Muscle and Nerve via MedWorm.com

Origin of ulnar compound muscle action potential investigated in patients with ulnar neuropathy at the wrist

Muscle and Nerve — Fri, 12 Mar 2010 00:00:00 +0100

The compound muscle action potential from the abductor digiti minimi muscle is bi-lobed, and its second peak is formed by far-field potentials (FFPs). We investigated their origin in two patients with ulnar neuropathy at the wrist that spared the hypothenar muscles. FFPs were lost or distorted, which indicated that the deep motor branch-innervated muscles, such as the interossei, mainly contributed to the FFPs, especially to their initial N1 and steep following P1 components. Muscle Nerve, 2010 (Source: Muscle and Nerve)

Predicting fatigue during electrically stimulated non-isometric contractions

Muscle and Nerve — Fri, 12 Mar 2010 00:00:00 +0100

Mathematical prediction of power loss during electrically stimulated contractions is of value to those trying to minimize fatigue and to those trying to decipher the relative contributions of force and velocity. Our objectives were to: (1) develop a model of non-isometric fatigue for electrical stimulation-induced, open-chain, repeated extensions of the leg at the knee; and (2) experimentally validate the model. A computer-controlled stimulator sent electrical pulses to surface electrodes on the thighs of 17 able-bodied subjects. Isometric and non-isometric non-fatiguing and fatiguing leg extension torque and/or angle at the knee were measured. Two existing mathematical models, one of non-isometric force and the other of isometric fatigue, were combined to develop the non-isometric force-f...

I-Z-I complexes in congenital myopathy

Muscle and Nerve — Fri, 12 Mar 2010 00:00:00 +0100

A 3-month-old boy with hypotonia at birth succumbed to a congenital myopathy. The major finding in his muscle biopsy corresponded to I-Z-I complexes described previously in embryonic skeletal muscle. A few previous myopathy cases have described findings suggestive of I-Z-I-like complexes. A mutation affecting mononuclear myoblasts or early myotubes was suspected, although an acquired lesion could not be ruled out. The findings may also have been altered by secondary events in this unusual case. Muscle Nerve, 2010 (Source: Muscle and Nerve)

Hereditary amyloidosis of the Finnish type in a German family: Clinical and electrophysiological presentation

Muscle and Nerve — Fri, 12 Mar 2010 00:00:00 +0100

Hereditary amyloidosis of the Finnish type (HAF, or familial amyloid polyneuropathy type IV) is an autosomal dominant disease that has been described most commonly in the Finnish population but has also been found in some other countries. Herein we report the first German family whose members suffer from this condition. There are no known Finnish ancestors. We performed clinical and electrophysiological examinations in 22 members of this family. All symptomatic family members suffered from facial palsy, and most of them had peripheral neuropathy. One patient had confirmed corneal lattice dystrophy. Additional symptoms were hypoglossal nerve involvement in 5 patients and oculomotor nerve palsy in 1 patient. The lips of all older patients appeared thickened. The causative G654A mutation in t...

Quantification method affects estimates of voluntary quadriceps activation

Muscle and Nerve — Fri, 12 Mar 2010 00:00:00 +0100

The aim of this study was to investigate the effect of quantification method on estimates of voluntary quadriceps muscle activation. Twenty-two people with no history of serious lower extremity injuries underwent voluntary quadriceps activation testing at 60° of knee flexion. Estimates of quadriceps activation were derived with: (1) a formula based on the interpolated twitch technique (ITT); (2) the central activation ratio (CAR); and (3) a modified central activation ratio. Predictive equations were developed that describe the relationships between the three methods. Significant differences (P < 0.001) were observed between the estimates of voluntary quadriceps muscle activation obtained using the three methods (ITT percent activation = 93.0 ± 6.4%, CAR = 95.9 ± 3.8%, modified CAR = 98...

Bedside diagnosis of rippling muscle disease in CAV3 p.A46T mutation carriers

Muscle and Nerve — Fri, 12 Mar 2010 00:00:00 +0100

Thirty-nine members, ages 1 to 67 years, of a Swedish family with rippling muscle disease (RMD) were investigated to assess genotype-phenotype correlations. Clinical, neurophysiological, and muscle morphological examinations were performed. Genetic analysis was performed in 38 individuals. Twenty-three patients had percussion-induced muscle mounding (PIMM) and percussion-induced rapid contractions (PIRC). Rippling and hyperCKemia were not found in all patients. Weakness was minor or absent. The electromyogram showed absence of electrical activity in ripples and PIMM, and muscle biopsy specimens confirmed caveolin-3 deficiency and absence of caveolae. Genetic analysis revealed a CAV3 c.G136A transition resulting in a p.A46T missense mutation in affected family members. The phenotype in thes...

HIV neuropathy in South Africans: Frequency, characteristics, and risk factors

Muscle and Nerve — Fri, 12 Mar 2010 00:00:00 +0100

The purpose was to estimate the frequency, characteristics, and risk factors of HIV-associated distal sensory polyneuropathy (DSP) among South Africans who attend an urban community-based clinic. In a cross-sectional study, neuropathy status was determined in 598 HIV-infected adults using validated tools (Brief Peripheral Neuropathy Screen and a modified version of the Total Neuropathy Score) to categorize subjects as DSP versus no DSP. Symptomatic DSP (SDSP) required the presence of at least two neuropathic signs together with symptoms. Clinical, anthropometric, and laboratory evaluations were prospectively performed. CD4 counts, antiretroviral therapy (ART), and questionnaires regarding previous tuberculosis (TB) and alcohol exposure were collected retrospectively. Approximately half (49...

Branched-chain amino acids protect against dexamethasone-induced soleus muscle atrophy in rats

Muscle and Nerve — Thu, 18 Feb 2010 00:00:00 +0100

We investigated the utility of branched-chain amino acids (BCAA) in dexamethasone-induced muscle atrophy. Dexamethasone (600 [mu]g/kg, intraperitoneally) and/or BCAA (600 mg/kg, orally) were administered for 5 days in rats, and the effect of BCAA on dexamethasone-induced muscle atrophy was evaluated. Dexamethasone decreased total protein concentration of rat soleus muscles. Concomitant administration of BCAA reversed the decrease. Dexamethasone decreased mean cross-sectional area of soleus muscle fibers, which was reversed by BCAA. Dexamethasone increased atrogin-1 expression, which has been reported to play a pivotal role in muscle atrophy. The increased expression of atrogin-1 mRNA was significantly attenuated by BCAA. Furthermore, dexamethasone-induced conversion from microtubule-associ...

Effects of prolonged repetitive stimulation of median, ulnar and peroneal nerves

Muscle and Nerve — Thu, 18 Feb 2010 00:00:00 +0100

In this study we describe the changes in CMAP with prolonged RNS among commonly tested normal nerves. Our findings have important implications with regard to RNS. Muscle Nerve, 2010 (Source: Muscle and Nerve)

Validation of an incremental motor unit number estimation technique in rabbits

Muscle and Nerve — Thu, 18 Feb 2010 00:00:00 +0100

Motor unit number estimation (MUNE) allows for quantitative assessment of functional motor units in a nerve. Several techniques have been applied to human studies. Although MUNE has been performed in animals to study neurological disorders, reproducibility has not been addressed. We analyzed the test-retest reproducibility of an incremental MUNE technique in rabbits and performed histological correlation. A peroneal MUNE was performed in 9 rabbits on two occasions separated by 30 days. MUNE was then performed on 18 rabbits prior to euthanize. A count of total fibers and a second count of large myelinated fibers were performed on nerve cross-sections. Test-retest reproducibility revealed an intraclass correlation coefficient (ICC) of 0.75. The average test-retest relative difference was 26....

Preservation of muscle spindles in a 27-year-old Duchenne muscular dystrophy patient: Importance for regenerative medicine strategies

Muscle and Nerve — Thu, 11 Feb 2010 00:00:00 +0100

No abstract. (Source: Muscle and Nerve)

Muscle weakness and atrophy are associated with decreased regenerative capacity and changes in mTOR signaling in skeletal muscles of venerable (18-24-month-old) dystrophic mdx mice

Muscle and Nerve — Thu, 11 Feb 2010 00:00:00 +0100

The muscles of mdx mice progressively deteriorate with age. We wanted to know whether this is associated with a decrease in regenerative capacity and/or changes in the mammalian target of rapamycin complex (mTOR) signaling pathway. Muscles of mdx mice aged 5 weeks, 5, 12, and 18-24 months were studied. Maximal force and muscle weight of the older mice were decreased as compared to younger adult mice. Activation of the mTOR signaling pathway, i.e., phosphorylation of Akt (also known as protein kinase B) and ribosomal protein S6 was also reduced in the older mice. Moreover, 14 days after cardiotoxin injury the degree of recovery of maximal force and muscle weight were less in the older mice. In contrast to younger mice, there was also activation of the mTOR pathway during regeneration in the...

Myopathy and parkinsonism in phosphoglycerate kinase deficiency

Muscle and Nerve — Thu, 11 Feb 2010 00:00:00 +0100

A 25-year-old man with exertional myoglobinuria had no evidence of hemolytic anemia, but he had severe parkinsonism that was responsive to levodopa. Phosphoglycerate kinase (PGK) activity was markedly decreased in muscle, and molecular analysis of the PGK1 gene identified the p.T378P mutation that was recently reported in a patient with isolated myopathy. This case reinforces the concept that PGK deficiency is a clinically heterogeneous disorder and raises the question of a relationship between PGK deficiency and idiopathic juvenile Parkinson disease. Muscle Nerve, 2010 (Source: Muscle and Nerve)

Induction of myogenic differentiation by SDF-1 via CXCR4 and CXCR7 receptors

Muscle and Nerve — Thu, 11 Feb 2010 00:00:00 +0100

The stromal cell-derived factor (SDF)-1/CXC receptor 4 (CXCR4) axis has been shown to play a role in skeletal muscle development, but its contribution to postnatal myogenesis and the role of the alternate SDF-1 receptor, CXC receptor 7 (CXCR7), are poorly characterized. Western blot analysis and real-time polymerase chain reaction (PCR) were performed to evaluate in vitro the effect of SDF-1 and CXCR4 and CXCR7 inhibition on myogenic differentiation. Proliferating myoblasts express CXCR4, CXCR7, and SDF-1; during myogenic differentiation, CXCR4 and CXCR7 levels are downregulated, and SDF-1 release is decreased. SDF-1 anticipates myosin heavy chain accumulation and myotube formation in both C2C12 myoblasts and satellite cells. Interestingly, inhibition of CXCR4 and CXCR7 signaling, either b...

Dorsal caudal tail and sciatic motor nerve conduction studies in adult mice: Technical aspects and normative data

Muscle and Nerve — Thu, 11 Feb 2010 00:00:00 +0100

Mice provide an important tool to investigate human neuromuscular disorders. The variability of electrophysiological techniques limits direct comparison between studies. The purpose of this study was to establish normative motor nerve conduction data in adult mice. The dorsal caudal tail nerve and sciatic nerve motor conduction studies were performed bilaterally on restrained anesthetized adult mice. The means and standard deviations for each electrophysiological parameter were determined in normal mice. Data were compared with inflammatory demyelinating polyneuropathy mice to determine whether these parameters discriminate between normal and abnormal peripheral nerves. Normal adult mice had a distal latency of 0.89 (±0.17) ms and 0.75 (±0.09) ms, distal compound motor unit action potent...

The inhibitory effect of a chewing task on a human jaw reflex

Muscle and Nerve — Thu, 11 Feb 2010 00:00:00 +0100

This study was undertaken to investigate whether an inhibitory jaw reflex could be modulated by experimentally controlled conditions that mimicked symptoms of temporomandibular disorders. Reflecting on previous work, we anticipated that these conditions might suppress the reflex. Electromyographic recordings were made from a masseter muscle in 18 subjects, while electrical stimuli were applied to the upper lip. An inhibitory reflex wave (mean latency 47 ms) was identified and quantified. Immediately following an accelerated chewing task, which in most cases produced muscle fatigue and/or pain, the size of the reflex wave decreased significantly by about 30%. The suppression of inhibitory jaw reflexes by fatigue and pain may result in positive feedback, which may contribute to the symptoms ...

SB431542 treatment promotes the hypertrophy of skeletal muscle fibers but decreases specific force

Muscle and Nerve — Thu, 11 Feb 2010 00:00:00 +0100

The small molecule inhibitor SB431542 inhibits activin type I receptors. The muscle growth-inhibitor myostatin binds to and signals via these receptors. The aim of this study was to test the hypothesis that SB431542 can inhibit myostatin-related Smad signaling and induce muscle growth in cultured C2C12 myotubes and increase growth and specific force in cultured Xenopus muscle fibers. The effect of SB431542 was assessed in vitro on C2C12 myotubes and ex vivo using mature Xenopus muscle fibers. SB431542 treatment reduced myostatin-induced C-terminal Smad2 phosphorylation and resulted in the formation of enlarged myotubes. However myogenin expression was unchanged, while p70 S6k phosphorylation at Thr389, total myosin heavy chain, and the rate of protein synthesis were all reduced. Mature Xen...

Minocycline-induced dermatomyositis

Muscle and Nerve — Fri, 29 Jan 2010 00:00:00 +0100

We report a previously healthy patient who developed a panniculitis and histopathologically proven dermatomyositis during treatment with minocycline for acne vulgaris. Her signs and symptoms resolved completely upon cessation of minocycline. This case illustrates a novel adverse effect of a widely prescribed medication. Muscle Nerve, 2010 (Source: Muscle and Nerve)

A novel CLCN1 mutation (G1652A) causing a mild phenotype of thomsen disease

Muscle and Nerve — Fri, 29 Jan 2010 00:00:00 +0100

We investigated a 62-year-old man who had mild clinical features of myotonia congenita. He was found to have a novel heterozygous G-to-A nucleotide substitution at position 1652 in exon 15 of the CLCN1 gene. Clinicogenetic studies performed on his family revealed that his asymptomatic son also shared the mutation. We conclude that a novel chloride channel mutation (G1652A) has caused a mild form of autosomal-dominant myotonia congenita (Thomsen disease) in this family. Muscle Nerve, 2010 (Source: Muscle and Nerve)

Small fiber neuropathy in female patients with fabry disease

Muscle and Nerve — Fri, 29 Jan 2010 00:00:00 +0100

Recent studies suggest that heterozygous female Fabry disease (FD) patients develop peripheral neuropathy. We used skin biopsy to define somatic and autonomic peripheral nerve characteristics in 21 females with FD who were mainly asymptomatic and had normal renal function. Somatic epidermal and dermal autonomic nerve fiber reductions were found, prevalently in the leg, and no differences were found between symptomatic and asymptomatic individuals. Our findings suggest that females with FD, although asymptomatic, may have somatic and autonomic small fiber neuropathy. Muscle Nerve, 2010 (Source: Muscle and Nerve)

Piriformis Syndrome

Muscle and Nerve — Fri, 29 Jan 2010 00:00:00 +0100

No abstract. (Source: Muscle and Nerve)

Effects of coil characteristics for femoral nerve magnetic stimulation

Muscle and Nerve — Fri, 29 Jan 2010 00:00:00 +0100

The aim of this study was to compare the efficiency of two coils used for femoral nerve magnetic stimulation and to compare them with electrical stimulation in inducing maximal response of the quadriceps. The mechanical and electromyographic (EMG) responses were dependent on the coil used. The 45-mm double coil showed greater efficiency to elicit a maximal quadriceps response, which was similar to electrical stimulation. Muscle Nerve, 2010 (Source: Muscle and Nerve)

Excitability properties of mouse motor axons in the mutant SOD1G93A model of amyotrophic lateral sclerosis

Muscle and Nerve — Thu, 21 Jan 2010 00:00:00 +0100

Non-invasive excitability studies of motor axons in patients with amyotrophic lateral sclerosis (ALS) have revealed a changing pattern of abnormal membrane properties with disease progression, but the heterogeneity of the changes has made it difficult to relate them to pathophysiology. The SOD1G93A mouse model of ALS displays more synchronous motoneuron pathology. Multiple excitability measures of caudal and sciatic nerves in mutant and wild-type mice were compared before onset of signs and during disease progression (4-19 weeks), and they were related to changes in muscle fiber histochemistry. Excitability differences indicated a modest membrane depolarization in SOD1G93A axons at about the time of symptom onset (8 weeks), possibly due to deficient energy supply. Previously described exci...

Role of renshaw cells in amyotrophic lateral sclerosis

Muscle and Nerve — Fri, 15 Jan 2010 00:00:00 +0100

In this article the role of Renshaw cell involvement in experimental amyotrophic lateral sclerosis (ALS) is discussed, with an emphasis on the anatomy, physiology, and possible role in motor control of Renshaw cells. These cells are located in lamina VII of the spinal cord, are excited by motor axon collaterals, and inhibit homonymous and synergistic motoneurons in a negative-feedback fashion (recurrent inhibition). Early dysfunction and/or loss of Renshaw cells has been suggested to occur in experimental ALS, and the hypothesis has been put forward that this may be the event that makes motoneurons more susceptible to glutamatergic toxicity in ALS. However, Renshaw cell properties and connectivity - in particular, the lack of recurrent inhibition in the more distal muscles of the limbs whe...

L1 radiculopathy mimicking meralgia paresthetica: A case report

Muscle and Nerve — Fri, 15 Jan 2010 00:00:00 +0100

L1 radiculopathy is very rare and difficult to diagnose with needle electromyography. A patient presented with pain and hypesthesia on the anterolateral aspect of the left thigh. Nerve conduction studies and needle electromyography were normal, except for the quadratus lumborum and iliopsoas muscles, which showed abnormal spontaneous activity and polyphasic motor unit potentials with reduced recruitment patterns. Magnetic resonance imaging of the lumbar spine showed disc extrusion of the L1-2 intervertebral space with upward migration. This case demonstrates the usefulness of examination of the quadratus lumborum in the diagnosis of L1 radiculopathy. Muscle Nerve, 2010 (Source: Muscle and Nerve)

Leucine attenuates skeletal muscle wasting via inhibition of ubiquitin ligases

Muscle and Nerve — Fri, 15 Jan 2010 00:00:00 +0100

The aim of this study was to assess the effect of leucine supplementation on elements of the ubiquitin-proteasome system (UPS) in rat skeletal muscle during immobilization. This effect was evaluated by submitting the animals to a leucine supplementation protocol during hindlimb immobilization, after which different parameters were determined, including: muscle mass; cross-sectional area (CSA); gene expression of E3 ligases/deubiquitinating enzymes; content of ubiquitinated proteins; and rate of protein synthesis. Our results show that leucine supplementation attenuates soleus muscle mass loss driven by immobilization. In addition, the marked decrease in the CSA in soleus muscle type I fibers, but not type II fibers, induced by immobilization was minimized by leucine feeding. Interestingly,...

Effects of stimulation frequency and pulse duration on fatigue and metabolic cost during a single bout of neuromuscular electrical stimulation

Muscle and Nerve — Fri, 15 Jan 2010 00:00:00 +0100

We have investigated the effects of stimulation frequency and pulse duration on fatigue and energy metabolism in rat gastrocnemius muscle during a single bout of neuromuscular electrical stimulation (NMES). Electrical pulses were delivered at 100 Hz (1-ms pulse duration) and 20 Hz (5-ms pulse duration) for the high (HF) and low (LF) frequency protocols, respectively. As a standardization procedure, the averaged stimulation intensity, the averaged total charge, the initial peak torque, the duty cycle, the contraction duration and the torque-time integral were similar in both protocols. Fatigue was assessed using two testing trains delivered at a frequency of 100 Hz and 20 Hz before and after each protocol. Metabolic changes were investigated in vivo using 31P-magnetic resonance spectroscopy...

Construct and concurrent validation of the MG-QOL15 in the practice setting

Muscle and Nerve — Wed, 25 Nov 2009 00:00:00 +0100

Health-related quality of life (HRQOL) estimates can play an important role in patient care by providing information about the patient's perception of impairment and disability and the degree to which the patient tolerates disease manifestations. The 15-item myasthenia gravis quality of life scale (MG-QOL15) is an HRQOL evaluative instrument specific to patients with myasthenia gravis (MG) that was designed to be easy to administer and interpret. In this multicenter study we demonstrate the construct validity of the MG-QOL15 in the practice setting. To assess the construct validity, score distributions were examined for test items in different MG patient groups that represent the clinical spectrum of the disease. For example, patients in remission more frequently scored test items as norma...

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Muscle and Nerve — Wed, 25 Nov 2009 00:00:00 +0100

No abstract. (Source: Muscle and Nerve)

Ultrasonography in patients with ulnar neuropathy at the elbow: Comparison of cross-sectional area and swelling ratio with electrophysiological severity

Muscle and Nerve — Wed, 25 Nov 2009 00:00:00 +0100

The aim of this study was to determine the diagnostic value of ultrasonographic measurements in ulnar neuropathy at the elbow (UNE) and to assess the relationship between the measurements and the electrophysiological severity. The largest anteroposterior diameter (LAPD) and cross-sectional area (CSA) measurements of the ulnar nerve were noted at multiple levels along the arm, and the distal-to-proximal ratios were calculated. Almost all of the measurements and swelling ratios between patients and controls showed statistically significant differences. The largest CSA, distal/largest CSA ratio, CSA at the epicondyle, and proximal LAPD had larger areas under the curve than other measurements. The sensitivity and specificity in diagnosing UNE were 95% and 71% for the largest CSA, 83% and 85% f...

Familial, demyelinating sensory and motor polyneuropathy with conduction block

Muscle and Nerve — Wed, 25 Nov 2009 00:00:00 +0100

We report a mother and son with a prednisone-responsive, multifocal, demyelinating, predominantly sensory polyneuropathy that was associated with an isoleucine92valine polymorphism of lipopolysaccharide-induced TNF-alpha factor (LITAF). The mother had a multifocal, acquired, demyelinating sensory and motor polyneuropathy (MADSAM)-like presentation. The son developed left peroneal neuropathy during acute Lyme disease with a subsequent relapsing, MADSAM-like illness, despite antibiotic treatment. Both shared prednisone responsiveness and multifocal, demyelinating features electrophysiologically. MADSAM may be familial (FaDSAM) and respond to prednisone. Muscle Nerve, 2010 (Source: Muscle and Nerve)

Correlation between the combined sensory index and clinical outcome after carpal tunnel decompression: A retrospective review

Muscle and Nerve — Wed, 25 Nov 2009 00:00:00 +0100

The objective of this study was to examine the association between the CSI and symptom relief from pain and parasthesiae following surgical intervention. Retrospective chart review was performed on 272 patients, diagnosed with carpal tunnel syndrome by electrodiagnostic criteria, who proceeded to undergo open or endoscopic carpal tunnel release with postoperative follow-up at an academic medical center between 1996 and 2006. The CSI demonstrated statistical significance (P = 0.03) for correlation with resolution of pain and parasthesiae following carpal tunnel decompression. Patients with a CSI of 2.5-4.6 had the best prognosis for resolution of pain and parasthesiae following surgical intervention. Median compound muscle action potential (CMAP) amplitude and median motor latency were also...

The 6-minute walk test as a new outcome measure in Duchenne muscular dystrophy

Muscle and Nerve — Wed, 25 Nov 2009 00:00:00 +0100

Walking abnormalities are prominent in Duchenne muscular dystrophy (DMD). We modified the 6-minute walk test (6MWT) for use as an outcome measure in patients with DMD and evaluated its performance in 21 ambulatory boys with DMD and 34 healthy boys, ages 4 to 12 years. Boys with DMD were tested twice, [sim]1 week apart; controls were tested once. The groups had similar age, height, and weight. All tests were completed. Boys who fell recovered rapidly from falls without injury. Mean ± SD [range] 6-minute walk distance (6MWD) was lower in boys with DMD than in controls (366 ± 83 [125-481] m vs. 621 ± 68 [479-754] m; P < 0.0001; unpaired t-test). Test-retest correlation for boys with DMD was high (r = 0.91). Stride length (R2 = 0.89; P < 0.0001) was the major determinant of 6MWD for both bo...

Limited diagnostic value of enzyme analysis in patients with mitochondrial tRNA mutations

Muscle and Nerve — Wed, 25 Nov 2009 00:00:00 +0100

We evaluated the diagnostic value of respiratory chain (RC) enzyme analysis of muscle in adult patients with mitochondrial myopathy (MM). RC enzyme activity was measured in muscle biopsies from 39 patients who carry either the 3243A>G mutation, other tRNA point mutations, or single, large-scale deletions of mtDNA. Findings were compared with those obtained from asymptomatic relatives with the 3243A>G mutation, myotonic dystrophy patients, and healthy subjects. Plasma lactate concentration, maximal oxygen uptake, and ragged-red fibers/cytochrome c-negative fibers in muscle were also determined. Only 10% of patients with the 3243A>G point mutation had decreased enzyme activity of one or more RC complexes, whereas this was the case for 83% of patients with other point mutations and 62% of pat...

Short-term training adaptations in maximal motor unit firing rates and afterhyperpolarization duration

Muscle and Nerve — Wed, 25 Nov 2009 00:00:00 +0100

In this study we investigated age- and training-related adaptations in maximal motor unit firing rates and the duration of the motoneuron afterhyperpolarization (AHP) in the dorsiflexor muscles of the foot. Subjects included 30 young (21.9 ± 3.1 years) and 30 older (72.9 ± 4.6 years) individuals, who were randomly assigned to a control or training group. Maximal voluntary force (MVC), maximal motor unit firing rate, and motoneuron AHP duration were measured on two occasions. The training group participated in six dorsiflexor exercise training sessions between test and retest. At baseline, young subjects had higher MVC force and maximal motor unit firing rate, and shorter AHP duration, compared with older subjects. Young and older subjects in the trained group demonstrated a respective 17...

Psychosocial dysfunction in the first year after Guillain-Barré syndrome

Muscle and Nerve — Wed, 25 Nov 2009 00:00:00 +0100

In this investigation we study the impact of Guillain-Barré syndrome (GBS) on psychological distress, depressive symptoms, and health status of patients during the first year after GBS. At 3, 6, and 12 months, patients were given the General Health Questionnaire, the Sickness Impact Profile, and the Center for Epidemiologic Studies Depression Scale. Eighty-five patients participated. Psychological distress and depressive symptoms were present but improved between 3 and 6 months. At 12 months the psychosocial health status was still impaired. Patients who perceived their physical residua to be moderately to seriously disruptive and patients with muscle ache and cramps had worse scores on all scales. It can be concluded that most of the improvement occurred in the first 6 months. Psychosoci...

Insights of the effects of polyethylene glycol 400 on mammalian and avian nerve terminals

Muscle and Nerve — Wed, 25 Nov 2009 00:00:00 +0100

Polyethylene glycol (PEG) has been widely used as a solvent among other applications. An ideal solvent is one that does not interfere with an in vitro biological system, unless it is a bioactive agent. Herein, a facilitatory neurotransmission effect was exhibited by PEG (20 [mu]M) in mammalian (67 ± 12.5%, n = 4) and avian (74 ± 6.8%, n = 6) neuromuscular preparations. In curarized preparations, PEG did not reverse the neurotransmission blockade induced by D-tubocurarine (D-Tc, 5.8 [mu]M, n = 6) as promoted by neostigmine (12 [mu]M, n = 4). A possible presynaptic action of PEG was ruled out, because quantal acetylcholine (ACh) content was similar to the control Tyrode-incubated mammalian preparation. PEG showed improved sarcolemmal sensitivity, both under direct (sarcolemma) and indirect...

Atypical double nerve lesion after humeral fracture: Diagnosis by ultrasound

Muscle and Nerve — Fri, 13 Nov 2009 00:00:00 +0100

No abstract. (Source: Muscle and Nerve)

Diabetic neuropathy: Electrophysiological and morphological study of peripheral nerve degeneration and regeneration in transgenic mice that express IFN[beta] in [beta] cells

Muscle and Nerve — Fri, 13 Nov 2009 00:00:00 +0100

This study was undertaken to characterize the degenerative and regenerative responses of peripheral nerves after induced sciatic nerve damage in transgenic rat insulin I promoter / human interferon beta (RIP/IFN[beta]) mice made diabetic with a low dose of streptozotocin (STZ) as an animal model of diabetic complications. In vivo, histological and immunohistological studies of cutaneous and sciatic nerves were performed after left sciatic crush. Functional tests, cutaneous innervation, and sciatic nerve evaluation showed pronounced neurological reduction in all groups 2 weeks after crush. All animals showed a gradual recovery but this was markedly slower in diabetic animals in comparison with normoglycemic animals. The delay in regeneration in diabetic RIP/IFN[beta] mice resulted in an inc...

Chemotherapy is successful in sporadic late onset nemaline myopathy (SLONM) with monoclonal gammopathy

Muscle and Nerve — Fri, 13 Nov 2009 00:00:00 +0100

No abstract. (Source: Muscle and Nerve)

Multilevel ulnar neuropathy caused by multiple intraneural hemangiomas

Muscle and Nerve — Fri, 13 Nov 2009 00:00:00 +0100

We report the case of a 47-year-old man with multilevel ulnar neuropathy caused by multiple intraneural hemangiomas in an ipsilateral ulnar nerve. Multilevel ulnar neuropathy was detected by electrodiagnosis, and intraneural hemangiomas were suggested by ultrasonographic evaluation before the operation. Careful surgical excision under an operating microscope ameliorated the patient's symptoms without recurrence. Muscle Nerve, 2010 (Source: Muscle and Nerve)

Ocular myasthenia gravis in a senior population: Diagnosis, therapy, and prognosis

Muscle and Nerve — Fri, 13 Nov 2009 00:00:00 +0100

The objectives of this study were (I) to explore the prognosis of ocular myasthenia gravis (OMG) in patients with onset at age 70 years and above (i.e. senior persons); (2) to identify predictors of secondary generalization in this age group; and 3) to address the effects of immunotherapy on this population of patients. We performed a retrospective analysis of 39 patients with myasthenia gravis who presented with only ocular signs and symptoms after age 70 years. Generalized myasthenia gravis (GMG) developed in 12 OMG patients (31%). None of the GMG patients required ventilator assistance or a feeding tube, Of the 12 ocular patients progressing to GMG, only one (8%) received immunotherapy prior to generalization. Of those OMG patients who did not progress to OMG, 52% received immunomodulat...

Genetic variability in the myostatin gene does not explain the muscle hypertrophy and clinical penetrance in myotonia congenita

Muscle and Nerve — Fri, 13 Nov 2009 00:00:00 +0100

No abstract. (Source: Muscle and Nerve)

Acute-onset chronic inflammatory demyelinating polyneuropathy with cranial nerve involvement, dysautonomia, respiratory failure, and autoantibodies

Muscle and Nerve — Fri, 13 Nov 2009 00:00:00 +0100

We examined a 27-year-old woman who developed rapidly progressive quadriplegia and acute respiratory failure that required mechanical ventilation in the intensive care unit. It was unclear whether this was a presentation of Guillain-Barré syndrome (GBS) or acute-onset chronic inflammatory demyelinating polyradiculoneuropathy (A-CIDP). Remarkable features included multiple cranial nerve involvement, respiratory failure, dysautonomia, and skin manifestations. Several autoantibodies were elevated, including antinuclear (ANA), anticardiolipin (aCL), thyroid, and calcium-sensing receptor (CaSR) autoantibodies. The patient was initially diagnosed with GBS and treated with intravenous immunoglobulin (IVIg). After almost complete recovery, relapse with quadriplegia and respiratory failure was obs...

The illusion of severe carpal tunnel syndrome (CTS)

Muscle and Nerve — Fri, 13 Nov 2009 00:00:00 +0100

In this report we present a young woman with mild bilateral CTS, based on electrophysiological studies, in whom marked thenar atrophy was on a congenital basis related to the VATER association (vertebral anomalies, anal atresia, tracheoesophageal fistula, and radial or renal abnormalities). Muscle Nerve, 2010 (Source: Muscle and Nerve)

A Patient with neurofibromatosis type 1 and Charcot-Marie-Tooth disease type 1B

Muscle and Nerve — Fri, 13 Nov 2009 00:00:00 +0100

We describe a patient with both neurofibromatosis type 1 and Charcot-Marie-Tooth disease type 1B. Although one might expect an overwhelming tumor burden due to the combination of these two disorders, the two mutations did not appear to interact. Muscle Nerve, 2010 (Source: Muscle and Nerve)

Diffuse large B-cell lymphoma presenting as piriformis syndrome

Muscle and Nerve — Fri, 13 Nov 2009 00:00:00 +0100

Piriformis syndrome (PS) is a rare condition characterized by pain and paresthesia of the buttock, often radiating to the posterior thigh. A patient with sciatica that was clinically suspicious for PS, underwent diagnostic work-up. A diagnosis of diffuse large B-cell lymphoma with neurolymphomatosis (NL) was made. To our knowledge, this is the first report of NL presenting as PS. NL is a possible cause of secondary PS. Muscle Nerve, 2010 (Source: Muscle and Nerve)

Schwann cells as a source of insulin-like growth factor-1 for extraocular muscles

Muscle and Nerve — Fri, 13 Nov 2009 00:00:00 +0100

Precise force regulation is fundamentally important for extraocular muscle (EOM) function. Insulin-like growth factor-1 (IGF-1) plays a major role in EOM force regulation, but the source of endogenous IGF-1 is unclear. Multiple IGF-1 sources may supply EOMs, including: the EOM itself; the systemic circulation; innervating motoneurons; and Schwann cells within nerves. IGF-1 expression was measured in chicken during oculomotor system maturation by using real-time polymerase chain reaction (PCR). Accumulation of radiolabeled IGF-1 in EOMs was compared after either injection into the vascular circulation or into the trochlear nerve. Schwann cells were the most prominent IGF-1 source. A microtubule-dependent mechanism exists to anterogradely transport IGF-1 to EOMs. EOMs were significantly more...

Redetermination of the optimal stimulation intensity modifies resting H-reflex recovery after a sustained moderate-intensity muscle contraction

Muscle and Nerve — Fri, 13 Nov 2009 00:00:00 +0100

This study aimed to determine whether the time-course of maximal resting H-reflex amplitude (Hmax) recovery after a prolonged moderate-intensity muscle contraction differs according to the optimal stimulation intensity used (predetermined vs. readjusted). Thirteen males performed a sustained isometric plantar flexion at 40% of their maximal voluntary contraction torque output until exhaustion. Hmax of the soleus muscle was recorded before and 2, 6, 10, and 14 min after the end of the contraction, then normalized by the respective maximal M-wave to form the Hmax/Mmax ratio. During recovery, pre- and redetermined optimal stimulation intensities (mini-recruitment curve drawn before each recovery measurement) were applied randomly to measure Hmax. When using redetermined stimulation intensitie...

Evidence of gender-specific motor templates to resist valgus loading at the knee

Muscle and Nerve — Fri, 13 Nov 2009 00:00:00 +0100

In this study, we sought to explore the effect of gender on volitional and reflex neuromuscular responses to a rapid valgus perturbation at the knee applied under "intervene" and "do not intervene" conditions. Multiple 7° ramp-and-hold valgus perturbations were applied at the neutrally extended knee of 12 male and 12 female healthy subjects, while surface electromyography over the quadriceps and hamstrings recorded the neuromuscular response. Volitional responses did not vary between groups, perhaps reflecting the relative novelty of the loading direction. However, reflex responses observed under the "do not intervene" paradigm did vary by gender. Males demonstrated much more frequent and consistent reflex muscle activation than females. Moreover, muscle activation patterns were gender-sp...

Clinical and electrophysiological parameters distinguishing acute-onset chronic inflammatory demyelinating polyneuropathy from acute inflammatory demyelinating polyneuropathy

Muscle and Nerve — Fri, 30 Oct 2009 00:00:00 +0100

This study suggests that patients presenting acutely with a demyelinating polyneuropathy and the aforementioned clinical features should be closely monitored as they may be more likely to have CIDP at follow-up. Muscle Nerve, 2009 (Source: Muscle and Nerve)

Martin-Gruber anastomosis with anomalous superficial radial innervation to ulnar dorsum of hand: A pitfall when common variants coexist

Muscle and Nerve — Fri, 30 Oct 2009 00:00:00 +0100

The Martin-Gruber anastomosis (MGA) is the most common anatomic variation in the upper extremity. Anomalous superficial radial innervation to the ulnar dorsum of the hand is the most common cause of an absent dorsal ulnar cutaneous (DUC) response. The coexistence of these variants introduces a relatively common yet underrecognized potential pitfall in nerve conduction studies (NCS). We performed confirmatory NCS in two cases referred for ulnar neuropathy in the forearm (case 1) and at the elbow (UNE, case 2). Initial NCS in both cases suggested ulnar nerve injury at the forearm and elbow, respectively, based on an apparent conduction block in ulnar motor fibers in the forearm (case 1) and elbow (case 2), and absent DUC responses. Additional NCS documented an MGA in the mid-forearm (case 1)...

Clinical and electrophysiological parameters that distinguishing acute-onset chronic inflammatory demyelinating polyneuropathy from acute inflammatory demyelinating polyneuropathy

Muscle and Nerve — Fri, 30 Oct 2009 00:00:00 +0100

Kinetics of neuromuscular changes during low-frequency electrical stimulation

Muscle and Nerve — Fri, 30 Oct 2009 00:00:00 +0100

The purpose of the study was to examine the time course of neuromuscular fatigue components during a low-frequency electrostimulation (ES) session. Three bouts of 17 trains of stimulation at 30 HZ (4 s on, 6 s off) were used to electrically induce fatigue in the plantar flexor muscles. Before and after every 17-train bout, torque, electromyographic activity [expressed as root mean square (RMS) and median frequency (MF) values], evoked potentials (M-wave and H-reflex), and the level of voluntary activation (LOA, using twitch interpolation technique) were assessed. Torque during maximal voluntary contraction decreased significantly from the very first stimulation bout (-6.6 ± 1.11%, P < 0.001) and throughout the session (-10.32 ± 1.68% and -11.53 ± 1.27%, for the second and third bouts, r...

Magnetic resonance imaging diagnosis of panniculitis in dermatomyositis

Muscle and Nerve — Fri, 30 Oct 2009 00:00:00 +0100

No abstract. (Source: Muscle and Nerve)

Clinical findings in MuSK-antibody positive myasthenia gravis: A U.S. experience

Muscle and Nerve — Fri, 30 Oct 2009 00:00:00 +0100

We performed a retrospective chart review on 53 muscle-specific kinase antibody (MuSK-Ab)-positive myasthenia gravis (MG) patients at nine university-based centers in the U.S. Of these, 66% were Caucasian, 85% were women, and age of onset was 9-79 years. Twenty-seven patients were nonresponsive to anticholinesterase therapy. Myasthenia Gravis Foundation of America improvement status was achieved in 53% patients on corticosteroids, 51% with plasma exchange, and in 20% on intravenous immunoglobulin (IVIG). Thymectomy was beneficial in 7/18 patients at 3 years. Long-term ([ge]3 years) outcome was very favorable in 58% of patients who achieved remission and/or minimal manifestation status. Overall, 73% improved. There was one MG-related death. This survey reinforces several cardinal features o...

Coactivation at the ankle joint is not sufficient to estimate agonist and antagonist mechanical contribution

Muscle and Nerve — Fri, 30 Oct 2009 00:00:00 +0100

The aim of this study was to assess, via an electromyographic (EMG) biofeedback method, the mechanical contribution of both agonist and antagonist muscles during maximal voluntary contraction (MVC). We compared this original method with the MVC-EMGmax ratio and the torque/EMG relationship method, both of which are commonly used to estimate antagonist torque. The plantarflexion (PF) and dorsiflexion (DF) MVCs were measured simultaneously with EMG activity of triceps surae (TS) and tibialis anterior in 15 young adults (mean age 23 years). Antagonist torques obtained from the torque/EMG relationship and EMG biofeedback methods appeared to be similar. TS antagonist torque had a major mechanical impact on DF MVC ([sim]42%). EMG coactivation is significantly different than normalized antagonist ...

Joint angle dependence of intermuscle difference in postactivation potentiation

Muscle and Nerve — Fri, 30 Oct 2009 00:00:00 +0100

The purpose of this study was to examine the effect of ankle joint angle on the intermuscle difference in postactivation potentiation (PAP) between the medial gastrocnemius (MG) and soleus (SOL) muscles. At the neutral position of joint angle, dorsiflexion of 20°, and plantarflexion of 20°, twitch responses were evoked by stimulating the posterior tibial nerve with supramaximal intensity before and after a 10-s maximal voluntary plantarflexion at each joint angle. Mechanical properties of the MG and SOL muscles were assessed simultaneously and separately by using mechanomyography (MMG), and the extent of potentiation of each muscle was evaluated by peak-to-peak amplitude of the MMG signal. The MG showed greater potentiation than the soleus after the conditioning MVC in the neutral and do...

Coexistent autoimmune autonomic ganglionopathy and myasthenia gravis associated with non-small-cell lung cancer

Muscle and Nerve — Fri, 30 Oct 2009 00:00:00 +0100

We report the case of a 55-year-old man with non-small-cell lung cancer who underwent radiation, chemotherapy with carbotaxol and paclitaxel, and left upper lobe removal 2 years prior to evaluation. He was referred for disabling orthostatic hypotension (113/69 mm Hg supine and 66/47 mm Hg standing after 10 minutes) without a compensatory heart rate increase (57 to 59 beats per minute), fatigue, and constipation with episodes of ileus. Clinical examination showed mild ptosis bilaterally, fatiguable neck flexor weakness, and hip flexor weakness. Blood pressure response to Valsalva maneuver was abnormal with an absence of phase 4 overshoot and a Valsalva heart rate ratio of 1.04. Plasma norepinephrine level was low (79 pg/ml supine, 330 pg/ml standing). Single-fiber electromyography of the ri...

Unusual Charcot-Marie-Tooth phenotype due to a mutation within the intracellular domain of myelin protein zero

Muscle and Nerve — Fri, 30 Oct 2009 00:00:00 +0100

We report a family with a missense mutation, c.700G>T p.Asp234Tyr (deviant nomenclature: c.670G>T, p.Asp224Tyr), within the intracellular domain of myelin protein zero, who has distal sensorimotor symptoms, cramps, restless legs syndrome, neuropathic pain, and carpal tunnel syndrome. The index patient responded to intravenous immunoglobulin and immunosuppression, so there may be a possible secondary autoimmune process, probably triggered by altered antigen presentation due to mutated MPZ protein. Muscle Nerve, 2009 (Source: Muscle and Nerve)

Tibialis anterior branch involvement in fibular intraneural ganglia

Muscle and Nerve — Fri, 30 Oct 2009 00:00:00 +0100

This study characterizes the cystic involvement of this tibialis anterior branch and evaluates its significance. The magnetic resonance imaging (MRI) and clinical data of 23 patients with fibular intraneural ganglia were retrospectively reviewed. The tibialis anterior branch was consistently involved with the cyst, and this involvement, although variable, was more prominent than the cystic involvement of other terminal branches of the fibular nerve. The finding of cyst extension within a muscle end-organ branch seems likely to explain, in part, the characteristic clinical finding of preferential foot drop in patients with fibular intraneural ganglia. Muscle Nerve, 2009 (Source: Muscle and Nerve)

Homozygosity for dominant mutations increases severity of muscle channelopathies

Muscle and Nerve — Fri, 30 Oct 2009 00:00:00 +0100

We report herein the first cases of homozygous patients for sodium channel mutations responsible for paramyotonia congenita (I1393T) or hypokalemic periodic paralysis (R1132Q). A parallel was drawn between this unprecedented situation and that of myotonia congenita by including patients homozygous or heterozygous for the CLCN1 I556N channel mutation, which is known for incomplete dominance and penetrance. Standardized electromyographic (EMG) protocols combining exercise and cold served as provocative tests to compare homozygotes with heterozygotes for each of the three mutations. Surface-recorded compound muscle action potentials (CMAPs) were used to monitor muscle electrical activity, and myotonic discharges were evaluated by needle EMG. In heterozygous patients, exercise tests disclosed ...

Muscle imaging analogies in a cohort of patients with different clinical phenotypes caused by LMNA gene mutations

Muscle and Nerve — Fri, 30 Oct 2009 00:00:00 +0100

This study demonstrates that LMNA-gene-mutated patients devoid of any clinically detectable skeletal muscle involvement have the same pattern of leg muscle involvement as patients with overt skeletal muscle compromise. This finding suggests the presence of a continuum of skeletal muscle involvement among phenotypes of LMNA-gene-mutation-related skeletalmyopathy and cardiomyopathy. Muscle Nerve, 2009 (Source: Muscle and Nerve)

Early effects of carbachol on the morphology of motor endplates of mammalian skeletal muscle fibers

Muscle and Nerve — Fri, 30 Oct 2009 00:00:00 +0100

Long-term disturbance of the calcium homeostasis of motor endplates (MEPs) causes necrosis of muscle fibers. The onset of morphological changes in response to this disturbance, particularly in relation to the fiber type, is presently unknown. Omohyoid muscles of mice were incubated for 1-30 minutes in 0.1 mM carbachol, an acetylcholine agonist that causes an inward calcium current. In these muscles, the structural changes of the sarcomeres and the MEP sarcoplasm were evaluated at the light- and electron-microscopic level. Predominantly in type I fibers, carbachol incubation resulted in strong contractures of the sarcomeres underlying the MEPs. Owing to these contractures, the usual beret-like form of the MEP-associated sarcoplasm was deformed into a mushroom-like body. Consequently, the sq...

HIV lumbosacral radiculoplexus neuropathy mimicking lymphoma: Diffuse infiltrative lymphocytosis syndrome (DILS) restricted to nerve?

Muscle and Nerve — Fri, 30 Oct 2009 00:00:00 +0100

Diffuse infiltrative lymphocytosis syndrome (DILS) is a hyperimmune reaction against HIV. It leads to MHC-restricted clonal expansion of CD8 T cells characterized by circulating CD8 hyperlymphocytosis and CD8 T-cell infiltration in organs. Our patient presented with painful lumbosacral radiculoplexus neuropathy and tested positive for HIV. Nerve biopsy showed large collections of CD8 lymphocytes suspicious for lymphoma. Symptoms, signs, and repeat biopsy improved with antiretroviral treatment. The presentation and treatment response suggest that this case is localized DILS. Muscle Nerve, 2009 (Source: Muscle and Nerve)

Driving with polyneuropathy

Muscle and Nerve — Fri, 30 Oct 2009 00:00:00 +0100

Polyneuropathy may result in pain, numbness, and weakness, which may in turn affect driving ability. Medications used to treat neuropathic pain may alter cognition, which may further affect driving. Although such impairments have engendered questions about the driving safety in this group of patients, the rate of motor vehicle accidents (MVAs) in patients with neuropathy has not been studied rigorously. We surveyed patients with neuropathy from three medical centers for reported accident rate, and we analyzed variables related to increased risk for accidents compared to National Highway Traffic Safety Administration data. Surveys from 260 subjects demonstrated that 40.6% were involved in traffic accidents (0.11 accidents/year). Their accident rate was 10.8 MVAs per million vehicle miles tr...

Rituximab in the management of refractory myasthenia gravis

Muscle and Nerve — Wed, 21 Oct 2009 23:00:00 +0100

In this study, patients with refractory MG who were treated with rituximab were identified. A review of patients referred to the Yale Neuromuscular Clinic was performed. Patients with refractory MG who were treated with rituximab were reviewed for response to treatment. Patients who had muscle-specific kinase (MuSK+) or acetylcholine receptor (AChR+) antibodies were included. Six patients were identified who met the criteria described. All patients tolerated rituximab without side effects and had a reduced need for immunosuppressants and/or improvement in clinical function. Patients with refractory MG appeared to respond to rituximab in this small, retrospective study. This result suggests that a larger, prospective trial is indicated. Muscle Nerve, 2009 (Source: Muscle and Nerve)

Sporadic late onset nemaline myopathy responsive to IVIg and immunotherapy

Muscle and Nerve — Wed, 21 Oct 2009 23:00:00 +0100

We report two HIV-negative SLONM/monoclonal gammopathy patients who improved following intravenous immunoglobulin (IVIg) treatment alone or in combination with immunosuppressant agents. This favorable response to treatment suggests that a dysimmune mechanism is operative in some SLONM individuals. We suggest that IVIg deserves initial consideration for SLONM therapy. Muscle Nerve, 2009 (Source: Muscle and Nerve)

Reply to: Myotonic disorder without myotonia?

Muscle and Nerve — Wed, 21 Oct 2009 23:00:00 +0100

No abstract. (Source: Muscle and Nerve)

Does display sensitivity influence motor latency determination?

Muscle and Nerve — Wed, 07 Oct 2009 23:00:00 +0100

It is known that display sensitivity can affect onset latency measurement of compound muscle action potentials (CMAPs). We compared two display sensitivities with respect to intrarater and interrater reliability and measured to what degree display sensitivity influences the motor latency. We asked seven raters to mark the onset points of median CMAPs from 24 patients printed with display sensitivities of 5 mV/division and 0.5 mV/division on paper. The onset latencies were measured, and intraclass correlation coefficients (ICCs) were calculated. Most of the raters had excellent intrarater repeatability within a single sensitivity display setting. In contrast, the intrarater reliability using two different sensitivity settings was poor. ICCs calculated for interrater reliability were 0.93 at...

Factors associated with response to calcineurin inhibitors in myasthenia gravis

Muscle and Nerve — Wed, 07 Oct 2009 23:00:00 +0100

The objective was to assess which clinical factors of patients with myasthenia gravis (MG) are associated with responsiveness to calcineurin inhibitors (CNIs, cyclosporine and tacrolimus). We retrospectively analyzed the 6-month effects of CNIs in 62 MG patients. We excluded the influence of other immune treatments and determined factors associated with response to CNIs. The frequency of patients who achieved neither a [ge]3-point reduction in quantitative MG score nor a [ge]25% reduction in daily dose of prednisolone (poor responders) reached 35.5% (22/62) and 64.5% (40/62), respectively, compared with patients who achieved at least one of these improvements (responders). Neither dose nor blood concentration of CNIs differed between groups. Multivariate logistic regression analysis reveal...

Use of evans blue dye to compare limb muscles in exercised young and old mdx mice

Muscle and Nerve — Tue, 06 Oct 2009 23:00:00 +0100

Evans blue dye (EBD) is used to mark damaged and permeable muscle fibers in mouse models of muscular dystrophy and as an endpoint in therapeutic trials. We counted EBD-positive muscle fibers and extracted EBD from muscles sampled throughout the hindlimbs in young adult and old mdx mice to determine if the natural variability in morphology would allow measurement of a functional improvement in one limb compared to the contralateral limb. Following one bout of rotarod or treadmill exercise that greatly increased serum creatine kinase levels, the number of EBD+ muscle fibers in 12-19-month-old mdx mice increased 3-fold, EBD in the muscles increased, and, importantly, contralateral pairs of muscles contained similar amounts of EBD. In contrast, the intra- and interlimb amounts of EBD in 2-7-mo...

Ros-mediated activation of NF-[kappa]B and Foxo during muscle disuse

Muscle and Nerve — Tue, 06 Oct 2009 23:00:00 +0100

We examined reactive oxygen species as upstream activators of nuclear factor [kappa]B; (NF-[kappa]B) and forkhead box O (Foxo) in skeletal muscle during disuse atrophy. Catalase, an enzyme that degrades H2O2, was overexpressed in soleus muscles via plasmid injection prior to 7 days of hindlimb immobilization. The increased catalase activity abolished immobilization-induced transactivation of both NF-[kappa]B and Foxo and attenuated the loss of muscle mass. Thus, H2O2 may be an important initiator of these signaling pathways that lead to muscle atrophy. Muscle Nerve, 2009 (Source: Muscle and Nerve)

Central nervous system involvement in axonal Charcot-Marie-Tooth disease

Muscle and Nerve — Tue, 06 Oct 2009 23:00:00 +0100

No abstract. (Source: Muscle and Nerve)

Facioscapulohumeral muscular dystrophy: Do neurotrophins play a role?

Muscle and Nerve — Tue, 06 Oct 2009 23:00:00 +0100

Although the molecular defect of facioscapulohumeral muscular dystrophy (FSHD) is well established and involves the contraction of the polymorphic 3.3 kb D4Z4 repeat on the subtelomeric region of chromosome 4q35, the pathologic effects of this deletion remain largely unknown. As a consequence, no specific treatment for FSHD is at present available. Thus, there is the need to explore new areas in an attempt to better characterize pathophysiological alterations in FSHD that might be useful for managing the disease. Neurotrophins (nerve growth factor, brain-derived neurotrophic factor, neurotrophin-3, and neurotrophin-4/5) are a class of proteins involved in the development, maintenance, and function of neurons of the peripheral and central nervous systems. In addition, neurotrophins and thei...

Effects of exercise and muscle type on BDNF, NT-4/5, and TrKB expression in skeletal muscle

Muscle and Nerve — Tue, 06 Oct 2009 23:00:00 +0100

Muscle-derived neurotrophins are thought to contribute to the adaptation of skeletal muscle to exercise, but the effects of brief exercise interventions on BDNF, NT-4/5, and trkB are not understood. RNA was extracted for RT-PCR from soleus and medial gastrocnemius of Sprague-Dawley rats exercised on a treadmill at speeds up to 20 m/min at 5% incline for 5 or 10 days. BDNF expression was elevated in soleus following 5 days (184%, P < 0.001) but not 10 days of exercise. NT-4/5 and trkB were not affected at either time-point. BDNF mRNA was significantly higher in soleus at rest when compared with medial gastrocnemius (193%, P < 0.05). No significant effects of muscle type were detected for NT-4/5 and trkB. Our results indicate differential control of BDNF expression between soleus and medial ...

Syrian hamster infected with Leishmania infantum: A new experimental model for inflammatory myopathies

Muscle and Nerve — Tue, 06 Oct 2009 23:00:00 +0100

Idiopathic inflammatory myopathies (IIMs) are inflammatory disorders of unknown origin. On the basis of clinical, histopathological, and immunological features, they can be differentiated into three major and distinct subsets: dermatomyositis; polymyositis; and inclusion-body myositis. Although a few animal models for IIM are currently available, they lack several characteristic aspects of IIMs. The aim of our study was to examine skeletal muscle involvement in an experimental animal model of visceral leishmaniasis, a disseminated infection caused by the protozoan parasite Leishmania infantum, and to compare features of associated inflammation with those of human IIM. Syrian hamsters infected intraperitoneally with amastigotes of L. infantum were killed at 3 or 4 months post-infection, and...

Sonographic measurements of longitudinal median nerve sliding in patients following nerve repair

Muscle and Nerve — Tue, 06 Oct 2009 23:00:00 +0100

Nerve sliding may be restricted following nerve repair. This could result in increased tension across the repair site and lead to poor functional recovery of the nerve. Ultrasound was used to examine longitudinal median nerve sliding in 10 patients who had previously undergone nerve repair surgery following complete division of the median nerve. The median longitudinal movement in the forearm in response to metacarpophalangeal (MCP) joint movements was 2.15 mm on the injured side, compared with 2.54 mm on the uninjured side, a difference that was significant. There was a significant reduction in nerve sliding following repair (median = 8%, range -8% to 54%; P = 0.02), which correlated with time from injury to surgery (rho = 0.87; P = 0.001). These results indicate that ultrasound can be us...

Added sampling improves reproducibility of multipoint motor unit estimates

Muscle and Nerve — Tue, 06 Oct 2009 23:00:00 +0100

Motor unit number estimation (MUNE) has been used to track motor unit attrition. Studies have used the modified multiple-point stimulation (MPS) technique, collecting three surface motor unit action potentials (sMUAPs) from 3 sites to calculate MUNE. Factoring additional sMUAPs should theoretically improve reproducibility, but the optimal number has not been defined. We evaluated the effect of increased sMUAP sampling on test-retest reproducibility of the modified MPS MUNE technique and found that MUNE reproducibility increased with additional sampling. Muscle Nerve, 2009 (Source: Muscle and Nerve)

Non-lethal neonatal neuromuscular variant of glycogenosis type IV with novel GBE1 mutations

Muscle and Nerve — Tue, 06 Oct 2009 23:00:00 +0100

We report a recent case of the severe congenital variant of glycogen storage disease type IV with prolonged survival. The patient was found to be a compound heterozygote for two novel mutations, a missense mutation in exon 5 (p.H188P, c.563A>C) and a severe mutation in intron 5 (c.691+2T>C). We propose that the genotype and the quality of medical care may account for the severe but non-lethal phenotype. Muscle Nerve, 2009 (Source: Muscle and Nerve)

Conduction block of peripheral nerve using high-frequency alternating currents delivered through an intrafascicular electrode

Muscle and Nerve — Tue, 06 Oct 2009 23:00:00 +0100

In this study we show that high-frequency conduction block is feasible using intrafascicular electrodes. Muscle Nerve, 2009 (Source: Muscle and Nerve)

Sensory ataxic neuropathy dysarthria and ophthalmoparesis (SANDO) in a sibling pair with a homozygous p.A467T POLG mutation

Muscle and Nerve — Tue, 06 Oct 2009 23:00:00 +0100

Two siblings who developed fifth-decade-onset, concurrent progressive sensory ataxia, dysarthria, and ophthalmoparesis were found to be homozygous for the p.A467T mutation of the polymerase gamma (POLG) gene. The clinical course in both subjects was progression to severe disability. The enlarging spectrum of sensory ataxic neuropathies associated with mitochondrial DNA (mtDNA) instability and POLG mutations should be recognized and considered in the differential diagnosis of this unusual presentation. Muscle Nerve, 2009 (Source: Muscle and Nerve)

Muscle strength and fatigue in patients with generalized myasthenia gravis

Muscle and Nerve — Tue, 06 Oct 2009 23:00:00 +0100

The objective of this study was to quantify, by direct measurement of muscle force, the strength and fatigue of patients with MG. A maximal voluntary isometric contraction protocol of shoulder abductors was used in conjunction with conventional fatigue and disease-severity instruments. Results from patients with (D-MG) and without (ND-MG) decrement on repetitive nerve stimulation (RNS) of the spinal accessory and axillary nerves were compared with healthy controls. Patients with MG reported greater fatigue than controls. Muscle strength was lowest in the D-MG group, followed by the ND-MG group and controls. Normalized shoulder abduction fatigue and recovery values did not differ between the D-MG and ND-MG groups or controls. The RNS decrement appears to relate best to disease severity and ...

Linearity and reliability of the mechanomyographic amplitude versus dynamic torque relationships for the superficial quadriceps femoris muscles

Muscle and Nerve — Tue, 06 Oct 2009 23:00:00 +0100

The purpose of this investigation was to examine the linearity and reliability of the mechanomyographic (MMG) amplitude versus dynamic torque relationships for the vastus lateralis (VL), rectus femoris (RF), and vastus medialis (VM) muscles. Nine healthy men and 11 healthy women performed submaximal to maximal, concentric, isokinetic muscle actions of the leg extensors at 30° s-1 on two occasions. Surface MMG signals were detected from the VL, RF, and VM of the dominant thigh during both trials. The ranges of the coefficients of determination for the MMG amplitude versus dynamic torque relationships were 0.01-0.94 for the VL, 0.01-0.84 for the RF, and 0.19-0.96 for the VM. The intraclass correlation coefficients for the linear MMG amplitude versus torque slope coefficients were 0.823 (VL)...

Immune-mediated necrotizing myopathy associated with statins

Muscle and Nerve — Tue, 06 Oct 2009 23:00:00 +0100

We report patients from two neuromuscular centers who were evaluated between the years 2000 and 2008 and met the following criteria: (1) proximal muscle weakness occurring during or after treatment with statins; (2) elevated serum creatine kinase (CK); (3) persistence of weakness and elevated CK despite discontinuation of the statin; (4) improvement with immunosuppressive agents; and (5) muscle biopsy showing necrotizing myopathy without significant inflammation. Twenty-five patients fulfilled our inclusion criteria. Twenty-four patients required multiple immunosuppressive agents. Fifteen patients relapsed after being tapered off immunosuppressive therapy. Exposure to statins prior to onset was significantly higher in patients with necrotizing myopathy (82%) as compared to those with derma...

Frequency and predictors of nonalcoholic fatty liver disease in myotonic dystrophy

Muscle and Nerve — Tue, 06 Oct 2009 23:00:00 +0100

Nonalcoholic fatty liver disease (NAFLD) is a common chronic liver disease that is strongly associated with insulin resistance. Myotonic dystrophy (DM1) is the most common form of adult-onset muscular dystrophy, and there is a high frequency of insulin resistance due to insulin receptor mRNA splicing defects in muscle tissue. The frequency and predictors of NAFLD in this population have not been described. Thirty-six patients with DM1 were prospectively assessed for the presence of NAFLD and insulin resistance. NAFLD was defined by abnormal liver chemistry tests with ultrasound or pathologic evidence of steatosis in the absence of other liver disease. Abnormal liver chemistry tests were found in 44% of DM1 patients (mean ALT 73 ± 21 U/L, AST 53 ± 15 U/L), and 87% were attributable to NAF...

Primary AL amyloid polyneuropathy successfully treated with high-dose melphalan followed by autologous stem cell transplantation

Muscle and Nerve — Tue, 06 Oct 2009 23:00:00 +0100

We report 2 patients with polyneuropathy associated with amyloid derived from light chains (AL) who were treated successfully with high-dose melphalan followed by autologous peripheral blood stem cell transplantation (HDM/SCT). Neuropathic symptoms improved in conjunction with normalization of serum-free light chains. In addition to amyloid deposits in tissues, an amyloidogenic light chain itself produced by abnormal plasma cells might be harmful to peripheral nerve function, and thus HDM/SCT seems to be a promising therapy for primary AL amyloid polyneuropathy. Muscle Nerve, 2009 (Source: Muscle and Nerve)

In vivo assessment of HCN channel current (Ih) in human motor axons

Muscle and Nerve — Tue, 06 Oct 2009 23:00:00 +0100

This study demonstrates a reliable method for in vivo assessment of Ih, and also serves to document the normal variability in nerve excitability properties within subjects. Muscle Nerve, 2009 (Source: Muscle and Nerve)

Skeletal muscle cell MHC I expression: Implications for statin-induced myopathy

Muscle and Nerve — Tue, 06 Oct 2009 23:00:00 +0100

Statins can induce necrotizing or inflammatory myopathies in some patients. Increased major histocompatibility complex class I (MHC I) expression has been shown in muscle biopsies of statin-induced myopathy. Therefore, we investigated the effect of statins on the expression of MHC I in muscle cells. Using flow cytometry and polymerase chain reaction (PCR), the rhabdomyosarcoma cell line TE671 and primary cultured skeletal muscle cells (SKMC) were investigated for MHC I expression after incubation with different statins and/or interferon-gamma (IFN-[gamma]). TE671 and SKMC express MHC I in the untreated condition. Statins alone reduced the expression of MHC I in SKMC and had no effect on MHC I in TE671 cells. Statins potentiated the MHC I-inducing effect of IFN-[gamma] in TE671, but not in ...

Prolonged compound muscle action potential duration in critical illness myopathy

Muscle and Nerve — Tue, 06 Oct 2009 23:00:00 +0100

Critical illness myopathy (CIM) is a frequent cause of generalized weakness in the intensive care unit. Prolonged compound muscle action potential (CMAP) durations have been described in this patient population, and this study presents further data on CMAP duration in normal controls and patients with CIM. The findings highlight the importance of testing multiple nerve muscle combinations in weak, critically ill patients. Recognition of this pattern, which has not been widely described, can facilitate the diagnosis of CIM. Muscle Nerve, 2009 (Source: Muscle and Nerve)

Prospective study of peripheral neuropathy in Machado-Joseph disease

Muscle and Nerve — Thu, 01 Oct 2009 23:00:00 +0100

Peripheral neuropathy (PN) has long been recognized in Machado-Joseph disease (MJD), but its natural history is an unsettled issue. Therefore, we prospectively assessed 40 with MJD for 13 months with nerve conduction (NC) studies and the revised total neuropathy score (TNSr) to study the progression of PN. There was no significant change in the TNSr score over the follow-up period. In contrast, the average sural sensory nerve action potential (SNAP) amplitude decreased significantly over the same interval from a mean of 13.2 [mu]V to 9.8 [mu]V (P < 0.001). There was an inverse correlation between the change in the sural SNAP amplitude and the length of the CAG triplet repeat expansion (r = 0.574, P < 0.001). The reduction in the mean sural SNAP amplitude also correlated with progression of...

Effect of locally delivered IGF-1 on nerve regeneration during aging: An experimental study in rats

Muscle and Nerve — Thu, 01 Oct 2009 23:00:00 +0100

Age is an important predictor of neuromuscular recovery after peripheral nerve injury. Insulin-like growth factor 1 (IGF-1) is a potent neurotrophic factor that is known to decline with increasing age. The purpose of this study was to determine if locally delivered IGF-1 would improve nerve regeneration and neuromuscular recovery in aged animals. Young and aged rats underwent nerve transection and repair with either saline or IGF-1 continuously delivered to the site of the nerve repair. After 3 months, nerve regeneration and neuromuscular junction morphology were assessed. In both young and aged animals, IGF-1 significantly improved axon number, diameter, and density. IGF-1 also significantly increased myelination and Schwann cell activity and preserved the morphology of the postsynaptic n...

Role of gelatinases in disuse-induced skeletal muscle atrophy

Muscle and Nerve — Mon, 28 Sep 2009 23:00:00 +0100

In this study we examined the specific roles of gelatinase A and B in disuse-induced skeletal muscle atrophy using knockout mice. Although both gelatinase A and B are highly upregulated in disused muscle, only gelatinase A null mice had significantly reduced muscle atrophy as compared to wildtype littermates. Type IV collagen and laminin, two major components of basement membrane, were relatively well-preserved in disused muscle in gelatinase A null mice, but not in gelatinase B null mice. These findings suggest that gelatinase A, and not gelatinase B, plays a critical role in disuse-induced skeletal muscle atrophy. Muscle Nerve, 2009 (Source: Muscle and Nerve)

Neuronal and glial cerebrospinal fluid protein biomarkers are elevated after West Nile Virus infection

Muscle and Nerve — Mon, 28 Sep 2009 23:00:00 +0100

Neurotrophic West Nile virus (WNV) disease is a severe arbovirus infection in which neuronal loss is the likely anatomical substrate for the high morbidity and mortality. We investigated whether cerebrospinal fluid (CSF) protein biomarkers were elevated in vivo and related to disease severity in patients with WNV infection. This exploratory study included 114 patients (24 acute WNV, 77 noninflammatory controls, six peripheral neuropathies, seven aseptic meningoencephalitis). CSF levels of neuronal (neurofilaments, NfH-SMI35) and glial (glial fibrillary acidic protein, GFAP, S100B) biomarkers were measured by enzyme-linked immunosorbent assay (ELISA). Immunocytochemistry was performed in two fatal WNV cases. A significant proportion of patients with WNV had pathological CSF levels for NfH-S...

Neuromuscular diseases associated with HIV-1 infection

Muscle and Nerve — Sun, 20 Sep 2009 23:00:00 +0100

Neuromuscular disorders are common in human immunodeficiency virus (HIV); they occur at all stages of disease and affect all parts of the peripheral nervous system. These disorders have diverse etiologies including HIV itself, immune suppression and dysregulation, comorbid illnesses and infections, and side effects of medications. In this article, we review the following HIV-associated conditions: distal symmetric polyneuropathy; inflammatory demyelinating polyneuropathy; mononeuropathy; mononeuropathy multiplex; autonomic neuropathy; progressive polyradiculopathy due to cytomegalovirus; herpes zoster; myopathy; and other, rarer disorders. Muscle Nerve, 2009 (Source: Muscle and Nerve)

Histological validation of ultrasound-guided neurography in early nerve regeneration

Muscle and Nerve — Sun, 20 Sep 2009 23:00:00 +0100

In this study, ultrasound-guided near-nerve measurements were validated against axon diameter counts in rabbits during a 15-week regeneration period after a crush lesion of their peroneal nerve. The course of the nerve was determined ultrasonically, and the active near-nerve needle electrode was maneuvered just next to the nerve under ultrasound guidance. Measured action potentials were compared with axon diameter counts from histological sections of these same nerves. A moderate to good positive correlation was found, which reached a maximum of 0.7 at a cut-off of 3 [mu]m, corresponding to the minimal size of the myelinated axons. Our results suggest that, following a similar validation study in humans, ultrasound-guided near-nerve neurography may be clinically useful when early evaluatio...

C-fiber function assessed by the laser doppler imager flare technique and acetylcholine iontophoresis