Muscle action potential scans and ultrasound imaging in neurofibromatosis type 2

Amyotrophic lateral sclerosis (ALS) is characterised by a progressive loss of motor units and the reinnervation of denervated muscle fibres by surviving motor axons. This reinnervation preserves muscle function until symptom onset, when some 60-80% of motor units have been lost. We have studied the changes in surviving motor neurons by comparing the nerve excitability properties of 31 single motor axons from patients with ALS with those from 21 single motor axons in control subjects. ALS motor axons were classified as coming from moderately or severely affected muscles according to the compound muscle action potential amplitude of the parent muscle. Compared with control units, thresholds were increased, and there was reduced inward and outward rectification and greater superexcitability following a conditioning impulse. These abnormalities were greater in axons from severely affected muscles, and were correlated with loss of fine motor skills. A mathematical model indicated that 99.1% of the differences between the moderately affected ALS and control units could be explained by a reduction in the expression of all ion channels. For the severely affected units, modelling required, in addition, an increase in the current leak through and under the myelin sheath. This might be expected if the anchoring proteins responsible for the paranodal seal were reduced. We conclude that changes in axonal excitability identified in ALS patients are best explained by a failure in the supply of ion channel and other membrane proteins from the diseased motor neuron, a conclusion consistent with recent animal and in vitro human data.

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“…An estimate of the number of motor units was made using a CMAP scan and the MSCANFit method (Bostock, ; Farschtschi et al . ; Jacobsen et al . ).…”

Section: Methodsmentioning

confidence: 99%

In vivo evidence for reduced ion channel expression in motor axons of patients with amyotrophic lateral sclerosis

Howells

Matamala

Park

et al. 2018

The Journal of Physiology

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“…2016). In a previous study, MScan was tested on patients with neurofibromatosis type 2, where it revealed denervation and reinnervation in peripheral nerves suggesting that it may be used to quantify and monitor disease progression (Farschtschi, et al 2016). …”

Section: For This Reason Several Motor Unit Number Estimation (Mune)mentioning

confidence: 99%

Reproducibility, and sensitivity to motor unit loss in amyotrophic lateral sclerosis, of a novel MUNE method: MScanFit MUNE

Bostock

Fuglsang‐Frederiksen

Duez

et al. 2017

Clinical Neurophysiology

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Highlights:-MScan is a novel promising MUNE method with good reproducibility and clinical potential.-MScan and MPS are better at discriminating between ALS patients and healthy controls than MUNIX.-Only MScan manages to distinguish patients with less certainty of ALS from healthy controls. AbstractObjective: To examine inter-and intra-rater reproducibility and sensitivity to motor unit loss of a novel motor unit number estimation (MUNE) method, MScanFit MUNE (MScan), compared to two traditional MUNE methods; Multiple point stimulation MUNE (MPS) and Motor Unit Number Index (MUNIX).Methods: Twenty-two ALS patients and 20 sex-and age-matched healthy controls were included.MPS, MUNIX, and MScan were performed twice each by two blinded physicians. Reproducibility of MUNE values was assessed by coefficient of variation (CV) and intra class correlation coefficient (ICC). Ability to detect motor unit loss was assessed by ROC curves and area under the curve (AUC). The times taken for each of the methods were recorded. Results:MScan was more reproducible than MPS and MUNIX both between and within operators.The mean CV for MScan (12.3%) was significantly lower than for MPS (24.7%) or MUNIX (21.5%). All methods had ICC>0.94. MScan and Munix were significantly quicker to perform than MPS (6.3m vs. 13.2m). MScan (AUC= 0.930) and MPS (AUC=0.899) were significantly better at discriminating between patients and healthy controls than MUNIX (AUC=0.831). Conclusions:MScan was more consistent than MPS or MUNIX and better at distinguishing ALS patients from healthy subjects.Significance: MScan may improve detection and assessment of motor unit loss.

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“…A recent study also found a high incidence of schwannomas on HRUS: in 8 of 10 NF2 patients presenting for routine visits at the outpatient clinic, at least 1 schwannoma was observed, but the correlation with clinical symptoms was not described . Another recent study showed that abnormal, hypoechoic fascicular structures were frequently observed in NF2 patients with neuropathy . The authors did not find schwannomas in their patients, but only median nerves were investigated.…”

Section: Discussionmentioning

confidence: 93%

“…10 Another recent study showed that abnormal, hypoechoic fascicular structures were frequently observed in NF2 patients with neuropathy. 15 The authors did not find schwannomas in their patients, but only median nerves were investigated. In our study, we also frequently observed focal nerve enlargement and hypoechoic fascicles.…”

Section: Discussionmentioning

confidence: 94%

“…3,[10][11][12][13] Previous studies of patients with DM from the United States and Italy have suggested a limited role for smoking, alcohol consumption, and obesity in DM-related tumor predisposition. 14,15 This study assesses factors associated with benign and malignant tumors separately, using data we collected from patients enrolled in the UK Myotonic Dystrophy Patient Registry (UK DM Registry).…”

Section: Discussionmentioning

confidence: 99%

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Nerve ultrasound shows subclinical peripheral nerve involvement in neurofibromatosis type 2

et al. 2017

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Muscle action potential scans and ultrasound imaging in neurofibromatosis type 2

Abstract: In contrast to conventional nerve conduction studies, CMAP scan MUNE in combination with US nerve imaging can quantify the NF2-associated neuropathy and may help to monitor disease progression and drug treatments. Muscle Nerve 55: 350-358, 2017.

Cited by 16 publications

References 47 publications

In vivo evidence for reduced ion channel expression in motor axons of patients with amyotrophic lateral sclerosis

In vivo evidence for reduced ion channel expression in motor axons of patients with amyotrophic lateral sclerosis

Reproducibility, and sensitivity to motor unit loss in amyotrophic lateral sclerosis, of a novel MUNE method: MScanFit MUNE

Nerve ultrasound shows subclinical peripheral nerve involvement in neurofibromatosis type 2

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