Biomedical subjects

B Falck

Publications and source records attributed to B Falck.

At least 19 recordsLinked to original sources

PubMed1997

F-wave latency, the most sensitive nerve conduction parameter in patients with diabetes mellitus.

In this study we examined the diagnostic sensitivity of minimal F-wave latency, F-wave persistence, motor nerve conduction velocity (MCV), and amplitude of the compound motor action potential (CMAP) of the median, ulnar, tibial, and peroneal nerves, and of sensory conduction velocity (SCV) and sensory nerve action potential (SNAP) amplitude of the sural nerve in 82 diabetic patients. For the median, ulnar, and tibial nerves the Z scores of the minimal F-wave latency were significantly larger than those of the MCV, and for all four motor nerves the Z scores of the minimal F-wave latency were significantly larger than those of the amplitude of the CMAP. The Z scores of the peroneal minimal F-wave latency exceeded those of peroneal MCV, sural SCV, and sural SNAP. F-wave persistence did not differ significantly from the reference values. In conclusion, minimal F-wave latency is the most sensitive measure for detection of nerve pathology and should be considered in electrophysiological studies of diabetic patients.

Action Potentials↗

PubMed1997

Postpolio muscular dysfunction: relationships between muscle energy metabolism, subjective symptoms, magnetic resonance imaging, electromyography, and muscle strength.

Eleven patients with previous polio were studied. The concentration of energy-related metabolites and energy charge was measured from the vastus lateralis muscle, as was isometric muscle strength of knee extension. Cross-sectional area of the quadriceps femoris muscle was calculated from magnetic resonance imaging. Reinnervation was studied using macroelectromyography. Muscle weakness, pain, and newly acquired muscle weakness in the legs was estimated by the patients. The findings in the legs in which the patients experienced new loss of muscle function were compared with the stable legs. There were no significant differences between these groups in any of the objectively measured variables. Only hip pain correlated with new loss of muscle function. Creatine phosphate was decreased in 5 patients. The symptoms and subjective muscle strength did not correlate with any of the objective measurements. There were no significant relationships between energy-related metabolites and postpolio symptoms.

Adult↗

PubMed1997

The role of electromyography in neurology.

A review is given of the role of electromyography (EMG) for diagnosis, pathophysiological description and monitoring of patients with disorders of the peripheral nervous system. Various EMG methods are presented and their principal differences are discussed. The usefulness of these methods varies depending on the pathology to be studied. With modern quantitative methods for analysis, EMG has become more sensitive and accurate and is therefore an important part in the evaluation of the neurologic patient. EMG results are usually combined with findings from other neurophysiological investigations (neurography, evoked potentials), histochemistry, biochemistry and most importantly with the clinical signs to give as complete a picture of the condition as possible. The usefulness of EMG depends on a number of factors other than the quality of the investigation as such. These aspects are discussed briefly.

Electromyography↗

PubMed1997

Motor unit size estimation: confrontation of surface EMG with macro EMG.

Surface EMG (SEMG) is little used for diagnostic purposes in clinical neurophysiology, mainly because it provides little direct information on individual motor units (MUs). One of the techniques to estimate the MU size is intra-muscular Macro EMG. The present study compares SEMG with Macro EMG. Fifty-eight channel SEMG was recorded simultaneously with Macro EMG. Individual MUPs were obtained by single fiber triggered averaging. All recordings were made from the biceps brachii of healthy subjects during voluntary contraction at low force. High positive correlations were found between all Macro and Surface motor unit potential (MUP) parameters: area, peak-to-peak amplitude, negative peak amplitude and positive peak amplitude. The MUPs recorded with SEMG were dependent on the distance between the MU and the skin surface. Normalizing the SEMG parameters for MU location did not improve the correlation coefficient between the parameters of both techniques. The two measurement techniques had almost the same relative range in MUP parameters in any individual subject compared to the others, especially after normalizing the surface MUP parameters for MU location. MUPs recorded with this type of SEMG provide useful information about the MU size.

Adult↗

PubMed1997

Proximal myotonic dystrophy--a family with autosomal dominant muscular dystrophy, cataracts, hearing loss and hypogonadism: heterogeneity of proximal myotonic syndromes?

We describe a family with an autosomal dominant, multisystem disorder, consisting of late-onset proximal muscular dystrophy, electrophysiological myotonia, cataracts, late-onset deafness and male hypogonadism. Four patients were available for clinical examinations. Examination of asymptomatic family members revealed another patient with bilateral cataracts but without definite muscle disorder. Five deceased members of the family had proximal muscle weakness, reportedly or confirmed in medical records. Molecular examination of genomic DNA showed no expansion of the unstable (CTG)n trinucleotide repeat on chromosome 19q13.3 associated with myotonic dystrophy (DM). Linkage to two loci implicated in other myotonic disorders, the muscle chloride channel (CLCN1) gene, and the muscle sodium channel (SCN4A) gene, was assessed and excluded. The clinical findings differ from those described in proximal myotonic myopathy (PROMM), in terms of the more severe muscle involvement with atrophy of affected muscles and the hearing loss. These findings suggest phenotypic and probably genetic heterogeneity among the proximal myotonic syndromes.

Adult↗

PubMed1996

Evaluation of the diagnostic performance of the expert EMG assistant MUNIN.

The diagnostic performance of the medical expert system MUNIN for diagnosis of neuromuscular disorders was evaluated on a set of 30 test cases. The cases were provided by 7 experienced electromyographers who were subsequently invited to participate in the evaluation. To reasonably cover the range of disorders, the electromyographers were asked to provide cases from patients with different types of muscular dystrophy, with neuromuscular transmission disorders, with motor neurone disease, and with different types of polyneuropathies. In addition, patients with a range of local neuropathies were provided. Out of the 30 cases, 11 cases were evaluated by an "almost peer review" method and the remaining 19 cases were evaluated by a "silver standard" method. The number of cases evaluated by "almost peer review" was limited to 11 due to time constraints on the evaluation procedure. During the "almost peer review," each electromyographer was asked to diagnose patients, using a vocabulary that closely resembled MUNIN's vocabulary. Subsequently, we attempted to provide a consensus diagnosis for the patients based on discussion among the participating electromyographers. The electromyographers were also asked to assess how well MUNIN had performed in each case. The remaining 19 cases were evaluated by a "silver standard" procedure, where MUNIN's diagnosis was compared to the diagnosis of the expert who provided the case. The results indicated that MUNIN performed well, and the electromyographers considered "that MUNIN performed at the same level as an experienced neurophysiologist." In particular, it was noted that MUNIN handled cases with conflicting findings well, and that it was able to diagnose patients with multiple diseases.

Diagnostic Services↗

PubMed1996

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↗

PubMed1996

Quantitative motor unit potential analysis.

A review of quantitative methods for electromyography is given. Background information about motor unit anatomy, physiology, and pathology is provided to explain some of the presented electrophysiological phenomena. Different aspects of quantitation, such as motor unit action potential parameters, automatic analysis methods, reference values, and findings in abnormal conditions, are discussed.

Axons↗

PubMed1996

Multi-MUP EMG analysis in clinical routine.

A new quantitative motor unit potential (MUP) analysis method, called Multi-MUP analysis, is described. Multi-MUP analysis is a type of decomposition analysis of the EMG signal. At each recording site six different MUPs may be recorded during an epoch of 4.8 sec. A study of 20-30 MUPs including editing takes 3-7 minutes. Compared to many other MUP analysis methods it is faster and more user friendly, therefore it can be used in daily routine EMG analysis. The differences to methods based on manual analysis, spike-triggered averaging, template matching and decomposition are discussed. The main advantages of Multi-MUP analysis are: (1) quick acquisition of many MUPs; (2) simultaneous collection of several MUPs at one recording site; (3) possibility to analyze not only low threshold MUPs; (4) less bias in the selection of MUPs and (5) the reproducibility of the results that allow the same reference values to be used in different laboratories. So far we have successfully used this method in clinical routine for four years on more than five thousand patients.

Electromyography↗

PubMed1995

Can the size principle be detected in conventional EMG recordings?

According to Henneman's size principle, small motor units are recruited before large ones. It is commonly believed that this can be detected in routine conventional EMG recordings even among the earliest recruited motor units. That is, the MUP amplitude, area, and thickness should increase with recruitment order. We studied the first four motor unit potentials (MUPs) recruited within the pickup area of the electrodes. Data were obtained from 179 different sites in monopolar recordings and in 153 concentric recordings from 5 health subjects. In the pooled material, amplitude, area, and thickness increased slightly between consecutively recruited MUPs. However, at individual recording sites the size of consecutively recruited MUPs varied considerably. At some recording sites the first recruited MUP had the largest amplitude and the later MUPs has successively smaller amplitudes. We conclude that, at individual recording sites, the size principle cannot be detected in low threshold motor units with monopolar or concentric EMG electrodes. The reason for this is the small uptake area of these electrodes in relation to the motor unit territory.

Action Potentials↗

PubMed1995

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↗

PubMed1995

Multi-MUP EMG analysis--a two year experience in daily clinical work.

A new quantitative motor unit potential (MUP) analysis method, called multi-MUP analysis, is described. Multi-MUP analysis is a type of decomposition analysis of the EMG signal. At each site 6 different MUPs may be recorded during an epoch of 4.8 sec. Calculation time is about 3 sec. A study of 20-30 MUPs including editing takes 4-8 min. Compared to many earlier MUP analysis methods it is faster and more user friendly, therefore it can be used in daily routine EMG analysis. The accuracy and reliability of the method are good. The differences from methods based on manual analysis, spike triggered averaging, template matching and decomposition are discussed. The main advantages of multi-MUP analysis are: (1) quick acquisition of many MUPs; (2) simultaneous collection of several MUPs at one recording site; (3) possibility to analyze not only low threshold MUPs; (4) less bias in the selection of MUPs; and (5) the reproducibility of the results that allow the same reference values to be used in different laboratories. So far we have successfully used this method for 2 years on more than 2000 patients.

Electromyography↗

PubMed1994

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↗

PubMed1994

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↗

PubMed1994

Distributional changes of Langerhans cells in human skin during irritant contact dermatitis.

We used light and electron microscopic immunocytochemistry to study distributional changes in the human Langerhans cell (LC) system during the first 14 days of a mild irritancy caused by sodium lauryl sulphate (SLS). A marked initial decrease in epidermal LC was noted possibly resulting from migration from the epidermis to the dermis and from irreversible cell damage. Several studies have previously found an unchanged number of LC in SLS-induced contact irritant dermatitis, but these studies may not have taken into account the fact that SLS is effectively absorbed from the test chamber. Unless certain precautions are taken the SLS concentration rapidly falls to topical levels that have no effect on the LC system. Simultaneously with the decrease in the epidermis we observed an increase in dermal CD1a+ cells, confirming an often reported finding. There is, however, no consensus as to the identity of these cells, and several authors have reported that such cells lack LC granules and thus these cells have often been classed as indeterminate cells. We found that, during irritant contact dermatitis, provided an adequate number of sections were scrutinized in the electron microscope, all dermal CD1+ cells contained Birbeck granules.

Adult↗

PubMed1994

New approaches to motor unit potential analysis.

The current state of motor unit potential (MUP) analysis is reviewed. New quantitative analysis methods are described and compared with traditional manual measurements. The emphasis in this review is on a new method, multi-MUP analysis and the detection of individual outliers. Multi-MUP analysis is based on decomposition EMG. The main advantage of these new methods is that they save time and allow immediate comparison between obtained results and reference values. The results are repeatable and independent of the investigator.

Animals↗

PubMed1994

Evaluation of Epilepsy Expert--a decision support system.

Epilepsy Expert is a decision support system based on the International Classification of Epilepsies and Epileptic Syndromes (1989). The aim of this study was to evaluate the Epilepsy Expert. First the diagnostic performance was validated. This was done in 3 stages: collection of the patient cases, determination of the 'correct diagnoses' and testing the system. How the users perceived the functionality of the system was studied by using an inquiry. Three physicians, experts of epilepsy, from different hospitals were asked to choose 10 patients. In the patient description was a short history, a detailed description of the seizure, EEG findings and their own diagnosis. Next, each expert made a diagnosis of the cases supplied by other experts by using the International Classification of Epilepsies and Epileptic Syndromes. The 'correct diagnosis' (so-called majority agreement) was the diagnosis given by the majority of the experts. The diagnosis of each expert was compared with the 'correct diagnosis'. The diagnoses obtained by the Epilepsy Expert were then compared with the 'correct diagnoses'. In the evaluation the expert physicians agreed on 37% of cases and all 3 disagreed on 17%. A majority agreed on 25 cases, which were used in the evaluation. In these 25 cases the experts' (A,B,C) diagnoses were correct or partly correct in 100, 64, 80% of cases, respectively. The program's diagnoses were correct or partly correct in 80% (module I) and 76% (modules IV and V) of cases. In the evaluation Epilepsy Expert was found to be only partly successful. The main reason for this was the weakness of the international classification. However, the program seems to be very close to the level of the experts. According to this limited inquiry Epilepsy Expert is not suitable for clinical use, because it is, for example, too simple and does not contain enough information.

Adult↗

PubMed1994

Ultrasound, computed tomography and magnetic resonance imaging in myopathies: correlations with electromyography and histopathology.

Imaging of examinations by ultrasound (US), computerized tomography (CT) and low field magnetic resonance imaging (MRI) were compared with EMG and muscle biopsy findings in the same muscles of 33 patients with different neuromuscular diseases. None of the imaging methods revealed specific diagnostic details, but gave valuable information on the extent and distribution of muscle involvement. In myopathies all imaging modalities corresponded well with the EMG and histopathology findings, but in the neuropathies with minimal tissue destruction EMG was, understandably, more sensitive. The imaging characteristics of MR were as good as those of CT, but MRI has the advantage of not requiring ionizing radiation. US is the most economical method and it was found to be, despite its lower resolution, very informative in the hands of an experienced examiner, especially for the detection of fibrosis. The good agreement of histopathology with pathologic imaging and EMG findings implies that the accuracy of muscle biopsy increases, if its site is selected on the basis of imaging and/or EMG examination.

Adipocytes↗