Anterior tibialis CMAP amplitude correlations with impairment in CMT1A

Farnesol Ameliorates Demyelinating Phenotype in a Cellular and Animal Model of Charcot-Marie-Tooth Disease Type 1A

Charcot-Marie-Tooth disease (CMT) is a genetically heterogeneous disease affecting the peripheral nervous system that is caused by either the demyelination of Schwann cells or degeneration of the peripheral axon. Currently, there are no treatment options to improve the degeneration of peripheral nerves in CMT patients. In this research, we assessed the potency of farnesol for improving the demyelinating phenotype using an animal model of CMT type 1A. In vitro treatment with farnesol facilitated myelin gene expression and ameliorated the myelination defect caused by PMP22 overexpression, the major causative gene in CMT. In vivo administration of farnesol enhanced the peripheral neuropathic phenotype, as shown by rotarod performance in a mouse model of CMT1A. Electrophysiologically, farnesol-administered CMT1A mice exhibited increased motor nerve conduction velocity and compound muscle action potential compared with control mice. The number and diameter of myelinated axons were also increased by farnesol treatment. The expression level of myelin protein zero (MPZ) was increased, while that of the demyelination marker, neural cell adhesion molecule (NCAM), was reduced by farnesol administration. These data imply that farnesol is efficacious in ameliorating the demyelinating phenotype of CMT, and further elucidation of the underlying mechanisms of farnesol’s effect on myelination might provide a potent therapeutic strategy for the demyelinating type of CMT.

Intraepineurial fat quantification and cross-sectional area analysis of the sciatic nerve using MRI in Charcot-Marie-Tooth disease type 1A patients

The objectives of this study were to assess the fat fraction (FF) and cross-sectional area (CSA) of the sciatic nerve in Charcot-Marie-Tooth disease type 1A (CMT1A) patients using Dixon-based proton density fat quantification MRI and to elucidate its potential association with clinical parameters. Thigh MRIs of 18 CMT1A patients and 18 age- and sex-matched volunteers enrolled for a previous study were reviewed. Analyses for FF and CSA of the sciatic nerve were performed at three levels (proximal to distal). CSA and FF were compared between the two groups and among the different levels within each group. The relationship between the MRI parameters and clinical data were assessed in the CMT1A patients. The CMT1A patients showed significantly higher FF at level 3 (p = 0.0217) and significantly larger CSA at all three levels compared with the control participants (p < 0.0001). Comparisons among levels showed significantly higher FF for levels 2 and 3 than for level 1 and significantly larger CSA for level 2 compared with level 1 in CMT1A patients. CSA at level 3 correlated positively with the CMT neuropathy score version 2 (CMTNSv2). In conclusion, the sciatic nerve FF of CMT1A patients was significantly higher on level 3 compared with both the controls and the measurements taken on more proximal levels, suggesting the possibility of increased intraepineurial fat within the sciatic nerves of CMT1A patients, with a possible distal tendency. Sciatic nerve CSA at level 3 correlated significantly and positively with CMTNSv2, suggesting its potential value as an imaging marker for clinical severity.

Intramuscular pressure of human tibialis anterior muscle detects age-related changes in muscle performance

Intramuscular pressure (IMP) reflects forces produced by a muscle. Age is one of the determinants of skeletal muscle performance. The present study aimed to test whether IMP mirrors known age-related muscular changes. We simultaneously measured the tibialis anterior (TA) IMP, compound muscle action potential (CMAP), and ankle torque in thirteen older adults (60-80 years old) in vivo by applying different stimulation intensities and frequencies. We found significant positive correlations between the stimulation intensity and IMP and CMAP. Increasing stimulation frequency caused ankle torque and IMP to increase. The electromechanical delay (EMD) (36 ms) was longer than the onset of IMP (IMPD) (29 ms). Compared to the previously published data collected from young adults (21-40 years old) in identical conditions, the TA CMAP and IMP of older adults at maximum intensity of stimulation were 23.8% and 39.6% lower, respectively. For different stimulation frequencies, CMAP, IMP, as well as ankle torque of older adults were 20.5%, 24.2%, and 13.2% lower, respectively. Surprisingly, the EMD did not exhibit any difference between young and older adults and the IMPD was consistent with the EMD. Data supporting the hypotheses suggest that IMP measurement is an indicator of muscle performance in older adults.

New evidence for secondary axonal degeneration in demyelinating neuropathies

Development of peripheral nervous system (PNS) myelin involves a coordinated series of events between growing axons and the Schwann cell (SC) progenitors that will eventually ensheath them. Myelin sheaths have evolved out of necessity to maintain rapid impulse propagation while accounting for body space constraints. However, myelinating SCs perform additional critical functions that are required to preserve axonal integrity including mitigating energy consumption by establishing the nodal architecture, regulating axon caliber by organizing axonal cytoskeleton networks, providing trophic and potentially metabolic support, possibly supplying genetic translation materials and protecting axons from toxic insults. The intermediate steps between the loss of these functions and the initiation of axon degeneration are unknown but the importance of these processes provides insightful clues. Prevalent demyelinating diseases of the PNS include the inherited neuropathies Charcot-Marie-Tooth Disease, Type 1 (CMT1) and Hereditary Neuropathy with Liability to Pressure Palsies (HNPP) and the inflammatory diseases Acute Inflammatory Demyelinating Polyneuropathy (AIDP) and Chronic Inflammatory Demyelinating Polyneuropathy (CIDP). Secondary axon degeneration is a common feature of demyelinating neuropathies and this process is often correlated with clinical deficits and long-lasting disability in patients. There is abundant electrophysiological and histological evidence for secondary axon degeneration in patients and rodent models of PNS demyelinating diseases. Fully understanding the involvement of secondary axon degeneration in these diseases is essential for expanding our knowledge of disease pathogenesis and prognosis, which will be essential for developing novel therapeutic strategies.

Comparison of gait patterns and functional measures between Charcot-Marie-Tooth disease type I and II in children to young adults

INTRODUCTION

Charcot-Marie-Tooth (CMT) disease is an inherited peripheral neuropathy that causes progressive distal extremity nerve degeneration and muscle atrophy which can negatively impact function, gait and quality of life. The purpose of this study was to determine if differences exist in gait patterns, clinical examination and functional measures between CMT type I (CMT1) and type II (CMT2) in childhood to young adults. It was hypothesized that individuals with CMT2 would present with greater ankle weakness, increased and/or prolonged ankle dorsiflexion in stance during gait and demonstrate greater disease severity on the CMT Pediatric Scale (CMTPedS) compared to CMT1.

METHODS

Twenty-seven individuals diagnosed with CMT1 or CMT2 underwent three-dimensional gait analysis, clinical examination and evaluation of disease severity using the CMTPedS. Subjects groups were divided based on CMT type: CMT1 (n = 20) and CMT2 (n = 7).

RESULTS

CMT2 group presented with a trend towards increased plantar flexion weakness compared to CMT1 of 61.1 ± 58.1 N to 137.9 ± 51.4 N (p < 0.012), respectively. CMT2 presented with significantly decreased dorsiflexion strength, 31.9 ± 30.9 N, compared to CMT1, 80.4 ± 37.4 N, (p < 0.0052) which negatively influenced gait patterns in CMT2. Associated gait findings demonstrated CMT2 group with significantly decreased peak ankle power generation in stance compared to CMT1 (1.46 ± 0.39 W/kg to 3.13 ± 0.98 W/kg respectively) (p < 0.0001). CMT1 was more likely to demonstrate a dorsiflexion moment in loading response than CMT2. There was a consistent trend of a higher score and therefore greater disease severity for CMT2 based on CMTPedS.

CONCLUSION

Study results suggest that at a given age, individuals with CMT2 have greater limitations in terms of gait function and disease severity than individuals with CMT1. Overall the CMT2 was shown to have greater gait limitations at the ankle during stance and swing with associated compensatory mechanisms at the knee and hip in swing.

Locomotor and skeletal muscle abnormalities in trembler J neuropathic mice

INTRODUCTION

Patients with hereditary peripheral neuropathies exhibit characteristic deformities of the hands and feet and have difficulty ambulating. To examine to what extent neuropathic animals recapitulate these deficits, we studied trembler J (TrJ) mice, which model early-onset demyelinating neuropathy.

METHODS

A cohort of 4-month-old female wild type and neuropathic mice were evaluated for locomotor measurements, neuromuscular function, and skeletal muscle proteolysis and morphometry.

RESULTS

Utilizing the DigiGait imaging system, we identified pronounced alterations in forepaw and hindpaw angles and a decrease in hindpaw area on the treadmill in neuropathic rodents. Torque production by the tibialis anterior (TA) muscle was significantly weakened and was paralleled by a decrease in myofiber cross-sectional area and an increase in muscle tissue proteolysis.

DISCUSSION

Our findings in TrJ mice reflect the phenotypic presentation of the human neuropathy in which patients exhibit weakness of the TA muscle resulting in foot drop and locomotor abnormalities. Muscle Nerve 57: 664-671, 2018.

Pmp22 mutant allele-specific siRNA alleviates demyelinating neuropathic phenotype in vivo

Charcot-Marie-Tooth disease (CMT) is a genetic disorder that can be caused by aberrations in >80 genes. CMT has heterogeneous modes of inheritance, including autosomal dominant, autosomal recessive, X-linked dominant, and X-linked recessive. Over 95% of cases are dominantly inherited. In this study, we investigated whether regulation of a mutant allele by an allele-specific small interfering RNA (siRNA) can alleviate the demyelinating neuropathic phenotype of CMT. We designed 19 different allele-specific siRNAs for Trembler J (Tr-J) mice harboring a naturally occurring mutation (Leu16Pro) in Pmp22. Using a luciferase assay, we identified an siRNA that specifically and selectively reduced the expression level of the mutant allele and reversed the low viability of Schwann cells caused by mutant Pmp22 over-expression in vitro. The in vivo efficacy of the allele-specific siRNA was assessed by its intraperitoneal injection to postnatal day 6 of Tr-J mice. Administration of the allele-specific siRNA to Tr-J mice significantly enhanced motor function and muscle volume, as assessed by the rotarod test and magnetic resonance imaging analysis, respectively. Increases in motor nerve conduction velocity and compound muscle action potentials were also observed in the treated mice. In addition, myelination, as evidenced by toluidine blue staining and electron microscopy, was augmented in the sciatic nerves of the mice after allele-specific siRNA treatment. After validating suppression of the Pmp22 mutant allele at the mRNA level in the Schwann cells of Tr-J mice, we observed increased expression levels of myelinating proteins such as myelin basic protein and myelin protein zero. These data indicate that selective suppression of the Pmp22 mutant allele by non-viral delivery of siRNA alleviates the demyelinating neuropathic phenotypes of CMT in vivo, implicating allele-specific siRNA treatment as a potent therapeutic strategy for dominantly inherited peripheral neuropathies.

Quantitative muscle ultrasound as a biomarker in Charcot-Marie-Tooth neuropathy

OBJECTIVE

The utility of quantitative muscle ultrasound as a marker of disease severity in Charcot-Marie-Tooth (CMT) disease subtypes was investigated.

METHODS

Muscle ultrasound was prospectively performed on 252 individual muscles from 21 CMT patients (9 CMT1A, 8 CMTX1, 4 CMT2A) and compared to 120 muscles from 10 age and gender-matched controls. Muscle ultrasound recorded echogenicity and thickness in representative muscles including first dorsal interosseus (FDI) and tibialis anterior (TA).

RESULTS

Muscle volume of FDI and thickness of TA correlated with MRC strength. Muscle echogenicity was significantly increased in FDI (65.05 vs 47.09; p<0.0001) and TA (89.45 vs 66.30; p<0.0001) of CMT patients. In TA, there was significantly higher muscle thickness (23 vs 18 vs 16mm; p<0.0001) and lower muscle echogenicity (80 vs 95 vs 108; p<0.0001) in CMT1A compared to CMTX1 and CMT2A. This corresponded to disease severity based on muscle strength (MRC grading CMT1A vs CMTX1 vs CMT2A: 59 vs 48 vs 44; p=0.002).

CONCLUSION

In CMT, quantitative muscle ultrasound of FDI and TA is a useful marker of disease severity.

SIGNIFICANCE

The current findings suggest that quantitative muscle ultrasound has potential as a surrogate marker of disease progression in future interventional trials in CMT.

Management of Charcot-Marie-Tooth disease: improving long-term care with a multidisciplinary approach

Charcot–Marie–Tooth (CMT) disease is the most common inherited neuropathy and one of the most common inherited diseases in humans. The diagnosis of CMT is traditionally made by the neurologic specialist, yet the optimal management of CMT patients includes genetic counselors, physical and occupational therapists, physiatrists, orthotists, mental health providers, and community resources. Rapidly developing genetic discoveries and novel gene discovery techniques continue to add a growing number of genetic subtypes of CMT. The first large clinical natural history and therapeutic trials have added to our knowledge of each CMT subtype and revealed how CMT impacts patient quality of life. In this review, we discuss several important trends in CMT research factors that will require a collaborative multidisciplinary approach. These include the development of large multicenter patient registries, standardized clinical instruments to assess disease progression and disability, and increasing recognition and use of patient-reported outcome measures. These developments will continue to guide strategies in long-term multidisciplinary efforts to maintain quality of life and preserve functionality in CMT patients.

Ascorbic acid for the treatment of Charcot-Marie-Tooth disease

BACKGROUND

Charcot-Marie-Tooth disease (CMT) comprises a large group of different forms of hereditary motor and sensory neuropathy. The molecular basis of several CMT subtypes has been clarified during the last 20 years. Since slowly progressive muscle weakness and sensory disturbances are the main features of these syndromes, treatments aim to improve motor impairment and sensory disturbances to improve abilities. Pharmacological treatment trials in CMT are rare. This review was derived from a Cochrane review, Treatment for Charcot Marie Tooth disease, which will be updated via this review and a forthcoming title, Treatments other than ascorbic acid for Charcot-Marie-Tooth disease.

OBJECTIVES

To assess the effects of ascorbic acid (vitamin C) treatment for CMT.

SEARCH METHODS

On 21 September 2015, we searched the Cochrane Neuromuscular Specialised Register, Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE and LILACS for randomised controlled trials (RCTs) of treatment for CMT. We also checked clinical trials registries for ongoing studies.

SELECTION CRITERIA

We included RCTs and quasi-RCTs of any ascorbic acid treatment for people with CMT. Where a study aimed to evaluate the treatment of general neuromuscular symptoms of people with peripheral neuropathy including CMT, we included the study if we were able to identify the effect of treatment in the CMT group. We did not include observational studies or case reports of ascorbic acid treatment in people with CMT.

DATA COLLECTION AND ANALYSIS

Two review authors (BG and JB) independently extracted the data and assessed study quality.

MAIN RESULTS

Six RCTs compared the effect of oral ascorbic acid (1 to 4 grams) and placebo treatment in CMT1A. In five trials involving adults with CMT1A, a total of 622 participants received ascorbic acid or placebo. Trials were largely at low risk of bias. There is high-quality evidence that ascorbic acid does not improve the course of CMT1A in adults as measured by the CMT neuropathy score (0 to 36 scale) at 12 months (mean difference (MD) -0.37; 95% confidence intervals (CI) -0.83 to 0.09; five studies; N = 533), or at 24 months (MD -0.21; 95% CI -0.81 to 0.39; three studies; N = 388). Ascorbic acid treatment showed a positive effect on the nine-hole peg test versus placebo (MD -1.16 seconds; 95% CI -1.96 to -0.37), but the clinical significance of this result is probably small. Meta-analyses of other secondary outcome parameters showed no relevant benefit of ascorbic acid. In one trial, 80 children with CMT1A received ascorbic acid or placebo. The trial showed no clinical benefit of ascorbic acid treatment. Adverse effects did not differ in their nature or abundance between ascorbic acid and placebo.

AUTHORS' CONCLUSIONS

High-quality evidence indicates that ascorbic acid does not improve the course of CMT1A in adults in terms of the outcome parameters used. According to low-quality evidence, ascorbic acid does not improve the course of CMT1A in children. However, CMT1A is slowly progressive and the outcome parameters show only small change over time. Longer study durations should be considered, and outcome parameters more sensitive to change over time should be designed and validated for future studies.

An exploratory randomised double-blind and placebo-controlled phase 2 study of a combination of baclofen, naltrexone and sorbitol (PXT3003) in patients with Charcot-Marie-Tooth disease type 1A

Background

Charcot-Marie-Tooth type 1A disease (CMT1A) is a rare orphan inherited neuropathy caused by an autosomal dominant duplication of a gene encoding for the structural myelin protein PMP22, which induces abnormal Schwann cell differentiation and dysmyelination, eventually leading to axonal suffering then loss and muscle wasting. We favour the idea that diseases can be more efficiently treated when targeting multiple disease-relevant pathways. In CMT1A patients, we therefore tested the potential of PXT3003, a low-dose combination of three already approved compounds (baclofen, naltrexone and sorbitol). Our study conceptually builds on preclinical experiments highlighting a pleiotropic mechanism of action that includes downregulation of PMP22. The primary objective was to assess safety and tolerability of PXT3003. The secondary objective aimed at an exploratory analysis of efficacy of PXT3003 in CMT1A, to be used for designing next clinical development stages (Phase 2b/3).

Methods

80 adult patients with mild-to-moderate CMT1A received in double-blind for 1 year Placebo or one of the three increasing doses of PXT3003 tested, in four equal groups. Safety and tolerability were assessed with the incidence of related adverse events. Efficacy was assessed using the Charcot-Marie-Tooth Neuropathy Score (CMTNS) and the Overall Neuropathy Limitations Scale (ONLS) as main endpoints, as well as various clinical and electrophysiological outcomes.

Results

This trial confirmed the safety and tolerability of PXT3003. The highest dose (HD) showed consistent evidence of improvement beyond stabilization. CMTNS and ONLS, with a significant improvement of respectively of 8% (0.4% - 16.2%) and 12.1% (2% - 23.2%) in the HD group versus the pool of all other groups, appear to be the most sensitive clinical endpoints to treatment despite their quasi-stability over one year under Placebo. Patients who did not deteriorate over one year were significantly more frequent in the HD group.

Conclusions

These results confirm that PXT3003 deserves further investigation in adults and could greatly benefit CMT1A-diagnosed children, usually less affected than adults.

Trial registration

EudraCT Number: 2010-023097-40. ClinicalTrials.gov Identifier: NCT01401257. The Committee for Orphan Medicinal Products issued in February 2014 a positive opinion on the application for orphan designation for PXT3003 (EMA/OD/193/13).

Electronic supplementary material

The online version of this article (doi:10.1186/s13023-014-0199-0) contains supplementary material, which is available to authorized users.

Recommendations to enable drug development for inherited neuropathies: Charcot-Marie-Tooth and Giant Axonal Neuropathy

Approximately 1 in 2500 Americans suffer from Charcot-Marie-Tooth (CMT) disease. The underlying disease mechanisms are unique in most forms of CMT, with many point mutations on various genes causing a toxic accumulation of misfolded proteins. Symptoms of the disease often present within the first two decades of life, with CMT1A patients having reduced compound muscle and sensory action potentials, slow nerve conduction velocities, sensory loss, progressive distal weakness, foot and hand deformities, decreased reflexes, bilateral foot drop and about 5% become wheelchair bound. In contrast, the ultra-rare disease Giant Axonal Neuropathy (GAN) is frequently described as a recessively inherited condition that results in progressive nerve death. GAN usually appears in early childhood and progresses slowly as neuronal injury becomes more severe and leads to death in the second or third decade. There are currently no treatments for any of the forms of CMTs or GAN. We suggest that further clinical studies should analyse electrical impedance myography as an outcome measure for CMT. Further, additional quality of life (QoL) assessments for these CMTs are required, and we need to identify GAN biomarkers as well as develop new genetic testing panels for both diseases. We propose that using the Global Registry of Inherited Neuropathy (GRIN) could be useful for many of these studies. Patient advocacy groups and professional organizations (such as the Hereditary Neuropathy Foundation (HNF), Hannah's Hope Fund (HHF), The Neuropathy Association (TNA) and the American Association of Neuromuscular and Electrodiagnostic Medicine (AANEM) can play a central role in educating clinicians and patients. Undertaking these studies will assist in the correct diagnosis of disease recruiting patients for clinical studies, and will ultimately improve the endpoints for clinical trials. By addressing obstacles that prevent industry investment in various forms of inherited neuropathies, we can envision treatment options for these rare diseases in the near future.

Evolution of Charcot-Marie-Tooth disease type 1A duplication: a 2-year clinico-electrophysiological and lower-limb muscle MRI longitudinal study

The objective of this study was to analyze Charcot-Marie-Tooth disease type 1A (CMT1A) evolution. We conducted a 2-year longitudinal study in 14 CMT1A patients and 14 age- and sex-matched controls. In the patients, we performed neurological examination with hand-held dynamometry, electrophysiology, and lower-limb muscle MRI, both at baseline and 2 years later, while controls were examined at baseline only. Patients' ages ranged from 12 to 51 years. Outstanding manifestations on initial evaluation included pes cavus, areflexia, lower-limb weakness, and foot hypopallesthesia. In evaluating muscle power, good correlation was observed between manual testing and dynamometry. Compared to controls, Lunge, 10-Meter-Walking, and 9-Hole-Peg tests were impaired. Their CMT neuropathy score and functional disability scale showed that patients exhibited mild phenotype and at most slight walking difficulty. Electrophysiology revealed marked nerve conduction slowing and variable compound muscle action potential amplitude reduction. On lower-limb muscle MRI, there was distally accentuated fatty infiltration accompanied by edema in calf muscles. All these clinico-electrophysiological and imaging findings remained almost unaltered during monitoring. Using multivariate analysis, no significant predictors of progression associated to the disease were obtained. We conclude that in the 2-year period of study, CMT1A patients showed mild progression with good concordance between clinico-electrophysiological and imaging findings.