Motor unit remodelling in multifocal motor neuropathy: The importance of axonal loss

Garg, Nidhi; Howells, James; Yiannikas, Con; Vucic, Steve; Krishnan, Arun V.; Spies, Judith M.; Bostock, Hugh; Mathey, Emily K.; Pollard, John D.; Park, Susanna B.; Kiernan, Matthew C.

doi:10.1016/j.clinph.2017.07.414

Cited by 28 publications

(27 citation statements)

References 23 publications

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“…Although the previously mentioned scan parameters give information about axonal excitability, denervation, and reinnervation, returners, in our opinion, may enhance the CMAP scan analysis. In some scans, Although there is one study providing a lesser lower limit for MScanFit MUNE, 41 our cutoff values were similar to those described in other reports. 42,43 In addition to being sensitive for discriminating ALS, MScanFit MUNE and CMAP scan parameters were highly correlated with one another.…”

Section: Discussionsupporting

confidence: 87%

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Parameters derived from compound muscle action potential scan for discriminating amyotrophic lateral sclerosis‐related denervation

et al. 2019

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Introduction The objective of this study was to determine compound muscle action potential (CMAP) scan parameters and MScanFit motor unit number estimation (MUNE) in patients with amyotrophic lateral sclerosis (ALS) and to compare the results in the abductor pollicis brevis (APB) to those in the abductor digiti minimi (ADM). Methods CMAP scans were recorded from the APB and ADM in 35 patients with ALS and 21 controls. MScanFit MUNE, neurophysiological index (NI), step%, returner%, and D50 were calculated. Results CMAP scan parameters including the returner%, MScanFit MUNE, and NI can distinguish ALS with high sensitivity and specificity. The electrophysiological parameters, with the exception of D50 (the number of largest consecutive differences of recorded responses generating 50% of maximum CMAP), showed more pronounced changes in the APB than in the ADM, even though most of the patients had normal APB/ADM amplitude ratios. Discussion CMAP scan parameters and MScanFit MUNE can be used in the evaluation of denervation and reinnervation and may herald the “split hand” in ALS.

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Section: Discussionsupporting

confidence: 87%

“…Although there is one study providing a lesser lower limit for MScanFit MUNE, our cutoff values were similar to those described in other reports . In addition to being sensitive for discriminating ALS, MScanFit MUNE and CMAP scan parameters were highly correlated with one another.…”

Section: Discussionsupporting

confidence: 85%

Parameters derived from compound muscle action potential scan for discriminating amyotrophic lateral sclerosis‐related denervation

et al. 2019

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“…Mathematical modelling suggested that these changes were best modelled by reduction in both Na + and K + channel function. Marked reduction in motor unit numbers associated with strikingly enlarged motor units have been identified distal to the site of block in patients with MMN . Furthermore, axonal degeneration has been shown to be strongly associated with block suggesting that the same pathophysiology is likely to account for both processes .…”

Section: Discussionmentioning

confidence: 99%

Conduction block in immune‐mediated neuropathy: paranodopathy versus axonopathy

Garg

Howells

et al. 2019

Euro J of Neurology

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Background and purpose Conduction block is a pathognomonic feature of immune‐mediated neuropathies. The aim of this study was to advance understanding of pathophysiology and conduction block in chronic inflammatory demyelinating polyneuropathy (CIDP) and multifocal motor neuropathy (MMN). Methods A multimodal approach was used, incorporating clinical phenotyping, neurophysiology, immunohistochemistry and structural assessments. Results Of 49 CIDP and 14 MMN patients, 25% and 79% had median nerve forearm block, respectively. Clinical scores were similar in CIDP patients with and without block. CIDP patients with median nerve block demonstrated markedly elevated thresholds and greater threshold changes in threshold electrotonus, whilst those without did not differ from healthy controls in electrotonus parameters. In contrast, MMN patients exhibited marked increases in superexcitability. Nerve size was similar in both CIDP groups at the site of axonal excitability. However, CIDP patients with block demonstrated more frequent paranodal serum binding to teased rat nerve fibres. In keeping with these findings, mathematical modelling of nerve excitability recordings in CIDP patients with block support the role of paranodal dysfunction and enhanced leakage of current between the node and internode. In contrast, changes in MMN probably resulted from a reduction in ion channel density along axons. Conclusions The underlying pathologies in CIDP and MMN are distinct. Conduction block in CIDP is associated with paranodal dysfunction which may be antibody‐mediated in a subset of patients. In contrast, MMN is characterized by channel dysfunction downstream from the site of block.

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“…In recent studies, MScan has been shown to be a fast, sensitive and reproducible method, which may be helpful in diagnoses and monitoring disease progression in neuromuscular disorders, particularly amyotrophic lateral sclerosis (ALS) (Jacobsen et al , 2017). So far the only published study of MScan in neuropathy has been one on multifocal motor neuropathy, which showed decreased MUNE values and increased motor unit sizes, whereas CMAP amplitudes were well-preserved (Garg et al , 2017). MScan has not previously been tested in diabetic neuropathy.…”

Section: Introductionmentioning

confidence: 99%

Detection of early motor involvement in diabetic polyneuropathy using a novel MUNE method – MScanFit MUNE

Kristensen

Bostock

Finnerup

et al. 2019

Clinical Neurophysiology

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Motor unit remodelling in multifocal motor neuropathy: The importance of axonal loss

Cited by 28 publications

References 23 publications

Parameters derived from compound muscle action potential scan for discriminating amyotrophic lateral sclerosis‐related denervation

Parameters derived from compound muscle action potential scan for discriminating amyotrophic lateral sclerosis‐related denervation

Conduction block in immune‐mediated neuropathy: paranodopathy versus axonopathy

Detection of early motor involvement in diabetic polyneuropathy using a novel MUNE method – MScanFit MUNE

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