Showing papers in "Muscle & Nerve in 1994"
TL;DR: The results indicate that satellite cell activation, division, and fusion is necessary for compensatory hypertrophy of fully mature muscle, and may be important to the understanding of the limits of recovery of inherited muscle myopathies treated by myogenic cell implantation.
Abstract: Hypertrophy of extensor digitorum longus muscle, overloaded by the removal of the synergist tibialis anterior (TA) muscle, in growing rats is inhibited if endogenous satellite cells are sterilized by exposure to irradiation. However, normal muscle growth is not eliminated, only diminished. To test whether irradiated, overloaded muscle can hypertrophy in the absence of normal growth-related stimuli, experiments were conducted on mature rats. TA muscle ablation caused hypertrophy of EDL muscle, characterized by a significant increase in muscle mass and the size of type IIx and type IIb fibers, and a proportional increase the number of myonuclei. When ablation was preceded by irradiation hypertrophy did not occur. The results indicate that satellite cell activation, division, and fusion is necessary for compensatory hypertrophy of fully mature muscle, and may be important to the understanding of the limits of recovery of inherited muscle myopathies treated by myogenic cell implantation. © 1994 John Wiley & Sons, Inc.
368 citations
TL;DR: These recent developments in the research concerning the function of the dystrophin–glycoprotein complex pave a way for the better understanding of the pathogenesis of muscular dyStrophies.
Abstract: Dystrophin, the protein product of the Duchenne muscular dystrophy (DMD) gene, is associated with a large oligomeric complex of sarcolemmal glycoproteins, including dystroglycan which provides a linkage to the extracellular matrix component, laminin. In patients with DMD, the absence of dystrophin leads to the loss in all of the dystrophin-associated proteins, causing the disruption of the linkage between the subsarcolemmal cytoskeleton and the extracellular matrix. This may render the sarcolemma vulnerable to physical stress. These recent developments in the research concerning the function of the dystrophin-glycoprotein complex pave a way for the better understanding of the pathogenesis of muscular dystrophies.
315 citations
TL;DR: Patients who had an evaluation of the right upper extremity that included motor and sensory conduction studies of the median and ulnar nerves were reviewed and those individuals who were classified as obese were 2.5 times more likely than slender individuals (BMI < 20) to be diagnosed with CTS.
Abstract: Increased weignt and, more recently, body mass index (BMI), have been suggested as risk factors for carpal tunnel syndrome (CTS). In an effort to determine the relative risk (RR) of obesity in the development of CTS, 949 patients who had an evaluation of the right upper extremity that included motor and sensory conduction studies of the median and ulnar nerves were reviewed. Of these patients, 261 were diagnosed with a median mononeuropathy at the wrist. Those individuals who were classified as obese (BMI > 29) were 2.5 times more likely than slender individuals (BMI < 20) to be diagnosed with CTS. Forty-three percent of obese women and 32% of obese men had the diagnosis of CTS compared to 21% of slender women and 0% of slender men. © 1994 John Wiley & Sons, Inc.
240 citations
TL;DR: This article reviews the literature on autonomic neuropathy in Guillain‐Barré syndrome and proposes a management scheme to accommodate it in the overall treatment of the neuropathy.
Abstract: Autonomic neuropathy is an important and common complication of Guillain-Barre syndrome (GBS). Manifestations be present in cardiovascular, sudomotor, gastrointestinal and other systems involving both sympathetic and parasympathetic fibers. Some apparently selective acute autonomic neuropathies may be subvarieties of GBS. Experimental work in animal models, pathological studies of GBS patients, and autonomic function studies have provided some help in the understanding of this complication. In managing GBS patients with autonomic dysfunction there are important practical considerations that can improve their care. In this article we review the literature on autonomic neuropathy in GBS and propose a management scheme to accommodate it in the overall treatment of the neuropathy.
216 citations
TL;DR: Electrophysiological findings in 7 intensive care unit patients who developed evidence of an acute myopathy in association with the use of nondepolarizing muscle blocking agents implicate nondEPolarizing Muscle blocking agents in the development of the myopathy.
Abstract: A series of recent reports have identified cases of a quadriplegic myopathy characterized by myofiber necrosis and loss of myosin filaments associated with the use of nondepolarizing muscle blocking agents and glucocorticoids. We report electrophysiological findings in 7 intensive care unit patients who developed evidence of an acute myopathy in association with the use of nondepolarizing muscle blocking agents. Several important features were identified: (i) a neuromuscular transmission deficit was observed in 3 patients up to 7 days following withdrawal of vecuronium; (ii) motor M potentials were of low amplitude, there was mild abnormal spontaneous activity on needle electromyography, and sensory conduction was relatively preserved; (iii) not all patients received glucocorticoids or were asthmatic; (iv) 2 patients given vecuronium had very high creatine kinase levels and developed acute renal failure associated with myoglobinuria; and (v) rises in motor M potentials accompanied clinical recovery. This complication of intensive care may be severe, but is reversible and possibly avoidable. Our findings implicate nondepolarizing muscle blocking agents in the development of the myopathy. Electrophysiological studies provide important prognostic guidance. © 1994 John Wiley & Sons, Inc.
183 citations
TL;DR: Results indicate that FK506 is a very useful immunosuppressive drug for myoblast transplantation in mice and other manipulations capable of increasing the participation of donor myoblasts to regeneration will have to be identified before new clinical trials are attempted.
Abstract: Transgenic CD1 mice expressing beta-galactosidase were used as myoblast donors. The myoblasts were injected in normal or mdx muscles previously irradiated and injected with notexin. Twenty-eight days after myoblast transplantation, the percentage of muscle fibers beta-glactosidase-positive was low in mice not immunosuppressed but was high (80%) in those treated with FK506. In mdx mice, muscle fibers expressing beta-galactosidase were also dystrophin positive. Most of the mice not treated with FK506 produced antibodies against the donor myoblasts. These results indicate that FK506 is a very useful immunosuppressive drug for myoblast transplantation in mice. Irradiation and notexin injection used in our experiments are, however, not feasible in humans. Other manipulations capable of increasing the participation of donor myoblasts to regeneration will therefore have to be identified before new clinical trials are attempted.
178 citations
TL;DR: The results are similar to those found at the neuromuscular junction in myasthenia gravis and are consistent with a reduced safety factor of cortical synaptic transmission in central nervous system fatigue.
Abstract: We have previously shown that the amplitudes of motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS) were transiently decreased after exercise, indicating fatigue of motor pathways in the central nervous system. The responsible mechanism is apparently decreased efficiency in the generation of the descending volleys in the motor cortex. We also noted a progressive decrement in amplitude from the first to the fourth MEP. To further clarify the mechanism of this phenomenon, 5 subjects were studied with TMS delivered at the rates of 0.1, 0.15, 0.3, 1, 3, and 6 Hz. The effect was best demonstrated at 0.3 Hz, and occurred after both isometric and isotonic exercise. Three of the subjects also had 0.3-Hz percutaneous electrical stimulation of the brainstem, and a decrement in MEP amplitude did not occur. Further, the delivery of TMS during muscle contraction after muscle fatigue failed to produce a decrement. The results are similar to those found at the neuromuscular junction in myasthenia gravis and are consistent with a reduced safety factor of cortical synaptic transmission in central nervous system fatigue.
162 citations
TL;DR: The anatomic site of origin of muscle fasciculations and cramps has been debated for many years and most of the evidence favors a very distal origin in the intramuscular motor nerve terminals.
Abstract: The anatomic site of origin of muscle fasciculations and cramps has been debated for many years. Many authors have argued for a central origin of the abnormal discharges in the anterior horn cells. However, most of the evidence favors a very distal origin in the intramuscular motor nerve terminals. The factors giving rise to these discharges are not well understood. Fasciculations may be related to chemical excitation of motor nerve terminals, whereas cramps may result from mechanical excitation of motor nerve terminals during muscle shortening. © 1994 John Wiley & Sons, Inc.
162 citations
TL;DR: In this paper, reference values of motor unit action potentials (MUAPs) were collected from healthy deltoid, brachial biceps, first dorsal interosseous, lateral vastus, and anterior tibial muscles in 105 subjects between 15 and 86 years.
Abstract: We collected reference values of motor unit action potentials (MUAPs) from healthy deltoid, brachial biceps, first dorsal interosseous, lateral vastus, and anterior tibial muscles in 105 subjects between 15 and 86 years. The MUAPs were recorded with a concentric needle electrode and extracted with a decomposition method we call multi-MUAP analysis. The main goal is to identify and extract MUAPs. Also, the firing pattern of the motor units can be followed. No significant changes with age were found for duration, spike duration, thickness, amplitude, area, size index, or number of phases in all muscles studied. We did not find any influence of gender or height. We found higher amplitudes and shorter durations compared with previous studies. This may be due to a higher contraction level that can be used with a decomposition technique. No right-left side differences were found. The coefficient of variation of the parameters in repeated examinations was small, which implies a good reliability of the measurements. Interexaminer variability of four investigators was not greater than in repeated studies.
162 citations
TL;DR: A randomized double‐blind controlled trial of deflazacort was conducted in 28 Duchenne muscular dystrophy patients, with significant improvement in climbing stairs, rising from a chair, Gower's maneuver, and walking after 6 months of treatment and a significant change in the MRC index after 2 years.
Abstract: A randomized double-blind controlled trial of deflazacort was conducted in 28 Duchenne muscular dystrophy patients either treated with deflazacort 2.0 mg/kg alternate-day therapy or placebo. The deflazacort group showed significant improvement in climbing stairs (P < 0.01), in rising from a chair, Gower's maneuver, and walking (P < 0.0025) after 6 months of treatment. After 1 year, all the above changes remained significantly improved and the MRC index was significantly better (P < 0.05) in the treated group. After 2 years, a significant change was found in the MRC index: higher scores in walking, chair rising (P < 0.02), and grade and time of Gower's maneuver (P < 0.05) were found. The mean time for loss of ambulation for the treated group after we started the trial was 33.2 +/- 9 months; for the placebo group it was 20.5 +/- 11 months (deflazacort vs. placebo group, P < 0.05) [corrected]. Our treated patients lost their ambulation at a median age of 11.8 years vs. 10.5 years in the placebo group. Side effects were mild, consisting of moderate weight gain and slight behavioral changes.
144 citations
TL;DR: Evidence of slowed PCr resynthesis following exercise in MS, which indicates impaired oxidative capacity in the skeletal muscle of this group, suggests that intramuscular changes consistent with deconditioning may be important in the altered muscle function of persons with MS.
Abstract: To determine whether skeletal muscle oxidative metabolism is impaired in multiple sclerosis (MS), 31 phosphorus magnetic resonance spectroscopy was used to measure the rate of intramuscular phosphocreatine (PCr) resynthesis following exercise in MS and controls. Thirteen MS patients underwent intermittent isometric tetanic contractions of the dorsiflexor muscles elicited by stimulation of the peroneal nerve. Eight healthy control subjects performed voluntary isometric exercise of the same muscles. During exercise, there were no differences between groups in the fall of either PCr or pH. However, the half-time (T-1/2) of PCr recovery following exercise was significantly longer in MS (2.3 ± 0.3 min) compared to controls (1.2 ± 0.1 min, P < 0.02). These data provide evidence of slowed PCr resynthesis following exercise in MS, which indicates impaired oxidative capacity in the skeletal muscle of this group. This finding suggests that intramuscular changes consistent with deconditioning may be important in the altered muscle function of persons with MS. © 1994 John Wiley & Sons, Inc.
TL;DR: Simulations showed that increased jitter of the constituent single fiber potentials increases the jiggle as expressed by an increase in CAD and decrease in CCC values, which will increase the information obtainable from routine EMG investigations.
Abstract: A method for quantifying shape variability, the jiggle, or motor unit potentials (MUPs) recorded with conventional EMG electrodes is presented Amplitude variability at each point of time of the MUP was analyzed Two new parameters are proposed: the normalized value of the consecutive amplitude differences (CAD), and the cross-correlational coefficient of the consecutive discharges (CCC) Simulations showed that increased jitter of the constituent single fiber potentials increases the jiggle as expressed by an increase in CAD and decrease in CCC values Even when the jitter value of each component was fixed, increased temporal dispersion increased the jiggle whereas an increased number of fibers decreased the jiggle This new method has been applied in normal subjects, patients with chronic neurogenic diseases and patients with ALS Jiggle was significantly increased in the ALS group, in agreement with visual observations We believe that this method for quantifying jiggle will increase the information obtainable from routine EMG investigations
TL;DR: It is concluded that metabolic factors do not play a significant role in the development of muscle fatigue during voluntary exercise in mild MS and activation failure beyond the muscle membrane(excitation–contraction coupling) may be important in MS.
Abstract: We investigated the role of metabolism in muscle fatigue during voluntary exercise in persons with mild multiple sclerosis (MS). Six MS and 8 healthy control subjects performed intermittent, progressive, isometric contractions of the ankle dorsiflexors, during which we measured maximum voluntary force (MVC), inorganic phosphate (Pi), phosphocreatine (PCr), and pH. During exercise, MVC fell sooner in MS, but by the end of exercise the relative decrease in MVC was similar in both groups. In contrast, at the end of exercise Pi/PCr increased to 1.86 +/- 0.22 in controls but to only 0.66 +/- 0.04 in MS (P < 0.01); likewise, pH was 6.75 +/- 0.04 in controls and unchanged (7.06 +/- 0.04) in MS (P < 0.01). The smaller metabolic change at the same relative exercise intensity suggests a failure of muscle activation that is present even in mild MS. Neurophysiologic measures of activation indicated some central activation failure and no neuromuscular junction impairment in MS, and suggested that activation failure beyond the muscle membrane (excitation-contraction coupling) may be important in MS. We conclude that metabolic factors do not play a significant role in the development of muscle fatigue during voluntary exercise in mild MS.
TL;DR: The cortical silent period was elicited by transcranial magnetic stimulation in 25 normal subjects and 19 patients with amyotrophic lateral sclerosis and there was a significant, linear, relation between the maximum C‐SP and disease duration of ALS.
Abstract: The cortical silent period (C-SP) was elicited by transcranial magnetic stimulation in 25 normal subjects and 19 patients with amyotrophic lateral sclerosis (ALS). The inhibitory (S-X) period was highly stimulus intensity (SI)-dependent (mean r2 = 0.89 for both normals and patients with ALS). The range of the C-SP (difference between maximum and minimum S-X intervals) was age-dependent for normals (r2 = 0.701, P < 0.001) but not patients with ALS. Means, maximums and ranges for the C-SP were not significantly different between normal and ALS groups and thresholds to cortical stimulation were also comparable. There was a significant, linear, relation between the maximum C-SP and disease duration of ALS (P = 0.002). The maximum C-SP was shorter early in the disease. It is hypothesized that the reduced inhibition early in the course of ALS might reflect glutamate-induced corticomotoneuronal excitotoxicity.
TL;DR: The aim of the present investigation was to define limits of normal values and to compare the diagnostic yield of assessing definitely abnormal values outliers, with conventional mean values of MUP parameters, and found that outliers were as sensitive as mean values in neuropathies and better in myopathies.
Abstract: In visual analysis of motor unit potentials it is common to decide abnormality by a few motor unit potentials with definitely abnormal amplitude, duration, and shape. The aim of the present investigation was to define limits of normal values and to compare the diagnostic yield of assessing definitely abnormal values outliers, with conventional mean values of MUP parameters. MUPs were extracted and measured with a new decomposition method. Reference values were obtained for three commonly studied muscles. Patients with various types of neuropathies and myopathies were studied in the same way with measurement of outliers and mean values. It was found that outliers were as sensitive as mean values in neuropathies and better in myopathies. Often an increased number of outliers could already be detected after only a few MUPs had been obtained. It would not have been necessary to obtain all 20 MUPs in these patients. The conclusion is that the outlier method is as sensitive as mean values. Because the number of MUPs required may be reduced, the investigation takes a shorter time and is less painful for the patient. If the degree of abnormality is to be quantified, calculation of mean values is still necessary. The combination of outliers and mean values may be the optimal way to detect and express abnormality.
TL;DR: Intramuscular injections into EDB provide a useful model for studying chemodenervation effects and confirm a primary peripheral action of the toxin, but a superimposed, transient central effect of the drug cannot be excluded.
Abstract: To characterize the time course of intramuscular botulinum toxin-induced paresis, we serially performed electrophysiological measurements and recorded the sonographic size of an extensor digitorum brevis (EDB) muscle in 10 human subjects before and after injecting the EDB with 10 units of botulinum-A toxin. All EDB CMAPs decreased within 48 h, with peak decline at day 21 (8.3 +/- 3.1 mV to 3.0 +/- 0.9 mV). Decline of mean rectified voltage during maximal voluntary contraction of the EDB paralleled the change in CMAP amplitude. Average decrements to 2-Hz repetitive stimulation never exceeded 6% (day 42) and exercise failed to facilitate significantly CMAP amplitude. Atrophy peaked at day 42. The F-wave to M-wave ratio increased at day 2; silent periods did not change. Our findings confirm a primary peripheral action of the toxin, but a superimposed, transient central effect of the drug cannot be excluded. Intramuscular injections into EDB provide a useful model for studying chemodenervation effects.
TL;DR: 3 patients with acute respiratory insufficiency who developed prolonged weakness following the discontinuation of ND‐NMBAs are reported, with pathology at both the neuromuscular junction and muscle likely due to corticosteroids.
Abstract: The long-term use of nondepolarizing neuromuscular blocking agents (ND-NMBA) has recently been implicated as a cause of prolonged muscle weakness, although the site of the lesion and the predisposing factors have been unclear. We report 3 patients (age 37–52 years) with acute respiratory insufficiency who developed prolonged weakness following the discontinuation of ND-NMBAs. Two patients also received intravenous corticosteroids. Renal function was normal but hepatic function was impaired in all patients, and all had acidosis. Electrophysiologic studies revealed low amplitude compound motor action potentials, normal sensory studies, and fibrillations. Repetitive stimulation at 2 Hz showed a decremental response in 2 patients. The serum vecuronium level measured in 1 patient 14 days after the drug had been discontinued was 172 ng/mL. A muscle biopsy in this patient showed loss of thick, myosin filaments. The weakness in these patients is due to pathology at both the neuromuscular junction (most likely due to ND-NMBA) and muscle (most likely due to corticosteroids). Hepatic dysfunction and acidosis are contributing risk factors. © 1994 John Wiley & Sons, Inc.
TL;DR: It is suggested that patients with MMN demonstrate widespread evidence of motor demyelination in addition to the well‐described PMCB, and that reduction of PMCB accounts for the increase in strength following therapy.
Abstract: Diagnosis of multifocal motor neuropathy (MMN), a syndrome characterized by progressive asymmetric weakness with intact sensation, is important because the disorder often responds to treatment. Multifocal partial motor conduction block (PMCB) has been emphasized as a cardinal feature in the diagnosis of this syndrome, but detailed nerve conduction studies are not available. Nine patients, ages 28–58, had chronic, progressive, asymmetric, predominantly distal limb weakness for 5–18 years. Sensation was normal and reflexes were reduced asymmetrically. Although all 9 demonstrated PMCB localized to short nerve segments, additional features of multifocal motor demyelination were present, including temporal dispersion (5 patients), segmentally reduced motor nerve conduction velocity (7 patients), prolonged distal motor latency (4 patients), and prolonged F-wave latency (9 patients). The strength of all patients improved after treatment with human immune globulin. A reduction in the degree of PMCB or an increase in the distal motor amplitude or both accompanied the clinical improvement. These studies suggest that patients with MMN demonstrate widespread evidence of motor demyelination in addition to the well-described PMCB, and that reduction of PMCB accounts for the increase in strength following therapy. © 1994 John Wiley & Sons, Inc.
TL;DR: Reflex testing can be utilized to demonstrate multiple lesions evoked by a single vascular event and evaluate dissemination of central nervous involvement in multiple sclerosis patients.
Abstract: The masseter and medial pterygoid stretch reflexes, the masseter inhibitory reflexes, and the blink reflexes are useful diagnostic tools for evaluation of brain stem disorders. The structures mediating these reflexes are largely known. Characteristic changes of the normal response patterns due to various lesions have been described. Distinct reflex abnormalities indicate lesions at specific sites. Multireflex testing improves the accuracy with which localization can be made. A number of lesions suspected on clinical data may be confirmed by reflex findings only and not by imaging studies. Reflex testing can be utilized to demonstrate multiple lesions evoked by a single vascular event and evaluate dissemination of central nervous involvement in multiple sclerosis patients.
TL;DR: It is shown that autoimmune neuropathy can be produced in rats with cyclosporine A (CsA), whose effects on T‐cell subsets are similar to those seen with FK506, and this phenomeno may have precipitated this dysimmune neuropathy in patients.
Abstract: FK506 is an important immunosuppressant that has shown great promise in the treatment of autoimmune diseases. Approximately 5% of patients receiving FK506 develop major central nervous system toxicity, but the peripheral nerves are usually spared. During 1990-1991, some 1000 patients received liver transplants under FK506 immunosuppression. Of these, 3 patients developed severe multifocal demyelinating sensorimotor polyneuropathy 2-10 weeks after initiation of FK506 therapy. Improvement followed plasmapheresis or intravenous immunoglobulin (IVIG), suggesting an immune-mediated cause. Although autoimmune neuropathy has been previously reported in immune-deficient states such as Hodgkin's disease and AIDS, it is not an expected complication of immunosuppressive therapy. However, others have shown that this phenomenon can be produced in rats with cyclosporine A (CsA), whose effects on T-cell subsets are similar to those seen with FK506. These T-cell subset changes may have precipitated this dysimmune neuropathy in our patients.
TL;DR: The advantages of the automated technique for collecting S‐MUAPs from the F‐response include the ready tolerance of the technique by subjects, the minimal amount of operator interaction required, and the additional information relating to the conduction velocities and latencies of single motor axons.
Abstract: An automated technique for estimating the number of motor units based on single motor unit action potentials in the F-response is described. The average surface detected motor unit action potential (S-MUAP) was calculated from the datapoint-by-datapoint average of a sample of S-MUAPs automatically selected from a population of F-responses. The technique was applied to the thenar muscles of young (n = 18, aged 31 +/- 11 years) and older (n = 15, aged 68 +/- 3) subjects. Motor unit number estimates based on the automated selection of S-MUAPs from the F-responses compared well with those derived using a computer-assisted manual method for selecting S-MUAPs from the F-response (automated 245 +/- 105 vs. manual 241 +/- 100, r = 0.93) and were similar to estimates obtained using multiple point stimulation (219 +/- 77). The advantages of the automated technique for collecting S-MUAPs from the F-response include the ready tolerance of the technique by subjects, the minimal amount of operator interaction required, and the additional information relating to the conduction velocities and latencies of single motor axons.
TL;DR: Clones of human myoblasts were able to fuse and produce dystrophin in injected muscles of immunodeficient mice and mdx mice receiving an effective immunosuppressive treatment and evidence of humoral and cellular rejection was observed following human myoblast transplantation.
Abstract: Normal human myoblasts were cloned and transplanted in the tibialis anterior of immunodeficient nude and SCID mice and in mdx mice under different immunosuppressive treatments (cyclosporine A, CsA; antilymphocyte serum, ALS) or not immunosuppressed. This permitted us to show the interaction of the immune system in the myoblast transplantation. The graft success was assessed by verifying signs of humoral and cellular immune reactions and the presence of dystrophin produced by the fusion of the donor myoblasts. This study showed that clones of human myoblasts were able to fuse and produce dystrophin in injected muscles of immunodeficient mice and mdx mice receiving an effective immunosuppressive treatment (i.e., ALS + CsA). However, the same pool of human myoblasts injected in mdx mice inadequately immunosuppressed (i.e. CsA alone or ALS alone) triggered an immune reaction and was rejected. Cells expressing CD4 and CDS antigens were observed in the injected muscles of mice treated with CsA alone. Therefore, evidence of humoral and cellular rejection was observed following human myoblast transplantation. © 1994 John Wiley & Sons, Inc.
TL;DR: The purpose of this study was to estimate the time needed to warm an extremity prior to measuring nerve conduction, and correlations were calculated between the skin temperature at the start of the investigation and the warming time necessary to obtain a good estimate of nerve Conduction variables at 36°C.
Abstract: The purpose of this study was to estimate the time needed to warm an extremity prior to measuring nerve conduction. In 8 normal subjects tibial and sural nerve conduction variables were measured during cooling and warming of the leg in water of 18 degrees C and 36 degrees C, respectively. During cooling, nerve conduction velocity (NCV) decreased and distal motor latency (DML), duration, and area of the compound muscle action potentials (CMAP), and compound nerve action potentials (CNAP) increased. The reverse occurred during warming. During cooling or warming the change in these variables became progressively smaller with time. The time course could therefore be described by an exponential relation, the parameters of which were determined. On the basis of these data, correlations were calculated between the skin temperature at the start of the investigation and the warming time needed to obtain a good estimate of nerve conduction variables at 36 degrees C. The use of correction factors, instead of actual warming, yielded acceptable errors only for NCV and not for the other variables.
TL;DR: It is confirmed that SMG is autoantibody mediated and that there are pathogenic IgG antibodies, and SMG appears to be a heterogeneous disorder and the target(s) for the antibodies may be diverse.
Abstract: Muscle weakness in myasthenia gravis is due to autoantibody-induced loss of functional acetylcholine receptors (AChR). About 15% of myasthenia gravis patients, however, do not have detectable anti-AChR antibodies. To investigate the effect of their plasma immunoglobulins on neuromuscular transmission, mice were injected with plasma (and in some cases purified immunoglobulin G (IgG)) from 7 "seronegative" myasthenia gravis (SMG) patients, and neuromuscular transmission parameters were examined. When injected for 15 days, all patients' plasma caused reductions in miniature endplate potential amplitudes, while endplate potential quantal content was significantly reduced by plasma from 4 of the 7 patients. There were no changes in ACh-induced depolarization or single channel properties, and 125I-alpha-bungarotoxin binding studies showed no effect on AChR number, except in 1 case. Purified IgG injected for 3 days had similar effects to plasma injected for 15 days. Our findings confirm that SMG is autoantibody mediated and that there are pathogenic IgG antibodies. SMG appears to be a heterogeneous disorder and the target(s) for the antibodies may be diverse.
TL;DR: Fiber electromyography (SFEMG) has proven to be a useful electrodiagnostic tool to assess defects of neuromuscular junction transmis.
Abstract: S i n g l e fiber electromyography (SFEMG) has proven to be a useful electrodiagnostic tool to assess defects of neuromuscular junction transmis
TL;DR: Continuous muscle fiber activity (Isaacs' syndrome) comprises a heterogeneous group of hereditary and acquired disorders that cause hyperexcitability of peripheral nerves that are associated with electrophysiologic evidence of peripheral neuropathy and some are not.
Abstract: Stiff-man syndrome is due to hyperexcitability of anterior horn cells, possibly related to interference with the synthesis or action of gamma-aminobutyric acid. Unexpected acoustic and exteroceptive stimuli produce exaggerated muscle responses. Needle electrode examination of involved muscles yields nonspecific findings and demonstrates involuntary motor unit activity. The appearance and firing pattern of motor units are normal except that agonist and antagonist muscles may contract concurrently. Continuous muscle fiber activity (Isaacs' syndrome) comprises a heterogeneous group of hereditary and acquired disorders that cause hyperexcitability of peripheral nerves. Some are associated with electrophysiologic evidence of peripheral neuropathy and some are not. Repetitive afterdischarges often follow the M-, H-, and F-waves. Needle electrode examination reveals an abnormal pattern of motor unit firing, consisting of myokymic discharges, doublets and multiplets, neuromyotonic discharges, and fasciculations. These abnormalities may occur alone or in combination.
TL;DR: The role of central, intracortical structures in the generation of essential tremor and postural tremor in Parkinson's disease is emphasized and resetting depended on the stimulus intensity, but was most closely correlated with the duration of the electromyographic silent period that followed the stimulus‐induced motor evoked potential.
Abstract: We studied the effects of transcranial motor cortex stimulation on the electromyographic characteristics of tremor in 9 patients with familial essential tremor and in 12 patients with postural tremor associated with Parkinson's disease. Transcranial magnetic stimulation reset both types of tremor equally. The resetting depended on the stimulus intensity, but was most closely correlated with the duration of the electromyographic silent period that followed the stimulus-induced motor evoked potential. Tremor resetting was present bilaterally even after focal, unilateral stimulation. Transcranial electrical stimulation failed to reset the tremor in either patient group. These results emphasize the role of central, intracortical structures in the generation of essential tremor and postural tremor in Parkinson's disease. © 1994 John Wiley & Sons, Inc.
TL;DR: 6 patients who 1–13 days postoperatively developed signs and symptoms which met the clinical and electrophysiologic criteria for IBN are presented.
Abstract: Idiopathic brachial neuritis (IBN) is a well-recognized clinical syndrome characterized by brachial pain followed by a patchy amyotrophy of muscles in the shoulder girdle and arm innervated by individual branches of the brachial plexus. Postsurgical IBN has not been widely recognized since Parsonage and Turner's original description in which 10% of patients had antecedent surgery. We present 6 patients who 1-13 days postoperatively developed signs and symptoms which met the clinical and electrophysiologic criteria for IBN. Postsurgical neuralgic amyotrophy is an under-recognized clinical entity which in most cases is ascribed to brachial plexus stretch injuries occurring during anesthesia. Early recognition of this condition may prevent unnecessary surgical exploration and allow for a more accurate prediction of functional recovery.
TL;DR: It was showed that the best diagnostic index for conduction block is the total area method and for abnormal temporal dispersion, the negative‐peak duration method.
Abstract: In order to find the best diagnostic index of conduction block and abnormal temporal dispersion, the amplitude, duration, and area of the compound muscle action potentials (CMAP) were studied in 40 normal controls and 28 patients with acquired demyelinating neuropathies. In the normal subjects, there was a substantial difference among the various nerves in the degree of CMAP amplitude reduction and CMAP duration prolongation with proximal stimulation, and thus different criteria should be used for conduction block or abnormal temporal dispersion for a given nerve. In 28 patients with demyelinating neuropathy, 58 of 207 (28%) tested nerve segments showed nerve conduction velocity (NCV) evidence of demyelination. To identify "demyelination" in these segments, conduction block was best detected by the total area method in 71% of cases, and abnormal temporal dispersion was best by the negative-peak duration method. This study showed that the best diagnostic index for conduction block is the total area method and for abnormal temporal dispersion, the negative-peak duration method.
TL;DR: It is concluded that maximum voluntary contraction is preferable to brief 20‐Hz RNS to demonstrate potentiation in LEMS because it is at least as sensitive and is less painful.
Abstract: We compared changes in amplitude and area of surface recorded compound motor action potentials (CMAPs) during 20-Hz repetitive nerve stimulation and after maximum voluntary contraction in patients with the Lambert-Eaton myasthenic syndrome (LEMS), myasthenia gravis (MG), and normal controls. There was greater potentiation of CMAP amplitude after voluntary contraction than during 20-Hz stimulation in 10 of 14 LEMS patients; CMAP area increased more after exercise than during 20-Hz stimulation in all LEMS patients. Although abnormal potentiation of CMAP area and amplitude was seen in equal numbers of LEMS patients, more LEMS patients demonstrated a greater than 100% potentiation of CMAP area than of CMAP amplitude. We conclude that maximum voluntary contraction is preferable to brief 20-Hz RNS to demonstrate potentiation in LEMS because it is at least as sensitive and is less painful. Measurement of CMAP area in LEMS patients is not better than measuring the change in CMAP amplitude in demonstrating abnormal potentiation. Testing of a single hand muscle for potentiation in LEMS does not demonstrate abnormal potentiation in all LEMS patients.