BACKGROUND: The rare nature of dystrophic and non-dystrophic myotonia has limited the available evidence on the efficacy of mexiletine as a potential treatment. To address this gap, we conducted a systematic review and meta-analysis to evaluate the effectiveness and safety of mexiletine for both dystrophic and non-dystrophic myotonic patients.
METHODS: The search was conducted on various electronic databases up to March 2023, for randomized clinical trials (RCTs) comparing mexiletine versus placebo in myotonic patients. A risk of bias assessment was carried out, and relevant data was extracted manually into an online sheet. RevMan software (version 5.4) was employed for analysis.
RESULTS: A total of five studies, comprising 186 patients, were included in the meta-analysis. Our findings showed that mexiletine was significantly more effective than placebo in improving stiffness score (SMD =  - 1.19, 95% CI [- 1.53, - 0.85]), as well as in reducing hand grip myotonia (MD =  - 1.36 s, 95% CI [- 1.83, - 0.89]). Mexiletine also significantly improved SF-36 Physical and Mental Component Score in patients with non-dystrophic myotonia only. Regarding safety, mexiletine did not significantly alter ECG parameters but was associated with greater gastrointestinal symptoms (GIT) compared to placebo (RR 3.7, 95% CI [1.79, 7.64]). Other adverse events showed no significant differences.
CONCLUSIONS: The results support that mexiletine is effective and safe in myotonic patients; however, it is associated with a higher risk of GIT symptoms. Due to the scarcity of published RCTs and the prevalence of GIT symptoms, we recommend further well-designed RCTs testing various drug combinations to reduce GIT symptoms.

UNASSIGNED: Sialidosis is a rare disorder caused by mutations in the NEU1 gene located on chromosome 6p21.3, constituting a group of autosomal recessive diseases. Enzyme activity analysis, electron microscopy examination and genetic testing are reliable methods for diagnosis. Despite previous reports on the disease, its rarity means that its clinical manifestations and prognosis still warrant attention due to the limited amount of information available.
UNASSIGNED: We report a case of a 40-year-old woman who was admitted to our hospital for worsening dysarthria of 16 years duration and facial and limb twitching that had been present for 2 years. Genetic testing was undertaken.
UNASSIGNED: Genetic testing confirmed type I sialidosis, the first reported instance of this disease in the Hainan Free Trade Port in China. The patient did not have the typical cherry-red spot in the fundus. Despite aggressive treatment, she died of status epilepticus 2 months later. This result indicates that the disease has a poor prognosis.
UNASSIGNED: Cherry-red spots in the fundus are characteristic features of type I sialidosis and it has been referred to as the cherry-red spot myoclonus syndrome. We hypothesise that environmental factors may also play a significant role. Overemphasis on the presence of cherry-red spots may mislead clinicians and delay diagnosis. Furthermore, patients presenting with isolated myoclonus should undergo visual evoked potential and somatosensory evoked potential tests, as well as genetic testing to confirm or rule out sialidosis.

Severe neonatal episodic laryngospasm (SNEL) is an ion channel disease characterized by recurrent life-threatening myotonia of respiratory muscle due to mutations in the voltage-gated sodium channel genes. Here we reported a newborn manifested as paroxysmal cyanosis and limb myotonia after birth. The neonate also developed muscle hypertrophy and stunted growth during the follow-up. Whole exome sequencing confirmed c.2395G>A, p.Ala799Thr heterozygous mutation of SCN4A. Carbamazepine was found to be effective on treating the disease. This case expands our understanding of the phenotype resulting from SCN4Amutations. By summarizing the characteristics of reported 16 cases in SNEL,we found they were mainly in the p.G1306E mutation. The common symptoms were upper airway muscle stiffness and feeding difficulties during neonates.When grow up, most patients have different degrees of recurrent attacks of myotonia and progressed muscle hypertrophy. Some of them have athlete-like special faces but all showed myotonic discharge in eletromyogram.
严重新生儿发作性喉痉挛(severe neonatal episodic laryngospasm，SNEL)是一种离子通道病，该病因钠电压门控通道4亚基(sodium voltage-gated channel alpha subunit 4 gene，SCN4A)基因突变导致反复发作性咽喉肌强直而危及新生儿生命。现报告1例在出生后出现阵发性发绀和四肢强直的新生儿病例，随访期间，患儿还出现四肢肌肥大和生长发育迟缓。全外显子测序证实该患儿存在SCN4A基因新型杂合突变(c.2395G>A, p.Ala799Thr)。卡马西平是治疗该病的有效药物。此病例扩展了我们对SCN4A基因突变表型的认识。总结已报道的16例SNEL病例特点，发现他们主要发生p.G1306E位点错义突变。相似症状表现为新生儿期上气道肌紧张和喂养困难，长大后多数患者表现为不同程度的发作性肌强直和进行性的肌肥大。一些患者出现“运动员”特征外貌，但几乎所有患者肌电图均有肌强直放电。.

Myotonia congenita (MC) is a rare genetic disease caused by mutations in the skeletal muscle chloride channel gene (CLCN1), encoding the voltage-gated chloride channel ClC-1 in skeletal muscle. Our study reported the clinical and molecular characteristics of six patients with MC and systematically review the literature on Chinese people. We retrospectively analyzed demographics, clinical features, family history, creatine kinase (CK), electromyography (EMG), treatment, and genotype data of our patients and reviewed the clinical data and CLCN1 mutations in literature. The median ages at examination and onset were 26.5 years (range 11-50 years) and 6.5 years (range 1.5-11 years), respectively, in our patients, and 21 years (range 3.5-65 years, n = 45) and 9 years (range 0.5-26 years, n = 50), respectively, in literature. Similar to previous reports, myotonia involved limb, lids, masticatory, and trunk muscles to varying degrees. Warm-up phenomenon (5/6), percussion myotonia (3/5), and grip myotonia (6/6) were common. Menstruation triggered myotonia in females, not observed in Chinese patients before. The proportion of abnormal CK levels (4/5) was higher than data from literature. Electromyography performed in six patients revealed myotonic changes (100%). Five novel CLCN1 mutations, including a splicing mutation (c.853 + 4A>G), a deletion mutation (c.2010_2014del), and three missense mutations (c.2527C>T, c.1727C>T, c.2017 G > C), were identified. The c.892 G > A (p.A298T) mutation was the most frequent mutation in the Chinese population. Our study expanded the clinical and genetic spectrum of patients with MC in the China. The MC phenotype in Chinese people is not different from that found in the West, while the genotype is different.

OBJECTIVE: Early distal muscle weakness and myotonia are typical clinical presentations in type I myotonic dystrophy (DM1). We present a DM1 case with unusual predominant proximal weakness without action myotonia.
METHODS: The chief complaint of this 48-year-old female was difficulty in raising her arms and frequent falling in recent years. On neurological examination, proximal muscle weakness was more pronounced than the distal muscle groups, in addition to facial involvement. Although she did not experience any action myotonia throughout her life, hand and tongue myotonia were readily inducible by percussion during neurological examination. The diagnosis of DM1 was later supported by electromyography and neuropathological studies, and confirmed by molecular testing. The pathological findings in this patient and the characteristic features in typical DM1 patients were briefly reviewed.
CONCLUSIONS: The unusual presentation of this DM1 patient suggests the importance of comprehensive neurological examination including percussion of thenar and tongue muscles, even in a patient with atypical distribution of muscle weakness and without a clear personal and family history of myotonia. In addition to molecular testing, muscle biopsy remains supportive in making the diagnosis.

OBJECTIVE: Previous studies have suggested that Helicobacter pylori (H. pylori) infections may be the cause of or worsen Parkinson\'s disease symptoms. In this meta-analysis, all relevant studies were reviewed to assess whether H. pylori treatment would benefit patients with Parkinson\'s disease.
METHODS: Systemically searches were carried out in MEDLINE and other popular databases. The software RevMan 5.2 was used for meta-analysis. The mean difference (MD) was used as the effect size to draw forest plots.
RESULTS: A total of 10 qualified studies were included. For bradykinesia, the pooled MD value of stride length was -75.76, 95% CI [-109.37, -42.15, P < 0.05]; for myotonia, the pooled MD value of torque to flex was 75.24, 95% CI [27.36, 123.13, P < 0.05]. The pooled MD value of Unified Parkinson\'s Disease Rating Scale (UPDRS)-III scores before and after treatment was 6.27, 95% CI [1.30, 11.24, P < 0.05], suggesting that UPDRS-III scores improved in response to H. pylori treatment. The pooled MD value of levodopa onset time (min) was 14.91, 95% CI [8.92, 20.90, P < 0.05].
CONCLUSIONS: H. pylori treatment may improve the stride length in the bradykinesia index and significantly improve UPDRS-III scores.

UNASSIGNED: Myotonia is found in a number of muscle diseases, including myotonic dystrophy and non-dystrophic myotonia. The resulting symptoms of myotonia can interfere with daily activities such as walking or climbing the stairs. Due to the rarity of both these conditions, pharmacological treatment of myotonia is largely anecdotal and is led by specialist clinicians who tend to favour the use of mexiletine, a class 1b antiarrhythmic sodium antagonist.
UNASSIGNED: To identify and review randomised controlled trials in order to assess the efficacy and safety of use of mexiletine in myotonic dystrophy and non-dystrophic myotonia for two different patient cases.
UNASSIGNED: The literature search was conducted using MEDLINE, EMBASE and The Cochrane Library (from January 1990 to December 2014). Specialist neurology centres were also contacted.
UNASSIGNED: All randomised controlled trials between January 1990 and December 2014 which compared the use of mexiletine for the treatment of myotonia in patients who suffer from myotonic dystrophy and non-dystrophic were included in this review. Primary outcome: reduction of clinical myotonia.
UNASSIGNED: Two randomised controlled trials were included for review. Both studies are underpowered; however, there is evidence to support the use of mexiletine for the improvement of clinical myotonia.
UNASSIGNED: Larger randomised controlled trials are required, which look at the functional effect of myotonia as a primary outcome (ie, stair test) and the long-term use of mexiletine. This is needed to establish the ongoing efficacy and safety of the long-term use of mexiletine in the management of myotonia.

Many outcome assessments used in myotonic dystrophy type 1 (DM1) were developed in other populations. Therefore, reliability and validity of these must be established in DM1 populations.
A structured literature review was conducted to identify muscle strength and performance-based functional outcome assessments used in DM1 and to review the DM1-specific reliability and validity evidence for those outcome assessments.
Eighteen articles met inclusion criteria and were included in the review. The quantitative muscle testing technique and manual muscle testing were the key assessments of muscle strength. Reliability and validity evidence was also noted for several functional assessments of upper extremity (e.g., Purdue Pegboard Test) and lower extremity function (6-Minute Walk Test).
This review identified a few measures with encouraging reliability and validity for use in a DM1 populations but highlighted the need for more research. Muscle Nerve 56: 78-85, 2017.

Myotonia congenita (MC), paramyotonia congenita (PC) and sodium channel myotonias(SCM) were belonged to Non-dystrophic myotonias, in which muscle relaxation is delayed after voluntary or evoked contraction. These diseases can not be simply distinguished only based on symptoms and signs but also on genetics: more than 100 mutations in the CLCN1 gene have been associated with MC, while at least 20 mutations in the SCN4A gene have been associated with PC and SCM. Most of these genetics studies have been conducted outside China, only several MC, PC, and SCM families accepted gene scan were reported in China. Therefore we analyzed genetic mutations in CLCN1 and SCN4A in 10 Chinese families clinically diagnosed with Non-dystrophic myotonias. Our result revealed 12 potential disease-causing mutations(3 mutations were novel) that were present in the probands and affected family members. We also reviewed all available literature on mutations linked to these 3 disease in Chinese populations. Our results may help identify genetic determinants as well as clarify genotype-phenotype relationships.

The myotonic disorders are a heterogeneous group of genetically determined diseases that are unified by the presence of myotonia, which is defined as failure of muscle relaxation after activation. The presentation of these disorders can range from asymptomatic electrical myotonia, as seen in some forms of myotonia congenita (MC), to severe disability with muscle weakness, cardiac conduction defects, and other systemic features as in myotonic dystrophy type I (DM1). In this review, we describe the clinical features and pathophysiology of the different myotonic disorders, their laboratory and electrophysiologic findings and briefly review the currently available treatments.