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Biomedical subjects

B Falck

Publications and source records attributed to B Falck.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1995

Motor nerve conduction studies: measurement principles and interpretation of findings.

Motor nerve conduction studies are reviewed. The principles of electrode placement, stimulus intensity, algorithms for measurement of parameters, causes of variability, reference values, and reporting are discussed. A rigorous standardization of methods has several advantages. The sensitivity of each method is increased without loss of specificity. In addition, reference values obtained in one laboratory can be used in other laboratories as well. Pathophysiological interpretation of findings in different types of neuropathies is also presented.

Adolescent↗
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↗
PubMed1994

Immunocytochemical detection of the carbohydrate antigen, Sialyl Lewis(x), in normal human skin and during irritant contact dermatitis.

Sialys Lewis(x) (SLex) is a ligand for the E-selectin and the interaction of E-selectin on the endothelium and SLex on T cells may be important for T-cell migration into the skin. We investigated the expression of SLex on Langerhans cells (LC) in normal skin and on LC repopulating epidermis deprived of LC due to a preceding irritant contact dermatitis. SLex was visualized by fluorescence and light microscopic immunocytochemistry using the monoclonal antibody, CSLEX-1. The results showed that about 40% of LC in normal epidermis express SLex. In the repopulation phase, most of the epidermal cells were CD1a+/SLex. We suggest that SLex is present on epidermal LC that have recently immigrated from the dermis.

Cell Movement↗
PubMed1994

DNA analysis in Finnish patients with hereditary neuropathy with liability to pressure palsies (HNPP).

Hereditary neuropathy with liability to pressure palsies (HNPP) is a dominantly inherited disorder that presents as recurrent mononeuropathies precipitated by apparently trivial traumas. The presence of a deletion in 17p11.2 was analysed in 13 Finnish families with HNPP. The deletion was found in all patients who were neurologically and neurophysiologically confirmed to have HNPP. In the problematic cases the detection of the gene defect is the method of choice in the diagnosis of HNPP. Analysis of DNA can also be used to detect clinically unaffected family members.

Chromosome Deletion↗
PubMed1993

Tibial muscular dystrophy. Late adult-onset distal myopathy in 66 Finnish patients.

OBJECTIVE: To clarify the classification of two previously reported groups of patients with anterior tibial distal dystrophy, to find additional patients with the disease, and to describe the clinical features of this disease. DESIGN: National survey of the records of patients with neuromuscular diseases in Finland. Findings of selected patients were compared with those of previously reported cases. PATIENTS: Thirty-six previously described patients and 30 additional patients from the current survey, with 41 symptomatic patients and 25 subjectively asymptomatic affected relatives. RESULTS: There were 66 patients with late adult-onset tibial muscular dystrophy. Symptoms appear after the age of 35 years with reduced ankle dorsiflexion, and progress is slow without marked disability. Facial muscles, upper extremities, and proximal muscles are usually spared. Muscle biopsy results reveal nonspecific dystrophic changes in clinically affected muscles, and frequently severe adipose replacement in the anterior tibial muscles occurs. Asymptomatic muscles have mild myopathic changes only. Vacuolar degeneration is detected in a minority of patients. Electromyography shows profound myopathic changes in the anterior tibial muscle, but extensor brevis muscles are well preserved. Computed tomography or magnetic resonance imaging of muscles discloses marked involvement of tibial extensor muscles and focal patches of fatty degeneration in various asymptomatic muscles. Pedigree data suggest autosomal dominant inheritance. CONCLUSIONS: Tibial muscular dystrophy might represent a new form of distal myopathy and it is rather common, at least in Finland.

Adolescent↗
PubMed1993

The lumbar multifidus muscle five years after surgery for a lumbar intervertebral disc herniation.

Biopsy specimens of the lumbar multifidus were obtained from 18 patients with lumbar disc herniation at operation and after a postoperative follow-up period of 5 years. The structure and morphometry of the muscle fibers were analyzed and these data were compared with intraoperative biopsy results and the clinical outcome of the operation. The main findings were: 1) on the basis of occupational handicap score 10 patients belonged in the "positive" and 8 in the "negative" outcome group; 2) the intraoperatively recorded selective type 2 muscle fiber atrophy and the extent of pathologic inner structure changes both decreased in the "positive" outcome group, whereas they persisted in the "negative" group; 3) grouping as a definite sign of reinnervation was seen in only two versus four patients of the "positive" versus "negative" outcome group; 4) the relative amount of adipose tissue within the muscle decreased more markedly in the "positive" outcome group. The authors propose that both inactivity and axonal injury (mainly of neurapraxia type) contribute to the selective type 2 atrophy and inner structure changes in disc patients' multifidus muscle. These pathologic structural changes correlated well with the clinical outcome, and most importantly they are reversible and can be diminished by adequate therapy.

Adult↗
PubMed1993

alpha-Amino-n-butyric acid methyl ester induces concentrative uptake of L-dopa in human Langerhans' cells normally not operative for L-dopa transport.

We recently reported the existence of two kinds of human epidermal Langerhans' cells (LC), one which can take up and accumulate L-dopa and one which cannot. The dopa(+) LC take up L-dopa by carrier-mediated exchange diffusion, that is, the influx of L-dopa and the outflow of an intracellular substance are linked via the same carrier. The nature of the fundamental difference between L-dopa(+) and L-dopa(-) cells has not been clarified. We have now found that alpha-amino-n-butyric acid methyl ester (ABA-OME) penetrates into intracellular compartments, perhaps endosomes or lysosomes, of all LC, where hydrolysis results in the accumulation of the free amino acid (ABA). This accumulation causes a considerable increase in osmotic pressure of the membrane-limited organelle, leading to influx of water and swelling. Co-incubation with L-dopa revealed an influx of L-dopa into LC which normally cannot take up this amino acid. It is suggested that these LC lack the capacity to synthesize and/or store the counterpart which allows L-dopa to enter the dopa(+) LC, but that ABA in the L-dopa(-) LC can function as an equivalent counterpart.

Adult↗
PubMed1992

Muscle pathology in idiopathic cricopharyngeal dysphagia. Enzyme histochemical and electron microscopic findings.

The structural changes in the cricopharyngeal muscle (CM) were examined ultrastructurally and by enzyme histochemistry in five patients suffering from idiopathic cricopharyngeal dysphagia (ICD). Diagnosis was established by fiberoptic esophagoscopy, esophageal manometry and cineradiography. Cricopharyngeal myotomy was performed with marked improvement in all patients. Intraoperatively, a biopsy was taken from the CM. Additionally, all patients underwent neurological examination for possible generalized muscle disease, and a biopsy was taken from a limb muscle. CM from nine cadavers without known history of dysphagia served as control. The control samples disclosed structural changes which were considered to be pathological in other skeletal muscles, and required that the criteria for CM pathology we modified accordingly. In three patients changes in CM histology suggested specific pathogenesis: one patient had evidence for a generalized myositis but was only symptomatic for dysphagia. Another patient had muscle fiber atrophy and slight inflammation in her CM, possibly due to alcohol abuse. The third patient had loss of CM fibers with replacement by connective tissue enough to cause functional disturbances. In two patients no cause for dysphagia was found in either immunohistochemistry or electron microscopic studies. These results demonstrate the special structural features of the CM and indicate that ICD can have multiple etiologies.

Adenosine Triphosphatases↗
PubMed1992

Diagnostic function of the microhuman prototype of the expert system--MUNIN.

This paper describes the diagnostic function of a prototype expert system for electromyography (EMG). The prototype was restricted to a limited "Microhuman" anatomy with only 6 muscles and 8 nerves, and a corresponding limitation on the number of local nerve lesions. It attempted to give a detailed description of the most important groups of generalized nerve and muscle disorders, and the commonly used parameters from needle EMG and nerve conduction studies were included. The system can be used both for "diagnostic" and for "causal" reasoning. In diagnostic reasoning, the system's probabilistic inference engine is used to reason from test results through 14 different aspects of neuromuscular pathophysiology to disorders. In causal reasoning, the system reasons in the opposite direction from disorders through pathophysiology to expected test results. The diagnostic function of the system was illustrated by 3 cases: a normal subject, a patient with a bilateral carpal tunnel syndrome and a patient with both a diabetic polyneuropathy and a bilateral carpal tunnel syndrome.

Carpal Tunnel Syndrome↗