Abstract
Introduction: Motor nerve conduction block (CB) is the main electrophysiological feature of multifocal motor neuropathy (MMN). Increased cross-sectional area (CSA) can be detected by nerve ultrasound in MMN. In this study, we aim to analyze the correlation between CB and CSA in MMN.Methods: Twelve patients with MMN were recruited. Ultrasonography tests and motor nerve conduction studies (NCSs) were performed on median and ulnar nerves simultaneously. CSA was measured at 10 consecutive sites on those nerves, meanwhile nerves were traced continuously and recorded thoroughly under ultrasound.Results: In motor NCSs, 12 definite CB and 12 probable CB areas were detected across standard segments of median and ulnar nerves. With ultrasound studies, increased CSA was detected at 36 sites. There were 9 standard segments with CB and increased CSA, 15 segments with CB but normal CSA, and 27 segments with increased CSA but no CB.Discussion: In MMN, motor nerve CB was not always consistent with increased CSA.
Highlights
Motor nerve conduction block (CB) is the main electrophysiological feature of multifocal motor neuropathy (MMN)
Common sites of nerve compression, such as the carpal canal and cubital tunnel did not reveal a prevalent cross-sectional area (CSA) increase in Multifocal motor neuropathy (MMN) patients comparing with healthy controls
With motor motor nerve conduction studies (NCS), 12 definite CB and 12 probable CB areas were detected across standard segments of median and ulnar nerves
Summary
Motor nerve conduction block (CB) is the main electrophysiological feature of multifocal motor neuropathy (MMN). Increased cross-sectional area (CSA) can be detected by nerve ultrasound in MMN. Multifocal motor neuropathy (MMN) was first described in 1988 [1] as a purely motor neuropathy affecting multiple motor nerves with conduction block (CB). The multifocal enlargement of peripheral nerves or cervical roots in nerve cross-sectional areas (CSAs) has been reported in MMN [2,3,4]. Multifocal CBs were distributed along the nerve in MMN; those studies only measured a few predetermined sites, providing limited morphologic information.
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