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BACKGROUND: The study was aimed to evaluate the EMG pattern in myopathy, in the muscles with early, slight abnormalities and in the muscles severely affected, and to analyze the sequence of abnormalities appearing with the progress of the impairment. MATERIAL AND METHOD: Fifty one boys with Duchenne muscular dystrophy were studied. Ninety nine proximal muscles (biceps brachii and rectus femoris) were examined. According to clinical criteria (defective force, atrophy) the muscles were assigned to the group of slight changes (group AB: 50 muscles) and to the group of severe abnormalities (group CD: 49 muscles). An own method of Functional-QEMG was applied in the CNEMG examination. RESULTS AND CONCLUSIONS: The sensitivity of the method applied allowed the detection of myogenic changes even at the subclinical, oligosymptomatic (group AB) stage of impairment. The earliest EMG abnormality detected was an increased percentage of the polyphasic potentials, even if other MUAPs parameters remained normal. However at this stage already a decrease appeared of amplitude, area and MUAPs duration, along with the decrease of IP amplitude and amplitude size. An increase of IP density and a slight increase of number of stable-shaped potentials (simple, but more often polyphasic) was also seen which we believed to reflect the compensatory process. At the further stage, when compensating mechanisms were no longer possible, a dramatic decrease appeared of the IP amplitude, amplitude size and density and, sometimes, also a decrease in the number of stable-shaped potentials. The structural changes such as decrease of amplitude, area and MUAPs duration also progressed. These findings reflect in our study the sequence of EMG abnormalities in the successive stages of myogenic lesion.

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BACKGROUND: The aim of this study was to compare the electromyographic pattern in Becker muscular dystrophy (BMD) with that found in Duchenne muscular dystrophy (DMD). MATERIAL AND METHOD: Fourteen men with BMD and 51 boys with DMD were investigated. Proximal muscles were examined: m. biceps brachii (BB) and m. rectus femoris (RF). They were divided according to the clinical criteria in two groups: of those with slight changes (group AB) and of those with severe abnormalities (CD). As in the Part I of the paper our own method of Functional-QEMG was applied in the CNEMG examination. RESULTS AND CONCLUSIONS: Spontaneous activity (fibrillations, complex repetitive discharges) was equally frequent in BMD and DMD. Linked potentials were rather frequent in either group. Myopathic features such as MUAPs low amplitude and area, polyphasic shape were seen in either condition, but more marked in DMD than in BMD. Evaluation of IP recordings revealed that IP amplitude (amplitude size) is low in DMD already at the early stage of lesion but normal or only slightly diminished in BMD. It might perhaps suggest different degrees of lesion in type II MUs between the compared types of muscular dystrophy.

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BACKGROUND AND PURPOSE: MuSK-positive myasthenia gravis (MG) is diagnosed in 0-48% of cases with generalized seronegative MG in different populations. The presence of anti-MuSK antibodies generally relates to a severe course and lack of response to thymectomy. We analyzed for the first time the serology and clinical characteristics of MuSK-positive MG in the Polish population. METHODS: One hundred and fifty-one patients were tested for the presence of anti-AChR and anti-MuSK antibodies: 62 with seronegative MG, including 14 with ocular seronegative MG, 48 age-matched patients with seropositive MG and 41 controls. RESULTS: All patients with seropositive MG and the disease controls were MuSK-negative. Anti-MuSK antibodies were detected only in four patients with seronegative MG (8.7% of generalized seronegative cases): three women and one man. All four had predominantly bulbar involvement, and underwent thymectomy, with no apparent benefit. All of them improved clinically after immunosuppressive treatment with remissions lasting up to 7 years. CONCLUSION: MuSK-positive MG is rare in Polish population accounting for only 8.7% of seronegative cases with generalized MG. This is consistent with emerging evidence for lower MuSK antibodies at more northerly latitudes.

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A study was made of the degree and sequence of neurophysiological changes during motor unit reorganisation in motor neuron disease (MND), spinal muscular atrophy (SMA), and prior polio. Concentric needle EMG was used in conjunction with our own computerized EMG-LAB system. Motor unit action potential (MUAP) parameters were measured in 543 muscles on weak and maximum effort. MUAP amplitude and area were found to increase in the early stages of damage, declining to normal or subnormal values in the course of the disease. It was concluded that in MND there is a pathological sequence: denervation--reinnervation--terminal denervation. The increase in MUAP amplitude and area in the early stages of lesion, reflecting reinnervation, was much greater in SMA than MND and most marked in prior polio. The eventual decrease is an expression of terminal decompensation.

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In classical quantitative analysis motor unit action potentials (MUAPs) parameters are useful in establishing diagnosis, but not in monitoring the functional status as expressed by clinical sings. This drawback is overcome by our new method called "Functional-QEMG", where the analysis is based on structural and functional changes of all acting motor units (MUs). The automatic classification of normal versus myogenic or neurogenic disorder together with the assessment of their severity is performed by special computer-assisted diagnostic procedures. The classification is based on individual MUAPs size (structure) and their functional properties determined in unique "Mapping-MUAP" program. This classification is further confirmed by the adequate to a given pathology the structural reorganisation of all acting MUs. In consequence theirs functional properties are changing as the compensatory mechanisms to generate the optimal force in structurally changed acting MUs. Thus, the effectiveness of compensatory process is used for quantitative assessment of severity of the disease from simultaneously recorded maximal effort pattern. Our experience during last ten years shown that such dynamical analysis is very useful in correlation with the clinical picture of examined patient to make the final conclusion of EMG investigation.

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OBJECTIVES: Electrophysiological studies of amyotrophic lateral sclerosis (ALS) patients reveal not only lower motor neuron involvement, but also widespread signs of its hyperexcitability. They might be the consequence of changes in the level of amino acids acting as neurotransmitters. MATERIAL AND METHODS: Electrophysiological examination of 31 patients with sporadic ALS was performed. A hyperexcitability index (HI) was created to describe the amount of double discharges, fasciculation potentials or 'giant' F-waves. Glutamate, aspartate, glycine and GABA concentration in serum and cerebrospinal fluid (CSF) were estimated, using the high performance liquid chromatography technique. RESULTS: The electrophysiological studies revealed marked variability in HI in the patients group. HI did not correlate with duration of the disease and the degree of disability expressed with Norris score, as well as with the level of excitatory or inhibitory amino acids in the body fluids. CONCLUSION: Hyperexcitability of the motor unit observed in ALS is not directly related to changes in serum and CSF level of amino acids acting as neurotransmitters.

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OBJECTIVES: Approximately 50% of patients treated with thymectomy have a chance for symptom-free life. However, immunological and neurophysiological abnormalities may be detected in patients with clinical remission. Although improvement usually parallels decrease in acetylcholine receptor antibody (AChRAb) levels and jitter values, there is a question what factors influence immunological and electrophysiological remission in a population of myasthenia gravis (MG) patients. METHODS: We analyzed retrospectively clinical data of 32 MG patients operated for generalized MG, followed-up at our department for 17.2 (4-31) years. They were in clinical remission for 12.8 (2-25) years. All of them had single fiber electromyograhy (SFEMG) of extensor digitorum communis muscle (EDC) muscle and estimation of AChRAb level at the end of follow-up. Their age at onset of MG was 17 years (6-48) and at thymectomy 19 (6.4-58) years. Tensilon test was positive in 30, repetitive nerve stimulation in 29 cases. RESULTS: Clinical remission was reached on average 4.2 years after thymectomy. SFEMG jitter value normalized in 60% of cases. AChRAb were negative only in 34% of patients. Jitter values correlated with AChRAb levels (P=0.006, r=0.5) but were not related to clinical factors. Only time to thymectomy correlated with time from thymectomy to clinical remission (P=0.001, r=0.5). CONCLUSIONS: Clinical remission is not always accompanied by normalization of SFEMG and AChRAb. Although normalization of neuromuscular transmission in patients with remission of MG is individual, short duration of MG before thymectomy increases the chance of early remission.

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In diagnostics of ALS the electrophysiologic investigation should be able to evaluate two fundamental processes: the primary process of the loss of some motoneuros--denervation, and secondary process of reinnervation. The most important diagnostic methods include the quantitative electromyography (EMG) evaluating several parameters of the motor unit potential (MUP) and of the maximal effort pattern. The earliest features are the signs of spontaneous activity (denervation) and the elevation of MUP amplitude and area (reinnervation). Finding of spontaneous activity in the tongue muscles as well as in the paraspinal muscles is of great diagnostic value. SFEMG may early detect increased density of muscle fibres (FD) and jitter elongation as signs of recent reinnervation. Electroneurography is critical in differentiation against the multifocal motor neuropathy with conduction block and other polyneuropathies. The aim of the electrophysiological investigations is also the evaluation of the intensity of lesion in the muscle investigated and, indirectly, the evaluation of the progress of the disease in serial studies. It might play a great role in prognosing and in monitoring of therapeutical trials. The abnormalities in the maximal effort pattern presenting as decrease of recording density and amplitude as well as of bioelectric activity indicate in the quantitative EMG a high degree of lesion. Those signs are accompanied by altered MUP parameters: decrease of MUP amplitude and area as compared with the former stages of reinnervation. Those signs express decompensation and denervation predominating over reinnervation. In SFEMG they present as FD decrease and in Macro-EMG as decrease of amplitude as compared to the reinnervation period. Serial investigations of amplitude of the potential resulting from supermaximal stimulation (CMAP), quantitative evaluation of the maximal voluntary isometric contraction (MVIC) and the assessment of the number of motor units (MUNE) are further valuable methods in monitoring of ALS progress.

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The frequency of involvement of sensory pathways in motor neuron disease (MND) remains the matter of controversy. For this reason the purpose of the present work was to test how often sensory system involvement might be detected by somatosensory evoked potentials (SEP) studies and then to verify the presence of alteration of the sensory conduction and to detect the frequency of abnormalities of somatosensory peripheral, spinal, subcortical and cortical potentials in MND. SEP were tested after median nerve stimulation at the wrist, recorded from Erb's point, Ce2, Ce7 and scalp. Pearson's correlation coefficients test and Wilcoxon rank-sum test were used for statistical analysis. 74 patients (22 women and 52 men) were examined. Mean age of patients was 54.07 +/- 11.24 years; mean duration of the disease -19.25 +/- 15.87 months. SEP were abnormal in 39 of 74 patients (about 53%) whereas the sensory NCV in median nerve was abnormal in 14 of 74 patients (19%). The most frequent pattern of abnormalities consisted of the absence or delay of cortical responses. The mean values of SEP latencies (N9, N11, N13, N20 and P25) were significantly increased in MND patients (p < 0.05) as compared with controls. The N9 and N11 latencies correlated with the duration of the disease. The results of our study (concerning a large group of MND patients) suggest that the involvement of sensory pathways is not rare in MND.

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We performed clinical and electrophysiological studies in 42 children with hereditary motor and sensory neuropathy type I and II (HMSN I and II) and in 103 members of their families. In 24 families with HMSN I the conduction velocity and latency were markedly changed in the nerves innervating the distal muscles (median, peroneal nerves) as well as proximal muscles (facial, axillary and musculocutaneous nerves). The changes were uniform in all motor and sensory nerves studied in a particular patient. The intensity of changes was similar in members of their families even when the clinical abnormalities were minimal, thus the degree of conduction velocity slowing was uniform within families. In adults with HMSN I (group A i B) we found less marked slowing of nerve conduction as compared to children (group P), the difference being significant (p < 0.001). It may suggest a slow process of peripheral nerves maturation despite the existing morbid condition. In patients of 18 families with HMSN II slight changes in conduction velocity were found only in nerves innervating the distal muscles, more evident in legs (peroneal and sural nerves). Conduction time of facial, axillary and musculo-cutaneous nerves was normal. The values of nerve conduction were not changing with patients' age. We recommend examining conduction time in facial, axillary or musculocutaneous nerve as a useful procedure for differentiation between HMSN I and II, especially in families with borderline conduction values in the nerves innervating distal muscles.

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Our material comparises 105 patients (62 men and 43 women) aged 26-73 years with amyotrophic lateral sclerosis (ALS). EMG examination confirmed the diagnosis of multilevel lesion of spinal motor neurons. Clinically, 94 of them had classical ALS, 3 had primary bulbar palsy (PBP), 6 had primary motor spinal atrophy (PSMA), and 2 had primary lateral sclerosis (PLS). Disease duration was 18.1 month, on the average, ranging from 2-60 months. In all patients motor and sensory nerve conduction was studied in median, peroneal and sural nerves. Conduction velocity, distal latency, F-wave latency of motor nerves, amplitude of M response and of sensory potentials were evaluated. Abnormalities were found most often in the motor fibres of median nerve: lowering of the M response amplitude in 44% of nerves studied, slowing of conduction velocity and elongation of distal latency in ca. 30%, elongation of F-wave latency in 27%. In the peroneal nerve the changes were less frequent: 38%, 21%, and 3%, respectively. They were also less marked. In the sensory fibres of median nerve slowing of conduction velocity was found in 25% of nerves, in sural nerve in 11%. Some slight decrease of amplitude of sensory potentials was seen in those nerves. The results obtained indicate a possibility of peripheral nerve lesion in the course of ALS which must be remembered in clinical diagnosing.

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We performed clinical and electrophysiological studies in 42 children with hereditary motor and sensory neuropathy type I and II (HMSN I and HMSN II) and in 103 members of their families. In 24 families with HMSN I the conduction velocity and the latency were markedly changed in the nerves innervating the distal muscles (median, peroneal nerves), as well as proximal muscles (facial, axillary, and musculocutaneous nerves). The changes were uniform in all motor and sensory nerves studied in the particular patient. No nerve conduction worsening with age has been found in cross-sectional analysis. In patients with HMSN I the conduction velocity was impaired even when the clinical abnormalities were minimal. The degree of the conduction velocity slowing was uniform within majority of the families. Homogeneity of conduction velocity slowing in individuals with HMSN I regardless of clinical expression suggests a primary myelin defect as an underlying cause. In patients from 18 families with HMSN II slight changes in conduction velocity were found only in the nerves innervating the distal muscles, the latency of axillary and facial nerves was within normal range. We recommend examining conduction time in facial and axillary nerves as a useful procedure for differentiation between HMSN I and II, especially in families with borderline conduction values in the long nerves.

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Ten cases of myasthenia are presented in which dysphonia was the initial sign. Isolated signs of dysphonia continued for several months or years, presenting diagnostic difficulties. Eventually neurologic examination followed by electrophysiological investigation (classical repetitive nerve stimulation and single fibre EMG) as well as edrophonium test allowed proper diagnosis of myasthenia, then confirmed by the clinical course. A possible diagnosis of myasthenia should be taken into consideration in cases with isolated dysphonic signs of uncertain origin.

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Twenty myasthenic patients were followed up who had in the years 1981-1982 full clinical remission (no drugs, no symptoms), lasting at that time at least several years. However, in 19 of them neuromuscular transmission defects were then found by single fibre electromyography (SFEMG). We then concluded that true remissions did not exist in myasthenia (J. Neurol., 1985, 231, 331). Recently, we were able to evaluate those patients. One patient, who had full long lasting remission after thymomectomy, died at the age of 69 of myocardial infarction in the course of a myasthenic relapse. Another patient had a relapse, 20 years after thymoma extirpation. Two patients had recurrent fluctuating relapses of myasthenia. One patient, who had undergone thymectomy in his childhood, developed immune thrombocytopenic syndrome. SFEMG done in 12 patients showed abnormalities in 5 cases only (mean jitter elongation, increased percentage of potential pairs with blocking and jitter elongation more than 55 microseconds). In 7 remaining patients the catamnesis covering more than 14 years revealed full clinical and electrophysiological remission. Thus, repeated analysis of the group of myasthenic patients with remission has lead us to revise our former opinion that there are no true remissions, clinical and electrophysiological, in myasthenia. They certainly occur but in some patients normalization of the electrophysiological pattern appears only several years after they have become clinically asymptomatic.

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We studied 78 patients with motor neuron disease (MND) using concentric needle electromyography. Analysis on weak and maximal effort was performed using our own, fully automated, computer method, EMG-LAB. In addition to the conventional parameters of single motor unit action potentials (MUAPs) and interference pattern, new criteria were applied: the range of the acting motor units and the functional recruitment order. A total of 375 muscles of MND patients and 120 control muscles were investigated. The electromyographic data were analyzed separately in five groups of muscles, classified A, B, C, D, and E according to their clinical condition. Those results allowed us to discern six neurophysiological stages (N(0,1,2,3,4,5)) from the early to the most advanced phase. It has been confirmed that reinnervation in MND is adequate to compensate for the loss of over 50% of motor neurons but it is only a transitory phase in the morbid course. At stages N(O-5), the electrophysiological data reflect structural and functional integrity of the functioning motor units. Evaluation of not only single MUAPs but also of the full range of acting motor units and their recruitment order allowed a deeper look into the underlying pathophysiological mechanisms.

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The solely dysphonia symptom as atypical and relatively rare onset of myasthenia gravis is difficult to diagnose. We present 11 cases of myasthenia, where dysphonia was one and only one symptom of illness during several months to several years. The evidences of dysphonia were the fatigability and nasality of speech, as well as chronic hoarseness. The diagnosis of myasthenia was very difficult in this period and was often preceded by lengthy laryngological and neurological examination. In our paper we present the criteria proper for myasthenia diagnosis in which repetitive electrostimulation test and high-sensitive SFEMG method are used.

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We have sought associations with the muscle acetylcholine receptor alpha-subunit gene (CHRNA1) in autoimmune myasthenia gravis (MG) patients from three ethnic groups; Caucasians and South Africans of Black and Mixed-Ancestry. We found a significant association with the HB*15 CA repeat allele in unrelated Black myasthenics (n = 18; RR = 2.85; pX2 = 0.04) compared with 52 ethnically matched controls. A family-based association study and linkage analysis in Caucasian simplex and multiplex families supported a positive association at this locus with the longer alleles, including HB*14 to *18. However, no significant cosegregation of the disease with the HB alleles could be demonstrated in affected sib pairs. Our results suggest that the CHRNA1 locus harbours a minor susceptibility gene for developing MG, though we cannot rule out linkage disequilibrium with another major gene locus on chromosome 2.

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