paolo Solla  15   16 , Maurizio Inghilleri  17   18 , Dario Cocito  19 , Francesco Habetswallner  10 , Alberto De Lorenzo  1 , Benedetta Sorrenti  3 , Maddalena Spalletti  20 , Elisa Vegezzi  21 , Christian Messina  6 , Barbara Risi  7 , Francesca Forcina  8 , Alessandra Fasolino  10 , Luca Gentile  11 , Alessandro Beronio  22 , Francesca Vitali  14 , Federica Moret  17 , Giacomo Iabichella  11 , Stefano Gazzina  23 , Corrado Cabona  12 , Claudia Cutellè  1 , Elisa Bianchi  24 , Eduardo Nobile-Orazio  1   25 ; Italian MMN Database Study Group
Affiliations

Nerve Conduction Abnormalities Beyond Conduction Block in Multifocal Motor Neuropathy. Impact on Diagnostic Criteria Accuracy

Pietro Emiliano Doneddu et al. Eur J Neurol. 2025 Sep.

Abstract

Background: Multifocal motor neuropathy (MMN) is a rare motor neuropathy diagnosed by identifying motor conduction block (CB), which may be absent or transient. This study aimed to evaluate nerve conduction abnormalities beyond CB and their diagnostic value.

Methods: A retrospective analysis included patients fulfilling the 2010 EFNS/PNS clinical criteria for MMN and controls with axonal polyneuropathy, lower motor neuron disease, or chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). Electrophysiological studies evaluated motor distal latency prolongation, reduced motor conduction velocity, prolonged F-wave latency, absence of F-waves, abnormal temporal dispersion, and distal CMAP duration prolongation. The 2010 EFNS/PNS criteria for MMN were compared to an 'extended' set incorporating additional electrophysiological parameters.

Results: A total of 70 MMN patients and 359 controls were included. At least one nerve conduction abnormality, excluding motor CB, was detected in one or more nerve segments unaffected by CB in 71% of MMN patients, significantly more frequently than in axonal polyneuropathy or lower motor neuron disease patients. These parameters included abnormal temporal dispersion (47%), distal CMAP duration prolongation (31%), reduced motor conduction velocity (26%), absence of F-waves (9%), prolonged F-wave latency (6%), and motor distal latency prolongation (3%). Incorporating these parameters increased sensitivity for diagnosing probable/definite MMN by 26% (p < 0.001; compared to EFNS/PNS criteria), with minimal impact on specificity, even when compared to CIDP patients.

Conclusion: Including additional electrophysiological parameters into the diagnostic criteria for MMN may enhance diagnostic sensitivity while maintaining comparable specificity. The observation of nerve conduction abnormalities beyond CB indicates a broader electrophysiological profile for MMN.

Keywords: MMN; conduction block; diagnosis; diagnostic criteria; multifocal motor neuropathy.

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Conflict of interest statement

Pietro Emiliano Doneddu reports personal fees for Advisory from ArgenX, and received travel grants to attend scientific meetings from CSL Behring and Kedrion. Giuseppe Cosentino has received travel grants to attend scientific meetings from CSL Behring and Kedrion. Massimiliano Filosto has served on scientific advisory boards for CSL Behring, Sanofi, and Amicus, and has received travel grants from Sanofi, Biogen, Kedrion, and CSL Behring to attend scientific meeting. Anna Mazzeo has received travel grants from Kedrion and CSL Behring to attend scientific meeting. Maurizio Inghilleri has received travel grants to attend scientific meetings from CSL Behring, ArgenX, and Alexion. Federica Moret has received travel grants to attend scientific meetings from CSL Behring, ArgenX, and Alexion. Eduardo Nobile‐Orazio reports personal fees for Advisory or Scientific Board from ArgenX—Belgium, Takeda—Italy and USA, CSL Behring—Italy and USA, Janssen—USA, Kedrion—Italy, LFB—France, Roche—Switzerland, Sanofi—USA. The other authors declare no conflicts of interest.

Figures

FIGURE 1
FIGURE 1
Flowchart of patients' selection for sensitivity and specificity analyses comparing the 2010 EFNS/PNS and ‘extended’ criteria for MMN. CIDP = chronic inflammatory demyelinating polyradiculoneuropathy, CMAP = compound muscle action potential, EFNS/PNS = European Federation of Neurological Societies/Peripheral Nerve Society, MMN = multifocal motor neuropathy, n = number, NCS = nerve conduction study.
FIGURE 2
FIGURE 2
Representative examples of temporal dispersion in patients with MMN. Panels A, B, C, and D demonstrate temporal dispersion in the motor nerves of four patients who meet the 2010 European Federation of Neurological Societies/Peripheral Nerve Society (EFNS/PNS) clinical criteria for multifocal motor neuropathy (MMN). These patients had a mean disease duration of 6 years (range 4–10 years), with normal sensory nerve conduction studies, and all responded to intravenous immunoglobulin therapy. All four patients are regularly followed by the authors (PED, ENO) at the Humanitas Research Institute.
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