摘要:

AbstractThe diagnosis of periodic paralysis (PP) can be aided by demonstrating a decrease in compound motor action potential (CMAP) amplitude after several minutes of exercise. We report a case of secondary hypokalemic PP due to thyrotoxicosis in which the decrease in the CMAP amplitude after exercise dramatically improved after treatment, when a euthyroid state was achieved. The exercise test is a useful electropghysiologic means of monitoring the neuromuscular status of patients with thyrotoxic periodic paralysis prior to, and after treatment of the thyrotoxicosis.

ISSN:0148-639X    

DOI:10.1002/mus.880151002

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractNeuromusuclar transmission was studied in the rat phrenic nerve–hemidiaphragm preparation with acetylcholinesterase (AChE) partially inactivated. Enzyme inhibition resulted in (1) increased single‐twitch tension of the diaphragm; (2) compound muscle action potential (CMAP) containing repetitive discharges; (3) stimulus‐induced antidromic backfiring (SIAB) seen in the phrenic nerve; and (4) repetitive nerve stimulation (RNS) eliciting a decrement—increment (D‐I) phenomenon (i.e., amplitude reduction maximal with the second CMAP). Using a high‐calcium and low‐magnesium solution, SIAB and the decrement of the second CMAP during RNS were intensified, whereas closely spaced trains and (+)‐tubocurarine (TC) abolished SIAB and simultaneously prevented the decrement of the second CMAP. Importantly, low concentrations of (+)‐TC prevented SIAB in the phrenic nerve, while the repetitive discharges of the CMAP and the increase in twitch tension remained unaffected. This observation suggests that preterminal nicotinic receptors stimulated by released acetylcholine induce SIAB, whereas postsynaptic events are less important in the generation of SIAB. SIAB, a presynaptic event, appears to be responsible for the transient impairment of the neuromuscular transmission, i.e., t

ISSN:0148-639X    

DOI:10.1002/mus.880151003

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractUsing a concentric macro electrode, both the concentric and macro action potentials of a motor unit were analyzed for duration, area, and amplitude. Eighty‐six different motor units were analyzed from the tibialis anterior muscle in 10 normal subjects. The aim of this work was to compare concentric and macro action potential measurements of the same motor unit. The study revealed significant correlations between concentric and macro samples, with the concentric potential's area correlating better with the macro potential than its amplitude. This shows that the 10 to 15 muscle fibers studied by the concentric electrode serve as a good sample of the motor unit as a whole. We briefly review the technique used in concentric macro EMG, as well as describe the methods used for collecting and comparing both concentric and macro action potentials. © 1992 John Wiley&Sons, I

ISSN:0148-639X    

DOI:10.1002/mus.880151004

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractIn the second part of this study we investigate the correlations between the concentric and conmac action potentials in motor units of individuals with diseases of muscle and nerve. We studied 86 myopathic and 86 neurogenic motor units and compared their concentric and conmac action potentials. In the patients with myopathy, we found that the concentric motor unit action potential's (MUAP) area correlates strongly with the conmac potential, even better than in normals, while its amplitude correlates less. In the neurogenic group, we found that both the concentric MUAP's area and amplitude correlated very well with their conmac counterpart, more so than in normals. Thus, in pathology, as in normals, measuring the concentric MUAP's area in addition to its amplitude adds to the diagnostic sensitivity of motor unit potential measurements. These findings are discussed in light of the known dynamic and architectural motor unit changes which take place in the myopathic and neurogenic motor unit. © 1992 John Wiley&Sons, Inc

ISSN:0148-639X    

DOI:10.1002/mus.880151005

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractThe distribution of mercury within the brainstem and spinal cord of mice was investigated with the autometallographic technique after intramuscular administration of a single dose of mercuric mercury (HgCl2). Deposits of mercury were localized to motor neurons of the spinal cord and to to brainstem motor nuclei; i.e., neurons with their peripheral projections outside the blood‐brain barrier. Unilateral ligation of the hypoglossal nerve prior to the injection of HgCl2prevented the accumulation of mercury deposits in the ipsilateral hypoglossal nucleus. The selective accumulation of mercury in spinal and brainstem motoneurons is most probably due to a leakage of metal‐protein complexes form capillaries in muscle into myoneural junctions, followed by uptake into nerve terminals and retrograde axonal transport. The possible link between this process and the developmentof motor neuron degeneration in ALS is discussed. © 1992 John Wiley&Sons,

ISSN:0148-639X    

DOI:10.1002/mus.880151006

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractAssociations among measures of median, ulnar, and sural nerve conduction and age, skin temperature, sex, and anthropometric factors were evaluated in a population of 105 healthy, asymptomatic adults without occupational exposure to highly repetitive or forceful hand exertions. Height was negatively associated with sensory amplitude in all nerves tested (P<0.001), and positively associated with median and ulnar sensory distal latencies (P<0.01) and sural latency (P<0.001). Index finger circumference was negatively associated with median and ulnar sensory amplitudes (P<0.05). Sex, in isolation from highly correlated anthropometric factors such as height, was not found to be a significant predictor of median or ulnar nerve conduction measures. Equations using age, height, and finger circumference for prediction of normal values are presented. Failure to adjust normal nerve conduction values for these factors decreases the diagnostic specificity and sensitivity of the described measures, and may result in misclassification of individuals. © 1992 John Wiley&Sons, Inc

ISSN:0148-639X    

DOI:10.1002/mus.880151007

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractContractile properties of diaphragm (DIA) from mdx and control mice were compared with those of hindlimb muscles [soleus (SOL) and extensor digitorum longus (EDL)] in vitro. Mice ranged in age from 2 weeks to 1.5 years. Muscles were directly stimulated and properties measured were: contraction time, half‐relaxation time, active tension per unit area, fatigue index, and maximal velocity of shortening (Vmax). Active tension decreased significantly with age in mdx DIA but not in control DIA. SOL and EDL active tensions were less in mdx than control over the whole age range and did not decrease with age.Vmaxwas decreased in mdx DIA, but not in mdx SOL or EDL. These results demonstrate that DIA is more affected by muscular dystrophy than hindlimb muscles. Since many Duchenne patients exhibit respiratory distress, this differential expression of dystrophy in diaphragm, as compared to limb muscles, may have important clinical implications. © 1992 John Wiley&Sons, I

ISSN:0148-639X    

DOI:10.1002/mus.880151008

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractNerve conduction studies (NCS) are an integral part of the evaluation of amyotrophic lateral sclerosis (ALS) patients and are useful in distinguishing ALS from disorders that mimic it. The question often arises whether in the presence of severe atrophy and reduction of the compound muscle action potential amplitude, abnormal conduction velocity (CV), distal latency (DL), of F‐wave latency (F) exceeds what can be expected from ALS alone. To determine the limits of abnormality in classic ALS, we prospectively evaluated NCS data from 61 patients who met a strict clinical definition of ALS. We ralated CV, DL, and F to distal evoked amplitude (AMP) in peroneal (n= 63 observations), median (n= 50), and ulnar (n= 52) nerves. In nerves with reduced AMP, CV rarely fell to less than 80% of the lower limit of normal, and DL and F rarely exceeded 1.25 times the upper limit of normal. Utilizing the entire data set and regression analyses, 95% confidence limits for expected values for CV, F, and DL as a function of AMP were calculated. These limits thus derived suggest criteria for NCS abnormalities in ALS and may by useful in differentiating ALS from other illnesses. © 1992 John Wiley&Sons, I

ISSN:0148-639X    

DOI:10.1002/mus.880151009

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractNerve ischemia is considered one of etiological factors in the development of structural changes in peripheral nerves associated with diabetes mellitus. To assess the effect of mild ischemia on diabetic nerve, a subthreshold dose of polystyrene microspheres was indected intraarterially to occlude microvessels of the sciatic nerve and its branches in 20‐week streptozotccin‐induced diabetic and control rats. Diabetic sciatic and tibial nerves showed severe pathological change of myelinated fibers, whereas nondiabetic nerves were normal or had minor structural abnormalities. Morphometrical evaluation confirmed a greater frequency of abnormal myelinated fibers in diabetic nerves especially in central fascicular regions. The result indicate that diabetic nerve has an increased morphological susceptibility to nerve ischemia. Endoneurial hypoxia, which may result from hemorheological and vascular abnormalities, is likely to cause a lowered threshold to ischemic tolerance in diabetic nerve. This increased vulnerability to ischemia may render diabetic nerve unduly susceptible to hyperglycemia‐induced systemic tissue abnormalities. © 1992 John Wiley&Son

ISSN:0148-639X    

DOI:10.1002/mus.880151010

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractMuscle weakness, studied in 4 patients with multiple sclerosis (MS), was compared with values from normal subjects. Twitch occlusion showed that normal subjects could activate their muscles maximally, but patients rarely achieved>60% activation. In both groups, motoneuron firing rates increased linearly with force. Consistent with the reduced level of activation, MCV firing rates in MS muscles rarely exceeded 17 Hz (compared with ∼24 Hz for normals). However, for right and left muscles of one patient, mean maximum firing rates were 14.2 ± 2 Hz and 8.0 ± 2 Hz, but her muscles could be activated to levels>92% and 60%, respectively. This patient's ability to achieve higher than expected forces at low firing rates was probably due to her slow muscle contractile speeds, especially ½‐relaxation time (75 to 115 ms, cf. ∼60 ms for normals), and high twitch/tetanus ratio (0.4, cf. 0.2). © 1992 John Wiley&

ISSN:0148-639X    

DOI:10.1002/mus.880151011

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY