Multifocal motor neuropathy: correlation of nerve ultrasound, electrophysiological, and clinical findings.

We present nerve ultrasound findings in multifocal motor neuropathy (MMN) and examine their correlation with electrophysiology and functional disability. Eighty healthy controls and 12 MMN patients underwent clinical, sonographic, and electrophysiological evaluation a mean of 3.5 years (standard deviation [SD] ± 2.1) after disease onset. Nerve ultrasound revealed significantly higher cross-sectional area (CSA) values of the median (forearm, p < 0.001), ulnar (p < 0.001), and tibial nerve (ankle, p < 0.001) when compared with controls. Electroneurography documented signs of significantly lower values of the motor conduction velocity and compound muscle action potentials (cMAPs) in the upper arm nerves (median, ulnar, radial, p < 0.001). A significant correlation between sonographic and electrophysiological findings in the MMN group was found only between cMAP and CSA of the median nerve at the upper arm (r = 0.851, p < 0.001). Neither nerve sonography nor electrophysiology correlated with functional disability. MMN seems to show inhomogeneous CSA enlargement in various peripheral nerves, with weak correlation to electrophysiological findings. Neither nerve sonography nor electrophysiology correlated with functional disability. Multicentre, prospective studies are required to prove the applicability and diagnostic values of these findings.