Criteria for the diagnosis of multifocalmotor neuropathy

Definite MMN
1. Weakness without objective sensory loss in the distribution of two or more named nerves; during the early stage, the finding of diffuse symmetric weakness rules out MMN
2. Definite conduction block in two or more sites outside common entrapment sites (defined as a decrease of more than 40 % in median or ulnar (not radial) CMAP area or 50 % or more in CMAP amplitude with an increase of less than 30 % in CMAP duration).
3. Normal sensory nerve conduction velocity across the sites with block.
4. Normal sensory nerve conductions for all nerves tested with a minimum of three tested.
5. Absent UMN signs including spastic tone, clonus, extensor plantars, and pseudobulbar palsy

Probable MMN
1. Weakness without objective sensory loss in the distribution of two or more named nerves; during the early stage, the finding of diffuse symmetric weakness rules out MMN
2. The presence of one of the following: probably conduction block in two or more sites outside common entrapment areas, or definite block in one segment and probable block in another outside common entrapment areas.
3. Normal sensory velocities outside the same areas with motor conduction block when study of the segment is technically feasible (ie. not required for segments proximal to the axilla or popliteal fossa).
4. Normal sensory nerve conductions for all nerves tested with a minimum of three tested.
5. Absent UMN signs including spastic tone, clonus, extensor plantars, and pseudobulbar palsy.
(as cited in NEJM 2007; 357:2710, adapted from Olney et al. Muscle Nerve 2003;27:117-121).