Hi,
This may help or make it more confusing. I took the following from this website:
http://www.emedicine.com/neuro/TOPIC724.HTM
Clinical and electrodiagnostic criteria for the diagnosis of MMN include the following:
Definite MMN
Weakness without objective sensory loss in the distribution of 2 or more nerves is present.
Definite conduction block is present in 2 or more motor nerves outside of common entrapment sites.
Sensory nerve conduction velocity is normal across the segments with demonstrated motor conduction block.
Results are normal for sensory nerve conduction studies on all tested nerves, with a minimum of 3 nerves tested.
Upper motor neuron signs, including spasticity, clonus, extensor plantar response, and pseudobulbar palsy are absent.
Probable MMN
Weakness without objective sensory loss in the distribution of 2 or more nerves.
The presence of either (1) probable conduction block in 2 or more motor nerve segments that are not common entrapment sites or (2) definite conduction block in one motor nerve and probable conduction block in a different motor nerve segment (uncommon entrapment sites).
Sensory nerve conduction velocity is normal across the segments with demonstrated motor conduction block.
Results are normal for sensory nerve conduction studies on all tested nerves, with a minimum of 3 nerves tested.
Upper motor neuron signs, such as spasticity, clonus, extensor plantar response, and pseudobulbar palsy are absent.