Muscle & Nerve. Supplement

No abstract text is available yet for this article.

No abstract text is available yet for this article.

The future role of clinical neurophysiology is considered in the light of its achievements. It is argued that there is a need to develop methods for specific diagnosis, especially in neuropathies. There is also an unmet requirement for the development of techniques for the prediction of treatment outcomes and for the measurement of changes during the natural history of neuromuscular disorders and their treatment. These issues are not addressed by currently available clinical test methods.

It all started in 1950 with the introduction of the first commercially available electromyography (EMG) system. From 1950 to 1973 was the era of the analog EMG systems: EMG signals were recorded, and subsequent analyses were carried out manually on film or paper. From 1973 to 1982, the first modular digital EMG systems were introduced. Dedicated analysis modules were introduced, but detailed analysis was still done on paper. In 1982, the first system controlled by a microprocessor was introduced. From 1982 to 1993, many new ways of analyzing EMG signals and basic reporting features were implemented in the EMG systems...

The Department of Clinical Neurophysiology in Uppsala, Sweden, has reached a high degree of computerization. Patient booking, administration, recording equipment, reporting, and telemedicine are linked components forming an integrated laboratory. Today's configuration is a result of the continuous development and implementation of new technologies. During the 1960s and 1970s, the focus was set on the development of signal analysis procedures. The introduction of personal computers and a local network was the main interest during the 1980s...

This is a review of the activities at the Department and Institution of Clinical Neurophysiology at Uppsala University Hospital from 1967 to 2001. The most important routine clinical methods are briefly described, and a summary of some of the research projects is given.

The author recounts the lessons taught by single-fiber electromyography that reached him through the medium of low-frequency attenuation and a small concentric needle electrode. He concludes that it is difficult to imagine practicing electromyography today without the benefits that have flowed from the work of Erik Stålberg and his colleagues.

Rippling muscle disease (RMD) is a benign myopathy with symptoms and signs of muscular hyperexcitability. The typical finding is electrically silent muscle contractions provoked by mechanical stimuli and stretch. After the first description in 1975, there have been several publications on this disorder. Although RMD most often is reported with autosomal dominant inheritance, some sporadic cases are found, and an association with other diseases such as myasthenia gravis has also been reported. The pathophysiological mechanism is still not clarified...

Quantitative motor unit potential (MUP) analysis, which is a leading method of quantitative evaluation of concentric needle electromyography, has several inherent limitations. First, the most essential features of neurogenic or myogenic changes manifest as recruitment abnormalities, rather than as changes in MUP morphology. Second, two factors related to MUP sampling, focusing and level of contraction, greatly influence the parameters of sampled MUPs. Third, the MUP duration, considered to be the cardinal parameter in MUP analysis, has several drawbacks, including low stability and low discriminant sensitivity...

This article gives an overview of what multichannel surface electromyography can teach us about a motor unit. Background information is given about the generation of surface electromyography in general and surface motor unit potentials in particular. Furthermore, we describe how surface motor unit potentials are related to several motor unit characteristics, such as size, location, neuromuscular junction position, fiber length, fiber type, and metabolic fiber properties. In addition, we show how the spatial characteristics of multichannel surface electromyography can be used to obtain single-surface motor unit potentials...

The possibility that spinal cord pathology following trauma can be assessed with early changes in the spinal cord evoked potentials (SCEPs) was examined in a rat model. Spinal cord injury (SCI) was produced in Equithesin-anesthetized (3 ml/kg, i.p.) rats through a longitudinal incision into the right dorsal horn at the T10-11 segments. The SCEPs were recorded with epidural electrodes placed over the T9 (rostral) segment of the cord. The SCEPs consisted of a small positive amplitude and a broad and high negative amplitude (NA)...

Different types of spontaneous activity may be found during electromyographic examinations in patients with spinal cord diseases. Syringomyelia and intramedullary tumor patients may show continuous motor unit activity, synchronous motor unit potentials, myokymic discharges, segmental and propriospinal myoclonus, and respiratory synkinesis. These types of discharges are less commonly encountered in other types of spinal cord lesions. It is suggested that the derangement of inhibitory mechanisms by a central spinal cord lesion may favor the appearance of abnormal spontaneous activity...

Different electromyography (EMG) machines store their data in different formats that vary from manufacturer to manufacturer and even between different EMG machines from the same manufacturer. As advanced as these machines are today, it is necessary in most cases to use faxes, scanners, or a common interface such as Adobe's file format to exchange data between them. A possible solution to this problem is to translate the EMG machine's data output into a common format that can be read (and displayed) by commonly available programs or, even better, by a Web browser...

A special electromyography (EMG) method, scanning EMG, was introduced by Stålberg and Antoni in 1980 to study the electrophysiological cross sections and sizes of motor units. Scanning EMG gives a new approach for the evaluation of the electrical properties of motor units, providing new data on the normal anatomical distribution of muscle fibers and its changes in different pathologies of the muscle. The description of scanning EMG recordings required the introduction of new parameters (lengths of motor unit cross sections, fractions of motor units, and silent areas), in addition to those used with conventional EMG recordings, and the traditional parameters (duration, amplitude, etc...

The meaningfulness of routine conduction velocity studies can be increased when so-called late responses (F waves, H reflex, and intermediate late responses) are considered. The techniques to elicit different types of late responses are described as well as their occurrence in physiological and pathological conditions. Late responses are muscle action potentials of different origins and different configurations, and they have different clinical implications. F waves are recurrent discharges of alpha-motor neurons that have diagnostic value in patients with demyelinating neuropathies and proximal lesions of peripheral nerves...

Isaacs' syndrome (acquired neuromyotonia) is an antibody-mediated potassium channel disorder (channelopathy). The target channel proteins of the antigens are voltage-gated potassium channels (VGKCs), especially dendrotoxin-sensitive fast potassium channels. The suppression of voltage-gated outward K(+) current by antibodies induces hyperexcitability of the peripheral nerve. Patch clamp studies show that antibodies may not directly block the kinetics of VGKCs but may decrease channel density. Electrophysiological, pharmacological, and immunological findings indicate that the site of origin of spontaneous discharges is principally in the distal portion of the motor nerve and/or within the terminal arborization...

In electromyography, one assesses the pathophysiology on the basis of the waveform characteristics of the recorded signal. This requires detailed knowledge of the relationship between the waveform generators and the waveform measurements. Models and computer simulations can be used to explore this relationship in an efficient manner. Combining models with experimental methods will allow us to define new measurements and new rules of interpretation. This is discussed with some of the models developed for electromyography signal analysis...

The background for the macroelectromyography technique, which was developed by Erik Stålberg to measure the size of motor unit potentials in human muscles, is reviewed. The method employs a modified single-fiber electrode with a large nonselective recording surface capable of recording the activity from all the fibers of a motor unit. The findings in normal subjects and its application in the study of motor unit recruitment are described. The value of the technique in the investigation, diagnosis, and monitoring of various neuromuscular diseases, including primary myopathies and neurogenic conditions, is discussed...

The development of microneurography, which began in the laboratory of clinical neurophysiology in Uppsala, is described.

Jitter measurement with axonal microstimulation was used to study synaptic function at 115 neuromuscular junctions (NMJs) of normal subjects at various stimulation rates. Jitter was lowest at 0.5 Hz; it increased slightly at 1, 2, and 5 Hz and remained at that level at 10 Hz (a light work load) and 20 Hz (a heavy work load); and it increased further at 50 Hz (an extreme load). This pattern was seen for the majority of the NMJs, suggesting a high safety factor of neuromuscular transmission maintained rather uniformly over a wide range of discharge rates...