bluuebunny/crossref_metadata_2025 huggingface dataset:
Stimulation SFEMG in myasthenia gravis
Authors: Jabre Joe F. , Chirico‐Post Jeannette , Weiner Mark
Published: January 2005

The diagnostic usefulness of single‐fiber electromyography (SFEMG) in the diagnosis of neuromuscular transmission disorders is well established. Increased jitter is one of the earliest indications of abnormality. In patients with severe weakness, tremor, or altered consciousness, performance of the study is difficult because of the degree of cooperation needed.

We studied five patients and eight normal subjects with voluntary and stimulation SFEMG techniques. Our results, in search of normal values and changes with pathology, revealed differences in the values of jitter and the percentage of abnormal fibers between both techniques. The mean consecutive difference (MCD) is smaller (on average 30% less), and the percentage of abnormal fibers is lower (on average 10% less) with the stimulation technique. These differences are largely explained by the jitter measurement of one endplate with the stimulation technique versus two endplates with the voluntary. They may also be related, however, to the difference in motor unit populations sampled with each technique.
The effect of cholinesterase inhibitors on SFEMG in myasthenia gravis
Authors: Massey Janice M. , Sanders Donald B. , Howard James F.
Published: January 2005

We report four patients with myasthenia gravis (MG) in whom single‐fiber electromyography (SFEMG) jitter measurements were normal in some muscles while they were taking pyridostigmine and became abnormal 2–14 days after the medication was discontinued. When the abnormality of neuromuscular transmission in MG is mild, cholinesterase inhibitors may mask the findings of increased jitter on SFEMG.
Relationship of manual muscle testing to objective strength measurements
Authors: Aitkens Susan , Lord Janet , Bernauer Edmund , Fowler William M. , Lieberman James S. , Berck Peter
Published: January 2005

This study investigates the relationship between manual muscle test scores (MMT) and quantitative isometric strength measurements (QIS). It also evaluates the implications of that relationship for design of therapeutic trials. Extension and flexion strength at the elbows, hips, and knees of 21 neuromuscular disease patients were tested a total of 26 times utilizing both MMT and QIS testing. Paired data were evaluated with Spearman ranked correlation coefficients, and then QIS was predicted from MMT using Lowess, a consistent form of nonparametric regression. Finally, the implications of the Lowess analysis for designing a therapeutic trial were evaluated.

MMT and QIS measurements were significantly correlated in all movements tested. Lowess analysis yielded prediction errors ranging from 16 to 24% of QIS range. Analysis of the sample size needed for a therapeutic trial suggested that a protocol measuring MMT would require more subjects for the same level of statistical significance as a protocol measuring QIS. Since it was not possible to reliably predict QIS values from MMT scores, such conversions are not appropriate for clinical use. This inconsistent relationship between MMT and QIS carries major implications for the design of therapeutic trials. Since therapeutic trials are time consuming, expensive, and most centers do not have large numbers of individuals available, using QIS as an outcome measure is a preferable research design.
Simulation of myopathic motor unit action potentials
Authors: Nandedkar Sanjeev D. , Sanders Donald B.
Published: January 2005

Normal motor units (MUs) were simulated and their architecture altered to simulate the changes produced by myopathy. The concentric needle electromyographic recordings of motor unit action potentials (MUAPs) from the MUs were then also simulated. These simulated MUAPs showed features that are seen in myopathy: normal amplitude and slightly reduced area, MUAPs with simple waveform and reduced duration, and complex MUAPs with normal or increased duration. The MUAP waveforms were complex because of increased variability of fiber diameter and not because of loss of muscle fibers. The MUAP duration increased when the variability of fiber diameter increased. Finally, MUAPs similar to those seen in neurogenic diseases were produced from MUs in which the only abnormality was increased variability of fiber diameter.
Caffeine sensitivity of sarcoplasmic reticulum of fast and slow fibers from normal and malignant hyperthermia human muscle
Authors: Salviati Giovanni , Betto Romeo , Ceoldo Stefania , Tegazzin Vincenzo , Puppa Andrea Della
Published: January 2005

We have carried out a comparative study of caffeine sensitivity of the sarcoplasmic reticulum (SR) of fast and slow normal human fibers chemically skinned. Human slow‐fiber SR is more sensitive to caffeine than fast fiber SR; however, it releases less calcium and at a lower rate than the SR of fast fibers when exposed to threshold concentrations of caffeine. These results indicate that the SR calcium release mechanisms of SR of fast and slow human fibers are homologous but not identical. An increased sensitivity of SR to caffeine is found in both fast and slow fibers from human malignant hyperthermia muscle. However, fast fibers seem to be the most affected, since their caffeine threshold for contraction is very close to that of slow fibers.
Carpal tunnel syndrome in Lyme borreliosis
Authors: Halperin John J. , Volkman David J. , Luft Benjamin J. , Dattwyler Raymond J.
Published: January 2005

Neurophysiologic evidence of median nerve entrapment in the carpal tunnel was present in 25% of patients with late Lyme borreliosis. Sixty‐eight of 76 consecutive, prospectively studied patients with late Lyme underwent neurophysiologic testing. Nineteen reported intermittent hand paresthesias; 17 had neurophysiologically confirmed carpal tunnel syndrome. This was not consistently associated with clinically apparent wrist arthritis or with neurophysiologically evident peripheral neuropathy. We conclude that a significant proportion of patients with late Lyme borreliosis develop carpal tunnel syndrome.
Comparison of sympathetic skin response with quantitative sudomotor axon reflex test in diabetic neuropathy
Authors: Maselli Ricardo A. , Jaspan Jonathan B. , Soliven Betty C. , Green Andrew J. , Spire Jean‐Paul , Arnason Barry G. W.
Published: January 2005

The sympathetic skin response (SSR), the quantitative sudomotor axon reflex test (Q‐SART), and cardiac beat‐to‐beat variability with respiration as measured by the expiratory/inspiratory ratio (E/I ratio) were studied in 39 patients with diabetic neuropathy of whom 33 also had one or more symptoms of autonomic involvement. In the lower extremities 87% of the patients with an absent SSR had an abnormal Q‐SART (P < 0.001), and 81% of patients with the SSR present had a normal Q‐SART (P < 0.02). The E/I ratio was abnormal in all but one of 23 patients with an absent SSR in the foot, and a normal E/I ratio was present only in those patients (n = 7) with the SSR present in hand and foot, and in an eighth patient who had SSR absent in the foot and present in the hand. A similar correlation was found between the E/I ratio and the Q‐SART in the foot, although 4 of 25 patients with an abnormal foot Q‐SART had a normal E/I ratio. We conclude that the concordance of results of the SSR and Q‐SART supports the combined use of these tests to uncover early distal sympathetic failure in diabetic neuropathy.
The spectrum of changes on 20 nerve biopsies in patients with HIV infection
Authors: Chaunu Marie‐Pierre , Ratinahirana Herilavitra , Raphael Martine , Hénin Dominique , Leport Catherine , Brun‐Vezinet Francoise , Léger Jean‐Marc , Brunet Pascal , Hauw Jean‐Jacques
Published: January 2005

Nerve and muscle blopsies were performed on 20 patients with HIV infection and peripheral neuropathy. Nine patients had distal symmetrical peripheral neuropathy (DSPN) (six ARC and three AIDS), six had inflammatory demyelinating polyneuropathy (IDP) (three ARC, one AIDS, and two otherwise asymptomatic patients), one had mononeuropathy multiplex (MM) (AIDS), 1 had mononeuropathy (ARC), one had meningoradiculitis (AIDS), and two had areflexia‐associated lymphocytic meningitides (ARC). DSPN exhibited axonal degeneration in four of nine cases and was associated with segmental demyelination in five of nine cases. IDP exhibited segmental demyelination associated with axonal degeneration in four of six cases. Demyelination was more frequent in asymptomatic patients (2 of 2 cases) and in ARC (7 of 12 cases), whereas axonal degeneration was predominant in AIDS (6 of 6 cases). Mononuclear cell infiltration was seen in 1 of 2 asympatomatic patients and in 11 of 12 ARC patients but was exceptionally found in AIDS (1 of 6 cases). Involvement of the walls of small vessels, mostly venules (“subacute microvasculitis”), was found in 1 of 2 asymptomatic patients, in 8 of 12 ARC patients, and never in AIDS. The polyclonal mononuclear cell population was composed mainly of Leu 2 (TB) positive cells in seven cases of ARC. No virions were seen in electron microscopy. HIV was isolated in two cases from the CSF or the nerve biopsy.
The role of collagen crosslinking in the increased stiffness of avian dystrophic muscle
Authors: Feit Howard , Kawai Masataka , Mostafapour A. Shanaz
Published: January 2005

The resting tension and stiffness in the range of sarcomere lengths 2.4–3.6 μm were studied in highly inbred normal and dystrophic chicken pectoral muscle bundles, and the results were compared with the collagen content and the extent of crosslinkage of the collagen. All parameters increased in the order normal homozygote (003/003) < heterozygote (003/433) < dystrophic homozygote (433/433) chickens, with the data from the heterozygotes being halfway between the two homozygotes, thus exhibiting a semidominant inheritance pattern. In separate experiments, lathyrism was induced by treating normal (412/412) and dystrophic (413/413) chickens with α‐acetoaminonitrile, an inhibitor of lysyl oxydase, the enzyme responsible for the initiation of collagen crosslinkage formation. These experiments showed that the tension and stiffness in response to passive stretch did not change with lathyrism in normal muscles, whereas the tension and stiffness decreased significantly with lathyrism in dystrophic muscles. The collagen content did not change with lathryrism in both normal and dystrophic muscles. These results indicate that the increased content of collagen crosslinkages is the basis for the increased resting tension and stiffness in the dystrophic muscles of the chicken, and that the effects can be reversed by treatment with an inhibitor of collagen crosslinkage formation.
Accumulation of collagen and altered fiber‐type ratios as indicators of abnormal muscle gene expression in the mdx dystrophic mouse
Authors: Marshall P. A. , Williams P. E. , Goldspink G.
Published: January 2005

The growth and development of the X‐linked muscular dystrophy mutant mouse (mdx) was compared with a control group from 3 weeks to 1 year old. Quantitative cytological analysis of the soleus muscle revealed cycles of degeneration, regeneration, and hypertrophy, and at any one time it was difficult to assess the extent of the disease based on muscle fiber size. One noticeable difference even in the youngest muscles studied was the reduced numbers of slow oxidative fibers and the increased number of fast glycolytic fibers in the mdx soleus muscles. The collagen of the connective tissue components of selectively stained sections was determined by computerized image analysis. Marked accumulation of collagen was found in both the endomysium and perimysium of the dystrophic muscles as compared with age‐matched controls. Since the mdx mouse is a result of the same type of genetic defect as in human Duchenne muscular dystrophy, this model could thus be used to assess the effectiveness of various therapeutic approaches, including gene therapy using muscle fibrosis and fiber type proportions as the indicators.
Focal nerve injury: Guidance factors during axonal regeneration
Authors: Thomas P. K.
Published: January 2005

Regeneration of axons after nerve injury is not random but is often not precise, particularly after injuries that involve nerve transection. The factors that guide regenerating axons toward appropriate terminations are complex, but developments in neurobiology are beginning to indicate the mechanisms that are involved. These include neurotrophic and neurite promoting factors, chemotactic influences from peripheral tissues, and the properties of the extracellular matrix. Understanding these mechanisms may indicate means of improving functional recovery after nerve injury.
SFEMG improvement with remission in the cancer‐associated Lambert–Eaton myasthenic syndrome
Authors: Oh Shin J.
Published: January 2005

In two patients with the Lambert–Eaton myasthenic syndrome (LEMS) and small‐cell lung carcinoma (SLLC), therapy for LEMS was effective when combined with cancer therapy. The serial SFEMG tests showed a corresponding improvement with remission of the LEMS and proved to be a better and earlier indicator of the changing clinical status than the repetitive nerve stimulation test. Thus, we conclude that the SFEMG is useful in the follow‐up evaluation of patients with this condition.
Adynamia episodica hereditaria: What causes the weakness?
Authors: Ricker Kenneth , Camacho Luis M. , Grafe Peter , Lehmann‐Horn Frank , Rüdel Reinhardt
Published: January 2005

The cause of weakness was investigated in a patient with adynamia episodica hereditaria without myotonia. A pattern of exercise and rest produced episodes of hyperkalemic periodic paralysis. In addition, local muscle weakness was induced by forearm cooling. Investigations on isolated intercostal muscle demonstrated that a high potassium concentration in the bathing solution triggered a noninactivating membrane current causing depolarization of the muscle fibers. This current was carried by sodium as it could be inhibited by tetrodotoxin. The abnormal sodium conductance led to an increase of sodium within the fibers. This was demonstrated directly by intracellular recordings. Weakness induced by rest after exercise and cold‐induced weakness appeared to have different pathomechanisms. In the cold, the muscle fibers retained a normal resting potential, but their excitability was reduced and their mechanical threshold was increased. These findings also provide evidence that the mechanism of cold‐induced weakness in adynamia episodica is distinctly different from the cold‐induced weakness that occurs in paramyotonia congenita.
The effects of taurine on pharmacologically induced myotonia
Authors: Camerino Diana Conte , De Luca Annamaria , Mambrini Mercede , Ferrannini Ermanno , Franconi Flavia , Giotti Alberto , Bryant Shirley H.
Published: January 2005

Taurine reduces the excitability of striated muscle fibers by increasing the membrane conductance to chloride ions (GCI). This action was tested on rats made myotonic by drugs that block GCI by different mechanisms. Experiments were made “in vivo” using electromyographic (EMG) recordings and “in vitro” with intracellular microelectrode recordings from extensor digitorum longus muscle fibers. Taurine did not antagonize the myotonic discharges produced in vivo by anthracene‐9‐carboxylic acid, nor did it restore GCI lowered in vitro by this agent. However, when myotonia was chronically induced by 20,25 diazacholesterol, taurine given chronically in vivo or acutely in vitro antagonized the EMG myotonia as well as the reduced GCI and increased excitability of single fibers. We conclude that taurine acts directly on chloride channels to modify their kinetics. Our findings suggest that further clinical studies on the use of taurine in muscle disease involving abnormal excitability or chloride channel function will be useful.
Role of nerve and tension in maturation of posthatching slow‐tonic muscle in chicken
Authors: Gardahaut Marie‐France C. , Rouaud Thierry P. , Renaud Didier , Khaskiye Ahmad , Le Douarin Georges H.
Published: January 2005

The role of motor innervation and muscle tension in the posthatching maturation of the slow‐tonic anterior latissimus dorsi (ALD) muscle of the chicken has been investigated. Modification of the muscle tension was obtained either by maintaining ALD in a shortened state or by stretching, after or without denervation. In denervated as well as in innervated ALD, shortening resulted in atrophy and inhibition of developmental change in muscle fiber population. In contrast, stretch causes hypertrophy, transformation of all 3B fibers, increase in SM2 isomyosin expression, and decrease in Ca2+‐activated myosin ATPase in innervated or denervated ALD. On the other hand oxidative activity in ALD fibers was strikingly reduced after denervation even in presence of stretch‐induced hypertrophy. This study suggests that a passive stretch can be involved in some, but not all, changes in ALD characteristics occurring after denervation and may be also involved in normal posthatching development of the slow‐tonic muscle. Possible clinical implications of these results in relation to treatments for preventing muscle atrophy resulting from immobilization or disuse are suggested.
The positive inotropic effect of epinephrine on skeletal muscle: A brief review
Authors: Williams Jay H. , Barnes William S.
Published: January 2005

Chronic and acute administration of epinephrine or related sympathomimetic agents are typically prescribed for the treatment of clinical disorders such as hypotension, anaphylactic and allergic reactions, and bronchial asthma. In addition to its effects on these infirmaties and on carbohydrate metabolism, epinephrine also exerts a positive inotropic effect on fast‐contracting skeletal muscle in a variety of animal species. At present, the precise mechanisms responsible for the inotropic effect are not known. This communication reviews the positive inotropic effects of epinephrine on fastcontracting skeletal muscle and discusses possible mechanisms which might mediate this phenomenon. Epinephrine potentiates muscle twitches via the second messenger, cAMP, secondary to hormone binding to membrane‐bound beta‐receptors. Cyclic AMP then acts to increase carbohydrate metabolism, alter sodium/potassium exchange, phosphorylate myosin isozymes, and/or alter intracellular calcium exchange. Based on theoretical grounds, the first three mechanisms can be excluded. Therefore, it is tentatively hypothesized that the effect is due to cAMP‐enhanced calcium exchange within the muscle fiber and/or to increased influx of extracellular calcium. This notion is consistent with the mechanism of the positive inotropic effects of epinephrine on cardiac tissue. If this hypothesis is correct, it would also suggest a role, at least under some conditions, for extracellular calcium in the process of skeletal muscle excitation–contraction coupling.
Far‐field and cortical somatosensory evoked potentials in motor neuron disease
Authors: Zanette Giampietro , Polo Alberto , Gasperini Marcella , Bertolasi Laura , De Grandis Domenico
Published: January 2005

We examined median somatosensory evoked potentials (SEPs) in 26 patients with sporadic motor neuron disease (MND). SEPs were recorded with multiple scalp derivations, using both the midfront and the earlobe as references for each subject. Central conduction time (CCT) was abnormal in three patients, but only when using the midfront reference. Moreover, an exclusive alteration of the early prerolandic potentials potentials (absent or delayed P20 and/or P22) was noted using the earlobe reference in amyotrophic lateral sclerosis and in progressive bulbar palsy (54% and 50% of patients, respectively) but not in progressive muscular atrophy. These findings correlated with clinical evidence of upper motor neuron signs and with the severity of the disease. In agreement with recentviews regarding the sources of the early anterior cortical responses, neuronal loss in the motor cortex may be considered as affecting the generator sites of these potentials.
Conduction block in neuropathies with necrotizing vasculitis
Authors: Ropert Angèle , Metral Stéphane
Published: January 2005

Thirty‐two patients with a mononeuropathy multiplex associated with a systemic necrotizing vasculitis were studied. The main abnormality was a loss of motor and sensory axons confirmed by electrophysiological and histological methods. A conduction block was observed in five patients, but only one was at a usual site of compression. Based on previous pathological studies and the experimental data in human and animals, the mechanism of the block is proposed to be ischemic. It is suggested that a conduction block in one nerve in a neuropathy with two or more individual nerves affected and with electrophysiological features of axonal degeneration may be due to a vasculitis.
Limits of normal nerve function during high‐frequency stimulation
Authors: Robinson Lawrence R. , Nielsen Viggo Kamp
Published: January 2005

We studied the effects of prolonged high‐frequency stimulation in normal rat tail nerves. Nerves could conduct impulses at 50 Hz for 5 hours without complete conduction block. However, over time there was a significant decrease in amplitude and increase in latency of the compound nerve action potential (CNAP), which gradually became desynchronized. Changes were influenced by the frequency of stimulation. When stimulating over 30 minutes at 20, 50, 100, and 143 Hz the amplitude decreased to 89%, 79%, 67%, and 65% of baseline values, respectively, whereas the latency was only significantly increased at 100 and 143Hz. All changes were reversible upon cessation of stimulation. Changes could not be attributed to focal block at the site of stimulation. These changes in the CNAP may reflect functional limitations of the axon membrane which may have pathophysiological implications for the study of neuropathies and focal nerve lesions.
Acoustic and surface EMG diagnosis of pediatric muscle disease
Authors: Barry Daniel T. , Gordon Kevin E. , Hinton George G.
Published: January 2005

The ratio of acoustic myography (AMG) amplitude to surface electromyography (EMG) amplitude is proposed as a measure of mechanical output compared with electrical activity of the contractile system. AMG to EMG ratios were measured from 16 children with muscle disease diagnosed by clinical criteria, EMG, and/or muscle biopsy. These were compared with the ratios from 11 normal volunteers spanning the same age range (7‐16 years). AMG to EMG ratios were significantly (P > 0.01) different for the two populations. Using a linear discriminant function to define the normal range for AMG to EMG ratios yielded a sensitivity of 82% (13 of 16 abnormals diagnosed) and a specificity of 91% (10 of 11 normals). These findings suggest that surface recordings may provide significant diagnostic information in muscle disease. The accuracy may be improved further by using additional muscles (e.g., paraspinals) and evoked twitches.
On the specificity of the acetylcholinesterase defect in dystrophic mice
Authors: Skau Kenneth A.
Published: January 2005

The tetrameric form of acetylcholinesterase (AChE) in ReJ/129 dystrophic mice was demonstrated to be absent from endplate‐poor regions of skeletal muscle but present in endplate‐rich regions. Skeletal muscle secreted normal amounts of this form of AChE. Visceral organs had normal amounts and distribution of the AChE molecular forms. These results suggest that the AChE defect in dystrophic mice is limited to skeletal muscle, and the defect does not reflect an abnormality of AChE synthesis but probably reflects an inability to incorporate the enzyme into skeletal muscle membranes.
EMG evaluation of the floppy infant: Differential diagnosis and technical aspects
Authors: Jones H. Royden
Published: January 2005

Electromyographic examination of the newborn and young infant provides a relatively uncommon challenge to most electromyographers. The usual reason for referral for electromyographic studies in the newborn and young infant is to evaluate a floppy baby. The electromyographer must not only be aware of important differences in normal physiologic parameters but must also be familiar with a spectrum of diseases that are not typically encountered in the adult. The results of electromyography must also be correlated with the normal maturation of neuromuscular function. Although the most common pathophysiologic mechanisms affecting the peripheral motor unit are infantile motor neuron disease and the congenital myopathies, a large number of other disease entities warrant careful consideration.
A comparison of magnetic and electrical stimulation of spinal nerves
Authors: Evans B. A. , Daube J. R. , Litchy W. J.
Published: January 2005

The utility of the magnetic coil for stimulation of the cervical spinal nerves was compared to electrical stimulation by a monopolar needle cathode placed onto the spinal lamina in six volunteers. No statistical difference in average amplitudes or areas of evoked CMAPs was found although the size of the magnetic coil evoked potentials was less at C7–8 in several subjects. Electrical stimulation resulted in depolarization at a more proximal site. Electrical stimulation was associated with more discomfort, especially at C5–6. We conclude that electrical stimulation using a monopolar needle as the cathode is the superior technique for the clinical electrophysiologic study of the proximal brachial plexus and cervical spinal nerves.
A noninvasive procedure to detect muscle weakness in the mdx mouse
Authors: Carlson C. G. , Makiejus R. V.
Published: January 2005

The forward pulling tension exerted by individual mice was measured nearly isometrically in a simple apparatus designed to determine whole body tension (WBT). WBT determinations on control (C57BI10/SnJ) and experimental (C57BI10‐mdx) mice indicate muscle weakness which lasts throughoout the lifespan of mdx mice. Direct muscle stimulation experiments in vivo also showed significant decreases in peak twitch and tetanic tensions in adult mdx muscle with no obvious alterations in twitch time course or in twitch: tetanus rations. We suggest that the noninvasive WBT procedure may be used to partially assess various therapies on this murine model of Duchenne muscular dystrophy.
Schwartz–Jampel syndrome: II. Na+ channel defect causes myotonia
Authors: Lehmann‐Horn Frank , Iaizzo Paul A. , Frane Christian , Hatt Hanns , Spaans Frank
Published: January 2005

Skeletal muscle fibers from a patient with Schwartz–Jampel syndrome were studied in vitro. The fibers had normal resting membrane potentials, but their resting [Ca2+]i was elevated. The resting potentials were unstable and spontaneous depolarizations caused twitching in all fibers. Stimulated contractions were characterized by markedly slowed relaxation which was due to electrical after‐activity. Neither curare (0.7 μM), tocainide (50 μM), nor phenytoin (80 μM) had an effect on the myotonic activity. In contrast, procainamide (200 μM) suppressed the hyperexcitability without affecting the twitch amplitude. The steady‐state current‐voltage relation was normal in 5 fibers, but altered in 3 others. These latter fibers had an increased specific membrane resistance owing to a decreased Cl‐ conductance. The Na+ channels were investigated in the cell‐attached patch clamp mode. In all patches on either type of fiber, depolarizing pulses elicited delayed, synchronized openings of Na+ channels. These abnormal openings occurred even after the surface membrane repolarized. We hypothesize that these altered membrane conductances are responsible for the hyperexcitability and the associated slowed relaxation.
Suprascapular nerve compression at the spinoglenoid notch
Authors: Kiss Gábor , Kómár JóZSEF
Published: January 2005

A 52‐year‐old man developed isolated atrophy of the infraspinatus muscle. The suprascapular nerve was compressed at the spinoglenoid notch by a hypertrophied inferior transverse scapular ligament.
Invited review: Peripheral neuropathy in Sjogren' syndrome
Authors: Kaplan Jerry G. , Rosenberg Richard , Reinitz Elizabeth , Buchbinder Shalom , Schaumburg Herbert H.
Published: January 2005

Our experience and review of the literature reveal that Sjogren' syndrome (SS) is an important, poorly recognized cause of peripheral neuropathy. Several forms of peripheral nerve dysfunction occur in SS including trigeminal sensory neuropathy, mononeuropathy multiplex, distal sensory neuropathy, distal sensorimotor peripheral neuropathy and a pure sensory neuronopathy syndrome. Rarely, chronic relapsing inflammatory polyneuropathy and multiple cranial neuropathies appear. Clinical evidence of glandular in volvement is often minimal or absent when patients with SS develop peripheral neuropathy; and the diagnosis of the underlying condition is elusive. We review clinical and laboratory features of this disorder and suggest appropriate evaluation of patients with neuropathy and suspected SS.
Insulin effects in denervated and non‐weight‐bearing rat soleus muscle
Authors: Tischler Marc E. , Satarug Soisungwan , Eisenfeld Steven H. , Henriksen Erik J. , Rosenberg Sara B.
Published: January 2005

Previous reports indicated that glucose uptake in denervated muscle is resistant to insulin, while in non‐weight‐bearing (unweighted) muscle this effect of insuling is enhanced. To extend the comparison of these differences, insulin effects on amino acid uptake and protein metabolism were studied in soleus muscles subjected to denervation or unweighting. Denervated muscle showed insulin resistance of both 2‐deoxy[1,2‐3H] glucose and ‐[methyl‐3H]aminoisobutyric acid uptake whereas unweighted muscle showed an increased or normal response, respectively. Atrophy was greater in denervated than in unweighted muscle, apparently due to faster protein degradation by insulin was generally less in denervated than in unweighted muscle, apparently due to faster protein degradation. The stimulation of protein synthesis and the inhibition of protein degradation by insulin was generally less in denervated than in unweighted muscle. Since metabolic measurements in denervated‐unweighted muscles did not differ from those in denervated‐weight‐bearing muscles, effects of denervation must be independent of leg posture.
A theoretical calculation of the electric field induced by magnetic stimulation of a peripheral nerve
Authors: Roth Bradley J. , Cohen Leonardo G. , Hallett Mark , Friauf Walter , Basser Peter J.
Published: January 2005

A mathematical model is presented that predicts the electric field induced in the arm during magnetic stimulation of a peripheral nerve. The arm is represented as a homogeneous, cylindrical volume conductor. The electric field arises from two sources: the time‐varying magnetic field and the accumulation of charge on the arm surface. In magnetic stimulation both of these contributions are significant. The magnitude of the electric field is greatest near the surface of the arm, and is well localized. Various coil orientations are examined; the smallest electric fields are induced when the coil is perpendicular to the arm surface, the largest when the coil is parallel. These results are consistent with many experimental observations in the literature, and aid in the basic understanding of magnetic stimulation of the peripheral nervous system.
Neuromuscular transmission in the mdx mouse
Authors: Nagel Alexandre , Lehmann‐Horn Frank , Engel Andrew G.
Published: January 2005

The mdx mouse is an animal model for human Duchenne dystrophy. In both disorders, the muscle fiber plasma membrane is rendered selectively vulnerable by dystrophin deficiency. In both disorders there are also ultrastructural abnormalities involving the postsynaptic membrane of the neuromuscular junction. The object of this electrophysiologic study was to determine whether the observed ultrastructural abnormalities at the mdx neuromuscular junction are associated with an abnormality of neuromuscular transmission. In comparison with age‐matched control mice, the mdx mice show an abnormal, age‐dependent decrease of the amplitude of the miniature end‐plate potential and aconcomitant increase in the quantal content of the end‐plate potential. Consequently, the safety margin of neuromuscular transmission is not impaired.
Spatial dispersion of magnetic stimulation in peripheral nerves
Authors: Cros Didier , Day Timothy J. , Shahani Bhagwan T.
Published: January 2005

To assess the longitudinal dispersion of the stimulus induced by the magnetic coil, collision experiments were performed in seven normal ulnar nerves. A supramaximal electrical stimulus S1 was delivered at the wrist, and followed by a supramaximal stimulus S2 in the upper arm, which was either electrical (electrical collision studies), or magnetic (magnetic collision studies). The interstimulus interval was varied by 0.2 msec increments from the time of complete cancellation of the S2 evoked motor response onwards, to include the entire span of recovery of that compound motor action potential. Collision curves were obtained for both magnetic and electrical stimuli by plotting the amplitude of the motor response elicited by S2 as a function of the interstimulus interval. In all seven normal ulnar nerves, comparison of the collision curves showed that the S2 evoked motor response is restored significantly more slowly when magnetic stimulation is used. This finding is best explained by longitudinal dispersion of the stimulus induced by the magnetic coil relative to conventional electrical stimulation, the large fibers being stimulated further away from the coil than the small ones. This interpretation is confirmed by the findings obtained with the same method in two cases of ulnar neuropathy, and by comparison of different intensities of magnetic stimulation.
Latencies of peripheral nerve and cerebral evoked responses to air‐puff and electrical stimuli
Authors: Hashimoto Isao , Yoshikawa Kazuyoshi , Sasaki Makoto
Published: January 2005

This study examined the latency relationship between mechanically and electrically elicited sensory nerve action potentials (SNAPs) and the somatosensory‐evoked potentials (SEPs) they produce. Brief air‐puff and electrical stimuli were applied to the tip of the index finger in separate trials and SNAPs from the median nerve at the wrist and SEPs from the scalp were recorded for each stimulus presentation. Air‐puff evoked SNAPs were polyphasic, usually consisting of 2 to 4 separate waves, unlike triphasic activity elicited by electrical stimulation. The SEPs produced by these 2 distinct forms of inputs, however, were similar in morphology. The latencies of the initial components of SNAPs and SEPs were longer for air‐puff stimulation. The conduction time, however, of the fastest afferent volleys from the wrist to cortex was not significantly different for air‐puff (20.52 ± 1.06 ms, mean ± SD) and electrical stimulation (20.17 ± 0.66 ms). It is therefore concluded that the latency delays for air‐puff evoked SNAPs and SEPs are due solely to a transduction time at the skin receptors and not due to differences in conduction velocities as suggested in the previous literature.
Reversible myeloneuropathy of nitrous oxide abuse: Serial electrophysiological studies
Authors: Vishnubhakat S. Murthy , Beresford H. Richard
Published: January 2005

Detailed electrophysiological studies were performed in 4 patients with myeloneuropathy induced by abuse of nitrous oxide for 1 to 4 years. All presented with paresthesias, weakness, and Lhermitte's phenomena, and exhibited signs of sensorimotor polyneuropathy, ataxia, and arreflexia. Two had subnormal serum vitamin B12 levels. Baseline electrophysilogic testing revealed reduced motor unit potentials, prolonged F wave latencies, absent H refelxes, denervation potentials, and delays in motor and sensory conduction. Three had peripheral and nuchal delay after median nerve stimulation. All were reevaluated after 3 to 12 months abstinence and treatment with vitamin B12, and all showed substantial clinical improvement. Parallel improvement in electrophysiologic findings occurred, but residual minor conduction delays, loss of H reflexes, electromyographic evidence of denervation, or abnormalities of posterior tibial SEP were noted. These findings confirm the reversibility of myeloneuropathy of nitrous oxide abuse and describe the profile of electrophysiologic recovery in subjects who abstain from further neurotoxic exposure.
Abnormal single motor unit behavior in the upper motor neuron syndrome
Authors: Shahani Bhagwan T. , Wierzbicka Margaret M. , Parker Stephen W.
Published: January 2005

We studied the discharge pattern of single motor units (SMUs) in the left and right biceps muscles from a patient with nonspastic weakness of the left arm. Detailed statistical analysis of the behavior of discharge patterns of 4 of 4 single motor units on the affected side showed abnormalities with characteristic features of an upper motor neuron lesion. Five out of 5 single motor units recorded from the right biceps were normal. An upper motor neuron lesion affecting the left arm, predicted by our results, was confirmed by magnetic resonance imaging (MRI), which showed a lesion in the right precentral gyrus. It appears that changes in single motor unit firing characteristics, caused by an upper motor neuron lesion, can be detected at a time when there is no evidence of increased “tone” and/or hyperreflexia (spasticity) in the affected extremity.
Paraneoplastic vasculitic neuropathy: A treatable neuropathy
Authors: Oh Shin J. , Slaughter Robert , Harrell Lindy
Published: January 2005

Paraneoplastic vasculitic neuropathy has been recently described. We report the first case of this disorder which responded both clinically and electrophysiologically to cyclophosphamide treatment. A 54hyphen;year‐old women with a history of metastatic endometrial carcinoma in remission had asymmetrical polyneuropathy, electrophysiological findings consistent with a diffuse axonal neuropathy, high sedimentation rate and spinal fluid protein, and microvasculitis with axonal degeneration on nerve biopsy. The patient was treated with 150 mg of cyclophosphamide daily with gradual clinical and electrophysiological improvement.
Human acid maltase‐deficient myogenic cell transformation with origin‐defective SV40: Characterization of a cloned line
Authors: Usuki Fusako , Higuchi Itsuro , Soejima Yasuko , Hattori Masakazu , Maruyama Ikuro , Osame Mitsuhiro
Published: January 2005

A clonal human skeletal muscle cell line showing acid maltase deficiency (AMD) was established through the transfection of origin‐defective SV40 DNA. The low acid α‐glucosidase activity and glycogenosomes in this clone corresponded to AMD. This clone, in spite of loading glycogenosomes, was competent not only as to proliferation without contact inhibition but also as to myogenic differentiation to some extent. Dexamethasone promoted the formation by the transformant of multinucleated myotubes, which expressed acetylcholine receptors. The existence of glycogenosomes did not seem to affect the proliferation or differentiation of myoblasts. The aberrant acid α‐glucosidase expressed in the transformed myogenic clone was shown to be biochemically identical to that in AMD fibroblasts. This transformant should be of great value for investigating the pathogenesis of AMD because of the possibility of supplying semi‐permanently a uniform myogenic cell line expressing AMD.
Dystrophic changes in mdx muscle regenerating from denervation and devascularization
Authors: Anderson Judy E.
Published: January 2005

The regenerative capacity of young mdx muscle after a denervating and devascularizing injury (DD) was examined in extensor digitorum longus (EDL) and compared with that of age‐matched control mouse EDL. DD of the right EDL was produced at the age approximating the onset of dystrophy in the mdx model, and mice recovered for 2 weeks. Contralateral unoperated EDLs from mdx and control mice served as internal controls for histopathology, myofiber cross‐sectional area (CSA), and ultrastructure of fiber regeneration in DD‐EDL. Mdx DD‐EDL were composed of small, uniformly mature myofibers with mostly peripheral nuclei. This contrasted with control DD‐EDL in which fibers were centrally nucleated. In addition, the unoperated mdx EDL exhibited the central nucleation of spontaneous recovery from dystrophy. The CSA distribution of mdx DD‐EDL myofibers was significantly shifted toward smaller CSA compared with unoperated mdx EDL, although mean CSA did not differ between the two mdx muscle groups. The CSA distribution of control DD‐EDL was significantly different and shifted toward smaller CSA from both unoperated control EDL and from mdx DD‐EDL distributions. Ultrastructural features of dystrophy were present in both mdx DD‐EDL and in the unoperated mdx EDL, although they appeared more prevalent in the latter. These results suggest that short‐term plasticity of mdx muscle recovery from imposed injury may be greater than that of normal muscle in establishing a regenerating fiber population.
Arrangement of fiber types within fascicles of human vastus lateralis muscle
Authors: Pernuš Franjo , Eržen Ida
Published: January 2005

A total of 106 fascicles at 6 predetermined areas of the vastus lateralis muscle from 9 healthy men, aged 18 to 40 years, were analyzed. Fibers in a fascicle were divided into layers according to their relation to the perimysium. In each layer the proportions of type 1 and 2, subdivided into 2a, 2b, and 2c fibers were determined and normalized by the fiber type proportion in the whole fascicle. A consistent arrangement of fiber types within the fascicles was obtained, regardless of subject, sampling site, fiber type proportion, and fascicle size. A high proportion of 2b fibers on the border, a prevalence of type 1 fibers in the layer beneath, and a rather uniform distribution of 2a fibers in all layers are the main characteristics of the distribution of fibers in a fascicle. Developmental processes in fiber type differentiation most probably constitute the basis for fiber type arrangement, which can further be influenced by local factors.
The extent and time course of motoneuron involvement in amyotrophic lateral sclerosis
Authors: Dantes Marita , McComas Alan
Published: January 2005

The numbers and relative sizes of motor units have been estimated in 373 muscles of 123 patients with ALS: 74 of the muscles were examined on more than one occasion. The median duration between the onset of symptoms and the initial examination was 12 months; by this time, approximately 90% of the tested muscles showed losses of motor units. The evoked motor unit potentials continued to enlarge in most, but not all, muscles as the disease progressed. Once a muscle became affected by the disease process, the average time‐course was such that the motor unit population halved in each 6‐month period of the first year and diminished more slowly thereafter. A small proportion of patients was encountered in whom the disease progressed much more slowly and there were occasional large fluctuations in the motor unit estimates suggestive of reversible motoneuron dysfunction.
Age‐Related changes and tissue distribution of parvalbumin in normal and dystrophic mice of strain 129 ReJ
Authors: Greaves Douglas S. , Dufresne Michael J. , Fackrell Hugh B. , Warner Alden H.
Published: January 2005

In murine muscular dystrophy, hindlimb muscle contains a functionally defective thiol protease inhibitor (TPI) which has been implicated in the onset and progression of the disease in mice. More recently, this protease inhibitor has been identified as parvalbumin, a calcium binding protein. In this study, a polyclonal antibody against mouse muscle parvalbumin was used to study the concentration and distribution of this protein in normal and dystrophic male mice at various ages. Immunodetection assays were used to screen extracts of hindlimb, forelimb, brain, heart, lung, liver, and kidney in 60‐day‐old normal and dystrophic male mice for parvalbumin content. Parvalbumin was detected in relatively high amounts in both hindlimb and forelimb muscle extracts, while much lower concentrations were detected in brains of normal and dystrophic animals. No parvalbumin was detected in the lung, liver, heart, or kidney extracts using the immunoassay. With aging, the parvalbumin concentration in hindlimb muscle of normal mice remained fairly constant for 90 days, whereupon the level increased at 120 days. In contrast, the parvalbumin concentration in hindlimb muscle of dystrophic mice decreased steadily with age to about 22%% of normal animals at 120 days. The parvalbumin content was also reduced in dystrophic brain.
Invited review: Motor unit estimation: Methods, results, and present status
Authors: McComas Alan J.
Published: January 2005

The renewed interest in motor unit estimation (counting) has coincided with the introduction of computer‐based methodology and with the application of the technique to proximal as well as distal muscles. The advantages and disadvantages of the different methods are considered, together with the assumptions inherent in this type of examination. In normal subjects, the extensor digitorum brevis (EDB) muscle has approximately 200 motor units while each of the intrinsic muscles of the hand has about 100 units; larger muscles in the limbs contain greater numbers of units. Beyond the age of 60 years, there is a decline in the number of functioning motor units in both proximal and distal muscles. In denervating disorders, motor unit estimation is useful for diagnosis and assessment; abnormal values may often be observed in muscles judged clinically to be unaffected. Serial studies have enabled the rate of motor unit loss to be determined in ALS and in spinal muscular atrophy. Depletion of motor units has also been found following upper motoneuron lesions caused by injury to the spinal cord or by cerebral hemorrhage; trans‐synaptic dysfunction has been presumed responsible. Rather surprisingly, reduced numbers of motor units have been observed in a variety of myopathic disorders; of these, the most consistent abnormalities have been reported in myotonic muscular dystrophy.
An endogenous inhibitor of calcium‐activated neutral protease in UMX 7.1 hamster dystrophy
Authors: Nakamura Megumi , Imajoh‐Ohmi Shinobu , Suzuki Koichi , Kawashima Seiichi
Published: January 2005

An endogenous inhibitor for calcium‐activated neutral protease (CANP) from skeletal and cardiac muscles of muscular dystrophic hamsters (UMX 7.1) was compared with that from normal control animals at 4 and 10 weeks of age by Western blotting using antibody raised against CANP inhibitor. Fragmented CANP inhibitor was found in dystrophic skeletal muscles in all cases at both ages, while only intact inhibitor was detected in the skeletal muscle of the normal hamsters. A total absence of intact inhibitor was shown in one 10‐week‐old dystrophic hamster. In contrast, there was little difference in CANP inhibitor from heart between dystrophic and control hamsters at 4 weeks. However, fragmentation similar to that in skeletal muscle was seen in the heart inhibitor in a few of the 10‐week‐old dystrophic hamsters.
Muscle fiber recovery functions studied with double pulse stimulation
Authors: Mihelin Marjan , Trontelj Jože V. , Stålberg Erik
Published: January 2005

Direct electrical stimulation with paired pulses at varied intervals was used to study the propagation velocity and action potential amplitude recovery functions (VRF and ARF) of single muscle fibers. Following a subnormal period with slowed conduction, most of the muscle fibers tested in healthy subjects showed a period of supernormal propagation velocity starting at 3 to 12 ms, with a peak between about 5 and 15 ms, a mean increase of 7%, and an approximately logarithmic decay toward 1 second. The onset of supernormality was earlier in muscle fibers from patients with muscular dystrophy and significantly delayed in those from denervated muscles. Denervated muscle fibers also had a significantly longer refractory period.