| Summary: | Background/Aim. Multifocal motor neuropathy (MMN) is an immune-mediated
disorder characterized by slowly progressive asymetrical weakness of limbs
without sensory loss. The objective of this study was to investigate the
involvement of brachial plexus using combined cervical magnetic stimulation
and magnetic resonance imaging (MRI) of plexus brachialis in patients with
MMN. We payed special attention to the nerve roots forming nerves inervating
weak muscles, but without detectable conduction block (CB) using conventional
nerve conduction studies. Methods. Nine patients with proven MMN were
included in the study. In all of them MRI of the cervical spine and brachial
plexus was performed using a Siemens Avanto 1.5 T unit, applying T1 and turbo
spinecho T1 sequence, axial turbo spin-echo T2 sequence and a coronal
fat-saturated turbo spin-echo T2 sequence. Results. In all the patients
severe asymmetric distal weakness of muscles inervated by radial, ulnar,
median and peroneal nerves was observed and the most striking presentation
was bilateral wrist and finger drop. Three of them had additional proximal
weakness of muscles inervated by axillar and femoral nerves. The majority of
the patients had slightly increased cerebrospinal fluid (CSF) protein
content. Six of the patients had positive serum polyclonal IgM anti-GM1
antibodies. Electromyoneurography (EMG) showed neurogenic changes, the most
severe in distal muscles inervated by radial nerves. All the patients had
persistent partial CBs outside the usual sites of nerve compression in
radial, ulnar, median and peroneal nerves. In three of the patients cervical
magnetic stimulation suggested proximal CBs between cervical root emergence
and Erb’s point (prolonged motor root conduction time). In all the patients
T2-weighted MRI revealed increased signal intensity in at least one cervical
root, truncus or fasciculus of brachial plexus. Conclusion. We found clinical
correlation between muscle weakness, prolonged motor root conduction time and
MRI abnormalities of the brachial plexus, which was of the greatest
importance in the nerves without CB inervating weak muscles.
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