Table 3.

Electrophysiological criteria for conduction block⁸

Definite*

Negative peak CMAP area reduction on proximal versus distal stimulation of at least 50% regardless of nerve segment length (median, ulnar, and peroneal).

Negative peak CMAP amplitude on stimulation of the distal nerve segment >20% of the lower limit of normal and >1 mV.

Increase of proximal to distal negative peak CMAP duration of ≤30%.

Probable*

Negative peak CMAP area reduction of at least 30% over a long segment (eg, wrist to elbow or elbow to axilla) of an upper limb nerve with increase of proximal to distal negative peak CMAP duration of ≤30%.

Or negative peak CMAP area reduction of at least 50% with an increase of proximal to distal negative peak CMAP duration of >30%.

Notes:

^*In MMN, sensory nerve conduction in the nerve segments with CB are normal. Copyright © 2010 Peripheral Nerve Society. Reproduced with permission from John Wiley & Sons, Inc. Joint Task Force of the EFNS and the PNS. European Federation of Neurological Societies/Peripheral Nerve Society guideline on management of multifocal motor neuropathy. Report of a joint task force of the European Federation of Neurological Societies and the Peripheral Nerve Society – first revision. J Peripher Nerv Syst. 2010;15(4):295–301.

Abbreviations: CB, conduction block; CMAP, compound muscle action potential; MMN, multifocal motor neuropathy.