Marieke van Rosmalen

General discussion 135 8 MMN Limitations Slowly progressive, asymmetric, predominantly distal weakness without sensory dysfunction. Decreased or absent tendon reflexes in affected limb; predominant upper limb involvement; age of onset 20-65 years; no bulbar signs, upper motor neuron features, other neuropathies or myopathies. Atypical variants of CIDP may be difficult to recognize, differentiation of MMN and early stages of ALS may be difficult Definite motor conduction block: CMAP area reduction ≥ 50% over a long segment, or a CMAP amplitude reduction of ≥ 30% over a short distance. Probable motor conduction block: CMAP amplitude reduction of ≥ 30% over a long segment. Slowing of conduction compatible with demyelination: motor conduction velocity < 75% of LLN; distal motor latency or shortest F-wave latency > 130% of ULN or absence of F-waves. Normal sensory conduction in arm segments with conduction block. Normal SNAP amplitudes. Extensive protocol that is not always completely performed; protocol requires specific expertise (signs of demyelination could be easily missed); protocol costs a lot of time; NCS are often burdensome to patients Expensive, risk of adverse events, no clear definition (or biomarker) of treatment response Qualitative assessment without cut-off values for nerve size Invasive procedure, sample bias Fulfills all clinical criteria + CSF protein < 1 g/L + definite NCS and normal sensory conduction Fulfills part of clinical criteria + CSF protein < 1 g/L + probable NCS and normal sensory conduction Fulfills part of clinical criteria + elevated anti GM1- bodies or abnormal MRI results or slowing of conduction and normal sensory conduction