Standards of instrumentation of EMG. The International Federation of Clinical Neurophysiology.
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Computers↗
Biomedical subjects
C Bischoff
Publications and source records attributed to C Bischoff.
Repair pathways for processing of 8-oxoguanine in DNA by mammalian cell extracts.
The repair pathways involved in the removal of 8-oxo-7, 8-dihydroguanine (8-oxoguanine) in DNA by mammalian cell extracts have been examined. Closed circular DNA constructs containing a single 8-oxoguanine at a defined site were used as substrates to determine the patch size generated after in vitro repair by mammalian cell extracts. Restriction analysis of the repair incorporation in the vicinity of the lesion indicated that up to 75% of the 8-oxoguanine was repaired via the single nucleotide replacement mechanism in both human and mouse cell extracts. Approximately 25% of the 8-oxoguanine lesions were repaired by the long patch repair pathway. Repair incorporation 5' to the lesion, characteristic for nucleotide excision repair, was not significant. Elimination of the DNA polymerase beta (polbeta)-dependent single nucleotide base excision repair pathway in extracts prepared from polbeta-deficient mouse cells resulted in extension of the repair gap to 4-5 nucleotides 3' to the lesion in 50% of the repair events, suggesting the increased involvement of the long patch repair pathway. However, about one-half of the 8-oxoguanine repair was still accomplished through replacement of only one nucleotide in the polbeta-deficient cell extracts. These data indicate the existence of an alternative polbeta-independent single nucleotide repair patch pathway for processing of 8-oxoguanine in DNA.
Animals↗
Dysfunctional voiding in women: which muscles are responsible?
OBJECTIVE: To analyse the striated external urethral sphincter (EUS) and pelvic floor muscles using two different electromyography (EMG) techniques in women with dysfunctional voiding and/or urinary retention. PATIENTS AND METHODS: Fifteen women (mean age 38.2 years, range 18-61) with dysfunctional voiding and/or unexplained voiding dysfunction associated with urinary retention were examined neurologically and urologically; urodynamics and kinesiological EMG of the bilateral pubococcygeal and external urethral striated sphincter muscles were obtained. In an additional neurophysiological session, concentric-needle EMG of the external urethral sphincter was performed. RESULTS: Kinesiological EMG recordings revealed inappropriate pelvic floor muscle activation during voiding in 11 and EUS activation in four women. Concentric needle EMG of the EUS revealed complex repetitive discharges in the four women with inappropriate urethral sphincter activation recorded by kinesiological EMG during voiding. Biofeedback training led to improvement in women with inappropriate pubococcygeal activation but not in those with urethral sphincter complex repetitive discharges. CONCLUSION: Urodynamic examinations in combination with kinesiological EMG examination of the pubococcygeal and external urethral sphincter muscles revealed two groups of women with dysfunctional voiding. Further diagnostic evaluation of such patients with concentric-needle EMG is mandatory. The differentiation of the two groups is therapeutically relevant.
Adolescent↗
Electromyography of the external anal sphincter in patients with Parkinson's disease and multiple system atrophy: frequency of abnormal spontaneous activity and polyphasic motor unit potentials.
Electromyographic studies of the external anal sphincter muscle have received increasing attention in the differential diagnosis of patients with parkinsonism. Based on the fact that the external anal sphincter muscle is partly innervated by fibers that originate in Onuf's nucleus in the segments S2-S4 of the spinal cord, an increased duration of the motor unit potentials (MUPs) and an increased polyphasia may reflect neuronal loss of these lower motor neurons characteristic for multiple system atrophy. We report the results of anal sphincter electromyography in 15 patients with clinically probable multiple system atrophy (MSA) and 10 patients with Parkinson's disease (PD). There was no significant difference between patients with MSA and patients with PD concerning the duration of MUPs, mean number of phases, and rate of polyphasic motor potentials. There was a tendency for a longer mean duration and increased polyphasia in patients with MSA compared to patients with PD. Spontaneous activity was recorded in 11 of 15 patients with MSA occurring especially in patients with MSA of the striatonigral type, but not in patients with PD. In this study, the duration of MUPs and the rate of polyphasia were unreliable criteria in the electrophysiological differential diagnosis of patients with parkinsonism. Abnormal spontaneous activity, although difficult to detect, is a more specific marker for neuronal degeneration of Onuf's nucleus occurring in patients with MSA.
Adult↗
[The significance of leukoaraiosis. A current evaluation and differential diagnosis].
Bilateral symmetric changes in the cerebral hemispheric white matter are found with increasing frequency using CT and MRI techniques. These unspecific changes of the white matter signal are often called leukoaraiosis. They differ from the normal white matter signal. These changes are found with increasing frequency in persons older than 60 years and also patients with dementia and cerebrovascular diseases. The pathogenesis, clinical significance and morphological substrate are unclear. The aim of this review is to summarise the actual knowledge about the etiology and clinical signs and symptoms found in patients with leukoaraiosis. This term should not be used when white matter changes are found in patients younger than 35 years, with an unilateral onset, asymmetric distribution, and extensive changes all over the infra- and supratentorial white matter area. Neuroradiological and clinical criteria are given to differentiate between leukoaraiosis and diseases of the white matter, especially enlarged Virchow-Robin spaces, lacunar infarction, subcortical arteriosclerotic angiopathy (Binswanger's disease), leukoencephalopathy of different origin, and demyelinating diseases.
Adult↗
Assessment of functional hemispheric asymmetry by bilateral simultaneous cerebral blood flow velocity monitoring.
The aim of this study was to investigate side-to-side differences of simultaneously measured middle cerebral artery (MCA) blood flow velocities during various hemisphere-specific tasks. Using a transcranial Doppler device, flow velocity changes of 24 healthy, right-handed subjects were monitored simultaneously in the left and right MCA during different hemisphere-specific tasks. Mean flow velocity (MFV) curves were averaged for each individual subject and task. Simultaneously, heart rate, blood pressure and end-tidal carbon dioxide (CO2) were measured in a subgroup of six subjects. When compared with the resting state, all stimuli produced significant (p < 0.001) bilateral MFV increases, ranging from 2.5-9.2%. A lateralization of MFV increases with a significantly (p < 0.001) more pronounced increase in MFV in the hemisphere contralateral to the performing band was observed both during simple sequential finger movements and a complex spatial task. During the complex spatial task, consistently higher MFV increases were observed in the right MCA (p < 0.001), regardless of the side of task performance. Recognition of pictorial material presented as part of a memory task, also resulted in a side-to-side difference of respective MFV increases (right > left, p < 0.001), whereas memorization did not. Whereas bilateral MFV elevations observed during stimulation with white noise were only discrete and not lateralized, exposure to overt speech produced significantly higher (p < 0.001) MFV increases in the left MCA. The time course of the MFV reaction showed a rapid increase with an initial maximum after 4-5 s. Heart rate, blood pressure, and end-tidal CO2 showed only subtle changes during the stimulation periods. In conclusion, the observed side-to-side differences of MFV reaction in the left and right MCA concur with current functional imaging data. Bilateral simultaneous repetitive transcranial Doppler monitoring is a sensitive method to detect cerebral perfusion asymmetries caused by hemisphere-specific activation, and thus may be helpful for noninvasive assessment of hemispheric dominance for language.
Adult↗
Significance of A-waves recorded in routine motor nerve conduction studies.
The occurrence of A-waves during routine F-wave studies was investigated in 556 consecutive patients referred to the Department of Clinical Neurophysiology at the University Hospital in Uppsala for various neuromuscular disorders. Altogether, 2367 nerves in the upper and lower extremities were studied. An A-wave, with a nearly constant latency and a uniform shape on consecutive stimulations, could be recorded in 184 nerves (7.8%) out of 124 patients (22.3%). More than 50% of patients with A-waves had various types of polyneuropathies. Of all patients with polyneuropathy, 65% had at least one nerve with A-waves. A-waves occurred somewhat less frequently in patients with radiculopathies. In other proximal local nerve lesions they were found less often and only exceptionally in patients with distal nerve lesions. A-waves were present in 6 out of 10 patients with motor neurone diseases. There was no correlation between the number of A-waves found in one nerve or the number of nerves in a given patient with A-waves and the aetiology or severity of the underlying disease. A-waves were found in 11 patients referred for various neurological symptoms in whom other neurophysiological findings were normal. This might be interpreted as an early sign of underlying disease because in 100 healthy controls no A-waves could be elicited, with the exception of 3 subjects who had A-waves in the abductor hallucis muscle when the tibial nerve was stimulated. We conclude that the appearance of A-waves should be considered a sign of either a local nerve lesion or a generalised neuropathy in all other nerves except for the tibial nerve.
Electromyography↗
Relationships between delayed ischemic dysfunctions and intracranial hemodynamics following subarachnoid hemorrhage.
Delayed ischemic dysfunctions (DID) are one of the main complications following subarachnoid hemorrhage. It was the aim of our study to analyse the possible prognostic value of different transcranial Doppler ultrasonography parameters and to elucidate the risk of developing DID with particular reference to the intracranial pressure. The relative change of mean blood flow velocity and of corresponding cerebral circulatory resistance index as well as the intracranial pressure were determined in 44 patients with spontaneous subarachnoid hemorrhage. No relationship was found between the occurrence and extent of DID and the relative change of mean flow velocity during the clinical course. In contrast, there was a significant correlation between the relative change of the cerebral circulatory resistance index and the occurrence of DID. While patients without or with reversible DID showed a decreased resistance index compared to the initial value (without DID: -17% +/- 15%; reversible DID: -3% +/- 14%), patients with irreversible DID had a significant increase of the resistance index (+14% +/- 9%). Accordingly, patients with irreversible DID showed a significant increase of intracranial pressure compared to the patients with reversible DID. We conclude that the evaluation of relative changes of the cerebral circulatory resistance index by bedside monitoring is a useful tool to predict the occurrence of subarachnoid hemorrhage-associated DID and has therapeutic impact.
Adolescent↗
[The relationship between nursing and medicine].
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Hierarchy, Social↗
Influence of recording site within the muscle on motor unit potentials.
The influence of the recording site on the motor unit potentials (MUPs) was investigated in the brachial biceps muscle of 8 healthy subjects. The MUPs were recorded with a concentric needle electrode and analyzed with a new decomposition EMG program we call multi-MUP analysis. MUPs had shorter durations and smaller amplitudes at superficial recording sites than at deeper sites in the muscle. This is mainly due to the cannula of the concentric electrode, which records a higher potential at superficial recording sites and partially cancels the recorded potentials from the tip in a differential recording. The MUPs had longer durations and higher amplitudes distally than in the middle of the muscle. The longer durations and spike durations are probably due to increased temporal dispersion at a greater distance from the endplate zone. We do not have an adequate explanation for the larger amplitudes distally in the biceps, they may be due to anatomical factors. To increase the diagnostic sensitivity of quantitative MUP analysis the recordings should be obtained from standardized recording sites.
Adult↗
Comparison of various coils used for magnetic stimulation of peripheral motor nerves: physiological considerations and consequences for diagnostic use.
We compared the ability of 4 magnetic coils to activate peripheral nerves in healthy subjects. No differences in motor threshold intensities were found between the coils, but the intensities needed to elicit maximum compound muscle action potential (CMAP) amplitudes were different. For superficial nerves maximum CMAPs in comparison with electrical stimulation were usually but not always found. CMAPs were at their maximum only when the direction of induced current flowed from proximal to distal and when a certain part of the coil was over the nerve. Distal nerve stimulation was time consuming. Due to artifacts many stimuli were necessary and sometimes no maximum CMAP could be elicited. CMAPs were much less sensitive to position changes of the coil than to changes in an electrical stimulator. Small circular coils were superior to larger coils in terms of the lower intensities necessary to elicit maximum CMAPs, better focusing of the stimulus, and less artifacts. For deep nerves amplitudes were always submaximal. Coactivation of nearby nerves and underlying muscles was another main drawback especially at proximal sites and for coils of large diameter. Despite better focusing, double coils are less useful due to their great diameter. Magnetic stimulation cannot replace electrical neurography at the moment, even if different coils are used at different sites of stimulation.
Action Potentials↗
Outliers, a way to detect abnormality in quantitative EMG.
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.
Electromyography↗
Reference values of motor unit action potentials obtained with multi-MUAP analysis.
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.
Action Potentials↗
Magnetically induced muscle contraction is caused by motor nerve stimulation and not by direct muscle activation.
When magnetically stimulating peripheral nerves, a local cocontraction of muscle under the coil is observed. We assessed whether this contraction results from: (1) magnetic stimulation of motor nerves, or (2) direct depolarization of the muscle membrane. Wrist extensor muscles of normal subjects were magnetically stimulated with the coil placed directly above the muscle. Neuromuscular transmission was then blocked by atracurium using a technique of local curarization. As a reference, the radial nerve was stimulated electrically. Magnetic and electrical stimuli were applied alternatingly every 10 s. Twitch force of wrist extension was measured isometrically over a period of about 70 min including the phase of complete neuromuscular block. Twitch amplitudes elicited by magnetic and electrical stimuli were equivalent during the whole experiment. These results suggest that muscle cocontraction following magnetic stimulation results from depolarization of terminal motor nerve branches.
Action Potentials↗
Blink reflex investigation using magnetic stimulation.
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Adult↗
Repetitive magnetic nerve stimulation: technical considerations and clinical use in the assessment of neuromuscular transmission.
We assessed to what extent repetitive magnetic stimulation can replace the electrical method. Fifteen healthy subjects and 3 patients with myasthenia gravis were investigated using stimulation of the median, ulnar, axillary and accessory nerves. Single, as well as 3/sec repetitive magnetic and electrical stimuli were applied. When comparing the results of magnetic vs. electrical stimulation, amplitudes, areas and shapes of compound muscle action potentials were not significantly different. Although single magnetic stimuli were much less uncomfortable than the electrical stimuli, differences in comfort were much smaller in the repetitive protocol, because muscular contractions under the magnetic stimulation coil caused unpleasant movements of, for example, the neck. Additional problems arose from technical limitations of the prototype magnetic stimulator used: stimulation intensity was significantly limited, resulting in an inability to elicit supramaximal responses in 11 of the 154 investigations. Overheating of the stimulator coil forced us to give the coil extra time to cool down. These problems might be solved in the future by more focused stimulus geometry and introduction of cooling devices. It is concluded that magnetic stimulation can elicit responses which are equivalent to the electrical method in repetitive nerve stimulation. At present due to some shortcomings it cannot replace electrical stimulation in routine repetitive nerve stimulation.
Adult↗
The value of magnetic stimulation in the diagnosis of radiculopathies.
We studied 42 patients with cervical and lumbar radiculopathies using magnetic stimulation. Prolonged latencies following magnetic stimulation of the brain, the paravertebral spinal nerve, or both, showed a highly significant correlation with muscle weakness in clinical testing (24 of 26 patients with weakness had pathological motor evoked potentials) as well as with spontaneous activity of the target muscles in needle electromyography (24 of 25 subjects). The determination of both the central and the peripheral motor conduction time was found to be essential in patients with radiculopathies, because different patterns of latency changes correlated with different morphological results in computed tomography: in patients diagnosed as having a lateral compression of the nerve root the peripheral nerve latency was delayed; whereas, in patients with more medially localized herniations, a prolonged central motor latency was the most frequent finding. This study posits that combined magnetic stimulation of the brain and nerve root is an effective and painless technique for the noninvasive evaluation of nerve root function.
Adult↗
PC-based system for an objective quantification of manual movement disability for clinical and scientific purposes.
In clinical management and research of movement disorders exact knowledge about the extent of motor impairment is essential. This paper presents a computer program which allows for an objective measurement of manual movement disability. The program was developed for standard hardware and can easily be used in a variety of clinical and research environments. The program runs on MS-DOS computers and uses a Microsoft computer mouse as the only input device. The temporal resolution is 100 Hz, the spatial resolution 400 dots per inch. The user may choose between standard test sets or he may design sets according to his individual needs from a pool of available protocols which includes tracking tasks, ballistic tasks, complex sequential tasks, and finger tapping. All tasks are implemented in a similar way in order to keep the test environment as consistent as possible for the patient. The patient must usually carry out movements which correspond to the movements of a target symbol on the computer screen. This entails the manipulation of a follower symbol, also visible on the computer screen, via the computer mouse. The program itself and the theoretical background of the protocols are described in the paper. Additionally, preliminary results from pilot experiments are presented.
Computer Simulation↗