Table 2.

Electrophysiological criteria for conduction block^* [Van Schaik et al. 2010].

1. Definite motor CB

Negative peak CMAP area reduction on proximal vs. distal stimulation of at least 50% whatever the nerve segment length (median, ulnar, and peroneal). Negative peak CMAP amplitude on stimulation of the distal part of the segment with motor CB must be >20% of the lower limit of normal and >1 mV and increase of proximal to distal negative peak CMAP duration must be ⩽30%

2. Probable motor CB*

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

OR

Negative peak CMAP area reduction of at least 50% (same as definite) with an increase of proximal to distal negative peak CMAP duration >30%

3. Normal sensory nerve conduction in upper limb segments with CB (see exclusion criteria)

CB, conduction block; CMAP, compound muscle action potential.

^*Evidence for CB must be found at sites distinct from common entrapment or compression syndromes.