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Biomedical subjects

E Zalewska

Publications and source records attributed to E Zalewska.

At least 19 recordsLinked to original sources
PubMed2005

Atypical motor unit potentials in Emery-Dreifuss muscular dystrophy (EDMD).

OBJECTIVE: The aim of the study was to analyse electromyographic changes in Emery-Dreifuss muscular dystrophy (EDMD) that are atypical for myopathy. Our special interest was focused on high amplitude polyphasic motor unit potentials (MUPs), also termed irregular MUPs. METHODS: We studied 21 EDMD patients with the diagnosis based on clinical data, DNA analysis and immunohistochemical muscle studies. Rectus femoris muscle biopsies were investigated in all affected patients. Electrophysiological investigations involved quantitative concentric needle electromyography (CNEMG) of biceps brachii (BB) and rectus femoris (RF) muscles. Simulation studies were performed to approximate the number, diameter and distribution of muscle fibers, which contribute to irregular MUPs. RESULTS: The EMG data in EDMD were compatible with myopathy. Irregular MUPs showed longer duration, larger area, size index and higher amplitude then simple ones (P < 0.05). The approximation of features of muscle fibers contributing to irregular MUP also indicated smaller (<45 microm) and larger (>55 microm) diameters than normal (50 +/- 5 microm). Muscle biopsy specimens revealed the variable muscle fiber size due to atrophy, hypertrophy, and muscle fiber splitting. CONCLUSIONS: Irregular MUPs recorded in EDMD are due to hypertrophied and atrophied fibers as well as increased fiber density. They reflect reorganization of the motor unit in a slow progression myopathic process (muscle fiber hypertrophy and splitting). SIGNIFICANCE: Irregular MUPs in EDMD most probably reflect increased variability of the muscle fiber size.

Adolescent↗
PubMed2004

Modeling studies on irregular motor unit potentials.

OBJECTIVE: The aim of these modeling studies on the generation of motor unit potentials (MUPs) was to establish the influence of MU parameters and recording conditions on the shape irregularity of MUPs. The focus was on the dependence of the irregularity of MUPs on fiber density, fiber diameters and the recording distance from the end-plate zone. METHODS: The study was performed using the 'EMG Simulator' software for modeling of MUP and our own software for calculations. RESULTS: The results indicate that the irregularity of a MUP increases with increased recording distance from the end-plate zone and decreases with increased fiber diameter and/or with increased fiber density. The quantitative relationship between these factors has been derived. CONCLUSIONS: The relationships determine the structural conditions in which irregular potential may be generated and therefore may be helpful in the interpretation of atypical MUPs.

Action Potentials↗
PubMed2000

Effectiveness of motor unit potentials classification using various parameters and indexes.

OBJECTIVES: The aim of this study was to compare the effectiveness of quantities such as amplitude, duration, area, size index, number of peaks and irregularity coefficient applied to the classification of motor unit action potentials (MUAPs) in neuromuscular disorders. METHODS: We have analyzed 215 potentials recorded from 20 neurogenic patients and 240 potentials recorded from 14 myogenic patients. The statistical values for each parameter and correlation coefficients between parameters have been analyzed. RESULTS: The percentages of potentials unclassified by amplitude, duration, area/amplitude, area and size index were 31, 34, 28, 15 and 15%, respectively. Neither the number of phases and turns nor the irregularity coefficient may be used for the differentiation between neuro- and myogenic groups. There was also a set of MUAPs that were not properly classified by any of the above parameters. Among the unclassified potentials there were more potentials from myogenic cases. These unclassified myogenic MUAPs were predominantly irregular, whereas most of the unclassified neurogenic MUAPs were simple. In neurogenic cases, parameters describing the size of the potential (amplitude, duration, area) were not significantly correlated with those describing the shape (number of phases and turns), whereas in myogenic cases some correlation between these parameters was significant. CONCLUSIONS: MUAP quantities, due to the different correlation between them in myogenic and neurogenic disorders, have different sensitivities. Indexes were more sensitive than simple parameters and were also much more effective in the evaluation of atypical potentials.

Action Potentials↗
PubMed1998

Shape irregularity of motor unit potentials in some neuromuscular disorders.

The aim of this study was to test whether analysis of the irregularity of the motor unit potential waveform may supplement conventional evaluation. We have found that the irregularity is not a characteristic feature of potentials either in neurogenic disorders or in myopathy. We have found, however, that within myo- and neuropathic disorders, the irregularities differ between slow (such as Becker muscle dystrophy and chronic spinal muscle atrophy) and fast progressing processes (such as amyotrophic lateral sclerosis and Duchenne muscle dystrophy). These differences depend on the different number of phases and turns contributing to wave formation. In slowly progressing processes, very irregular potentials are more often polyphasic, whereas in acute processes they may be polyturn or polyphasic. The results suggest that it is the irregularity of the potential that provides new information, not available so far, on the activity of the pathological process.

Action Potentials↗
PubMed1995

Evaluation of MUAP shape irregularity--a new concept of quantification.

A coefficient for quantifying the shape irregularities of the motor unit action potential (MUAP) is introduced. This coefficient is defined as the "length" of action potential curve normalized by the signal's amplitude in such a way that it is independent on duration and amplitude. It characterizes only the MUAP shape. The irregularity coefficient may be used to measure the deviations of the potential from the normal MUAP. The properties of this coefficient and its relation to the conventional parameters describing MUAP shape, viz the number of phases and turns is discussed. The examples of classification of real signals according to this coefficient are presented.

Action Potentials↗
PubMed1993

Features of motor control in patients with proximal childhood spinal muscle atrophy (pilot study).

The differences in the motor performance during different tasks between 19 subjects suffering from SMA and 10 healthy controls were observed. The simultaneous EMG activity of twelve lower limbs and lower trunk muscles was recorded with surface electrodes. EMG data were automatically reduced and compared with data evaluated from performed by physiotherapist manual testing of muscle strength. Results showed characteristic differences between healthy and spinal muscular atrophy (SMA) subjects: 1. SMA patients display generally more activity occurring in numerous muscle groups and more spinal levels are activated. 2. SMA patients reveal a disturbed functional relation between the posterior and anterior compartments of muscles. 3. EMG activity in SMA patients is spreading out also to the contralateral muscle groups even during slight, unilateral singlejoint movements. Oligosegmental, plurisegmental and brain sources are probably responsible for mentioned phenomena. The reciprocal influences between reduced number of motoneurons (in SMA) and function of central movement generators results in different mode of movement execution in SMA patients.

Adolescent↗
PubMed1991

Quantitative evaluation of the motor unit potential complexity.

A method for MUAP complexity evaluation is proposed. A complexity coefficient intended for measuring potential complexity is defined, it is a product of filling factor and coefficients measuring the variability of signal parameters. This coefficient has been used to estimate quantitatively the degree of complexity and hence to order a set of potentials. The potential ordering agrees with intuitive expectation. So, it seems that this method may be appropriate for complexity evaluation, and could be applied in the study of remodeling process in neuro- and myopathic diseases.

Action Potentials↗