Diagnosis and treatment of hereditary transthyretin amyloidosis with polyneuropathy in the United States: Recommendations from a panel of experts.

Hereditary transthyretin (ATTRv; v for variant) amyloidosis is a rare, multisystem, progressive, and fatal disease in which polyneuropathy is a cardinal manifestation. Due to a lack of United States (US)-specific guidance on ATTRv amyloidosis with polyneuropathy, a panel of US-based expert clinicians convened to address identification, monitoring, and treatment of this disease. ATTRv amyloidosis with polyneuropathy should be suspected in unexplained progressive neuropathy, especially if associated with systemic symptoms or family history. The diagnosis is confirmed through genetic testing, biopsy, or cardiac technetium-based scintigraphy. Treatment should be initiated as soon as possible after diagnosis, with gene-silencing therapeutics recommended as a first-line option. Consensus is lacking on what represents "disease progression" during treatment; however, the aggressive natural history of this disease should be considered when evaluating the effectiveness of any therapy.

Multicenter expanded access program for access to investigational products for amyotrophic lateral sclerosis.

INTRODUCTION/AIMS: Expanded access (EA) is a Food and Drug Administration-regulated pathway to provide access to investigational products (IPs) to individuals with serious diseases who are ineligible for clinical trials. The aim of this report is to share the design and operations of a multicenter, multidrug EA program for amyotrophic lateral sclerosis (ALS) across nine US centers. METHODS: A central coordination center was established to design and conduct the program. Templated documents and processes were developed to streamline study design, regulatory submissions, and clinical operations across protocols. The program included three protocols and provided access to IPs that were being tested in respective regimens of the HEALEY ALS Platform Trial (verdiperstat, CNM-Au8, and pridopidine). Clinical and safety data were collected in all EA protocols (EAPs). The program cohorts comprised participants who were not eligible for the platform trial, including participants at advanced stages of disease progression and with long disease duration. RESULTS: A total of 85 participants were screened across the 3 EAPs from July 2021 to September 2022. The screen failure rate was 3.5%. Enrollment for the regimens of the platform trial was completed as planned and results informed the duration of the corresponding EAP. The verdiperstat EAP was concluded in December 2022. Mean duration of participation in the verdiperstat EAP was 5.8 ± 4.1 months. The CNM-Au8 and pridopidine EAPs are ongoing. DISCUSSION: Multicenter EAPs conducted in parallel to randomized clinical trials for ALS can successfully enroll participants who do not qualify for clinical trials.

Plasma proteomic analysis on neuropathic pain in idiopathic peripheral neuropathy patients.

BACKGROUND AND AIMS: Why only half of the idiopathic peripheral neuropathy (IPN) patients develop neuropathic pain remains unknown. By conducting a proteomics analysis on IPN patients, we aimed to discover proteins and new pathways that are associated with neuropathic pain. METHODS: We conducted unbiased mass-spectrometry proteomics analysis on blood plasma from 31 IPN patients with severe neuropathic pain and 29 IPN patients with no pain, to investigate protein biomarkers and protein-protein interactions associated with neuropathic pain. Univariate modeling was done with linear mixed modeling (LMM) and corrected for multiple testing. Multivariate modeling was performed using elastic net analysis and validated with internal cross-validation and bootstrapping. RESULTS: In the univariate analysis, 73 proteins showed a p-value <.05 and 12 proteins showed a p-value <.01. None were significant after Benjamini-Hochberg adjustment for multiple testing. Elastic net analysis created a model containing 12 proteins with reasonable discriminatory power to differentiate between painful and painless IPN (false-negative rate 0.10, false-positive rate 0.18, and an area under the curve 0.75). Eight of these 12 proteins were clustered into one interaction network, significantly enriched for the complement and coagulation pathway (Benjamini-Hochberg adjusted p-value = .0057), with complement component 3 (C3) as the central node. Bootstrap validation identified insulin-like growth factor-binding protein 2 (IGFBP2), complement factor H-related protein 4 (CFHR4), and ferritin light chain (FTL), as the most discriminatory proteins of the original 12 identified. INTERPRETATION: This proteomics analysis suggests a role for the complement system in neuropathic pain in IPN.

CIDP prognosis in patients with IVIG treatment-related fluctuations.

INTRODUCTION/AIMS: Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is an acquired immune-mediated peripheral nerve disorder with variable prognosis and long-term dependence on immunotherapy. Frequent assessment of grip strength can be a useful tool to identify intravenous immunoglobulin (IVIG) treatment-related fluctuations (TRFs) and optimize IVIG treatment in real-time, but the long-term implications of TRFs are unknown. We aimed to explore the impact that real-time TRFs had on long-term CIDP prognosis, strength impairment, and disability. METHODS: This retrospective observational cohort study analyzed standard of care clinical and treatment outcomes in patients who participated in a published prospective study of intra-IVIG-cycle grip strength quantification. Patients were analyzed based upon the presence or absence of TRFs, as determined in the initial prospective study. RESULTS: Data were available for 23 CIDP patients with a mean follow-up period of 44.7 mo. There were no differences in baseline or follow-up strength, disability, or IVIG usage in patients with a low number of fluctuations compared to those with a high number of fluctuations. In both groups, drug-free remission was achieved in about one-third of patients. DISCUSSION: TRFs are important to identify in order to optimize treatment in real time, but poorly predict long-term disease activity status. The presence of minor TRFs are unlikely to result in substantial accumulation of disability over time. Periodic IVIG optimization trials using objective outcomes are encouraged in all CIDP patients receiving chronic IVIG treatment as a means to identify the lowest effective IVIG dose and frequency.

Peripheral Neuropathy Research Registry: A prospective cohort.

The Peripheral Neuropathy Research Registry (PNRR) is a prospective cohort of peripheral neuropathy (PN) patients focused on idiopathic axonal peripheral neuropathy. Patients with diabetic, human immunodeficiency virus-, and chemotherapy-induced peripheral neuropathies are enrolled as comparison groups. The PNRR is a multi-center collaboration initiated and funded by the Foundation for Peripheral Neuropathy (FPN) with the objective to recruit a well characterized cohort of patients with different phenotypes and symptoms in each diagnostic category, and to advance research through development of biomarkers and identification of previously unknown causes of PN. The overall goal of the initiative is to find disease-altering treatments and better symptom relief for patients. We present the study design, types of data collected, and characteristics of the first 1150 patients enrolled. We also discuss ongoing analyses on this dataset, including untargeted-omics methodologies.

Pyrimethamine significantly lowers cerebrospinal fluid Cu/Zn superoxide dismutase in amyotrophic lateral sclerosis patients with SOD1 mutations.

OBJECTIVE: Cu/Zn superoxide dismutase (SOD1) reduction prolongs survival in SOD1-transgenic animal models. Pyrimethamine produces dose-dependent SOD1 reduction in cell culture systems. A previous phase 1 trial showed pyrimethamine lowers SOD1 levels in leukocytes in patients with SOD1 mutations. This study investigated whether pyrimethamine lowered SOD1 levels in the cerebrospinal fluid (CSF) in patients carrying SOD1 mutations linked to familial amyotrophic lateral sclerosis (fALS/SOD1). METHODS: A multicenter (5 sites), open-label, 9-month-duration, dose-ranging study was undertaken to determine the safety and efficacy of pyrimethamine to lower SOD1 levels in the CSF in fALS/SOD1. All participants underwent 3 lumbar punctures, blood draw, clinical assessment of strength, motor function, quality of life, and adverse effect assessments. SOD1 levels were measured in erythrocytes and CSF. Pyrimethamine was measured in plasma and CSF. Appel ALS score, ALS Functional Rating Scale-Revised, and McGill Quality of Life Single-Item Scale were measured at screening, visit 6, and visit 9. RESULTS: We enrolled 32 patients; 24 completed 6 visits (18 weeks), and 21 completed all study visits. A linear mixed effects model showed a significant reduction in CSF SOD1 at visit 6 (p < 0.001) with a mean reduction of 13.5% (95% confidence interval [CI] = 8.4-18.5) and at visit 9 (p < 0.001) with a mean reduction of 10.5% (95% CI = 5.2-15.8). INTERPRETATION: Pyrimethamine is safe and well tolerated in ALS. Pyrimethamine is capable of producing a significant reduction in total CSF SOD1 protein content in patients with ALS caused by different SOD1 mutations. Further long-term studies are warranted to assess clinical efficacy. Ann Neurol 2017;81:837-848.

Sporadic and hereditary amyotrophic lateral sclerosis (ALS).

Genetic discoveries in ALS have a significant impact on deciphering molecular mechanisms of motor neuron degeneration. The identification of SOD1 as the first genetic cause of ALS led to the engineering of the SOD1 mouse, the backbone of ALS research, and set the stage for future genetic breakthroughs. In addition, careful analysis of ALS pathology added valuable pieces to the ALS puzzle. From this joint effort, major pathogenic pathways emerged. Whereas the study of TDP43, FUS and C9ORF72 pointed to the possible involvement of RNA biology in motor neuron survival, recent work on P62 and UBQLN2 refocused research on protein degradation pathways. Despite all these efforts, the etiology of most cases of sporadic ALS remains elusive. Newly acquired genomic tools now allow the identification of genetic and epigenetic factors that can either increase ALS risk or modulate disease phenotype. These developments will certainly allow for better disease modeling to identify novel therapeutic targets for ALS. This article is part of a Special Issue entitled: Neuromuscular Diseases: Pathology and Molecular Pathogenesis.

Molecular mechanisms and animal models of spinal muscular atrophy.

Spinal muscular atrophy (SMA), the leading genetic cause of infant mortality, is characterized by the degeneration of spinal motor neurons and muscle atrophy. Although the genetic cause of SMA has been mapped to the Survival Motor Neuron1 (SMN1) gene, mechanisms underlying selective motor neuron degeneration in SMA remain largely unknown. Here we review the latest developments and our current understanding of the molecular mechanisms underlying SMA pathogenesis, focusing on the animal model systems that have been developed, as well as new diagnostic and treatment strategies that have been identified using these model systems. This article is part of a special issue entitled: Neuromuscular Diseases: Pathology and Molecular Pathogenesis.

Mutation in the novel nuclear-encoded mitochondrial protein CHCHD10 in a family with autosomal dominant mitochondrial myopathy.

Mitochondrial myopathies belong to a larger group of systemic diseases caused by morphological or biochemical abnormalities of mitochondria. Mitochondrial disorders can be caused by mutations in either the mitochondrial or nuclear genome. Only 5% of all mitochondrial disorders are autosomal dominant. We analyzed DNA from members of the previously reported Puerto Rican kindred with an autosomal dominant mitochondrial myopathy (Heimann-Patterson et al. 1997). Linkage analysis suggested a putative locus on the pericentric region of the long arm of chromosome 22 (22q11). Using the tools of integrative genomics, we established chromosome 22 open reading frame 16 (C22orf16) (later designated as CHCHD10) as the only high-scoring mitochondrial candidate gene in our minimal candidate region. Sequence analysis revealed a double-missense mutation (R15S and G58R) in cis in CHCHD10 which encodes a coiled coil-helix-coiled coil-helix protein of unknown function. These two mutations completely co-segregated with the disease phenotype and were absent in 1,481 Caucasian and 80 Hispanic (including 32 Puerto Rican) controls. Expression profiling showed that CHCHD10 is enriched in skeletal muscle. Mitochondrial localization of the CHCHD10 protein was confirmed using immunofluorescence in cells expressing either wild-type or mutant CHCHD10. We found that the expression of the G58R, but not the R15S, mutation induced mitochondrial fragmentation. Our findings identify a novel gene causing mitochondrial myopathy, thereby expanding the spectrum of mitochondrial myopathies caused by nuclear genes. Our findings also suggest a role for CHCHD10 in the morphologic remodeling of the mitochondria.

Phase 1/2 open-label dose-escalation study of plasmid DNA expressing two isoforms of hepatocyte growth factor in patients with painful diabetic peripheral neuropathy.

This study aimed to evaluate the safety and preliminary efficacy of intramuscular injections of plasmid DNA (VM202) expressing two isoforms of hepatocyte growth factor (HGF) in subjects with painful diabetic peripheral neuropathy (PDPN). Twelve patients in three cohorts (4, 8, and 16 mg) received two sets of VM202 injections separated by two weeks. Safety and tolerability were evaluated and the visual analog scale (VAS), the short form McGill questionnaire (SF-MPQ), and the brief pain inventory for patients with diabetic peripheral neuropathy (BPI-DPN) measured pain level throughout 12 months after treatment. No serious adverse events (AEs) were observed. The mean VAS was reduced from baseline by 47.2% (P = 0.002) at 6 months and by 44.1% (P = 0.005) at 12 months after treatment. The VAS scores for the 4, 8, and 16 mg dose cohorts at 6 months follow-up decreased in a dose-responsive manner, by 21% (P = 0.971), 53% (P = 0.014), and 62% (P = 0.001), respectively. The results with the BPI-DPN and SF-MPQ showed patterns similar to the VAS scores. In conclusion, VM202 treatment appeared to be safe, well tolerated, and sufficient to provide long term symptomatic relief and improvement in the quality of life in patients with PDPN.

Serum protein and imaging biomarkers after intermittent steroid treatment in muscular dystrophy.

Background: Weekly Steroids in Muscular Dystrophy (WSiMD) was a pilot study to evaluate once weekly prednisone in patients with Limb Girdle and Becker muscular dystrophy (LGMD and BMD, respectively). At study endpoint, there were trends towards increased lean mass, reduced fat mass, reduced creatine kinase and improved motor function. The investigation was motivated by studies in mouse muscular dystrophy models in which once weekly glucocorticoid exposure enhanced muscle strength and reduced fibrosis. Methods: WSiMD participants provided blood samples for aptamer serum profiling at baseline and after 6 months of weekly steroids. A subset completed magnetic resonance (MR) evaluation of muscle at study onset and endpoint. Results/Conclusions: At baseline compared to age and sex-matched healthy controls, the aggregate serum protein profile in the WSiMD cohort was dominated by muscle proteins, reflecting leak of muscle proteins into serum. Disease status produced more proteins differentially present in serum compared to steroid-treatment effect. Nonetheless, a response to prednisone was discernable in the WSiMD cohort, even at this low dose. Glucocorticoids downregulated muscle proteins and upregulated certain immune process- and matrix-associated proteins. Muscle MR fat fraction showed trends with functional status. The prednisone-responsive markers could be used in larger trial of prednisone efficacy.

Impact of Vutrisiran on Quality of Life and Physical Function in Patients with Hereditary Transthyretin-Mediated Amyloidosis with Polyneuropathy.

INTRODUCTION: Hereditary transthyretin (ATTRv; v for variant) amyloidosis, also known as hATTR amyloidosis, is a progressive and fatal disease associated with rapid deterioration of physical function and patients' quality of life (QOL). Vutrisiran, a subcutaneously administered RNA interference (RNAi) therapeutic that reduces hepatic production of transthyretin, was assessed in patients with ATTRv amyloidosis with polyneuropathy in the pivotal HELIOS-A study. METHODS: The phase 3 open-label HELIOS-A study investigated the efficacy and safety of vutrisiran in patients with ATTRv amyloidosis with polyneuropathy, compared with an external placebo group from the APOLLO study of the RNAi therapeutic patisiran. Measures of QOL and physical function were assessed. RESULTS: At month 18, vutrisiran improved Norfolk Quality of Life-Diabetic Neuropathy (Norfolk QOL-DN) total score (least squares mean difference [LSMD] in change from baseline [CFB]: -21.0; p = 1.84 × 10-10) and Norfolk QOL-DN domain scores, compared with external placebo. This benefit relative to external placebo was evident across all baseline polyneuropathy disability (PND) scores and most pronounced in patients with baseline PND scores I-II. Compared with external placebo, vutrisiran also demonstrated benefit in EuroQoL-Visual Analog Scale (EQ-VAS) score (LSMD in CFB: 13.7; nominal p = 2.21 × 10-7), 10-m walk test (LSMD in CFB: 0.239 m/s; p = 1.21 × 10-7), Rasch-built Overall Disability Score (LSMD in CFB: 8.4; p = 3.54 × 10-15), and modified body mass index (mBMI) (LSMD in CFB: 140.7; p = 4.16 × 10-15) at month 18. Overall, Norfolk QOL-DN, EQ-VAS, and mBMI improved from pretreatment baseline with vutrisiran, whereas all measures worsened from baseline in the external placebo group. At month 18, Karnofsky Performance Status was stable/improved from baseline in 58.2/13.1% with vutrisiran versus 34.7/8.1% with external placebo. CONCLUSION: Vutrisiran treatment provided significant clinical benefits in multiple measures of QOL and physical function in patients with ATTRv amyloidosis with polyneuropathy. Benefits were most pronounced in patients with earlier-stage disease, highlighting the importance of early diagnosis and treatment. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov: NCT03759379.

The natural history of ALS: Baseline characteristics from a multicenter clinical cohort.

BACKGROUND: Amyotrophic lateral sclerosis (ALS) is a rare disease with urgent need for improved treatment. Despite the acceleration of research in recent years, there is a need to understand the full natural history of the disease. As only 40% of people living with ALS are eligible for typical clinical trials, clinical trial datasets may not generalize to the full ALS population. While biomarker and cohort studies have more generous inclusion criteria, these too may not represent the full range of phenotypes, particularly if the burden for participation is high. To permit a complete understanding of the heterogeneity of ALS, comprehensive data on the full range of people with ALS is needed. METHODS: The ALS Natural History Consortium (ALS NHC) consists of nine ALS clinics and was created to build a comprehensive dataset reflective of the ALS population. At each clinic, most patients are asked to participate and about 95% do. After obtaining consent, a minimum dataset is abstracted from each participant's electronic health record. Participant burden is therefore minimal. RESULTS: Data on 1925 ALS patients were submitted as of 9 December 2022. ALS NHC participants were more heterogeneous relative to anonymized clinical trial data from the Pooled Resource Open-Access ALS Clinical Trials (PRO-ACT) database. The ALS NHC includes ALS patients of older age of onset and a broader distribution of El Escorial categories, than the PRO-ACT database. CONCLUSIONS: ALS NHC participants had a higher diversity of diagnostic and demographic data compared to ALS clinical trial participants.Key MessagesWhat is already known on this topic: Current knowledge of the natural history of ALS derives largely from regional and national registries that have broad representation of the population of people living with ALS but do not always collect covariates and clinical outcomes. Clinical studies with rich datasets of participant characteristics and validated clinical outcomes have stricter inclusion and exclusion criteria that may not be generalizable to the full ALS population.What this study adds: To bridge this gap, we collected baseline characteristics for a sample of the population of people living with ALS seen at a consortium of ALS clinics that collect extensive, pre-specified participant-level data, including validated outcome measures.How this study might affect research, practice, or policy: A clinic-based longitudinal dataset can improve our understanding of the natural history of ALS and can be used to inform the design and analysis of clinical trials and health economics studies, to help the prediction of clinical course, to find matched controls for open label extension trials and expanded access protocols, and to document real-world evidence of the impact of novel treatments and changes in care practice.

Primary lateral sclerosis natural history study - planning, designing, and early enrollment.

Introduction/Aims. Primary lateral sclerosis (PLS) is exceedingly rare and has been an enigmatic disease. Recent progress has drastically changed this perception, with early biomarkers being investigated and potential medications for PLS emerging at the preclinical stage. The aim of this paper is to describe a study of PLS natural history and discuss the limitations and proposed solutions to the study of a rare and slowly progressive disease. Methods. The PLS Natural History Study is a 30-site, 24-month, prospective study that is supported by multiple funding sources. The study aims to enroll 50 early PLS (disease duration ≤4 years) and 50 definite PLS (disease duration 4 to 15 years) participants using modified PLS Diagnostic Criteria. Smartphone-based assessments including semi-quantitative and quantitative measures and patient-reported outcomes are utilized. In-person quantitative measures are also completed during site visits. The change in the PLS Functional Rating Scale score is the primary outcome. The study utilizes the NeuroBANK® patient-centric data capture and management platform. The biostatistical analysis plan has been developed. Results. In one year, 28 participants have been recruited. Enrollment has been much slower than anticipated due to the COVID-19 pandemic, the rarity of PLS, and potential study competition for internal resources from ALS clinical trials. Discussion. We discuss the need for more innovative methods to enroll and study individuals with such rare diseases and propose a number of mechanisms by which more efficient enrollment could be facilitated.

An Open Label Exploratory Clinical Trial Evaluating Safety and Tolerability of Once-Weekly Prednisone in Becker and Limb-Girdle Muscular Dystrophy.

BACKGROUND: Glucocorticoid steroids are standard of care in Duchenne Muscular Dystrophy (DMD) to slow disease course. Use of glucocorticoids in other muscular dystrophies, including Becker (BMD) and Limb Girdle (LGMD), has been less explored. Recently, preclinical studies conducted in DMD and LGMD mouse models showed once-weekly prednisone was associated with improved muscle performance without activation of muscle atrophy genes. OBJECTIVE: To determine safety and tolerability of once-weekly prednisone in patients with LGMD and BMD. METHODS: We conducted an open label, exploratory single center study of of once-weekly prednisone at 0.75-1 mg/Kg in LGMD (n = 19) and BMD (n = 1) (mean age 35, range 18-60). The LGMD participants represented multiple different LGMD subtypes, and the study included ambulatory and non-ambulatory participants. Participants were assessed at baseline and 24 weeks for vital signs, blood biomarkers, and for patient-reported side effects. As secondary endpoints, functional muscle testing and body composition were measured. RESULTS: Over the 24-week study, there were no significant changes in blood pressure, HgbA1C, or lipid profiles. We observed a reduction in serum creatine kinase over the study interval. Whole body DEXA scanning suggested a possible increase in lean mass and a reduction in adiposity. Functional measures suggested trends in improved muscle performance. CONCLUSIONS: In this single center, open label pilot study, once-weekly prednisone was safe and well tolerated. Additional investigation of once-weekly prednisone in a larger cohort and for a longer period of time is warranted.

Real-world Adherence to Nusinersen in Adults with Spinal Muscular Atrophy in the US: A Multi-site Chart Review Study.

Limited evidence exists on real-world adherence to nusinersen for the treatment of spinal muscular atrophy (SMA). Data are presented from a multi-site retrospective chart review of 86 adults with SMA initiating nusinersen at nine US centers between January 2017 and February 2019. Seventy-nine (92%) adults remained on nusinersen during the study; 454 (92%) of 493 total nusinersen doses were received on time. Fifty-eight (67%) adults received all nusinersen doses on time. The majority of patients with at least one nonadherent dose resumed nusinersen on time. Most patients followed the dosing schedule across the loading and maintenance dose periods.

FUS-immunoreactive inclusions are a common feature in sporadic and non-SOD1 familial amyotrophic lateral sclerosis.

OBJECTIVE: Amyotrophic lateral sclerosis (ALS) is a fatal disorder of motor neuron degeneration. Most cases of ALS are sporadic (SALS), but about 5 to 10% of ALS cases are familial (FALS). Recent studies have shown that mutations in FUS are causal in approximately 4 to 5% of FALS and some apparent SALS cases. The pathogenic mechanism of the mutant FUS-mediated ALS and potential roles of FUS in non-FUS ALS remain to be investigated. METHODS: Immunostaining was performed on postmortem spinal cords from 78 ALS cases, including SALS (n = 52), ALS with dementia (ALS/dementia, n = 10), and FALS (n = 16). In addition, postmortem brains or spinal cords from 22 cases with or without frontotemporal lobar degeneration were also studied. In total, 100 cases were studied. RESULTS: FUS-immunoreactive inclusions were observed in spinal anterior horn neurons in all SALS and FALS cases, except for those with SOD1 mutations. The FUS-containing inclusions were also immunoreactive with antibodies to TDP43, p62, and ubiquitin. A fraction of tested FUS antibodies recognized FUS inclusions, and specific antigen retrieval protocol appeared to be important for detection of the skein-like FUS inclusions. INTERPRETATION: Although mutations in FUS account for only a small fraction of FALS and SALS, our data suggest that FUS protein may be a common component of the cellular inclusions in non-SOD1 ALS and some other neurodegenerative conditions, implying a shared pathogenic pathway underlying SALS, non-SOD1 FALS, ALS/dementia, and related disorders. Our data also indicate that SOD1-linked ALS may have a pathogenic pathway distinct from SALS and other types of FALS.

Recent advances in the genetics of hereditary axonal sensory-motor neuropathies type 2.

Hereditary axonal motor and sensory neuropathies or Charcot-Marie-Tooth disease type 2 (CMT2) are characterized clinically by distal muscle weakness and atrophy, sensory loss, and foot deformities. Conduction velocities are usually in the normal range or mildly slowed. The majority of CMT2 are autosomal-dominant but autosomal-recessive forms have been described. The number of genes associated with CMT2 have significantly increased in the past decade, with the gene causing CMT2C/SPSMA being the last one discovered. More than 10 genes are now associated with different subtypes of CMT2, which are classified from CMT2A to CMT2N. These genes have distinct functions, but some appear to be involved in common biological pathways, therefore, providing important clues for understanding the pathogenic mechanism of these heterogeneous disorders.

The accuracy of needle electrode placement by trainees in selected forearm muscles using verification by neuromuscular ultrasound.

INTRODUCTION: Anatomic landmarks alone may not always be sufficient to accurately guide electromyography (EMG) electrode needle placement. METHODS: Senior residents and fellows (n = 11) targeted 4 forearm muscles with anatomic landmarks alone versus with audiovisual EMG feedback. Accuracy of EMG needle placement was verified using neuromuscular ultrasound imaging. RESULTS: While relatively large and superficial FCR muscle was sampled at a rate of 100% with and without audiovisual EMG feedback, accuracy of deeper and/or smaller forearm muscles (FPL, EIP, and SUP) diminished significantly without audiovisual EMG feedback. DISCUSSION: Our study suggests that in clinical scenarios in which an electrodiagnostician relies on anatomic landmarks alone to target small and deep muscles, the risk of misplacement of needle electrode is increased. Consideration for neuromuscular ultrasound to augment training and/or real time guidance in EMG practice may be appropriate.