-
BioRxiv : the Preprint Server For... Jun 2024Pain is a prominent and debilitating symptom in myotonic disorders, yet its physiological mechanisms remain poorly understood. This study assessed preclinical pain-like...
Pain is a prominent and debilitating symptom in myotonic disorders, yet its physiological mechanisms remain poorly understood. This study assessed preclinical pain-like behavior in murine models of pharmacologically induced myotonia and myotonic dystrophy type 1 (DM1). In both myotonia congenita and DM1, impairment of the gene, which encodes skeletal muscle voltage-gated CLC-1 chloride channels, reduces chloride ion conductance in skeletal muscle cells, leading to prolonged muscle excitability and delayed relaxation after contraction. We used the CLC-1 antagonist anthracene-9- carboxylic acid (9-AC) at intraperitoneal doses of 30 or 60 mg/kg and HSA LR20b DM1 mice to model CLC-1-induced myotonia. Our experimental approach included pain behavioral testing, calcium imaging, and whole-cell current-clamp electrophysiology in mouse dorsal root ganglion (DRG) neurons. A single injection of 9-AC induced myotonia in mice, which persisted for several hours and resulted in long-lasting allodynic pain-like behavior. Similarly, HSA LR20b mice exhibited both allodynia and hyperalgesia. Despite these pain-like behaviors, DRG neurons did not show signs of hyperexcitability in either myotonic model. These findings suggest that myotonia induces nociplastic pain-like behavior in preclinical rodents, likely through central sensitization mechanisms rather than peripheral sensitization. This study provides insights into the pathophysiology of pain in myotonic disorders and highlights the potential of using myotonic mouse models to explore pain mechanisms and assess novel analgesics. Future research should focus on the central mechanisms involved in myotonia-induced pain and develop targeted therapies to alleviate this significant clinical burden.
PubMed: 38948724
DOI: 10.1101/2024.06.19.599732 -
European Journal of Human Genetics :... Mar 2016SCN5A mutations involving the α-subunit of the cardiac voltage-gated muscle sodium channel (NaV1.5) result in different cardiac channelopathies with an...
SCN5A mutations involving the α-subunit of the cardiac voltage-gated muscle sodium channel (NaV1.5) result in different cardiac channelopathies with an autosomal-dominant inheritance such as Brugada syndrome. On the other hand, mutations in SCN4A encoding the α-subunit of the skeletal voltage-gated sodium channel (NaV1.4) cause non-dystrophic myotonia and/or periodic paralysis. In this study, we investigated whether cardiac arrhythmias or channelopathies such as Brugada syndrome can be part of the clinical phenotype associated with SCN4A variants and whether patients with Brugada syndrome present with non-dystrophic myotonia or periodic paralysis and related gene mutations. We therefore screened seven families with different SCN4A variants and non-dystrophic myotonia phenotypes for Brugada syndrome and performed a neurological, neurophysiological and genetic work-up in 107 Brugada families. In the families with an SCN4A-associated non-dystrophic myotonia, three patients had a clinical diagnosis of Brugada syndrome, whereas we found a remarkably high prevalence of myotonic features involving different genes in the families with Brugada syndrome. One Brugada family carried an SCN4A variant that is predicted to probably affect function, one family suffered from a not genetically confirmed non-dystrophic myotonia, one family was diagnosed with myotonic dystrophy (DMPK gene) and one family had a Thomsen disease myotonia congenita (CLCN1 variant that affects function). Our findings and data suggest a possible involvement of SCN4A variants in the pathophysiological mechanism underlying the development of a spontaneous or drug-induced type 1 electrocardiographic pattern and the occurrence of malignant arrhythmias in some patients with Brugada syndrome.
Topics: Adult; Aged; Brugada Syndrome; Channelopathies; Electrocardiography; Electromyography; Female; Genetic Predisposition to Disease; Genetic Testing; Humans; Male; Middle Aged; Muscle, Skeletal; Mutation; Myocardium; NAV1.4 Voltage-Gated Sodium Channel; Phenotype; Ultrasonography
PubMed: 26036855
DOI: 10.1038/ejhg.2015.125 -
The Journal of Clinical Investigation Aug 2023BACKGROUNDFXLEARN, the first-ever large multisite trial of effects of disease-targeted pharmacotherapy on learning, was designed to explore a paradigm for measuring... (Randomized Controlled Trial)
Randomized Controlled Trial
BACKGROUNDFXLEARN, the first-ever large multisite trial of effects of disease-targeted pharmacotherapy on learning, was designed to explore a paradigm for measuring effects of mechanism-targeted treatment in fragile X syndrome (FXS). In FXLEARN, the effects of metabotropic glutamate receptor type 5 (mGluR5) negative allosteric modulator (NAM) AFQ056 on language learning were evaluated in 3- to 6-year-old children with FXS, expected to have more learning plasticity than adults, for whom prior trials of mGluR5 NAMs have failed.METHODSAfter a 4-month single-blind placebo lead-in, participants were randomized 1:1 to AFQ056 or placebo, with 2 months of dose optimization to the maximum tolerated dose, then 6 months of treatment during which a language-learning intervention was implemented for both groups. The primary outcome was a centrally scored videotaped communication measure, the Weighted Communication Scale (WCS). Secondary outcomes were objective performance-based and parent-reported cognitive and language measures.RESULTSFXLEARN enrolled 110 participants, randomized 99, and had 91 who completed the placebo-controlled period. Although both groups made language progress and there were no safety issues, the change in WCS score during the placebo-controlled period was not significantly different between the AFQ056 and placebo-treated groups, nor were there any significant between-group differences in change in any secondary measures.CONCLUSIONDespite the large body of evidence supporting use of mGluR5 NAMs in animal models of FXS, this study suggests that this mechanism of action does not translate into benefit for the human FXS population and that better strategies are needed to determine which mechanisms will translate from preclinical models to humans in genetic neurodevelopmental disorders.TRIAL REGISTRATIONClincalTrials.gov NCT02920892.FUNDING SOURCESNeuroNEXT network NIH grants U01NS096767, U24NS107200, U24NS107209, U01NS077323, U24NS107183, U24NS107168, U24NS107128, U24NS107199, U24NS107198, U24NS107166, U10NS077368, U01NS077366, U24NS107205, U01NS077179, and U01NS077352; NIH grant P50HD103526; and Novartis IIT grant AFQ056X2201T for provision of AFQ056.
Topics: Adult; Animals; Child; Humans; Fragile X Syndrome; Single-Blind Method; Learning; Language; Cleft Palate; Indoles; Malignant Hyperthermia; Myotonia Congenita
PubMed: 37651202
DOI: 10.1172/JCI171723 -
Pediatric Neurology Mar 2020Congenital myopathy is a heterogeneous group of muscle disorders characterized by muscle weakness and hypotonia. This condition is associated with a range of skeletal,... (Review)
Review
Congenital myopathy is a heterogeneous group of muscle disorders characterized by muscle weakness and hypotonia. This condition is associated with a range of skeletal, respiratory, and ophthalmologic complications and requires a multidisciplinary therapeutic approach aimed at maximizing the function and independence of patients. One promising direction for therapeutic intervention is physical exercise rehabilitation, given its demonstrated ability to promote muscle and bone health of patients with a variety of neuromuscular conditions. However, there are few data to assist health care professionals identify the optimal physical activity levels and exercise type, including the intensity, frequency, and duration. This lack of empirical evidence is particularly problematic given the fact that inappropriate exercise modes can potentially cause muscle damage in patients with congenital myopathy. In this article, we discuss the rationale behind the incorporation of two types of physical exercises, strength and aerobic training, into the clinical care of patients with congenital myopathy. Given the paucity of literature on the management of congenital myopathy, we review the results of published research on the treatment of both congenital myopathy and other neuromuscular diseases that could provide helpful insights into the physical rehabilitation of patients with congenital myopathy. We also discuss the potential benefits of vibration therapy, which has been studied in patients with other neuromuscular disorders over the last two decades. We conclude by proposing directions for future research on physical rehabilitation of patients with congenital myopathy.
Topics: Exercise Therapy; Humans; Myotonia Congenita; Vibration
PubMed: 31926608
DOI: 10.1016/j.pediatrneurol.2019.10.008 -
Medeniyet Medical Journal 2019Myotonia Congenita (MC) is a hereditary neuromuscular disorder caused by a mutation in chloride voltage-gated channel 1 (CLCN1) gene. The incidence of MC is estimated as...
OBJECTIVE
Myotonia Congenita (MC) is a hereditary neuromuscular disorder caused by a mutation in chloride voltage-gated channel 1 (CLCN1) gene. The incidence of MC is estimated as 1 in 100.000. The absence of left main coronary artery (LMCA) is a rare coronary anomaly. Here we present a family with four members who have MC variation carrier and cardiovascular risk.
METHOD
The demographic features, laboratory findings, anthropometric measurements and cardiological examination of the cases were recorded. In addition, CLCN1 gene was sequenced by NGS (Next Generation Sequencing Method) and possible causes of inherited thrombophilia risk including MTHFR (A1298C), Factor V Leiden (G1691A), Factor II (G20210A), MTHFR (C677T), Factor V Cambridge (G1091C), plasminogen activator inhibitor 1 (PAI-1) 4G/5G, APOE, APOB, ITGB, ACE (ins/del), FVHR2 and FGB gene alterations were evaluated.
RESULTS
Case 1 had homozygous c.1886T>C (p.Leu629Pro) alteration in CLCN1 gene and also coronary artery disease, myocardial infarction (MI) history, hyperlipidemia, primary hypertension, vertigo, lomber disc herniation and hearing loss. LMCA was not detected in coronary angiography in Case 1. Cases 2, 3 and 4 had heterozygous c.1886T>C (p.Leu629Pro) alteration with normal electrocardiographic and echocardiographic findings. Additionally, all of family members had genetic risk factors for the related gene, which lead to an increased risk of cardiovascular disease.
CONCLUSION
Since alteration of chloride channels in cardiomyocytes leads to variable myocardial involvement, cases with MC should be regularly followed for cardiovascular risk. Moreover, the cases with MC and with genetic profile associated with high cardiovascular risk should also be regularly followed up by cardiologists.
PubMed: 32821464
DOI: 10.5222/MMJ.2019.93357 -
Neurology Aug 2017To determine open-label, pilot study whether ranolazine could improve signs and symptoms of myotonia and muscle stiffness in patients with myotonia congenita (MC). (Clinical Trial)
Clinical Trial
OBJECTIVE
To determine open-label, pilot study whether ranolazine could improve signs and symptoms of myotonia and muscle stiffness in patients with myotonia congenita (MC).
METHODS
Thirteen participants were assessed at baseline and 2, 4, and 5 weeks. Ranolazine was started after baseline assessment (500 mg twice daily), increased as tolerated after week 2 (1,000 mg twice daily), and maintained until week 4. Outcomes included change from baseline to week 4 in self-reported severity of symptoms (stiffness, weakness, and pain), Timed Up and Go (TUG), hand grip and eyelid myotonia, and myotonia on EMG.
RESULTS
Self-reported severity of stiffness ( < 0.0001) and weakness ( < 0.01) was significantly improved compared with baseline. TUG and grip myotonia times were reduced ( = 0.03, = 0.01). EMG of the abductor digiti minimi and tibialis anterior showed significantly reduced myotonia duration ( < 0.001, < 0.01) at week 4. No participant discontinued ranolazine because of side effects.
CONCLUSIONS
Ranolazine appeared to be well tolerated over a period of 4 weeks in individuals with MC, and ranolazine resulted in improvement of signs and symptoms of muscle stiffness. The findings of this study suggest that ranolazine should be investigated in a larger controlled study.
CLASSIFICATION OF EVIDENCE
This study provides Class IV evidence that ranolazine improves myotonia in myotonia congenita.
Topics: Adolescent; Adult; Aged; Cardiovascular Agents; Electromyography; Female; Follow-Up Studies; Hand Strength; Humans; Male; Middle Aged; Myotonia Congenita; Pilot Projects; Ranolazine; Self Report; Severity of Illness Index; Treatment Outcome; Young Adult
PubMed: 28710329
DOI: 10.1212/WNL.0000000000004229 -
Experimental Neurology May 2019Patients with myotonia congenita suffer from muscle stiffness caused by muscle hyperexcitability. Although loss-of-function mutations in the ClC-1 muscle chloride...
Patients with myotonia congenita suffer from muscle stiffness caused by muscle hyperexcitability. Although loss-of-function mutations in the ClC-1 muscle chloride channel have been known for 25 years to cause myotonia congenita, this discovery has led to little progress on development of therapy. Currently, treatment is primarily focused on reducing hyperexcitability by blocking Na current. However, other approaches such as increasing K currents might also be effective. For example, the K channel activator retigabine, which opens KCNQ channels, is effective in treating epilepsy because it causes hyperpolarization of the resting membrane potential in neurons. In this study, we found that retigabine greatly reduced the duration of myotonia in vitro. Detailed study of its mechanism of action revealed that retigabine had no effect on any of the traditional measures of muscle excitability such as resting potential, input resistance or the properties of single action potentials. Instead it appears to shorten myotonia by activating K current during trains of action potentials. Retigabine also greatly reduced the severity of myotonia in vivo, which was measured using a muscle force transducer. Despite its efficacy in vivo, retigabine did not improve motor performance of mice with myotonia congenita. There are a number of potential explanations for the lack of motor improvement in vivo including central nervous system side effects. Nonetheless, the striking effectiveness of retigabine on muscle itself suggests that activating potassium currents is an effective method to treat disorders of muscle hyperexcitability.
Topics: Action Potentials; Animals; Behavior, Animal; Carbamates; Chloride Channels; In Vitro Techniques; KCNQ Potassium Channels; Membrane Potentials; Membrane Transport Modulators; Mice; Muscle Contraction; Muscle, Skeletal; Myotonia Congenita; Phenylenediamines; Psychomotor Performance
PubMed: 30738808
DOI: 10.1016/j.expneurol.2019.02.002 -
Neuromuscular Disorders : NMD Sep 2021Skeletal muscle sodium channelopathies due to SCN4A gene mutations have a broad clinical spectrum. However, each phenotype has been reported in few cases of Chinese...
Skeletal muscle sodium channelopathies due to SCN4A gene mutations have a broad clinical spectrum. However, each phenotype has been reported in few cases of Chinese origin. We present detailed phenotype and genotype data from a cohort of 40 cases with SCN4A gene mutations seen in neuromuscular diagnostic service in Huashan hospital, Fudan University. Cases were referred from 6 independent provinces from 2010 to 2018. A questionnaire covering demographics, precipitating factors, episodes of paralysis and myotonia was designed to collect the clinical information. Electrodiagnostic studies and muscle MRI were retrospectively analyzed. The clinical spectrum of patients included: 6 Hyperkalemic periodic paralysis (15%), 18 Hypokalemic periodic paralysis (45%), 7 sodium channel myotonia (17.5%), 4 paramyotonia congenita (10%) and 5 heterozygous asymptomatic mutation carriers (12.5%). Review of clinical information highlights a significant delay to diagnosis (median 15 years), reports of pain and myalgia in the majority of patients, male predominance, circadian rhythm and common precipitating factors. Electrodiagnostic studies revealed subclinical myotonic discharges and a positive long exercise test in asymptomatic carriers. Muscle MRI identified edema and fatty infiltration in gastrocnemius and soleus. A total of 13 reported and 2 novel SCN4A mutations were identified with most variants distributed in the transmembrane helix S4 to S6, with a hotspot mutation p.Arg675Gln accounting for 32.5% (13/40) of the cohort. Our study revealed a higher proportion of periodic paralysis in SCN4A-mutated patients compared with cohorts from England and the Netherlands. It also highlights the importance of electrodiagnostic studies in diagnosis and segregation studies.
Topics: Adult; Asian People; Channelopathies; China; Cohort Studies; Electromyography; Female; Genotype; Humans; Male; Mutation; Myotonia; Myotonic Disorders; NAV1.4 Voltage-Gated Sodium Channel; Paralyses, Familial Periodic; Pedigree; Phenotype; Retrospective Studies; Surveys and Questionnaires; Young Adult
PubMed: 33965302
DOI: 10.1016/j.nmd.2021.03.014 -
Journal of Child Neurology Sep 2015We retrospectively reviewed 2030 childhood electromyograms performed over an 11-year period (2004-2014). Twenty children (1%) with myotonic discharges were identified...
We retrospectively reviewed 2030 childhood electromyograms performed over an 11-year period (2004-2014). Twenty children (1%) with myotonic discharges were identified and placed into 2 groups. Group A (electrical and clinical myotonia) comprised 9 children (8 with myotonia congenita and 1 with paramyotonia congenita); all of them had diffuse myotonic discharges without clinical weakness or elevated creatine kinase. Group B (electrical myotonia without clinical myotonia) comprised 11 children (4 with inflammatory myopathy; 3, congenital myopathy, 3, muscular dystrophy; and 1, congenital muscular dystrophy). Clinical weakness was demonstrated in all of them and elevated creatine kinase in 6; all had a myopathic electromyogram and scattered myotonic discharges. We conclude that myotonic discharges are a rare but characteristic spontaneous discharge identified during electrodiagnostic studies in children. The presence of electrical and clinical myotonia provides helpful clues to differentiate between various muscle disorders in children.
Topics: Adolescent; Child; Child, Preschool; Creatine Kinase; Diagnosis, Differential; Electromyography; Female; Humans; Male; Muscle, Skeletal; Muscular Diseases; Myotonia; Neural Conduction; Retrospective Studies
PubMed: 25637645
DOI: 10.1177/0883073814559646 -
Current Opinion in Neurology Oct 2014This article reviews recent advances in clinical, genetic, diagnostic and pathophysiological aspects of the skeletal muscle channelopathies. (Review)
Review
PURPOSE OF REVIEW
This article reviews recent advances in clinical, genetic, diagnostic and pathophysiological aspects of the skeletal muscle channelopathies.
RECENT FINDINGS
Genetic advances include the use of the minigene assay to confirm pathogenicity of splice site mutations of CLC-1 chloride channels and a new gene association for Andersen-Tawil syndrome. Mutations causing a gating pore current have been established as a pathomechanism for hypokalaemic periodic paralysis. Mutations in nonchannel genes, including the mitochondrial mATP6/8 genes, have been linked to channelopathy-like episodic weakness. Advances in diagnostic tools include the use of MRI and muscle velocity recovery cycles to evaluate myotonia congenita patients. Specific neonatal presentations of sodium channel myotonia are now well documented. An international multicentre placebo-controlled randomized clinical trial established that mexiletine is an effective therapy in the nondystrophic myotonias. This is the first evidence-based treatment for a skeletal muscle channelopathy. Recent evidence in mouse models indicated that bumetanide can prevent attacks of hypokalaemic periodic paralysis, but this has not yet been tested in patient trials.
SUMMARY
Advances in genetic, clinical, diagnostic and pathomechanistic understanding of skeletal muscle channelopathies are being translated into improved therapies. Mexiletine is the first evidence-based treatment for nondystrophic myotonias. Bumetanide is effective in preventing attacks in mouse models of hypokalaemic periodic paralysis and now needs to be tested in patients.
Topics: Animals; Antigens, Neoplasm; Channelopathies; Disease Models, Animal; Humans; Membrane Transport Proteins; Muscular Diseases; Mutation
PubMed: 25188014
DOI: 10.1097/WCO.0000000000000127