Table 1.

Clinical criteria for multifocal motor neuropathy [Van Schaik et al. 2010].

Core criteria (both must be present)

1. Slowly progressive or stepwise progressive, focal, asymmetric* limb weakness, that is, motor involvement in the motor nerve distribution of at least two nerves, for more than 1 month.† If symptoms and signs are present only in the distribution of one nerve only a possible diagnosis can be made (Table 4)

2. No objective sensory abnormalities except for minor vibration sense abnormalities in the lower limbs‡

Supportive clinical criteria

3. Predominant upper limb involvement§

4. Decreased or absent tendon reflexes in the affected limb¶

5. Absence of cranial nerve involvement**

6. Cramps and fasciculations in the affected limb

7. Response in terms of disability or muscle strength to immunomodulatory treatment

Exclusion criteria

8. Upper motor neuron signs

9. Marked bulbar involvement

10. Sensory impairment more marked than minor vibration loss in the lower limbs

11. Diffuse symmetric weakness during the initial weeks

^*Asymmetric = a difference of 1 MRC grade if strength is MRC >3 and 2 MRC grades if strength is MRC ⩽ 3.

^†Usually more than 6 months.

^‡Sensory signs and symptoms may develop over the course of MMN.

^§At onset, predominantly lower limb involvement account for nearly 10% of the cases.

^¶Slightly increased tendon reflexes, in particular in the affected arm, have been reported and do not exclude the diagnosis of MMN provided criterion 8 is met.

^**Twelfth nerve palsy has been reported.