Responsiveness of clinical outcome measures in Charcot−Marie−Tooth disease

Quantitative MRI outcome measures in CMT1A using automated lower limb muscle segmentation

BACKGROUND

Lower limb muscle magnetic resonance imaging (MRI) obtained fat fraction (FF) can detect disease progression in patients with Charcot-Marie-Tooth disease 1A (CMT1A). However, analysis is time-consuming and requires manual segmentation of lower limb muscles. We aimed to assess the responsiveness, efficiency and accuracy of acquiring FF MRI using an artificial intelligence-enabled automated segmentation technique.

METHODS

We recruited 20 CMT1A patients and 7 controls for assessment at baseline and 12 months. The three-point-Dixon fat water separation technique was used to determine thigh-level and calf-level muscle FF at a single slice using regions of interest defined using Musclesense, a trained artificial neural network for lower limb muscle image segmentation. A quality control (QC) check and correction of the automated segmentations was undertaken by a trained observer.

RESULTS

The QC check took on average 30 seconds per slice to complete. Using QC checked segmentations, the mean calf-level FF increased significantly in CMT1A patients from baseline over an average follow-up of 12.5 months (1.15%±1.77%, paired t-test p=0.016). Standardised response mean (SRM) in patients was 0.65. Without QC checks, the mean FF change between baseline and follow-up, at 1.15%±1.68% (paired t-test p=0.01), was almost identical to that seen in the corrected data, with a similar overall SRM at 0.69.

CONCLUSIONS

Using automated image segmentation for the first time in a longitudinal study in CMT, we have demonstrated that calf FF has similar responsiveness to previously published data, is efficient with minimal time needed for QC checks and is accurate with minimal corrections needed.

Multicenter Validation of the Charcot-Marie-Tooth Functional Outcome Measure

BACKGROUND AND OBJECTIVES

Charcot-Marie-Tooth disease type 1A (CMT1A), caused by a duplication of PMP22, is the most common hereditary peripheral neuropathy. For participants with CMT1A, few clinical trials have been performed; however, multiple therapies have reached an advanced stage of preclinical development. In preparation for imminent clinical trials in participants with CMT1A, we have produced a Clinical Outcome Assessment (COA), known as the CMT-Functional Outcome Measure (CMT-FOM), in accordance with the FDA Roadmap to Patient-Focused Outcome Measurement to capture the key clinical end point of function.

METHODS

Participants were recruited through CMT clinics in the United States (n = 130), the United Kingdom (n = 52), and Italy (n = 32). To derive the most accurate signal with the fewest items to identify a therapeutic response, a series of validation studies were conducted including item and factor analysis, Rasch model analysis and testing of interrater reliability, discriminative ability, and convergent validity.

RESULTS

A total of 214 participants aged 18-75 years with CMT1A (58% female) were included in this study. Item, factor, and Rasch analysis supported the viability of the 12-item CMT-FOM as a unidimensional interval scale of function in adults with CMT1A. The CMT-FOM covers strength, upper and lower limb function, balance, and mobility. The 0-100 point scoring system showed good overall model fit, no evidence of misfitting items, and no person misfit, and it was well targeted for adults with CMT1A exhibiting high inter-rater reliability across a range of clinical settings and evaluators. The CMT-FOM was significantly correlated with the CMT Examination Score (r = 0.643; p < 0.001) and the Overall Neuropathy Limitation Scale (r = 0.516; p < 0.001). Significantly higher CMT-FOM total scores were observed in participants self-reporting daily trips and falls, unsteady ankles, hand tremor, and hand weakness (p < 0.05).

DISCUSSION

The CMT-FOM is a psychometrically robust multi-item, unidimensional, disease-specific COA covering strength, upper and lower limb function, balance, and mobility to capture how participants with CMT1A function to identify therapeutic efficacy.

Disease-specific wearable sensor algorithms for profiling activity, gait, and balance in individuals with Charcot-Marie-Tooth disease type 1A

BACKGROUND/AIMS

Charcot-Marie-Tooth Disease type 1A (CMT1A), the most common inherited peripheral neuropathy, is characterized by progressive sensory loss and weakness, which results in impaired mobility. Increased understanding of the genetics and pathophysiology of CMT1A has led to development of potential therapeutic agents, necessitating clinical trial readiness. Wearable sensors may provide useful outcome measures for future trials.

METHODS

Individuals with CMT1A and unaffected controls were recruited for this 12-month study. Participants wore sensors for in-clinic assessments and at-home, from which activity, gait, and balance metrics were derived. Mann-Whitney U tests were used to analyze group differences for activity, gait, and balance parameters. Test-retest reliability of gait and balance parameters and correlations of these parameters with clinical outcome assessments (COAs) were examined.

RESULTS

Thirty individuals, 15 CMT1A, and 15 controls, participated. Gait and balance metrics demonstrated moderate to excellent reliability. CMT1A participants had longer step durations (p < .001), shorter step lengths (p = .03), slower gait speeds (p < .001), and greater postural sway (p < .001) than healthy controls. Moderate correlations were found between CMT-Functional Outcome Measure and step length (r = -0.59; p = .02), and gait speed (r = 0.64; p = .01); 11 out of 15 CMT1A participants demonstrated significant increases in stride duration between the first and last quarter of the 6-min walk test, suggesting fatigue.

INTERPRETATION

In this initial study, gait and balance metrics derived from wearable sensors were reliable and associated with COAs in individuals with CMT1A. Larger longitudinal studies are needed to confirm our findings and evaluate sensitivity and utility of these disease-specific algorithms for clinical trial use.

Gene therapy and other novel treatment approaches for Charcot-Marie-Tooth disease

There is still no effective drug treatment available for Charcot-Marie-Tooth disease (CMT). Current management relies on rehabilitation therapy, surgery for skeletal deformities, and symptomatic treatment. The challenge is to find disease-modifying therapies. Several approaches, including gene silencing (by means of ASO, siRNA, shRNA, miRNA, CRISPR-Cas9 editing), to counteract the PMP22 gene overexpression in the most frequent CMT1A type are under investigation. PXT3003 is the compound in the most advanced phase for CMT1A, as a second phase-III trial is ongoing. Gene therapy to substitute defective genes (particularly in recessive forms associated with loss-of-function mutations) or insert novel ones (e.g., NT3 gene) are being developed and tested in animal models and in still exceptional cases have reached the clinical trial phase in humans. Novel treatment approaches are also aimed at developing compounds acting on pathways important for different CMT types. Modulation of the neuregulin pathway determining myelin thickness is promising for both hypo-demyelinating and hypermyelinating neuropathies; intervention on Unfolded Protein Response seems effective for rescuing misfolded myelin proteins such as MPZ in CMT1B. HDAC6 inhibitors improved axonal transport and ameliorated phenotypes in different CMT models. Other potential therapeutic strategies include targeting macrophages, lipid metabolism, and Nav1.8 sodium channel in demyelinating CMT and the P2×7 receptor, which regulates calcium influx into Schwann cells, in CMT1A. Further approaches are aimed at correcting metabolic abnormalities, including the accumulation of sorbitol caused by biallelic mutations in the sorbitol dehydrogenase (SORD) gene and of neurotoxic glycosphingolipids in HSN1.

Trials for Slowly Progressive Neurogenetic Diseases Need Surrogate Endpoints

Heritable neurological disorders provide insights into disease mechanisms that permit development of novel therapeutic approaches including antisense oligonucleotides, RNA interference, and gene replacement. Many neurogenetic diseases are rare and slowly progressive making it challenging to measure disease progression within short time frames. We share our experience developing clinical outcome assessments and disease biomarkers in the inherited peripheral neuropathies. We posit that carefully developed biomarkers from imaging, plasma, or skin can predict meaningful progression in functional and patient reported outcome assessments such that clinical trials of less than 2 years will be feasible for these rare and ultra-rare disorders. ANN NEUROL 2023;93:906-910.

Disease Progression in Charcot-Marie-Tooth Disease Related to MPZ Mutations: A Longitudinal Study

OBJECTIVE

The paucity of longitudinal natural history studies in MPZ neuropathy remains a barrier to clinical trials. We have completed a longitudinal natural history study in patients with MPZ neuropathies across 13 sites of the Inherited Neuropathies Consortium.

METHODS

Change in Charcot-Marie-Tooth Examination Score (CMTES) and Rasch modified CMTES (CMTES-R) were evaluated using longitudinal regression over a 5-year period in subjects with MPZ neuropathy. Data from 139 patients with MPZ neuropathy were examined.

RESULTS

The average baseline CMTES and CMTES-R were 10.84 (standard deviation [SD] = 6.0, range = 0-28) and 14.60 (SD = 7.56, range = 0-32), respectively. A mixed regression model showed significant change in CMTES at years 2-5 (mean change from baseline of 0.87 points at 2 years, p = 0.008). Subgroup analysis revealed greater change in CMTES at 2 years in subjects with axonal as compared to demyelinating neuropathy (mean change of 1.30 points [p = 0.016] vs 0.06 points [p = 0.889]). Patients with a moderate baseline neuropathy severity also showed more notable change, by estimate, than those with mild or severe neuropathy (mean 2-year change of 1.14 for baseline CMTES 8-14 [p = 0.025] vs -0.03 for baseline CMTES 0-7 [p = 0.958] and 0.25 for baseline CMTES ≥ 15 [p = 0.6897]). The progression in patients harboring specific MPZ mutations was highly variable.

INTERPRETATION

CMTES is sensitive to change over time in adult patients with axonal but not demyelinating forms of MPZ neuropathy. Change in CMTES was greatest in patients with moderate baseline disease severity. These findings will inform future clinical trials of MPZ neuropathies. ANN NEUROL 2023;93:563-576.

Anxiety and depression in Charcot-Marie-Tooth disease: data from the Italian CMT national registry

BACKGROUND

There is little information about neuropsychiatric comorbidities in Charcot-Marie-Tooth disease (CMT). We assessed frequency of anxiety, depression, and general distress in CMT.

METHODS

We administered online the Hospital Anxiety-Depression Scale (HADS) to CMT patients of the Italian registry and controls. HADS-A and HADS-D scores ≥ 11 defined the presence of anxiety/depression and HADS total score (HADS-T) ≥ 22 of general distress. We analysed correlation with disease severity and clinical characteristics, use of anxiolytics/antidepressants and analgesic/anti-inflammatory drugs.

RESULTS

We collected data from 252 CMT patients (137 females) and 56 controls. CMT patient scores for anxiety (mean ± standard deviation, 6.7 ± 4.8), depression (4.5 ± 4.0), and general distress (11.5 ± 8.1) did not differ from controls and the Italian population. However, compared to controls, the percentages of subjects with depression (10% vs 2%) and general distress (14% vs 4%) were significantly higher in CMT patients. We found no association between HADS scores and disease duration or CMT type. Patients with general distress showed more severe disease and higher rate of positive sensory symptoms. Depressed patients also had more severe disease. Nineteen percent of CMT patients took antidepressants/anxiolytics (12% daily) and 70% analgesic/anti-inflammatory drugs. Patients with anxiety, depression, and distress reported higher consumption of anxiolytics/antidepressants. About 50% of patients with depression and/or general distress did not receive any specific pharmacological treatment.

CONCLUSIONS

An appreciable proportion of CMT patients shows general distress and depression. Both correlated with disease severity and consumption of antidepressants/anxiolytics, suggesting that the disease itself is contributing to general distress and depression.

Patisiran Enhances Muscle Mass after Nine Months of Treatment in ATTRv Amyloidosis: A Study with Bioelectrical Impedance Analysis and Handgrip Strength

BACKGROUND AND AIMS

Hereditary transthyretin amyloidosis with polyneuropathy (ATTRv) is caused by mutations in the TTR gene, leading to misfolded monomers that aggregate generating amyloid fibrils. The clinical phenotype is heterogeneous, characterized by a multisystemic disease affecting the sensorimotor, autonomic functions along with other organs. Patisiran is a small interfering RNA acting as a TTR silencer approved for the treatment of ATTRv. Punctual and detailed instrumental biomarkers are on demand for ATTRv to measure the severity of the disease and monitor progression and response to treatment.

METHODS

Fifteen patients affected by ATTRv amyloidosis (66.4 ± 7.8 years, six males) were evaluated before the start of therapy with patisiran and after 9-months of follow-up. The clinical and instrumental evaluation included body weight and height; Coutinho stage; Neuropathy Impairment Score (NIS); Karnofsky performance status (KPS); Norfolk QOL Questionnaire; Six-minute walking test (6 MWT); nerve conduction studies; handgrip strength (HGS); and bioimpedance analysis (BIA).

RESULTS

Body composition significantly changed following the 9-months pharmacological treatment. In particular, the patients exhibited an increase in fat free mass, body cell mass, and body weight with a decrease in fat mass. A significant increase after 9 months of treatment was observed for the 6 MWT. Coutinho stage, KPS, NIS, NIS-W, nerve conduction studies, Norfolk, COMPASS-31 scale, and HGS remained unchanged.

CONCLUSIONS

BIA might represent a useful tool to assess the effects of multiorgan damage in ATTRv and to monitor disease progression and response to treatments. More evidence is still needed for HGS. Patisiran stabilizes polyneuropathy and preserves motor strength by increasing muscle mass after 9 months of treatment.

Accelerate Clinical Trials in Charcot-Marie-Tooth Disease (ACT-CMT): A Protocol to Address Clinical Trial Readiness in CMT1A

With therapeutic trials on the horizon for Charcot-Marie-Tooth type 1A (CMT1A), reliable, valid, and responsive clinical outcome assessments and biomarkers are essential. Accelerate Clinical Trials in CMT (ACT-CMT) is an international study designed to address important gaps in CMT1A clinical trial readiness including the lack of a validated, responsive functional outcome measure for adults, and a lack of validated biomarkers for multicenter application in clinical trials in CMT1A. The primary aims of ACT-CMT include validation of the Charcot-Marie-Tooth Functional Outcome Measure, magnetic resonance imaging of intramuscular fat accumulation as a lower limb motor biomarker, and in-vivo reflectance confocal microscopy of Meissner corpuscle sensory receptor density, a sensory biomarker. Initial studies have indicated that these measures are feasible, reliable and valid. A large prospective, multi-site study is necessary to fully validate and examine the responsiveness of these outcome measures in relation to existing outcomes for use in future clinical trials involving individuals with CMT1A. Two hundred 15 adults with CMT1A are being recruited to participate in this prospective, international, multi-center study. Serial assessments, up to 3 years, are performed and include the CMT-FOM, CMT Exam Score-Rasch, Overall Neuropathy Limitations Scale, CMT-Health Index, as well as nerve conduction studies, and magnetic resonance imaging and Meissner corpuscle biomarkers. Correlations using baseline data will be examined for validity. Longitudinal analyses will document the changes in function, intramuscular fat accumulation, Meissner corpuscle sensory receptor density. Lastly, we will use anchor-based and other statistical methods to determine the minimally clinically important change for these clinical outcome assessments and biomarkers in CMT1A. Reliable, and responsive clinical outcome assessments of function and disease progression biomarkers are urgently needed for application in early and late phase clinical trials in CMT1A. The ACT-CMT study protocol will address this need through the prospective, longitudinal, multicenter examination in unprecedented detail of novel and existing clinical outcome assessments and motor and sensory biomarkers, and enhance international clinical trial infrastructure, training and preparedness for future therapeutic trials in CMT and related neuropathies.

A longitudinal and cross-sectional study of plasma neurofilament light chain concentration in Charcot-Marie-Tooth disease

Advances in genetic technology and small molecule drug development have paved the way for clinical trials in Charcot-Marie-Tooth disease (CMT); however, the current FDA-approved clinical trial outcome measures are insensitive to detect a meaningful clinical response. There is, therefore, a need to identify sensitive outcome measures or clinically relevant biomarkers. The aim of this study was to further evaluate plasma neurofilament light chain (NFL) as a disease biomarker in CMT. Plasma NFL was measured using SIMOA technology in both a cross-sectional study of a US cohort of CMT patients and longitudinally over 6 years in a UK CMT cohort. In addition, plasma NFL was measured longitudinally in two mouse models of CMT2D. Plasma concentrations of NFL were increased in a US cohort of patients with CMT1B, CMT1X and CMT2A but not CMT2E compared with controls. In a separate UK cohort, over a 6-year interval, there was no significant change in plasma NFL concentration in CMT1A or HSN1, but a small but significant reduction in patients with CMT1X. Plasma NFL was increased in wild type compared to GARSC201R mice. There was no significant difference in plasma NFL in GARSP278KY compared to wild type mice. In patients with CMT1A, the small difference in cross-sectional NFL concentration vs healthy controls and the lack of change over time suggests that plasma NFL may lack sufficient sensitivity to detect a clinically meaningful treatment response in adulthood.

Motor Conduction Studies and Handgrip in Hereditary TTR Amyloidosis: Simple Tools to Evaluate the Upper Limbs

Purpose

Hereditary transthyretin amyloidosis with polyneuropathy (ATTRv) is caused by mutations in the TTR gene, leading to misfolded monomers that aggregate generating amyloid fibrils. The clinical phenotype is heterogeneous, and characterized by a multisystemic disease affecting the sensorimotor and autonomic functions along with other organs.

Materials and Methods

All the patients were assessed by complete neurological assessment, neurophysiological evaluation, of the median nerve, and handgrip analysis. The data are presented as means and standard deviations. Parametric and non-parametric assessments have been performed to identify differences between groups. Pearson's correlation has been carried out when appropriate.

Results

Twenty patients with ATTRv (66.1 ± 8.4 years; eight females) and 30 controls (61.1 ± 11.6 years; 16 females) were enrolled. Handgrip strength was reduced in patients with ATTR in both right and left hands compared to the controls. Significant differences were found between patients and controls in the right (handgrip right, HGS_R TTR 21.1 ± 13 kg vs. HGS_R Control 29.4 ± 11.3 kg, p = 0.017) and left (handgrip left, HGS_L TTR 22.2 ± 10.7 kg. vs. HGS_L Control 31 ± 11.3 kg, p = 0.007). NIS and CMAP amplitude of the median nerve were related to HGS measures for both hands in patients with ATTRv.

Conclusions

The progression of bilateral carpal tunnel syndrome is related to neurophysiological data in the median nerve in ATTRv. Also, handgrip measures might represent an important tool for the assessment of disease progression in ATTRv. We propose using a combination of CMAP amplitude and HGS for the assessment of hand motor strength in ATTRv.

A double-blind, placebo-controlled, randomized trial of PXT3003 for the treatment of Charcot-Marie-Tooth type 1A

BACKGROUND

Charcot-Marie-Tooth disease type 1A (CMT1A) is a rare, orphan, hereditary neuromuscular disorder with no cure and for which only symptomatic treatment is currently available. A previous phase 2 trial has shown preliminary evidence of efficacy for PXT3003 in treating CMT1A. This phase 3, international, randomized, double-blind, placebo-controlled study further investigated the efficacy and safety of high- or low-dose PXT3003 (baclofen/naltrexone/D-sorbitol [mg]: 6/0.70/210 or 3/0.35/105) in treating subjects with mild to moderate CMT1A.

METHODS

In this study, 323 subjects with mild-to-moderate CMT1A were randomly assigned in a 1:1:1 ratio to receive 5 mL of high- or low-dose PXT3003, or placebo, orally twice daily for up to 15 months. Efficacy was assessed using the change in Overall Neuropathy Limitations Scale total score from baseline to months 12 and 15 (primary endpoint). Secondary endpoints included the 10-m walk test and other assessments. The high-dose group was discontinued early due to unexpected crystal formation in the high-dose formulation, which resulted in an unanticipated high discontinuation rate, overall and especially in the high-dose group. The statistical analysis plan was adapted to account for the large amount of missing data before database lock, and a modified full analysis set was used in the main analyses. Two sensitivity analyses were performed to check the interpretation based on the use of the modified full analysis set.

RESULTS

High-dose PXT3003 demonstrated significant improvement in the Overall Neuropathy Limitations Scale total score vs placebo (mean difference: - 0.37 points; 97.5% CI [- 0.68 to - 0.06]; p = 0.008), and consistent treatment effects were shown in the sensitivity analyses. Both PXT3003 doses were safe and well-tolerated.

CONCLUSION

The high-dose group demonstrated a statistically significant improvement in the primary endpoint and a good safety profile. Overall, high-dose PXT3003 is a promising treatment option for patients with Charcot-Marie-Tooth disease type 1A.

Genotype-phenotype correlation in French patients with myelin protein zero gene-related inherited neuropathy

BACKGROUND AND PURPOSE

Preparations for clinical trials of unfolded protein response (UPR) inhibitors (such as Sephin1) that target the upregulated UPR in patients with Charcot-Marie-Tooth disease (CMT) carrying MPZ mutations are currently underway. The inclusion criteria for these trials are still being formulated. Our objective was to characterize the relation between genotypes and phenotypes in patients with CMT caused by MPZ mutations, and to refine the inclusion criteria for future trials.

METHODS

Clinical and neurophysiological data of CMT patients with MPZ mutations were retrospectively collected at 11 French reference centers.

RESULTS

Forty-four mutations in MPZ were identified in 91 patients from 61 families. There was considerable heterogeneity. The same mutation was found to cause either axonal or demyelinating neuropathy. Three groups were identified according to the age at disease onset. CMT Examination Score (CMTES) tended to be higher in the early (≤22 years) and adult (23-47 years) onset groups (mean CMTESv2 = 10.4 and 10.0, respectively) than in the late onset group (>47 years, mean CMTESv2 = 8.6, p = 0.47). There was a significant positive correlation between CMTESv2 and the age of patients in Groups I (p = 0.027) and II (p = 0.023), indicating that clinical severity progressed with age in these patients.

CONCLUSIONS

To optimize the selection of CMT patients carrying MPZ mutations for the upcoming trials, inclusion criteria should take into account the pathophysiology of the disease (upregulated UPR). Recruited patients should have a mild to moderate disease severity and a disease onset at between 18 and 50 years, as these patients exhibit significant disease progression over time.

Updated review of therapeutic strategies for Charcot-Marie-Tooth disease and related neuropathies

Introduction: Charcot-Marie-Tooth disease (CMT) and related neuropathies represent the most prevalent inherited neuromuscular disorders. Nonetheless, there is still no pharmacological treatment available for any CMT type. However, the landscape is rapidly evolving and several novel approaches are providing encouraging results in preclinical studies and leading to clinical trials.Areas covered: The authors review the most promising therapies under study and the ongoing/planned clinical trials. Several approaches to address PMP22 overexpression underlying CMT1A, the most frequent subtype, are being tested. Gene silencing, targeting PMP22, and gene therapy, to introduce specific genes or to substitute or modulate defective ones, are being experimented in animal models. Compounds acting on ER stress, unfolded protein response, neuregulin pathways, phosphoinositides metabolism, axonal transport and degeneration, inflammation, polyol pathway, deoxysphingolipid metabolism, purine nucleotide pool are potential therapeutic candidates for different forms of CMT and related neuropathies.Expert opinion: We are getting closer to find effective therapies for CMT, but are far behind the exciting examples of other genetic neuromuscular disorders. The authors analyze the possible reasons for this gap and the way to fill it. Preclinical and clinical research is ongoing with coordinated efforts and they are confident that in the next few years we will see the first effective treatments.

Natural history of Charcot-Marie-Tooth disease type 2A: a large international multicentre study

Mitofusin-2 (MFN2) is one of two ubiquitously expressed homologous proteins in eukaryote cells, playing a critical role in mitochondrial fusion. Mutations in MFN2 (most commonly autosomal dominant) cause Charcot-Marie-Tooth disease type 2A (CMT2A), the commonest axonal form of CMT, with significant allelic heterogeneity. Previous, moderately-sized, cross sectional genotype-phenotype studies of CMT2A have described the phenotypic spectrum of the disease, but longitudinal natural history studies are lacking. In this large multicentre prospective cohort study of 196 patients with dominant and autosomal recessive CMT2A, we present an in-depth genotype-phenotype study of the baseline characteristics of patients with CMT2A and longitudinal data (1–2 years) to describe the natural history. A childhood onset of autosomal dominant CMT2A is the most predictive marker of significant disease severity and is independent of the disease duration. When compared to adult onset autosomal dominant CMT2A, it is associated with significantly higher rates of use of ankle-foot orthoses, full-time use of wheelchair, dexterity difficulties and also has significantly higher CMT Examination Score (CMTESv2) and CMT Neuropathy Score (CMTNSv2) at initial assessment. Analysis of longitudinal data using the CMTESv2 and its Rasch-weighted counterpart, CMTESv2-R, show that over 1 year, the CMTESv2 increases significantly in autosomal dominant CMT2A (mean change 0.84 ± 2.42; two-tailed paired t-test P = 0.039). Furthermore, over 2 years both the CMTESv2 (mean change 0.97 ± 1.77; two-tailed paired t-test P = 0.003) and the CMTESv2-R (mean change 1.21 ± 2.52; two-tailed paired t-test P = 0.009) increase significantly with respective standardized response means of 0.55 and 0.48. In the paediatric CMT2A population (autosomal dominant and autosomal recessive CMT2A grouped together), the CMT Pediatric Scale increases significantly both over 1 year (mean change 2.24 ± 3.09; two-tailed paired t-test P = 0.009) and over 2 years (mean change 4.00 ± 3.79; two-tailed paired t-test P = 0.031) with respective standardized response means of 0.72 and 1.06. This cross-sectional and longitudinal study of the largest CMT2A cohort reported to date provides guidance for variant interpretation, informs prognosis and also provides natural history data that will guide clinical trial design.

Genetic and Clinical Features in 24 Chinese Distal Hereditary Motor Neuropathy Families

Background and Objectives: Distal hereditary motor neuropathy (dHMN) is a clinically and genetically heterogeneous group of inherited neuropathies. The objectives of this study were to report the clinical and genetic features of dHMN patients in a Chinese cohort.

Aims and Methods: We performed clinical assessments and whole-exome sequencing in 24 dHMN families from Mainland China. We conducted a retrospective analysis of the data and investigated the frequency and clinical features of patients with a confirmed mutation.

Results: Two novel heterozygous mutations in GARS, c.373G>C (p.E125Q) and c.1015G>A (p.G339R), were identified and corresponded to the typical dHMN-V phenotype. Together with families with WARS, SORD, SIGMAR1, and HSPB1 mutations, 29.2% of families (7/24) acquired a definite genetic diagnosis. One novel heterozygous variant of uncertain significance, c.1834G>A (p.G612S) in LRSAM1, was identified in a patient with mild dHMN phenotype.

Conclusion: Our study expanded the mutation spectrum of GARS mutations and added evidence that GARS mutations are associated with both axonal Charcot-Marie-Tooth and dHMN phenotypes. Mutations in genes encoding aminoamide tRNA synthetase (ARS) might be a frequent cause of autosomal dominant-dHMN, and SORD mutation might account for a majority of autosomal recessive-dHMN cases. The relatively low genetic diagnosis yield indicated more causative dHMN genes need to be discovered.

Validation of the Italian version of the Charcot-Marie-Tooth Health Index

The Charcot-Marie-Tooth Health Index (CMT-HI) is a disease-specific patient-reported outcome measure measuring overall disease burden in Charcot-Marie-Tooth (CMT) patients, designed for natural history studies and clinical trials in English-speaking affected individuals. We developed and validated its Italian Charcot-Marie-Tooth Health Index (I-CMT-HI) version. The questionnaire was translated and culturally adapted from source into Italian by two neurologists experienced in CMT and neuromuscular disorders (NMDs). The two translations were reviewed by a panel of seven experts in CMT and NMD. The provisional version was back-translated into English by a professional translator. The definitive Italian version was developed during a consensus teleconference by the panel and a patient representative from ACMT-Rete. A series of clinically and genetically characterized CMT patients completed the final questionnaire; 11 participated in a test-retest reliability assessment of the instrument. The I-CMT-HI was administered to 30 CMT patients (13 CMT1A, eight CMTX1, two CMT1B, two CMT1E, two CMT2I, one CMT2A, one CMT2N, one distal Hereditary Motor Neuropathy), with test-rest in 11:14 females and 16 males, aged (mean ± SD) 48.0 ± 16.4 years (range 18-81), with CMT Examination Score (CMTES) = 10.0 ± 4.4 (range 2-18). The I-CMT-HI mean total score was 29.4 ± 21.2 (range 0.1-60.3). The I-CMT-HI showed a high test-retest reliability: intraclass correlation coefficient = 0.95 (95% confidence interval, 0.84-0.99). No patient had difficulty in completing the questionnaire and none reported any problem with the questions' formulation. The total CMT-HI score was positively correlated with age and CMTES, with higher disease burden with increasing age and disease severity according to the CMTES. The I-CMT-HI is now ready for use in clinical studies in the Italian population.

Quantitative assessment of sciatic nerve changes in Charcot-Marie-Tooth type 1A patients using magnetic resonance neurography

BACKGROUND AND PURPOSE

Nerve tissue alterations have rarely been quantified in Charcot-Marie-Tooth type 1A (CMT1A) patients. The aim of the present study was to quantitatively assess the magnetic resonance imaging (MRI) anomalies of the sciatic and tibial nerves in CMT1A disease using quantitative neurography MRI. It was also intended to seek for correlations with clinical variables.

METHODS

Quantitative neurography MRI was used in order to assess differences in nerve volume, proton density and magnetization transfer ratio in the lower limbs of CMT1A patients and healthy controls. Disease severity was evaluated using the Charcot-Marie-Tooth Neuropathy Score version 2, Charcot-Marie-Tooth examination scores and Overall Neuropathy Limitations Scale scores. Electrophysiological measurements were performed in order to assess the compound motor action potential and the Motor Unit Number Index. Clinical impairment was evaluated using muscle strength measurements and Charcot-Marie-Tooth examination scores.

RESULTS

A total of 32 CMT1A patients were enrolled and compared to 13 healthy subjects. The 3D nerve volume, magnetization transfer ratio and proton density were significantly different in CMT1A patients for the whole sciatic and tibial nerve volume. The sciatic nerve volume was significantly correlated with the whole set of clinical scores whereas no correlation was found between the tibial nerve volume and the clinical scores.

CONCLUSION

Nerve injury could be quantified in vivo using quantitative neurography MRI and the corresponding biomarkers were correlated with clinical disability in CMT1A patients. The sensitivity of the selected metrics will have to be assessed through repeated measurements over time during longitudinal studies to evaluate structural nerve changes under treatment.

Are we prepared for clinical trials in Charcot-Marie-Tooth disease?

There has been considerable progress in developing treatments for Charcot-Marie-Tooth disease with a number of therapies either completing or nearing clinical trials. In the case of CMT1A, the commonest subtype of CMT, there have been more than five randomised, double blind placebo-controlled trials. Although these trials were negative for the primary outcome measure, considerable lessons have been learnt leading to the collection of large prospective natural history data sets with which to inform future trial design as well as the development of new and sensitive outcome measures. In this review we summarise the difficulties of conducting clinical trials in a slowly progressive disease such as CMT1A and the requirement for sensitive, reproducible and clinically relevant outcome measures. We summarise the current array of CMT specific outcome measures subdivided into clinical outcome measures, functional outcome measures, patient reported outcome measures, biomarkers of disease burden and treatment specific biomarkers of target engagement. Although there is now an array of CMT specific outcome measures, which collectively incorporate clinically relevant, sensitive and reproducible outputs, a single outcome measure incorporating all three qualities remains elusive.

A longitudinal study of CMT1A using Rasch analysis based CMT neuropathy and examination scores

OBJECTIVE

To evaluate the sensitivity of Rasch analysis-based, weighted Charcot-Marie-Tooth Neuropathy and Examination Scores (CMTNS-R and CMTES-R) to clinical progression in patients with Charcot-Marie-Tooth disease type 1A (CMT1A).

METHODS

Patients with CMT1A from 18 sites of the Inherited Neuropathies Consortium were evaluated between 2009 and 2018. Weighted CMTNS and CMTES modified category responses were developed with Rasch analysis of the standard scores. Change from baseline for CMTNS-R and CMTES-R was estimated with longitudinal regression models.

RESULTS

Baseline CMTNS-R and CMTES-R scores were available for 517 and 1,177 participants, respectively. Mean ± SD age of participants with available CMTES-R scores was 41 ± 18 (range 4-87) years, and 56% were female. Follow-up CMTES-R assessments at 1, 2, and 3 years were available for 377, 321, and 244 patients. A mixed regression model showed significant change in CMTES-R score at years 2 through 6 compared to baseline (mean change from baseline 0.59 points at 2 years, p = 0.0004, n = 321). Compared to the original CMTES, the CMTES-R revealed a 55% improvement in the standardized response mean (mean change/SD change) at 2 years (0.17 vs 0.11). Change in CMTES-R at 2 years was greatest in mildly to moderately affected patients (1.48-point mean change, 95% confidence interval 0.99-1.97, p < 0.0001, for baseline CMTES-R score 0-9).

CONCLUSION

The CMTES-R demonstrates change over time in patients with CMT1A and is more sensitive than the original CMTES. The CMTES-R was most sensitive to change in patients with mild to moderate baseline disease severity and failed to capture progression in patients with severe CMT1A.

CLINICALTRIALSGOV IDENTIFIER

NCT01193075.

Development of MRC Centre MRI calf muscle fat fraction protocol as a sensitive outcome measure in Hereditary Sensory Neuropathy Type 1

OBJECTIVES

Hereditary sensory neuropathy type 1 (HSN1) is a rare, slowly progressive neuropathy causing profound sensory deficits and often severe motor loss. L-serine supplementation is a possible candidate therapy but the lack of responsive outcome measures is a barrier for undertaking clinical trials in HSN1. We performed a 12-month natural history study to characterise the phenotype of HSN1 and to identify responsive outcome measures.

METHODS

Assessments included Charcot-Marie-Tooth Neuropathy Score version 2 (CMTNSv2), CMTNSv2-Rasch modified, nerve conduction studies, quantitative sensory testing, intraepidermal nerve fibre density (thigh), computerised myometry (lower limbs), plasma 1-deoxysphingolipid levels, calf-level intramuscular fat accumulation by MRI and patient-based questionnaires (Neuropathic Pain Symptom Inventory and 36-Short Form Health Survey version 2 [SF-36v2]).

RESULTS

35 patients with HSN1 were recruited. There was marked heterogeneity in the phenotype mainly due to differences between the sexes: males generally more severely affected. The outcome measures that significantly changed over 1 year and correlated with CMTNSv2, SF-36v2-physical component and disease duration were MRI determined calf intramuscular fat accumulation (mean change in overall calf fat fraction 2.36%, 95% CI 1.16 to 3.55, p=0.0004), pressure pain threshold on the hand (mean change 40 kPa, 95% CI 0.7 to 80, p=0.046) and myometric measurements of ankle plantar flexion (median change -0.5 Nm, IQR -9.5 to 0, p=0.0007), ankle inversion (mean change -0.89 Nm, 95% CI -1.66 to -0.12, p=0.03) and eversion (mean change -1.61 Nm, 95% CI -2.72 to -0.51, p=0.006). Intramuscular calf fat fraction was the most responsive outcome measure.

CONCLUSION

MRI determined calf muscle fat fraction shows validity and high responsiveness over 12 months and will be useful in HSN1 clinical trials.

A novel WARS mutation (p.Asp314Gly) identified in a Chinese distal hereditary motor neuropathy family

Distal hereditary motor neuropathy (dHMN) is a clinically and genetically heterogeneous group of inherited neuropathies characterized by distal limb muscle wasting and weakness with no or minimal sensory abnormalities. To investigate the clinical and genetic features of dHMN caused by WARS mutations in mainland China, we performed Sanger sequencing of the coding and untranslated region (UTR) regions of WARS in 160 unresolved dHMN and Charcot-Marie-Tooth (CMT) index patients. We detected a novel heterozygous variant c.941A>G (p.Asp314Gly) of WARS in an index patient from an autosomal dominant dHMN family including five affected members over three generations. The variant completely co-segregates with the dHMN phenotype in the family, and it was classified as likely pathogenic according to the American College of Medical Genetics and Genomics standards and guidelines. The clinical features included juvenile to adult onset (15-23 years), distal wasting and weakness, minimal sensory disturbance and length-dependent motor axonal degeneration with CMT examination score ranging from 6 to 10. Our report further confirms the role of WARS in dHMN and indicates that the variant c.941A>G (p.Asp314Gly) of WARS is related to a mild to moderate affected and later onset phenotype of dHMN.

Physical function and performance measures of children and adolescents with Charcot-Marie-Tooth disease

This study aimed to verify whether there are differences in foot type, physical function, and performance between children and adolescents with Charcot-Marie-Tooth disease (CMT) and their healthy counterparts, and whether an interval of 6 months, from the initial assessment, reveals any significant changes on physical performance and other specific physical measures of the lower limbs. Subjects and Methods: Participants between 6 and 17 years of age, with CMT (CMT group n = 40), were compared to healthy participants (Control group, n = 49). Twenty participants with CMT completed the follow-up. We collected anthropometric, goniometric (ankle and knee), and dynamometric (inversion, eversion, plantar flexors, dorsiflexors, knee, hip extensors) measures, agonist/antagonist ratios, feet alignment (Foot Posture Index - FPI), muscle power (Long Jump), Pediatric Balance Scale (PBS), and 10-meter walk test (10MWT). Results: Compared to Control, CMT showed reduced passive range of motion (ROM), weakness in all evaluated muscles, increased agonist/antagonist ratios, predominance of varus and lower performance (PBS and Long Jump). After 6 months, CMT measures did not change. Conclusion: The cross-sectional analysis showed reduced ROM, strength, power, and distal muscle imbalance, as well as secondary limitations (PBS and 10MWT) in children and adolescents with CMT. These biomechanical and functional alterations did not change at the 6-month follow-up.

Walking Speed Is Correlated With the Isokinetic Muscular Strength of the Knee in Patients With Charcot-Marie-Tooth Type 1A

Charcot-Marie-Tooth disease type 1A is the most common hereditary neuropathy. Affected individuals have a distal motor deficit, initially affecting the lower limbs and impairing walking performance. Isokinetic dynamometry can be used to objectively assess muscle strength of patients with neuromuscular disorders. No studies have evaluated the effect of muscle strength deficits of knee extensors and flexors on walking parameters for patients with Charcot-Marie-Tooth disease type 1A. The purpose of this study was to determine correlations between the isokinetic muscular strength of knee flexors and knee extensors and walk parameters for patients with Charcot-Marie-Tooth disease type 1A. isokinetic muscular strength of the knee was assessed on an isokinetic dynamometer (Cybex) and walking by instrumented walkway analysis (GaitRite). We included 33 patients (23 females, mean ± SD age 46.7 ± 13.3 yrs, mean ± SD body mass index 25.7 ± 4.6 kg/m). We found a correlation between walking speed and isokinetic muscular strength of knee extensors for the entire population and between walking speed and isokinetic muscular strength of knee extensors and knee flexors for patients younger than 50 yrs. Isokinetic dynamometry can provide objective measures of knee muscle strength, which is correlated with walking speed but not cadence or step/stride length of patients with Charcot-Marie-Tooth disease.

Quantifying gait impairment in individuals affected by Charcot-Marie-Tooth disease: the usefulness of gait profile score and gait variable score

Background: Gait analysis is a reliable tool to characterise ambulation in Charcot-Marie-Tooth, the obtained are complex data makes its use scarce in clinical practice. The use of synthetic measures may enable the clinician to easily interpret gait kinematics in Charcot-Marie-Tooth.Aims: To test the usefulness of Gait Profile Score as a method to quantify and monitor kinematic gait alterations in Charcot-Marie-Tooth.Methods: A group of patients with Charcot-Marie-Tooth and a control group underwent Gait Analysis. Neurological impairment was evaluated by means of the Charcot Marie Tooth neuropathy score in his original form and in the Rasch Analysis revised form. Differences in Kinematics scores induced by the pathology were assessed using the Mann-Whitney U test. The relationship between gait parameters and Charcot Marie Tooth neuropathy score was assessed by means of the Spearman correlation.Results: Twenty patients were enrolled. Mann-Whitney U test revealed a significant effect of the pathology on Gait Profile Score (p < 0.001). Charcot Marie Tooth neuropathy score was positively correlated with Gait Profile Score (Rho = 0.708, p = 0.001).Conclusion: Gait profile score can differentiate Charcot Marie Tooth from unaffected people and to quantify ambulation impairment, also identifying the joints more affected by the disease.Implications for rehabilitationPhysiotherapy and orthotics constitute the sole possible clinical approach for Charcot Marie Tooth, but the clinical scales are scarcely effective for assessing the rehabilitative outcome.Synthetic measures are able to summarize Charcot Marie tooth kinematics in a single score, and Gait Profile Score is able to differentiate patients with Charcot Marie tooth from healthy controls.Gait Profile Score is related to clinical disability as measured by the Charcot Marie tooth neuropathy score.

The Italian neuromuscular registry: a coordinated platform where patient organizations and clinicians collaborate for data collection and multiple usage

BACKGROUND

The worldwide landscape of patient registries in the neuromuscular disease (NMD) field has significantly changed in the last 10 years, with the international TREAT-NMD network acting as strong driver. At the same time, the European Medicines Agency and the large federations of rare disease patient organizations (POs), such as EURORDIS, contributed to a great cultural change, by promoting a paradigm shift from product-registries to patient-centred registries. In Italy, several NMD POs and Fondazione Telethon undertook the development of a TREAT-NMD linked patient registry in 2009, with the referring clinical network providing input and support to this initiative through the years. This article describes the outcome of this joint effort and shares the experience gained.

METHODS

The Italian NMD registry is based on an informatics technology platform, structured according to the most rigorous legal national and European requirements for management of patient sensitive data. A user-friendly web interface allows both direct patients and clinicians' participation. The platform's design permits expansion to incorporate new modules and new registries, and is suitable of interoperability with other international efforts.

RESULTS

When the Italian NMD Registry was initiated, an ad hoc legal entity (NMD Registry Association) was devised to manage registries' data. Currently, several disease-specific databases are hosted on the platform. They collect molecular and clinical details of individuals affected by Duchenne or Becker muscular dystrophy, Charcot-Marie-Tooth disease, transthyretin type-familial amyloidotic polyneuropathy, muscle glycogen storage disorders, spinal and bulbar muscular atrophy, and spinal muscular atrophy. These disease-specific registries are at different stage of development, and the NMD Registry itself has gone through several implementation steps to fulfil different technical and governance needs. The new governance model is based on the agreement between the NMD Registry Association and the professional societies representing the Italian NMD clinical network. Overall, up to now the NMD registry has collected data on more than 2000 individuals living with a NMD condition.

CONCLUSIONS

The Italian NMD Registry is a flexible platform that manages several condition-specific databases and is suitable to upgrade. All stakeholders participate in its management, with clear roles and responsibilities. This governance model has been key to its success. In fact, it favored patient empowerment and their direct participation in research, while also engaging the expert clinicians of the Italian network in the collection of accurate clinical data according to the best clinical practices.

Hidden hearing loss in patients with Charcot-Marie-Tooth disease type 1A

The aim of this study was to investigate hidden hearing loss in patients with Charcot-Marie-Tooth disease type 1 A (CMT1A), a common inherited demyelinating neuropathy. By using pure-tone audiometry, 43 patients with CMT1A and 60 healthy controls with normal sound detection abilities were enrolled. Speech perception in quiet and noisy backgrounds, spectral ripple discrimination (SRD), and temporal modulation detection (TMD) were measured. Although CMT1A patients and healthy controls had similar pure-tone thresholds and speech perception scores in a quiet background, CMT1A patients had significantly (p < 0.05) decreased speech perception ability in a noisy background compared to controls. CMT1A patients showed significantly decreased temporal and spectral resolution (both p < 0.05). Also, auditory temporal processing of CMT1A patients was correlated with speech perception in a noisy background (r = 0.447, p < 0.01) and median motor conduction velocity (r = 0.335, p < 0.05). Therefore, we assumed that demyelination of auditory nerve in CMT1A causes defective cochlear neurotransmission, which reduces temporal resolution and speech perception in a noisy background. Because the temporal resolution test was well correlated with the degree of demyelination in auditory and peripheral motor nerves, temporal resolution testing could be performed as an additional marker for CMT1A.

Outcome measures in the clinical evaluation of ambulatory Charcot-Marie-Tooth 1A subjects

BACKGROUND

The outcome measures (OMs) in clinical trials for Charcot-Marie-Tooth disease (CMT) still represent an issue. A recent study highlighted that three additional clinical OMs, the 10-Meter Walk Test (10MWT), the 9-Hole Peg Test, and foot dorsal flexion dynamometry, further improve discrimination between severely and mildly affected patients. Another study has recently assessed the validity and reliability of the 6-Minute Walk Test (6MWT).

AIM

The aim of this study was to identify the most useful scales in the clinical evaluation of CMT1A patients.

DESIGN

Observational study of the baseline data collected in a multicenter, prospective, randomized, single blind, controlled study to evaluate the efficacy and safety of an innovative rehabilitation protocol based on treadmill training, stretching, respiratory, and proprioceptive exercises (TreSPE study) in CMT1A patients.

SETTING

The outpatient service of the four Italian centers involved, which are specialized in hereditary neuropathies.

POPULATION

Fifty-three subjects with a clinical and genetically confirmed diagnosis of CMT1A.

METHODS

At baseline, in addition to the CMT Neuropathy Score, all subjects underwent walking evaluation (6MWT, 10MWT), balance assessment (Berg Balance Scale [BBS], Short Physical Performance Battery [SPPB]) and a subjective evaluation of quality of life (SF36) and walking ability (Walk12).

RESULTS

Analyzing the baseline data, as expected, we found a strong correlation between walk and balance evaluation, proving the validity of these tests in investigating the functional impairment of CMT1A subjects. Particularly, we found that subjects with better balance control walk at higher speed and perceive less limitations in their physical activities or motor skills. This can be reconducted to the fact that ankle stability depends upon different factors such as anatomy integrity, muscle strength and proprioception.

CONCLUSIONS

We identify the 6MWT, 10MWT, and SPPB as the most useful scales, in addition to the CMTNS, to evaluate the functional impairment of CMT1A patients who retain their walking capability and we suggest the use of SPPB because of its rapidity to assess balance and gait disorders in clinical settings.

CLINICAL REHABILITATION IMPACT

In the clinical practice it is important to evaluate patients comprehensively but rapidly. These outcome measures can help us to correctly assess balance and walking ability in CMT1A patients.

Plasma neurofilament light chain concentration in the inherited peripheral neuropathies

OBJECTIVE

To perform a cross-sectional study to determine whether plasma neurofilament light chain (NfL) concentration is elevated in patients with Charcot-Marie-Tooth disease (CMT) and if it correlates with disease severity.

METHODS

Blood samples were collected from 75 patients with CMT and 67 age-matched healthy controls over a 1-year period. Disease severity was measured using the Rasch modified CMT Examination and neuropathy scores. Plasma NfL concentration was measured using an in-house-developed Simoa assay.

RESULTS

Plasma NfL concentration was significantly higher in patients with CMT (median 26.0 pg/mL) compared to healthy controls (median 14.6 pg/mL, p < 0.0001) and correlated with disease severity as measured using the Rasch modified CMT examination (r = 0.43, p < 0.0001) and neuropathy (r = 0.37, p = 0.044) scores. Concentrations were also significantly higher when subdividing patients by genetic subtype (CMT1A, SPTLC1, and GJB1) or into demyelinating or axonal forms compared to healthy controls.

CONCLUSION

There are currently no validated blood biomarkers for peripheral neuropathy. The significantly raised plasma NfL concentration in patients with CMT and its correlation with disease severity suggest that plasma NfL holds promise as a biomarker of disease activity, not only for inherited neuropathies but for peripheral neuropathy in general.

Recent advances in the genetic neuropathies

PURPOSE OF REVIEW

Charcot-Marie-Tooth disease (CMT) is one of the commonest inherited neuromuscular diseases with a population prevalence of 1 in 2500. This review will cover recent advances in the genetics and pathomechanisms of CMT and how these are leading to the development of rational therapies.

RECENT FINDINGS

Pathomechanistic and therapeutic target advances in CMT include the identification of the ErbB receptor signalling pathway as a therapeutic target in CMT1A and pharmacological modification of the unfolded protein response in CMT1B. In CMT2D, due to mutations in glycyl-tRNA synthetase, vascular endothelial growth factor-mediated stimulation of the Nrp1 receptor has been identified as a therapeutic target. Preclinical advances have been accompanied by the publication of large natural history cohorts and the identification of a sensitive biomarker of disease (muscle MRI) that is able to detect disease progression in CMT1A over 1 year.

SUMMARY

Advances in next-generation sequencing technology, cell biology and animal models of CMT are paving the way for rational treatments. The combination of robust natural history data and the identification of sensitive biomarkers mean that we are now entering an exciting therapeutic era in the field of the genetic neuropathies.

Biomarkers predict outcome in Charcot-Marie-Tooth disease 1A

BACKGROUND

Charcot-Marie-Tooth disease type 1A (CMT1A) is the most common inherited neuropathy, a debilitating disease without known cure. Among patients with CMT1A, disease manifestation, progression and severity are strikingly variable, which poses major challenges for the development of new therapies. Hence, there is a strong need for sensitive outcome measures such as disease and progression biomarkers, which would add powerful tools to monitor therapeutic effects in CMT1A.

METHODS

We established a pan-European and American consortium comprising nine clinical centres including 311 patients with CMT1A in total. From all patients, the CMT neuropathy score and secondary outcome measures were obtained and a skin biopsy collected. In order to assess and validate disease severity and progression biomarkers, we performed qPCR on a set of 16 animal model-derived potential biomarkers in skin biopsy mRNA extracts.

RESULTS

In 266 patients with CMT1A, a cluster of eight cutaneous transcripts differentiates disease severity with a sensitivity and specificity of 90% and 76.1%, respectively. In an additional cohort of 45 patients with CMT1A, from whom a second skin biopsy was taken after 2-3 years, the cutaneous mRNA expression of GSTT2, CTSA, PPARG, CDA, ENPP1 and NRG1-Iis changing over time and correlates with disease progression.

CONCLUSIONS

In summary, we provide evidence that cutaneous transcripts in patients with CMT1A serve as disease severity and progression biomarkers and, if implemented into clinical trials, they could markedly accelerate the development of a therapy for CMT1A.

Natural history of Charcot-Marie-Tooth disease during childhood

OBJECTIVE

To determine the rate of disease progression in a longitudinal natural history study of children with Charcot-Marie-Tooth (CMT) disease.

METHODS

Two hundred six (103 female) participants aged 3 to 20 years enrolled in the Inherited Neuropathies Consortium were assessed at baseline and 2 years. Demographic, anthropometric, and diagnostic information were collected. Disease progression was assessed with the CMT Pediatric Scale (CMTPedS), a reliable Rasch-built linearly weighted disability scale evaluating fine and gross motor function, strength, sensation, and balance.

RESULTS

On average, CMTPedS Total scores progressed at a rate of 2.4 ± 4.9 over 2 years (14% change from baseline; p < 0.001). There was no difference between males and females (mean difference, 0.5; 95% confidence interval [CI], -0.9 to 1.9; p = 0.49). The most responsive CMTPedS items were dorsiflexion strength (z-score change, -0.3; 95% CI, -0.6 to -0.05; p = 0.02), balance (z-score change, -1.0; 95% CI, -1.9 to -0.09; p = 0.03), and long jump (z-score change, -0.4; 95% CI, -0.7 to -0.02; p = 0.04). Of the most common genetic subtypes, 111 participants with CMT1A/PMP22 duplication progressed by 1.8 ± 4.2 (12% change from baseline; p < 0.001), 9 participants with CMT1B/MPZ mutation progressed by 2.2 ± 5.1 (11% change), 6 participants with CMT2A/MFN2 mutation progressed by 6.2 ± 7.9 (23% change), and 7 participants with CMT4C/SH3TC2 mutations progressed by 3.0 ± 4.5 (12% change). Participants with CMT2A progressed faster than CMT1A (mean difference, -4.4; 95% CI, -8.1 to -0.8; p = 0.02). Children with CMT1A progressed consistently through early childhood (3-10 years) and adolescence (11-20 years; mean difference, 1.1; 95% CI, -0.6 to 2.7; p = 0.19), whereas CMT2A appeared to progress faster during early childhood than adolescence (mean difference, 10.0; 95% CI, -2.2 to 22.2; p = 0.08).

INTERPRETATION

Using the CMTPedS as an outcome measure of disease severity, children with CMT progress at a significant rate over 2 years. Understanding the rate at which children with CMT deteriorate is essential for adequately powering trials of disease-modifying interventions. Ann Neurol 2017;82:353-359.

Responsiveness of gait analysis parameters in a cohort of 71 CMT subjects

Detection of worsening in the slowly progressive Charcot-Marie-Tooth disease (CMT) is difficult. As previous clinical scales showed low responsiveness, novel outcome measures are under study, including innovative approaches such as quantitative muscle MRI and instrumented movement analysis. Since gait analysis proved able to reliably quantify CMT locomotor deficits, we aimed to explore whether it can be a sensitive-to-change outcome measure in CMT studies. Clinical and biomechanical evaluations were performed in 71 CMT subjects at baseline and after a mean (±sd) of 28.9 ± 9.5 months. Locomotor tasks included natural walking, ascending and descending steps. Instrumented analysis of such tasks provided indexes related to muscle strength (kinetic parameters) and joint movement (kinematic parameters). Parameter responsiveness was expressed as Standardized Response Mean (SRM). Considering the whole CMT group, several parameters showed moderate responsiveness; subgrouping subjects according to disease severity allowed reaching high responsiveness (SRM >0.80). CMT Examination Score showed moderate responsiveness (SRM 0.53) in the minimally affected group; kinematic parameters were more responsive in this group, whereas kinetic parameters in the most severely affected one. Biomechanical parameters can represent suitable outcome measures for CMT by showing moderate-to-high responsiveness. These data suggest that appropriate selection of patient population and outcome measures is crucial for clinical trials' design.

Pharmacology and drug development in rare diseases: the attractiveness and expertise of the French medical pharmacology

Developing drugs for rare disease can be challenging due to specific rare disease characteristics. The French Medical Pharmacology is structured and positioned to play a major role in orphan drug research and development due to the required expertise concentrated into pharmacology departments, exclusively implemented within the French university hospitals, public hospitals that are linked to a medical school (and often a pharmacy school) with numerous INSERM or CNRS labelled research units. In addition, these structures allow a close collaboration between researchers, academic institutions and biotech start-up (most of them being spin-off of the academic structures). Also, within university hospitals are located the clinical investigation centres, linking to the F-CRIN network and also to Inserm and hospitals, that enable care staff and researchers to be associated and clinical research protocols to be carried out on site, in full respect with ethic and regulatory aspects. As a consequence, this intra and multidisciplinary expertise offers all resource to elaborate a tailored approach for orphan drug development, in new entities as well as in repositioning. For preclinical development: drug screening, candidate selection (taking into account PK, metabolism, variability and potential toxicity) and preclinical models (iPS, animal models) that could allow a better translation to human research. For clinical development, we will mention here dose determination, safety evaluation and Orphan Drug Designation and Protocol Assistance preparation and submission. For post marketing evaluation and surveys, the pharmacovigilance, addictovigilance and pharmacoepidemiology expertise, combined with access to large databases allow a better approach to orphan drug use and safety. As outlined through two success stories (Charcot Marie Tooth, vascular Ehlers-Danlos syndrome), the added value of French Medical Pharmacology structures and expertise has been evidenced in the know-how, multidimensional and multidisciplinary approaches, allowing the development of numerous drugs that have been granted with Orphan Drug Designation and later Market Approval. Even if specific and possibly even more, the field of orphan drugs requires the respect of highest standards of safety and quality. French Medical Pharmacology intends to continue on this way and constantly improve his involvement in this field, committed to a single objective: answer the unmet medical need of patients with rare diseases.

Carpal tunnel syndrome in inherited neuropathies: A retrospective survey

INTRODUCTION

This study evaluates carpal tunnel syndrome (CTS) symptom severity, functional status, and outcome of CTS therapies in patients with inherited neuropathies.

METHODS

Validated questionnaires were used to compare symptom severity and functional status in patients with and without a diagnosis of CTS and a diagnosis of an inherited neuropathy.

RESULTS

309 patients with inherited neuropathies participated in this study. The CTS symptom severity score (SSS) was found to be the most useful tool in assessing CTS severity in patients with inherited neuropathy. Splint therapy and surgery were associated with significant improvement in carpal tunnel symptoms as measured through the SSS.

DISCUSSION

This study provides insight into the assessment of CTS symptom severity and patient-reported outcomes to CTS therapy in individuals with inherited neuropathies. The SSS appears useful for evaluation of CTS symptoms and patient-reported outcomes following CTS interventions in individuals with inherited neuropathies. Muscle Nerve 57: 388-394, 2018.

Magnetic resonance neurography and diffusion tensor imaging of the peripheral nerves in patients with Charcot-Marie-Tooth Type 1A

INTRODUCTION

Investigation of peripheral neuropathies by magnetic resonance neurography (MRN) may provide increased diagnostic accuracy when performed in combination with diffusion tensor imaging (DTI). This study seeks to evaluate DTI in the detection of neuropathic abnormalities in Charcot-Marie-Tooth type 1A (CMT1A).

METHODS

MRI of the sciatic and tibial nerves, including MRN and DTI, was prospectively performed in 15 CMT1A patients and 30 healthy controls (HCs). The following MRI parameters were evaluated and correlated with clinical and neurophysiological findings: T2-relaxation time, proton spin density (PD) and DTI (fractional anisotropy [FA] and apparent diffusion coefficient [ADC]).

RESULTS

DTI showed lower FA and higher ADC in CMT1A compared with HCs. T2 relaxation time showed no difference; however, PD of the sciatic nerve was higher in CMT1A. There were some close associations between neuropathy severity and MRN-DTI, with the closest correlation between FA and nerve conduction velocity in the sciatic nerve (r = 0.76, P < 0.01).

DISCUSSION

MRN-DTI evaluation of sciatic and tibial nerves improves the detection of nerve abnormalities in patients with CMT1A. Muscle Nerve 56: E78-E84, 2017.

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.

Novel outcome measures for Charcot-Marie-Tooth disease: validation and reliability of the 6-min walk test and StepWatch(™) Activity Monitor and identification of the walking features related to higher quality of life

BACKGROUND AND PURPOSE

Charcot-Marie-Tooth (CMT) disease is the most common inherited neuropathy, but therapeutic options have been limited to symptom management. Past pharmacological trials have failed, possibly due to insensitive outcome measures (OMs). The aim of the current study was to evaluate the validity and reliability of the 6-min walk test (6MWT) and StepWatch(™) Activity Monitoring (SAM) with other previously validated OMs in CMT disease.

METHODS

A prospective multicenter study was performed, consecutively enrolling 168 CMT patients (104 with CMT1A, 27 with CMT1B, 37 with X-linked CMT) from Italian centers specializing in CMT care.

RESULTS

Statistical analysis showed that the 6MWT was highly related with all previously used OMs. Some, but not all, SAM parameters were related to commonly used OMs but may provide more information about quality of life.

CONCLUSIONS

The current study demonstrated the validity and reliability of the 6MWT and SAM as OMs for CMT. Moreover, SAM provides data that correlate better with quality of life measures, making it useful in future rehabilitation trials.