摘要:

AbstractThe 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 dystro

ISSN:0148-639X    

DOI:10.1002/mus.880140702

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

年代:1991

数据来源: WILEY

摘要:

AbstractEfficient utilization of fatty acids to sustain prolonged physical efforts is thought to be dependent on the carnitine shuttle of muscle. A study has been carried out in 24 athletes (13 long‐distance runners and 11 sprinters). These subjects received placebo or L‐carnitine (1 g/orally b.i.d.) during a 6‐month period of training. In endurance athletes, training induced lowering of total and free muscle carnitine. Increase of esterified muscle carnitine was also observed. Post‐exertional overflow of acetylcarnitine and long chain acylcarnitine, as well as reduction of the free fraction was also noticed in the blood. Fasting plasma carnitine levels, however, were not affected in carnitine‐treated atheletes at rest. These changes were likely related with the significantly increased urinary excretion of esterified and total carnitine which occurred after physical exercise. In the sprinters only, a decrease in free and total carnitine of muscle was detected after training. Both these potentially unfavourable effects were prevented by oral administration of L‐carnitine. Our data suggest that training in endurance athletes, and to a lesser extent, in sprinters, is associated with a decrease in free and total carnitine of muscle, due to an increased overflow of short‐chain carnitine es

ISSN:0148-639X    

DOI:10.1002/mus.880140703

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

年代:1991

数据来源: WILEY

摘要:

AbstractA volume conductor is any medium with the capability of passively conducting a current between regions of potential difference. The monophasic positive intracellular action potential produces a monophasic negative extracellular waveform and a triphasic extracellular waveform in a poor and good volume conductor, respectively. The observed waveform characteristics are dependent upon both the recording electrode montage and the type of volume conductor surrounding the excitable tissue. The extracellular current flow associated with an action potential can be divided into two current sources flanking a central current sink. If a recording electrode is located over the negative current sink, a negative potential is observed. When the two current sources approach a recording electrode, a positive potential is recorded. If a positive deflection of the baseline is observed, one may conclude that the wave of depolarization under investigation did not originate under, but traveled toward, the recording location. Electric currents from external sources are free to propagate extraneurally as the body is a good volume conductor. Care must be taken to not activate nearby nerves and, subsequently, obtain a waveform contaminated with potentials from undesired sources. Additionally, electrical activity from neighboring muscles and nerves can summate in the volume conductor and yield responses capable of masking pathology. An understanding of the principles of volume conduction theory can help the electrodiagnostician avoid artifactual errors and erroneous conclusions.

ISSN:0148-639X    

DOI:10.1002/mus.880140704

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

年代:1991

数据来源: WILEY

摘要:

AbstractSerial muscle biopsies in a noncarcinomatous case of Lambert–Eaton myasthenic syndrome (LEMS) have shown progressive atrophy and loss of type 1 fibers, resulting in overwhelming type 2 predominance. A similar abnormality was found in a single biopsy from a second case of LEMS without associated carcinoma. Review of the literature suggests that type 2 fiber predominance has been observed in at least one other biopsied case. Interference with transmitter release caused by anti–voltage‐gated calcium channel antibodies may deprive type 1 muscle fibers of the low frequency discharge necessary to maintain their metabolic prope

ISSN:0148-639X    

DOI:10.1002/mus.880140705

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

年代:1991

数据来源: WILEY

摘要:

AbstractThirty patients with 32 acute peripheral arterial occlusions underwent nerve conduction and electromyographic studies at a mean of 12.4 months after the vascular occlusion. Compound action potentials showed greater reduction than conduction velocity (26% to 75% vs 8% to 13% lower than normal). All changes were more prominent in the legs than arms, including fibrillation potentials (64% vs 28%). Short motor unit potentials were seen in extent of abnormality vareid with location of occlusion. Signs of nerve damage were significantly decreased in patients who had early revascularization. The electrophysiologic findigns suggested exonal destruction rather than demyelination.

ISSN:0148-639X    

DOI:10.1002/mus.880140706

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

年代:1991

数据来源: WILEY

摘要:

AbstractSucrose gap and intra‐axonal recording technques were used to identify the types of ion channels and inward rectification that are present in regenerated axons of adult (>8 weeks) rat sciatic nerve after crush injury. In sucrose gap recordings, 4‐aminopyridine (4‐AP) led to slight broadening of the compound action potential (CAP) in normal nerve, and a greater broadening in regenerated nerves. By 12 days after sciatic nerve crush, regenerated nerves manifested an afterhyperpolarization (AHP) lasting up to 250 ms that was sensitive to tetraethylammonium (TEA). A similar TEA‐sensitive AHP could be elicited with repetitive stimulation. Hyperpolarizing constant current steps (0.1 to 0.5 mA; 600–900 ms duration) applied across the sucrose gap through regenerated axons evoked membrane hyperpolarizations with a depolarizing, Cs+‐sensitive relazation in the response to hyperpolarization, which is characteristic of inward rectification, occuring after about 70 ms. The relaxation was present as early as 21 days after nerve crush. Intra‐axonal recordings showed burst firing in 4‐AP that was terminated by an AHP that temporally correlated with the TEA‐sensitive AHP, and a relaxation in the respones to hyperpolazing current, similar to that of whole nerve recordings. The results demonstrate that in addition to voltagesensitive sodium channels and 4‐AP‐sensitive potassium channels, there are TEA‐sensitive and inwardly rectifying channels on mammalian regenerated

ISSN:0148-639X    

DOI:10.1002/mus.880140707

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

年代:1991

数据来源: WILEY

摘要:

AbstractUsing a new collision method, we measured motor nerve conduction velocities of the ulnar nerve in the forearm and the action potential amplitude of the abductor digit minimi muscle on 60 adults, ages 20 to 82 years and apparently free from diseases of the peripheral nervous system. Both maximal and minimal motor nerve conduction velocities were linear functions of age; 64.42 – 0.05 age and 60.45 – 0.12 age, respectively. The percentage of the minimal to the maximal motor nerve conduction velocities was expressed as 94.45 – 0.13 age. The maximum amplitude of evoked muscle action potentials was also correlated with age. This novel method may be useful in detecting pathology of motor nerve fibers which results in a decrease in submaximal conduction veloc

ISSN:0148-639X    

DOI:10.1002/mus.880140708

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

年代:1991

数据来源: WILEY

摘要:

AbstractPresented are real‐time ultrasound findings in partially and completely denervated muscles of 30 patients with focal neurpathy and various other disorders of the second motor neuron. Sonographic scans of affected muscles are analyzed in conjunction with unaffected muscles of the same individual, under identical examination conditions. Initial pathological ultrasound changes could be detected as soon as 2 weeks after an acute neurogenic lesion. In denervation, the echodensity of the muscle was high and the normal intramuscular pattern was decomposed. Findings were more intense in severe and longstanding denervation. Ultrasoudn‐indicated pathology correlated highly (chi‐square:P<0.001) with pathological sponteneous activity detected by electromyography. Focal and systemic neuropathies showed no differences in ultrasound pathology. Six cases with central motor palsy had normal sonograms. Poor spatial resolution of real‐time ultrasonography–as compared with CT and MRI–is compensated by its bedside availability, frequent repeatability without patient risk and discomfort, and its in vivo correlation of muscle morphology with musc

ISSN:0148-639X    

DOI:10.1002/mus.880140709

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe ideal electrodiagnostic procedure to assess possible plantar neuropathies continues to elude investigators. Motor studies are rarely abnormal, pure sensory studies may be difficult to obtain, needle electromyography can demonstrate membrane instability in normal feet. Mixed nerve plantar studies may be more diagnostically valuable than the other techniques but they also have shortcomings. In this report, a technique utilizing somatosensory evoked potentials to assess the medial and lateral plantar and calcaneal nerves is demonstrated. Normative data with respect to latencies, amplitudes, and side‐to‐side differences are presented. Two illustrative cases are also discussed in which the more standard techniques to evaluate plantar neuropathies fail to do so, but the SEP methodology suggests compromise of the intrinsic foot ner

ISSN:0148-639X    

DOI:10.1002/mus.880140710

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

年代:1991

数据来源: WILEY

摘要:

AbstractWe used single fiber electromyography (SFEMG) to study 42 patients who had enroleld in a double‐blind, placebo‐controlled trial undertaken to assess the efficacy of botulinum toxin (BTX) injection of neck muscles to treat torticollis. SFEMG in a limb muscle was performed before treatment, 2, and 12 weeks after injection of placebo or BTX. Before treatment, the mean jitter was 26.8 μsec in patients who were to receive BTX, and 25.7 μsec in the placebo group. Two weeks after injection, mean jitter in the group receiving BTX was 43.6 μsec. In the placebo group, it was 26.5 μsec (P=<.05). Twelve weeks after injection, mean jitter in the BTX group was 35.5; for the placebo group it was 24.5. Fiber density did not change in any patient during the study. There were no remote clinical effects of BTX. Injection of BTX into muscles affected with focal dystonia is a promising and safe treatment, but there are subclinical effects on uninjected

ISSN:0148-639X    

DOI:10.1002/mus.880140711

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

年代:1991

数据来源: WILEY