Comparison of MRI and motor evoked potential with triple stimulation technique for the detection of brachial plexus abnormalities in multifocal motor neuropathy

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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Progressive arm weakness and tonic hand spasm from multifocal motor neuropathy in the brachial plexus

Muscle & Nerve ◽

10.1002/mus.10409 ◽

2003 ◽

Vol 28 (2) ◽

pp. 242-245 ◽

Cited By ~ 3

Author(s):

R. Veltkamp ◽

M. Krause ◽

C. Schranz ◽

H.-M. Meinck

Keyword(s):

Brachial Plexus ◽

Multifocal Motor Neuropathy ◽

Motor Neuropathy

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Practical Electrophysiology for the Diagnosis of Multifocal Motor Neuropathy

European Neurological Review ◽

10.17925/enr.2012.07.02.118 ◽

2012 ◽

Vol 7 (2) ◽

pp. 118 ◽

Cited By ~ 1

Author(s):

Hessel Franssen ◽

Leonard H van den Berg ◽

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Keyword(s):

Clinical Picture ◽

Nerve Conduction ◽

Conduction Block ◽

Multifocal Motor Neuropathy ◽

Nerve Conduction Studies ◽

Motor Neuropathy ◽

Unique Combination ◽

Axon Loss ◽

Erb’S Point ◽

Stimulation Technique

Nerve conduction studies (NCS) are necessary to distinguish multifocal motor neuropathy (MMN) from other disorders with a similar clinical picture. In MMN, NCS may show a unique combination of conduction block (CB) or conduction slowing consistent with demyelination, whereas sensory conduction in the same nerve is normal. This contribution discusses a relatively simple and practical electrophysiological approach for the diagnosis of MMN that can be used by any neurologist who has had training in NCS. When diagnosing MMN, the most important practical points are: careful stimulation technique, investigation according to a standardised protocol that includes at least five nerves per arm with stimulation up to Erb’s point, understanding of and adherence to criteria for conduction block and demyelinative slowing and exclusion of nerves with marked axon loss.

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