Single-fiber electromyography in hyperCKemia: the value of fiber density

Although persistently raised serum creatine kinase (sCK), or hyperCKemia, is considered the biological hallmark of neuromuscular diseases, pauci- or asymptomatic- or isolated-hyperCKemia can often be found. Single-fiber electromyography (SFEMG) is an electrophysiological technique of great value in the assessment of neuromuscular, neuropathic and myopathic disorders. We hypothesize that SFEMG fiber density (FD) evaluation is able to detect subclinical electrophysiological abnormalities indicating a myopathic process in subjects with hyperCKemia. Nineteen subjects with hyperCKemia without evident clinical signs of muscle involvement and 15 healthy controls were studied. Electrophysiological investigations including nerve conduction studies (NCS), quantitative EMG (QEMG), SFEMG with focus on FD measurements, and muscle biopsy were performed. NCS, QEMG, SFEMG were normal in all controls. In subjects with hyperCKemia, NCS were normal; QEMG was abnormal in 5, while both SFEMG and muscle biopsy disclosed abnormalities in 12 subjects. The mean FD value was 2.6 ± 0.5 in the control and 4 ± 1.4 (p = 0.003) in the hyperCKemia group. SFEMG revealed subclinical changes in the majority of subjects with hyperCKemia. To the best of our knowledge, this is the first study demonstrating that SFEMG FD evaluation is able to detect the presence of muscle diseases, which are in a subclinical phase and would remain unidentified otherwise. SFEMG may be used to distinguish hyperCKemia associated to asymptomatic muscle disorders from idiopathic hyperCKemia. We believe that SFEMG FD evaluation should be added to the routine examinations in the screening of idiopathic hyperCKemia.     

轻微症状/无症状高肌酸激酶血症诊断方法指南解读及最新进展

基于证据导向的欧洲神经病学会联盟(European Federation of Neurological Societies,EFNS)发布的"轻微症状/无症状高肌酸激酶血症诊断方法"指南,对轻微症状/无症状高肌酸激酶血症的定义、临床表现、诊断流程和预后进行说明。轻微症状/无症状高肌酸激酶血症的定义是无任何客观肌肉疾病体征且血清肌酸激酶值高于正常值上限1.5倍。收集相关家族史并排除可能导致血清肌酸激酶水平升高的非神经肌肉源性病因是鉴别诊断首先需要解决的问题。对肌电图提示有肌源性改变、血清肌酸激酶值高于正常值3倍、年龄小于25岁或同时存在运动不耐受的患者进行肌肉活检可以提高疾病检出率。轻微症状/无症状高肌酸激酶血症的总体远期预后较好。     

Retrospective study of a large population of patients with asymptomatic or minimally symptomatic raised serum creatine kinase levels

A retrospective evaluation of asymptomatic subjects with persistent elevation of serum creatine kinase (CK) levels (hyperCKemia) was made in order to verify the presence of subclinical myopathy or idiopathic hyperCKemia and to define the most appropriate diagnostic pathway. Persistently increased serum CK levels are occasionally encountered in healthy individuals. In 1980 Rowland coined for them the term idiopathic hyperCKemia. Despite the increase of scientific knowledge, several healthy subjects with hyperCKemia still represent a problem for the clinician. We made a retrospective evaluation of 114 asymptomatic or minimally symptomatic individuals with incidentally detected persistent hyperCKemia. They underwent neurological examination and laboratory/instrumental evaluation. Skeletal muscle biopsy was performed and thoroughly investigated. Biochemical and genetic investigations were added in selected cases. Logistic regression analysis was applied. We diagnosed a neuromuscular disorder in 21 patients (18.4 %), and found, by muscle biopsy and/or EMG, pathological but not conclusive findings in 57 subjects (50 %). The statistic correlation between elevated serum CK levels and the probability of making a diagnosis changed according to the age of the patient. Conclusions Muscle biopsy is the basic tool for screening asymptomatic subjects with hyperCkemia. It allowed us to make a diagnosis of disease in 18.4 % of patients, and to detect skeletal muscle abnormalities in 38.6 % of the subjects. Interestingly, 31.6 % of individuals had completely normal muscle findings. These best fit the “diagnosis” of idiopathic hyperCKemia. Received: 13 March 2001, Received in revised form: 3 July 2001, Accepted: 5 July 2001     

Asymptomatic elevation of serum creatine kinase leading to the diagnosis of 4q35 facioscapulohumeral muscular dystrophy

Persistent, asymptomatic (hyperCKemia) may be the prelude to, or the sole manifestation of, a neuromuscular disease. However, the clinical spectrum of facioscapulohumeral muscular dystrophy (FSHD) ranges from asymptomatic individuals with minimal clinical signs to patients who are wheelchair-bound. We describe a patient with persistent, asymptomatic hyperCKemia who received the diagnosis of 4q35 FSHD after a thorough stepwise investigation.     

SHOULD patients with asymptomatic pompe disease be treated? A nationwide study in france

Introduction: Acid α‐glucosidase deficiency, that is, Pompe disease, is a glycogenosis for which enzyme replacement therapy (ERT) is available. It is not known whether patients diagnosed at an asymptomatic stage should be treated to prevent progression of the disease. Methods: We investigated 7 patients with asymptomatic Pompe disease identified from the French Pompe registry. Results: The patients had a mean age of 45 (range 24–75) years, a median follow‐up duration of 2 (range 1–22) years, and normal clinical examination, pulmonary function tests (PFTs), and echocardiography. All presented with at least 1 subclinical abnormality, including hyperCKemia, vacuolar myopathy, and muscle MRI abnormalities, suggesting that subclinical myopathy was present in all cases. Conclusions: Asymptomatic Pompe disease may remain clinically silent for decades, and affected patients should be monitored closely for overt myopathy using clinical examination, PFTs, and muscle MRI to determine when to start ERT. Muscle Nerve 51 : 884–889, 2015     

Aspirin non-responder status in patients with recurrent cerebral ischemic attacks

Background: Antiplatelet agents such as acetylsalicylic acid (aspirin) reduce the relative risk for cerebrovascular events in patients with cardiovascular or cerebrovascular disorders by approximately 23 %. Recent observations raise the possibility that aspirin resistance may contribute to the failure of aspirin treatment in a significant proportion of patients (aspirin non-responders). To evaluate the clinical relevance of aspirin non-responder status, we analysed platelet functions in symptomatic and asymptomatic patients treated with aspirin for secondary prevention of cardiovascular and cerebrovascular events. Methods: A total of 53 patients on 100 mg aspirin daily for secondary prevention (mean treatment duration > 60 months) were included. Patients were categorized as asymptomatic if they were free of cerebrovascular incidents for at least 24 months (n = 18). Symptomatic patients had suffered ischemic strokes or transient ischemic attacks within the previous 3 days (n = 35). Platelet function was assessed using the PFA–100 system that allows for quantitative assessment of platelet function, reporting platelet aggregatability as the time required to close a small aperture in a biologically active membrane. Results: Collagen/epinephrine closure times were significantly shorter in symptomatic patients than in asymptomatic patients (p < 0.01). Individual closing times were normal in 12 of 35 symptomatic patients (34 % non-responders) whereas all asymptomatic patients had prolonged closure times. Conclusions: Aspirin non-responder status may contribute to failure of aspirin therapy in the secondary prevention of cerebrovascular incidents in as much as 30–40 % of patients. Quantitative assessment of platelet functions may provide a means to predict aspirin treatment failure in individual patients and to re-direct therapeutic strategies. Received: 7 May 2002, Received in revised form: 28 August 2002, Accepted: 2 September 2002 Correspondence to Priv.-Doz. Dr. Helge Topka     

Frequency of calpain-3 c.550delA mutation in limb girdle muscular dystrophy type 2 and isolated hyperCKemia in German patients

OBJECTIVE: Calpain-3 deficiency is the most common cause of autosomal-recessive limb girdle muscular dystrophy (LGMD2). The c.550delA mutation in the CAPN3 gene was frequently identified in LGMD2A patients from Eastern Europe and is considered a Slavic founder mutation. METHODS: We screened for the c.550delA mutation in unrelated German patients with LGMD2 (n = 98) and in patients with asymptomatic or minimally symptomatic (myalgia or fatigue) hyperCKemia of unknown origin (n = 102). Results of Western blot analysis were available in 75 patients with LGMD2 and 65 patients with hyperCKemia. In samples that were heterozygous for the c.550delA mutation, the whole CAPN3 gene was analyzed by sequencing in order to detect the second mutation. RESULTS: The c.550delA mutation was found in 8.1% of LGMD2 (n = 1 homozygous, n = 7 heterozygous) and 1.9% of hyperCKemia patients (n = 2 heterozygous). In 8 of the 9 hetrozygous patients, a second CAPN3 mutation was identified by direct sequencing. Two mutations (Val509Phe and Gln565Stop) have not been reported before. Absent or deficient calpain-3 protein in Western blot analysis was found in 22.5% of the LGMD2 patients and 11% of the patients with hyperCKemia. Western blot results were available in 9 out of the 10 patients with genetically confirmed LGMD2A and were clearly abnormal in 6 patients, suspicious in 2 and entirely normal in 1. Two LGMD2 patients with the c.550delA mutation and onset within the first 2 decades had joint contractures. Muscle biopsy revealed inflammatory changes in three patients. CONCLUSION: The CAPN3 gene mutation c.550delA is rather frequently observed in German patients with LGMD2, but also occasionally in cases with isolated hyperCKemia.     

Normalization of creatine kinase level during pregnancy in idiopathic hyperCKemia

A 34-year-old previously healthy woman with no remarkable family history developed asymptomatic hyperCKemia at age 26. Over the next 6 years, hyperCKemia persisted (502-2562 IU/l; normal range<180). A muscle biopsy showed minimal nonspecific myopathy. Genetic analysis of blood and muscle samples showed no abnormality in the dystrophin gene. At age 33, she became pregnant for the first time and serum creatine kinase (CK) was normal at 170 IU/l in the third trimester. After delivery, hyperCKemia reappeared (715-2620) while her baby tested normal for CK. This is the first report of idiopathic hyperCKemia associated normalization of serum CK level during pregnancy, which has been reported in carriers of Duchenne muscular dystrophy.     

Screening test for malignant hyperthermia in patients with persistent hyperCKemia: A pilot study

Introduction: Persistently elevated serum creatine kinase (CK) is frequently associated with predisposition to malignant hyperthermia (MH). We investigated whether a minimally invasive metabolic test is suitable to diagnose MH susceptibility among patients with hyperCKemia. Methods: Thirty‐nine participants were included: 10 were MH susceptible (MHS); 21 MH were non‐susceptible (MHN); and 8 had MHN with persistent hyperCKemia >500 U/L. Microdialysis probes were inserted into the vastus lateralis muscle, and halothane or caffeine was injected via an attached microtubing catheter. Lactate concentrations in dialysis samples were measured spectrophotometrically. Results: Baseline lactate did not differ between the groups. After local application of halothane or caffeine, a significant lactate increase was detected only in the MHS group. Conclusions: Test results were not influenced by hyperCKemia. To avoid risks and complications of a surgical muscle biopsy this microdialysis test might be a useful screening tool for MH susceptibility among patients with persistent CK elevation. Muscle Nerve 47: 677–681, 2013     

Asymptomatic/pauci-symptomatic creatine kinase elevations (hyperckemia)

Neuromuscular clinicians are frequently asked to evaluate patients referred for asymptomatic elevations in creatine kinase (CK), a catalytic enzyme that combines creatine and ATP to form phosphocreatine and ADP. This reaction is crucial for cellular energy generation and metabolism. This laboratory finding, often referred to in simplified lexicon as asymptomatic hyperCKemia, continues to generate controversy at several levels, including definition, the extent of evaluation, and the yield of diagnostic testing. In this review, we summarize the literature based on series of patients with asymptomatic hyperCKemia and provide a rational clinical approach to reveal identifiable underlying causes. Muscle Nerve 47: 805–815, 2013     

Novel mutations in the fukutin gene in a boy with asymptomatic hyperCKemia

Mutations in the fukutin gene were first identified in Japanese patients with classic Fukuyama congenital muscular dystrophy, a severe form of congenital muscular dystrophy associated with cobblestone lissencephaly and ocular defects. Patients of different ethnicities and with milder phenotypes, including limb girdle muscular dystrophy and cardiomyopathy without brain impairment, have also been reported. The hallmark of this disorder, regardless of the clinical outcome, is moderate-to-severe hypoglycosylation of alpha-dystroglycan in muscle sections. We describe the case of a boy harboring two novel mutations in fukutin gene and presenting a five-year history of asymptomatic hyperCKemia, without overt muscle, brain or ocular involvement. Genetic investigations, guided by the presence of moderate myopathic changes on muscle biopsy with loss of immunodetectable alpha-dystroglycan, led to a definitive diagnosis. Cardiac and echocardiographic examinations at follow-up disclosed low normal left ventricular function but no active cardiovascular symptoms. We suggest that fukutin mutations should be sought in asymptomatic hyperCKemia and subclinical heart dysfunction.     

Muskeldystrophie infolge Anoctamin-5-Mutationen

Recessive mutations in the anoctamin 5 (ANO5) gene have been recently identified in families with limb girdle muscular dystrophy (LGMD2L) and distal non-dysferlin Miyoshi myopathy. Anoctamin 5 is supposed to be a putative calcium-activated chloride channel. We report five German patients (four index patients) with muscle dystrophy due to mutations in the ANO5 gene. Sequencing of the ANO5 exons 5, 13 and 20 was performed to screen for a common c.191dupA mutation and two other reported mutations (c.1295C>G and p.R758C). The whole coding region of the ANO5 gene was sequenced to identify new mutations. Phenotypically, three patients showed LGMD and one patient Miyoshi type distal myopathy. One sibling had asymptomatic hyperCKemia. The age at onset was 64, 38 and 40 years in patients with LGMD and 23 years in the patient with distal myopathy. The four symptomatic patients showed remarkable asymmetric muscle involvement. There was marked CK elevation (11 to 30 times). Electron microscopy showed multifocal gaps in the sarcolemmal membrane. All patients harboured the common c.191dupA mutation in at least one allele. Two patients with LGMD were homozygous and the third patient and his asymptomatic sister were compound heterozygous for the c.191dupA mutation and a novel p.T548I mutation. The patient with distal myopathy harboured the p.R758C mutation in the second allele. Mutations in the ANO5 gene seem to be a relatively common cause of muscular dystrophy in Germany. Cases with late onset or asymptomatic hyperCKemia can occur. Clinically, asymmetric manifestation is typical.     

Diagnostic outcome of muscle biopsy

Introduction: We reviewed the diagnostic yield of muscle biopsy according to the presence or absence of muscle weakness, hyperCKemia, and electromyogaphic (EMG) abnormalities. Methods: In a retrospective study, 698 muscle biopsy reports were analyzed. Logistic regression models for myopathy and specific myopathy were fit, and receiver‐operating characteristic (ROC) curves were generated to assess prediction accuracy. The probability of finding specific myopathy was considered the main indication of a positive muscle biopsy. Results: Isolated hyperCKemia was poorly predictive of either myopathy or specific myopathy. Combined myopathic EMG, proximal weakness, and hyperCKemia were predictive. The predictability increased proportionally to the creatine kinase (CK) level in patients with proximal weakness and myopathic EMG. Cross validation showed accuracy around 70% for a probability threshold of 50%. Conclusions: The presence of hyperCKemia, proximal weakness, and myopathic EMG together were associated with highly positive diagnostic outcome of muscle biopsy. Isolated hyperCKemia had a poor diagnostic yield. Muscle Nerve 51 :662–668, 2015     

Rhabdomyolysis: Review of the literature

Rhabdomyolysis is a serious and potentially life threatening condition. Although consensus criteria for rhabdomyolysis is lacking, a reasonable definition is elevation of serum creatine kinase activity of at least 10 times the upper limit of normal followed by a rapid decrease of the sCK level to (near) normal values. The clinical presentation can vary widely, classical features are myalgia, weakness and pigmenturia. However, this classic triad is seen in less than 10% of patients. Acute renal failure due to acute tubular necrosis as a result of mechanical obstruction by myoglobin is the most common complication, in particular if sCK is >16.000 IU/l, which may be as high as 100,000 IU/l. Mortality rate is approximately 10% and significantly higher in patients with acute renal failure. Timely recognition of rhabdomyolysis is key for treatment. In the acute phase, treatment should be aimed at preserving renal function, resolving compartment syndrome, restoring metabolic derangements, and volume replacement. Most patients experience only one episode of rhabdomyolysis, mostly by substance abuse, medication, trauma or epileptic seizures. In case of recurrent rhabdomyolysis, a history of exercise intolerance or a positive family history for neuromuscular disorders, further investigations are needed to identify the underlying, often genetic, disorder. We propose a diagnostic algorithm for use in clinical practice.     

Myotonia associated with caveolin-3 mutation

Introduction: Caveolin‐3 is a major component of the caveolae in skeletal and cardiac muscle.Mutations in the caveolin‐3 gene (CAV3) lead to a spectrum of clinical phenotypes including limb‐girdle muscular dystrophy 1C, distal myopathy, rippling muscle disease, isolated hyperCKemia, and cardiomyopathy. Case Report: A 24‐year‐old man with myalgia, muscle stiffness, and fatigue has normal strength and prominent myotonic discharges in the gastrocnemius. He also has epilepsy. He harbors a heterozygous CAV3 mutation, p.V57M. He has no mutations in CLCN1 and SCN4A, and he had normal genetic testing for myotonic dystrophy type 1 and type 2. Conclusions: Mutations in CAV3, and in particular p.V57M in CAV3, previously reported in isolated familial hyperCKemia, can be associated with electrical myotonia. Muscle Nerve 45: 897‐900, 2012     

Increased resting energy expenditure in subjects with Emery-Dreifuss muscular dystrophy

We have studied changes in energy expenditure and body composition in adult males with Emery-Dreifuss muscular dystrophy, age-matched males with hyperCKemia and age-matched healthy controls. All participants were studied twice, 2-3 years apart. Resting energy expenditure was studied by indirect calorimetry, lean body mass and body fat by dual X-ray absorptiometry, and muscle mass was estimated based on 24-h urinary creatinine excretion. At baseline and 2-3 years later, body fat was significantly higher (P < 0.011 and P < 0.003, respectively) and lean body mass significantly lower (P < 0.024 and P < 0.012, respectively) in patients with Emery-Dreifuss muscular dystrophy as compared to subjects with hyperCKemia and healthy controls. Resting energy expenditure, over the study period, increased significantly in patients with Emery-Dreifuss muscular dystrophy (P < 0.031), but not in patients with hyperCKemia nor in healthy controls. Our study suggests that patients with Emery-Dreifuss muscular dystrophy may have increased energy expenditure relative to healthy subjects. If not met by increased caloric intake, this greater energy expenditure may partially contribute to a further deterioration in their muscle performance.     

A Review of the Neural Mechanisms of Action and Clinical Efficiency of Riluzole in Treating Amyotrophic Lateral Sclerosis: What have we Learned in the Last Decade?

Amyotrophic lateral sclerosis (ALS) is a devastating and fatal neurodegenerative disease of adults which preferentially attacks the neuromotor system. Riluzole has been used as the only approved treatment for amyotrophic lateral sclerosis since 1995, but its mechanism(s) of action in slowing the progression of this disease remain obscure. Searching PubMed for “riluzole” found 705 articles published between January 1996 and June 2009. A systematic review of this literature found that riluzole had a wide range of effects on factors influencing neural activity in general, and the neuromotor system in particular. These effects occurred over a large dose range (<1 μM to >1 mM). Reported neural effects of riluzole included (in approximate ascending order of dose range): inhibition of persistent Na⁺ current = inhibition of repetitive firing < potentiation of calcium‐dependent K⁺ current < inhibition of neurotransmitter release < inhibition of fast Na⁺ current < inhibition of voltage‐gated Ca²⁺ current = promotion of neuronal survival or growth factors < inhibition of voltage‐gated K⁺ current = modulation of two‐pore K⁺ current = modulation of ligand‐gated neurotransmitter receptors = potentiation of glutamate transporters. Only the first four of these effects commonly occurred at clinically relevant concentrations of riluzole (plasma levels of 1–2 μM with three‐ to four‐fold higher concentrations in brain tissue). Treatment of human ALS patients or transgenic rodent models of ALS with riluzole most commonly produced a modest but significant extension of lifespan. Riluzole treatment was well tolerated in humans and animals. In animals, despite in vitro evidence that riluzole may inhibit rhythmic motor behaviors, in vivo administration of riluzole produced relatively minor effects on normal respiration parameters, but inhibited hypoxia‐induced gasping. This effect may have implications for the management of hypoventilation and sleep‐disordered breathing during end‐stage ALS in humans.     

HyperCKemia as the only sign of McArdle's disease in a child

An asymptomatic 13-year-old boy, who never complained of exercise intolerance or myalgia, was found to have markedly elevated serum creatine kinase (CK) levels during a routine check-up. General physical and neurologic examinations were normal. Surprisingly, histochemical and biochemical analysis of muscle showed myophosphorylase deficiency and genetic analysis showed that the patient was homozygous for the most common mutation encountered in McArdle's disease (R49X). This case illustrates the fuzzy correlation between molecular defect and clinical phenotype in patients with McArdle's disease, and suggests that a thorough study of the muscle biopsy is important in patients with idiopathic hyperCKemia for correct diagnosis and careful follow-up.     

Rivastigmine versus placebo in hyperhomocysteinemic Parkinson's disease dementia patients

The effects of rivastigmine versus placebo in Parkinson's disease dementia (PDD) patients with elevated or normal/low plasma homocysteine were determined. In this prospective analysis of a 24‐week, randomly assigned, placebo‐controlled study of rivastigmine in PDD, subpopulations comprised patients with plasma homocysteine ≥14 μmol/L (elevated) or <14 μmol/L (normal/low). Coprimary outcomes were the Alzheimer's Disease Assessment Scale–cognitive subscale (ADAS‐cog) and Alzheimer Disease Cooperative Society–Clinical Global Impression of Change (ADCS‐CGIC). Secondary outcomes included additional measures of cognition, including attention and executive function, daily function, and neuropsychiatric symptoms. Adverse events (AEs) were monitored. In total, 342 of 541 patients provided samples for analysis, from which 72% had elevated plasma homocysteine. Hyperhomocysteinemic patients showed treatment differences (rivastigmine vs. placebo) of 4.0 on ADAS‐cog and 0.7 on ADCS‐CGIC (both P < 0.01), and significant treatment differences on secondary outcomes. Rivastigmine‐ and placebo‐treated hyperhomocysteinemic patients (16.5% and 14.6%) discontinued the study because of AEs. Patients with normal/low homocysteine showed no treatment differences on primary or secondary outcomes (1.4 on the ADAS‐cog and 0.1 on ADCS‐CGIC, both P = ns); 16.7% and 10.3% rivastigmine‐ and placebo‐treated patients discontinued because of AEs. Elevated homocysteine was associated with greater rivastigmine treatment differences than normal/low homocysteine. © 2008 Movement Disorder Society     

Lux vs. wavelength in light treatment of Seasonal Affective Disorder

Objective: Published dosing guidelines for treatment of Seasonal Affective Disorder (SAD) refer to photopic lux, which is not appropriate for short‐wavelength light. Short wavelengths are most potent for many non‐visual responses to light. If SAD therapy were similarly mediated, standards utilizing lux risk overestimating necessary dose. We investigated antidepressant responses to light using two light‐emitting diode (LED) sources, each emitting substantial short‐wavelength light, but <2500 lux. Method: A randomized, double‐blind trial investigated 3‐week 45 min/day out‐patient treatment with blue‐appearing (goLITE^®) or blue‐enriched white‐appearing light in 18 moderately‐depressed adults (12F, 49.1 ± 9.5 years). Equivalent numbers of photons within the short‐wavelength range were emitted, but the white source emitted twice as many photons overall and seven‐fold more lux. Results: Depression ratings (SIGH‐ADS; http://www.cet.org ) decrease averaged 82% (SD = 17%) from baseline (P < 0.0001) in both white‐ and blue‐light groups. Both sources were well tolerated. Conclusion: Short‐wavelength LED light sources may be effective in SAD treatment at fewer lux than traditional fluorescent sources.