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'Single-Fiber EMG' (519)


Feb
2018

Monogenic defects of synaptic vesicle (SV) homeostasis have been implicated in many neurologic diseases, including autism, epilepsy, and movement disorders. In addition, abnormal vesicle exocytosis has been associated with several endocrine dysfunctions.
We report an 11 year old girl with learning disabilities, tremors, ataxia, transient hyperglycemia, and muscle fatigability responsive to albuterol sulfate.

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Sep
2016

Ocular myasthenia gravis (OMG) is sometimes difficult to diagnose and is probably both under-diagnosed and misdiagnosed. We studied the epidemiological parameters, relevant serology, electromyographic (EMG) findings, and the relationship between OMG and thymoma, thymus hyperplasia and other autoimmune disorders compared to generalized MG (GMG) in a case control study of 133 patients with MG (32 patients with OMG and 101 patients with GMG). The proportion of OMG among all MG patients was relatively high (24.

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Dec
2017

Immune checkpoint inhibitors have led to the development of new approaches for cancer treatment with positive outcomes. However, checkpoint blockade is associated with a unique spectrum of immune-related adverse events (irAEs), which may cause irreversible neurological deficits and even death.
We presented a case of a 57-year-old man with non-small-cell lung cancer.

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Feb
2018

Neostigmine test (NT) is a pharmacological test, demonstrating a clinical improvement in patients affected by myasthenia gravis (MG). We aim to compare clinical evaluation and neurophysiological recordings by concentric-needle single-fiber electromyography (CN-SFEMG) in response to acute administration of neostigmine in ocular and generalized MG patients. Twenty-three MG patients (10 with ocular MG and 13 with generalized MG) were evaluated before and after 90 min neostigmine 0.

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Mar
2018

We report a severe envenoming associated with minimal local symptoms following a Balkan adder (Vipera berus bosniensis) bite in South-Western Hungary. A 63-year-old male with a history of hypertension and sinus bradycardia (45/min) was bitten by a sub-adult specimen of V. b.

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Jan
2018

The aim was to determine motor unit morphology underpinning the various MUP waveforms using MUP analysis.
The simulation method is based on the decomposition of MUP into single fiber potentials. Number of fibers, fiber diameters and fiber to electrode distances were determined.

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Nov
2017

Ceylon krait (Bungarus ceylonicus) is a venomous elapid snake endemic to Sri Lanka. It inhabits shaded home gardens and forests in the wet zone of Sri Lanka and might creep into houses in the night. Despite frequent encounters with humans, reports of envenoming are very rare.

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Dec
2017

Deriving muscle fiber diameter from recorded single fiber potential.

Neurophysiol Clin 2017 Dec 20;47(5-6):413-417. Epub 2017 Nov 20.
Ewa Zalewska
The aim of the study was to estimate muscle fiber diameters through analysis of single muscle fiber potentials (SFPs) recorded in the frontalis muscle of a healthy subject.
Our previously developed analytical and graphic method to derive fiber diameter from the analysis of the negative peak duration and the amplitude of SFP, was applied to a sample of ten SFPs recorded in vivo.
Muscle fiber diameters derived from the simulation method for the sample of frontalis muscle SFPs are consistent with anatomical data for this muscle.

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Feb
2018

To summarize the electrophysiological characteristics of two cases of endplate acetylcholinesterase deficiency (EAD) related congenital myasthenic syndrome (CMS) caused by COLQ mutation and to discuss the possible mechanism of these electrophysiological phenomena.
Electrophysiological examinations were conducted including nerve conduction studies, routine electromyography (EMG), repetitive nerve stimulation (RNS) and single fiber EMG (SFEMG). The ulnar nerve was also stimulated at 50 Hz followed by 0.

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Dec
1969

Congenital myasthenic syndromes (CMS) are neuromuscular transmission disorders caused by mutations in genes encoding neuromuscular junction proteins. A 61-year-old female and her older sister showed bilateral ptosis, facial and proximal limb weakness, and scoliosis since childhood. Another female sibling had milder signs, while other family members were asymptomatic.

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Nov
2017

Pitfalls and errors in measuring jitter.

Clin Neurophysiol 2017 Nov 21;128(11):2233-2241. Epub 2017 Sep 21.
Erik Stålberg, Donald B Sanders, João Aris Kouyoumdjian
The safety factor of neuromuscular transmission can be assessed by measuring the neuromuscular jitter, which reflects the time variability of processes in the motor end-plate. Jitter is increased in any condition with disturbed end-plate function, such as myasthenic conditions and ongoing reinnervation. Jitter is increasingly being measured with concentric needle (CN) electrodes, which are more prone to artefacts than single fiber EMG recordings.

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Jun
2017

Seronegative ocular myasthenia gravis (OMG) is diagnosed by ocular symptoms with supporting SFEMG, typically of frontalis or extensor digitorum muscles. We aimed to determine the sensitivity and specificity of orbicularis oculi SFEMG to diagnose and exclude myasthenia gravis and predict response to therapy.
Orbicularis oculi SFEMG studies were conducted in 142 consecutive patients with symptoms and/or findings of OMG and negative AChR antibody during the period of 5 years.

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Jul
2017

Myasthenia gravis (MG) can lead to weakness in different patterns of muscle groups. Limb muscle weakness is most typically seen in a limb girdle pattern, although variants exist. In the current study, we aimed to describe a unique MG phenotype consisting of selective or predominant triceps muscle weakness.

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Nov
2017

A screening test is required to diagnose disorders of the neuromuscular junction (NMJ) in children. This Review describes the development of stimulation potential analysis with concentric needle electrodes (SPACE). This nomenclature was chosen to distinguish the technique from single-fiber methodology because of the difficulties in identifying single-fiber potentials in most studies, particularly those with the most severe abnormalities of the NMJ.

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May
2017

Myasthenia gravis (MG) is a chronic autoimmune neuromuscular disease characterized by weakness of bodily skeletal muscles. Office-based diagnostic tests such as repetitive nerve stimulation (RNS), single fiber electromyography (SFEMG), and the ice test, are used to refine the differential clinical diagnosis of this disease. Evaluating the clinical sensitivity and specificity of these tests, however, may be confounded by lack of a gold standard, non-blinding, incorporation bias, use of non-representative populations and retrospective data.

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Apr
2017

Autoantibodies against ion channels are the cause of numerous neurologic autoimmune disorders. Frequently, such pathogenic autoantibodies have a restricted epitope-specificity. In such cases, competing antibody formats devoid of pathogenic effector functions (blocker antibodies) have the potential to treat disease by displacing autoantibodies from their target.

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Jun
2016

The aim of this study was to re-evaluate jitter values of healthy subjects in whom pairs of single-fiber-like potentials were recorded from voluntary activated periocular muscles using a disposable 37-mm concentric needle electrode (CNE) with 2-kHz low-cut filtering.
We reviewed the recordings of 129 subjects (85 women; 44 men; mean age, 43.8±15.

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Dec
1969

We describe a patient with ocular myasthenia gravis, where single-fiber electromyography and testing for acetylcholine receptor and muscle-specific kinase antibodies were negative. However, antibodies to low-density lipoprotein receptor-related protein 4 (LRP4) were positive, and this prompted appropriate management. We recommend that testing for LRP4 antibodies be considered when the clinical suspicion for myasthenia gravis is high despite negative conventional diagnostic tests.

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May
2017

Botulinum is a potent neurotoxin with increasing indications for neurologic disorders. While clinical benefit manifests primarily due to local actions at the neuromuscular junction, regional and systemic effects do occur. Rarely, systemic symptoms including weakness, dysarthria, dysphagia and other side effects occur as a result of iatrogenic botulinum neurotoxicity.

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Dec
1969

Myasthenia gravis (MG) is an autoimmune neuromuscular disorder resulting from skeletal muscle weakness and fatigue. An early common symptom is fatigable weakness of the extrinsic ocular muscles; if symptoms remain confined to the ocular muscles after a few years, this is classified as ocular myasthenia gravis (OMG). Diagnosis of MG when there are mild, isolated ocular symptoms can be difficult, and currently available diagnostic techniques are insensitive, non-specific or technically cumbersome.

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May
2017

Seronegative myasthenia gravis associated with malignant thymoma.

Neuromuscul Disord 2017 May 2;27(5):417-418. Epub 2017 Feb 2.
Jason Richards, James F Howard
Myasthenia gravis (MG) is generally caused by antibodies directed against the neuromuscular junction, including antibodies against the postsynaptic nicotinic acetylcholine receptor (AChR). Pathologic abnormalities of the thymus gland, including thymoma, are associated with MG. We report a 56-year-old woman who presented with double vision.

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Dec
1969

Motor Unit Potential Jitter: A New Measure of Neuromuscular Transmission Instability.

IEEE Trans Neural Syst Rehabil Eng 2017 07 9;25(7):1018-1025. Epub 2017 Feb 9.
Meena AbdelMaseeh, Daniel W Stashuk
A new measure of neuromuscular transmission instability, motor unit potential (MUP) jitter, is introduced. MUP jitter can be estimated quickly using MUP trains (MUPTs) extracted from electromyographic (EMG) signals acquired using conventional clinical equipment and needle EMG electrodiagnostic protocols. The primary motivation for developing MUP jitter is to avoid the technical demands associated with estimating jitter using conventional single fiber EMG techniques.

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Sep
2017

Electrophysiological studies play an important role in the diagnosis of myasthenia gravis (MG). The objectives of this study was to explore the correlation of jitter and decrement with various clinical symptoms and signs and disease severity.
We performed a retrospective chart review of 75 MG patients who attended the neuromuscular clinic from April 2013 to May 2014.

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Aug
2017

We analyzed jitter recordings made with concentric needle electrode (CNE) single-fiber electromyography (SFEMG) in Lambert-Eaton myasthenia (LEM).
Fifteen subjects diagnosed with LEM were studied using CNE-SFEMG in the extensor digitorum (ED) and tibialis anterior (TA) muscles. CNE-SFEMG in the ED and TA was also used to evaluate 12 and 10 healthy controls (HCs), respectively.

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Jul
2017

The objective of this study was to determine if single-fiber electromyography (SFEMG) jitter accurately reflects change in severity in myasthenia gravis (MG).
We reviewed jitter and outcome data from all MG patients in our clinic who had at least 2 jitter measurements in the extensor digitorum or frontalis muscle.
Change in all parameters of jitter measured with SFEMG electrodes predicted clinical change with acceptable accuracy.

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Dec
1969

The diagnosis of myasthenia gravis in very young infants is a challenging one. In young infants, stimulated single-fiber electromyography (StimSFEMG) is the most appropriate technique, but it has serious limitations due to the absence of reference values in this subpopulation. Here we present our efforts to derive a reference range of jitter in a patient cohort of infants <3 years of age using the extrapolated norms, or e-norms, technique.

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Oct
2016

The literature lacks data on accuracy of single fiber electromyography (SFEMG) for myasthenia gravis (MG) patients followed longitudinally.
We included patients with a clinical suspicion of MG who received SFEMG and follow-up at our institution between 2003 and 2013. Data collected included demographics, symptom details, clinical deficits, other diagnostic testing results, MG medication regimen, duration on treatment, response to therapy, and ultimate diagnosis after follow-up.

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Nov
2016

Weakness and fatigue are frequent symptoms in myotonic dystrophy type 1 (DM1), mainly as a result of muscle impairment. However, neuromuscular junction (NMJ) abnormalities could play an additional role in determining these manifestations. We aimed to document the possible NMJ involvement in DM1.

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Oct
2016

To explore the increased diagnostic yield of repetitive nerve stimulation (RNS) following activation for myasthenia gravis (MG) diagnosis, and compare with testing an additional muscle at rest only.
We performed a retrospective chart review of patients diagnosed with MG attending the neuromuscular clinic from 2013 to 2015 and extracted data on electrophysiological studies, including frequency of decrement of 10% or above, with facial RNS at rest, and following activation.
The total cohort included 102 patients with MG, 65 with generalized, and 37 with ocular MG.

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Jun
2017

Age-associated muscle strength decline is a major contributing factor to increased late-life functional decline and comorbidity, and is strongly associated with early mortality. Although all parts of the neuromuscular system seem to be affected by aging, dying-back of motor axons likely plays a major role.
We compared the degeneration in ventral roots and neuromuscular junction denervation in young and aged mice and correlated the findings with strength and electrophysiological measures.

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Feb
2017

Repetitive nerve stimulation (RNS) showing ≥ 10% decrement is considered the cutoff for myasthenia gravis (MG), but this has never been validated. The objective of this study was to find an optimal validated cutoff value for decrement on RNS.
We performed retrospective chart review of patients who had electrophysiological assessment for possible MG from 2013 to 2015.

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Dec
1969

Nerve growth factor (NGF) is a protein important for growth and survival, but also for modulation of sensitivity of nociceptors and sympathetic neurons. The purpose of the present study was to investigate the effects of reduced NGF signaling in patients with hereditary sensory and autonomic neuropathies type V, congenital insensitivity to pain, caused by a mutation of the NGFβ gene, including a characterization of single nociceptive fibers using microneurography (MNG).
One homozygote and 2 heterozygote patients with this mutation were examined with electromyography/neurography, thermal testing, quantitative sudomotor axon reflex test, and electrically induced axon reflex erythema in addition to MNG.

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Jun
2016

One of the first questions asked by patients and family members when a diagnosis of amyotrophic lateral sclerosis is made is "what about stem cells?" The term "stem cells" has attractiveness to it, with the assumption that stem cell treatment (stem nerve cells) can replace lost nerve cells. There are perhaps 2 types of stem cell trials, those that are vetted by the Food and Drug Administration and those that have no official oversight and whose results are infrequently published. The issue of the latter was discussed in the last edition of this column.

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Dec
1969

Our objective was to compare the effect of different low-frequency filters on jitter parameters when stimulating the orbicularis oculi.
Ten healthy volunteers were studied. Jitter was expressed as the mean consecutive difference (MCD).

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Dec
1969

Single fiber electromyography (SFEMG) is the most sensitive diagnostic tool for diagnosis of myasthenia gravis (MG). Its prognostic value is not known.
We retrospectively analyzed the clinical course of 232 MG patients who presented with only mild symptoms and had SFEMG of the orbicularis oculi muscle.

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May
2016

Single-fiber electromyography (SFEMG) has been suggested as a quantitative method for supporting chronic partial denervation in amyotrophic lateral sclerosis (ALS) by the revised EI Escorial criteria. Although concentric needle (CN) electrodes have been used to assess jitter in myasthenia gravis patients and healthy controls, there are few reports using CN electrodes to assess motor unit instability and denervation in neurogenic diseases. The aim of this study was to determine whether quantitative changes in jitter and spike number using CN electrodes could be used for ALS studies.

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Dec
1969

The purpose of this study is to obtain normative values of the masseter muscle of myasthenia gravis (MG) patients and healthy volunteers by single-fiber electromyography (SFEMG). Stimulation of SFEMG in the masseter muscle was studied in 15 healthy volunteers (men 8, women 7; mean age 40.2, range 21-77) and 30 patients affected by MG (men 16, women 14; mean age 42.

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Oct
2015

Single-fiber electromyography (SFEMG) abnormality in the extensor digitorum communis (EDC) was reported in ocular myasthenia gravis (OMG), which indicated subclinical involvement beyond extraocular muscles in OMG patients. The relationship between the abnormal findings of SFEMG in EDC and the probability for OMG to develop generalized myasthenia gravis (GMG) is unknown. This retrospective study aimed to determine the predictive value of abnormality of SFEMG in EDC of OMG patients.

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Jun
2015

Isolated respiratory muscles weakness is an unusual presentation of Myasthenia Gravis (MG). We present a case of 49-year-old male with undiagnosed MG who presented with fluctuating dyspnea on exertion and at rest. There was no peripheral muscle involvement, diagnostic tests and standard electromyography was normal, and the serologic tests were negative.

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Aug
2015

Needle electromyography is an important tool in the diagnosis of neuromuscular diseases and has also been applied successfully in the evaluation of the vocal cord paralysis. Laryngeal electromyography, initially described by Weddell, is used to determine the cause of vocal cord paralysis and to differentiate organic from nonorganic causes of speech disorders. This test allows the diagnosis of lower motor neuron and nerve paralysis as well as myopathies.

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Sep
2015

Our aim in this study was to provide an updated literature review of electrodiagnostic testing in myasthenia gravis and Lambert-Eaton myasthenic syndrome.
A systematic review of the recent literature was performed using the following key words: myasthenia gravis (MG); Lambert-Eaton myasthenic syndrome (LEMS); electromyography (EMG); repetitive nerve stimulation (RNS); single-fiber electromyography (SFEMG); nerve conduction study; and normative values.
Several articles supported testing of facial, bulbar, and respiratory muscles in the diagnosis of neuromuscular junction (NMJ) disorders, including muscle-specific kinase antibody (MuSK)-seropositive MG.

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Dec
1969

There are 2 critical steps in neural regeneration: nerve fibres successfully crossing the suture and restoration of neuromuscular transmission. For the second step, the compound muscle action potential (CMAP) is the standard electrophysiological technique used to assess regeneration, but it is difficult to detect changes in the CMAP during early regeneration after nerve repair. There is a need for better, noninvasive quantitative electrophysiological techniques to assess regeneration in an earlier stage after nerve repair.

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Jun
2015

To characterize electromyographic abnormalities according to symptoms (asymptomatic, fatigue, pseudobotulism) reported 1 month after botulinum toxin injection.
Retrospective, single-center study comparing single-fiber electromyography (SFEMG) in the extensor digitorum communis (EDC) or orbicularis oculi (OO) muscles.
Hospital.

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Jun
2015

Collecting reference values in subpopulations such as infants and children can pose a daunting challenge to gather through epidemiologic studies. The authors propose to evaluate a method the authors refer to as extrapolated norms (e-norms) to derive Stimulated Single Fiber EMG jitter reference values from the laboratory data of pediatric and adult cohorts. Single Fiber EMG studies are considered the gold standard test for evaluation of neuromuscular transmission disorders.

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Feb
2015

Isolated laryngeal myasthenia gravis for 26 years.

Neuromuscul Disord 2015 Feb 22;25(2):153-4. Epub 2014 Oct 22.
Dimitri Renard, Amir Hedayat, Corinne Gagnard
Laryngeal myasthenia gravis is a relatively rare variant of myasthenia gravis. A vast portion of patients with initial laryngeal myasthenia gravis develop involvement of ocular and/or extra-ocular muscles during the years after symptom onset although a minority of laryngeal myasthenia gravis patients continues to have isolated laryngeal muscle involvement for several years. We present a 58-year-old woman with recurrent episodic isolated dysphonia (associated with diffuse bilateral vocal cord paresis on laryngoscopy) since the age of 32.

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Dec
1969

The main hypotheses regarding mechanisms of transient global amnesia (TGA) are ischemia in hippocampal structures, epileptic genesis, and migraine. In accordance with the hypothesis of a shared, common pathophysiological mechanism in both TGA and migraine, neuromuscular transmission (NMT) abnormalities previously found in migraine were also suspected in TGA.
The aim of our study was to analyze NMT in TGA patients to reveal a subclinical impairment of neuromuscular transmission as a possible indicator of underlying channelopathy, which would point to a shared etiology with migraine.

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Dec
1969

A carotid-cavernous fistula (CCF) is an abnormal communication between the carotid arterial system and the cavernous sinus. Common symptoms of CCFs include proptosis and ophthalmoplegia, but fluctuating diplopia and presence of ptosis are not typical.
We present an unusual case of CCF with fluctuating binocular diplopia and ptosis, mimicking myasthenia gravis.

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Aug
2014

Botulinum toxin type A is a potent muscle relaxant that blocks the transmission and release of acetylcholine at the neuromuscular junction. Intramuscular injection of botulinum toxin type A has served as an effective and safe therapy for strabismus and focal dystonia. However, muscular weakness is temporary and after 3-4 months, muscle strength usually recovers because functional recovery is mediated by nerve sprouting and reconstruction of the neuromuscular junction.

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Nov
2014

Miller Fisher syndrome is defined by a triad of symptoms, namely areflexia, ataxia, and ophthalmoparesis. The ophthalmoparesis is mostly severe, undulating weakness of eye movements with ptosis and increased fatigability resembling a neuromuscular transmission disorder. We present a 52-year-old man with severe Miller Fisher syndrome with a high level of anti-GQ1b antibodies and a presynaptic type of neuromuscular transmission disorder.

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Oct
2014

In diabetic patients, single-fiber electromyography (SFEMG) is often abnormal in the limb muscles and is considered unreliable in diagnosis of synaptic disorders. We aimed to compare SFEMG abnormalities of frontalis muscle (FM) and extensor digitorum communis muscle in diabetic patients with neuropathy and without neuropathy.
Stimulation SFEMG of FM and extensor digitorum communis muscle was performed in matched groups of 30 diabetic patients with neuropathy and 20 diabetic patients without neuropathy.

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