Criteria for early detection of conduction block in multifocal motor neuropathy (MMN): A study based on control populations and follow-up of MMN patients

Alberto Cappellari, Eduardo Nobile-Orazio, Nicoletta Meucci, Giulia Levi Minzi, Guglielmo Scarlato, Sergio Barbieri

Research output: Contribution to journalArticle


Motor conduction block (MCB) has been used as the main diagnostic criterion in multifocal motor neuropathy (MMN). Nonetheless, no agreed definition of block currently exists; the proposed required percent decrement of proximal compound muscle action potential (CMAP) amplitude varies from > 20% to > 50%. The aim of this work was to evaluate, through a follow-up study of patients with MMN, the behaviour of MCB over time. The percent decrement and temporal dispersion of proximal CMAP have also been calculated in normal controls and in patients affected by amyotrophic lateral sclerosis (ALS). The results show that MCB in patients with MMN is a dynamic entity which greatly varies over time and that a > 50% CMAP amplitued reduction may well be preceded by a smaller decrement that is nonetheless indicative of focal myelin damage in the appropriate clinical context. This datum and the results obtained in the control group and in patients with ALS suggest that a reappraisal of the diagnostic criteria for MCB, in cases with clinical and electrophysiological data strongly indicative of MMN, should be considered. Since MMN is a treatable disorder, the use of the proposed less restrictive criteria for the identification of MCB could allow for a promp and more effective treatment.

Original languageEnglish
Pages (from-to)625-630
Number of pages6
JournalJournal of Neurology
Issue number10
Publication statusPublished - 1997



  • Amyotrophic lateral sclerosis
  • Conduction block
  • Diagnostic criteria
  • Electrophysiological follow-up
  • Multifocal motor neuropathy

ASJC Scopus subject areas

  • Clinical Neurology
  • Neurology

Cite this