Biomedical subjects

Machiel J Zwarts

Publications and source records attributed to Machiel J Zwarts.

10 recordsLinked to original sources

PubMed2004

Muscle-fiber conduction velocity and electromyography as diagnostic tools in patients with suspected inflammatory myopathy: a prospective study.

Combinations of different techniques can increase the diagnostic yield from neurophysiological examination of muscle. In 25 patients with suspected inflammatory myopathy, we prospectively performed needle electromyography (EMG) and measured muscle-fiber conduction velocity (MFCV) in a single muscle, using a technique with direct muscle-fiber stimulation and recording. Results of MFCV were compared with final diagnosis, EMG, and needle muscle biopsy. Diagnostic accuracy of combined MFCV and EMG studies was 72%, compared to 60% for EMG alone. This improvement was due to a gain in specificity. The MFCV did not prove useful in discriminating inflammatory myopathy from other myopathies. Furthermore, we found a correlation of 92% between variability of MFCV and myopathic changes in muscle biopsy. We conclude that the utility of electrodiagnostic examination can be increased if EMG examination is combined with MFCV studies.

Action Potentials↗

PubMed2003

Relative contributions of central and peripheral factors to fatigue during a maximal sustained effort.

Local muscle fatigue can originate from both peripheral and central factors. The relative contribution of these factors in the course of a fatiguing contraction in 20 healthy subjects was determined. While subjects made a 2-min sustained maximal voluntary contraction (MVC) of the biceps brachii, muscle fibre conduction velocity (MFCV) was determined with surface electromyography (SEMG) as a representation of developing peripheral fatigue. To quantify the amount of peripheral fatigue, the force development following a train of electrical stimuli on the endplate before and after the contraction were compared. To measure force loss caused by central factors, superimposed electrical stimulation was used during the contraction. By two different methods the influence of peripheral fatigue on the superimposed force responses was taken into account. The first method compared the force response with the actual voluntary force, the second -which seemed more valid - used an estimation of peripheral fatigue based on linear interpolation between the force responses during rest before and after sustained contraction. During the contraction, voluntary force decreased to 38%. Peripheral fatigue was responsible for the larger part of this decline (89%). The other part, which was calculated as 12%, was caused by an increase of central activation failure. The decline of MFCV indicated that peripheral fatigue increased predominantly during the first half of the contraction and stayed at a constant level during the latter part. In contrast, central fatigue mainly induced a force decrease in the second part of the contraction. The different mechanisms which could be responsible for this change of emphasis from peripheral to central factors are discussed.

Adult↗

PubMed2003

Multichannel surface EMG: basic aspects and clinical utility.

The generation of the surface electromyogram (sEMG) is described with regard to the properties of the single muscle fiber action potential as source, the physical aspects of volume conduction and recording configuration, and the properties and firing pattern of motor units (MUs). The spatial aspect of the motor unit action potential (MUP) is emphasized in relation to the results of high-density, multichannel sEMG measurements. The endplate zone, depth, size, and position of MUs can be estimated. The use of muscle fiber conduction velocity measurements in channelopathies and the changes in pathological fatigue are described. Using the unique patterns of spatial spread of MUPs over the skin (MU fingerprint), MU classification and the determination of firing moments is done noninvasively. Clinical applications of high-density sEMG measurements are reviewed. Emerging possibilities provided by MUP size and fingerprint measurements in neuromuscular disease and motor control are discussed. We conclude that multichannel sEMG adds unique, and sometimes indispensable, spatial information to our knowledge of the motor unit.

Action Potentials↗

PubMed2003

Motor evoked potentials of the lower extremity in predicting motor recovery and ambulation after stroke: a cohort study.

OBJECTIVE: To assess the prognostic value of motor evoked potentials (MEPs) in the lower extremity with respect to motor recovery and functional recovery in stroke patients. DESIGN: Cohort study. SETTING: The department of neurology at a university hospital. PARTICIPANTS: Thirty-eight acute-stroke patients with complete paralysis (paralysis subgroup) or severe paresis (paresis subgroup) of the lower extremity. MEPs of the vastus medialis and the tibialis anterior muscles were recorded between days 3 and 10 after stroke onset. INTERVENTIONS: Not applicable. Main outcome measures A separate proximal leg motor score (maximum, 16 points) and crural motor score (maximum, 2 points) were defined within the lower-limb subset of the original Fugl-Meyer Motor Assessment to evaluate the motor performance at regular intervals until 6 months after stroke. The transfer item of the Barthel Index and the Functional Ambulation Categories scores were used to assess transfer and walking ability. RESULTS: For the paralysis subgroup (n=30), the follow-up was complete in 27 patients (2 patients died, 1 patient underwent above-knee amputation). At 26 weeks, 20 patients experienced proximal motor recovery (mean score +/- standard deviation, 11.70+/-4.48), and 12 of them also showed crural motor recovery (mean score, 1.40+/-.51). Nine patients (33%) could perform an independent transfer safely, and 7 (26%) had learned to walk independently. Analysis revealed significant relationships for tibialis anterior muscle MEPs and motor recovery of crural leg muscles (odds ratio [OR]=18.00; 95% confidence interval [CI], 1.31-894.40), but not for vastus medialis muscle MEPs and proximal motor recovery (OR=6.00; 95% CI,.53-303.00). We found no association between vastus medialis muscle MEPs and recovery of ambulation. However, tibialis anterior muscle MEPs seemed to provide a test with prognostic value for the ability to perform independent transfers (OR=17.50; 95% CI, 1.36-267.00), but not for walking (OR=5.25; 95% CI,.40-77.57). Patients in the paresis subgroup experienced more favorable motor and functional recovery than did those in the paralysis subgroup. CONCLUSIONS: Tibialis anterior muscle MEPs registered in subacute phase after stroke may provide important prognostic information, both for motor recovery of the crural muscles and for the ability to perform independent transfers in patients with initial complete paralysis of the lower extremity. Vastus medialis muscle MEPs were not predictive for motor and functional recovery.

Adult↗

PubMed2003

Contralateral reinnervation of midline muscles in nonidiopathic facial palsy.

The purpose of this study was to analyze contralateral reinnervation of the facial nerve in eight patients with complete facial palsy after surgery or trauma and seven healthy volunteers. All patients had contralateral reinnervation of facial muscles as demonstrated by electrical nerve stimulation versus none of the control subjects. Four patients had facial muscle movements at the site of the damaged nerve. In one patient this was entirely the result of contralateral reinnervation, whereas the other three patients had innervation both ipsilaterally and contralaterally. This implies that renewed facial muscle activity should be examined considering the origin of the reinnervation, either contralateral or ipsilateral. Contralateral reinnervation is a common phenomenon after total facial palsy and can occur alongside ipsilateral reinnervation. It can be mistaken for adequate reinnervation of the damaged nerve, causing postponement of dynamic reconstruction therapy.

Action Potentials↗

PubMed2003

Motor evoked potentials in predicting recovery from upper extremity paralysis after acute stroke.

OBJECTIVE: The use of motor evoked potentials (MEPs) in predicting recovery after stroke still appears to be somehow equivocal. We assessed the prognostic value of MEPs with respect to arm and hand motor recovery in acute stroke patients. METHODS: This cohort study included 43 consecutive acute stroke patients with complete paralysis of the upper extremity. MEPs of the abductor digiti minimi muscle (ADM) and the biceps brachii muscle (BB) were obtained within 10 days after stroke onset. The upper limb subset of the Fugl-Meyer Motor Assessment was used to evaluate the motor performance at regular intervals until 6 months after stroke. RESULTS: The follow-up was complete in 40 patients (2 patients died and 1 patient had a recurrent stroke); 14 patients showed motor recovery of the arm and their mean 26-week arm motor score was 17.93 (range 3-30, SD 11.68); hand motor recovery occurred in 11 patients and their mean 26-week hand motor score was 11.09 (range 4-14, SD 4.10). Stepwise logistic regression revealed prognostic models for both arm and hand motor recovery based on BB MEPs (odds ratio 7.69, confidence interval, CI, 1.16-50.95) and ADM MEPs (odds ratio 16.20, CI 2.51-104.40), respectively. CONCLUSIONS: The predictive significance of MEPs with respect to motor recovery of the upper extremity was obvious in our homogeneous sample of patients. This agrees with the paradigm that motor recovery after infarction is strongly dependent on a critical residual sparing of the corticospinal function. In this context, the test properties of MEPs in predicting motor recovery are discussed. The added value of MEPs with respect to motor recovery of the upper extremity should be regarded as established for patients with initial paralysis, especially since clinical examination alone lacks the possibility to detect the potential for motor recovery in these cases.

Adolescent↗

PubMed2002

Nonmuscular involvement in merosin-negative congenital muscular dystrophy.

The spectrum of nonmuscular involvement in six children with merosin-negative congenital muscular dystrophy is described. In all children, biochemical, neuroradiologic, cardiac, and neurophysiologic studies were performed. Cerebral structures that were myelinated at gestation, including internal capsule, corpus callosum, brainstem, and cerebellar white matter, demonstrated no abnormalities, whereas the periventricular and subcortical white matter, which were myelinated in the first postnatal year, demonstrated signs of leukoencephalopathy. Cerebrospinal fluid analysis revealed an elevated albumin cerebrospinal fluid to serum ratio in the younger children. Electroencephalogram results were abnormal in the two elder children. One child suffered from congestive cardiomyopathy. The increase in nerve conduction velocity in these children over the years lagged behind those of healthy patients, pointing to a demyelinating neuropathy. We conclude that in merosin-negative congenital muscular dystrophy patients, nonmuscular involvement includes the central and peripheral nervous system and the heart. The pattern of myelination of the brain and nerve conduction slowing suggests a myelination arrest. Merosin deficiency can give rise to a congestive cardiomyopathy, which is of no clinical relevance in the majority of children.

Adult↗

PubMed2002

Systematic review for the early prediction of motor and functional outcome after stroke by using motor-evoked potentials.

OBJECTIVE: To clarify the prognostic value of motor-evoked potentials (MEPs) in predicting motor and functional outcomes after acute stroke. DATA SOURCES: A computer-aided search to identify original prognostic studies published from 1988 through 2000; relevant references cited in the retrieved articles were also included. STUDY SELECTION: A preliminary screening selected studies in which transcranial magnetic stimulation was assessed as a prognostic determinant for outcome at the level of impairments (motor recovery) and disabilities (functional recovery). The studies were then subjected to a critical review according to a priori methodologic criteria. DATA EXTRACTION: Data from the studies were used to construct contingency tables with MEPs as a prognostic determinant. The distribution of cells was statistically assessed with the Fisher exact test. The prognostic test properties were expressed as sensitivity and specificity. The clinical significance was determined by odds ratios. DATA SYNTHESIS: Of 85 potentially relevant studies, 20 met the criteria for the preliminary screening; after the critical review, 5 studies were included for analysis and discussion. CONCLUSIONS: Analysis of the data from the 5 studies indicated obvious evidence for the prognostic value of MEPs for both motor and functional recovery. The prognostic test properties for subgroups of patients could be established. In predicting motor recovery of the upper extremity, the specificity was consistently very high for subgroups of patients with paralysis or severe paresis; this test property might be used in clinical practice. We discuss the prognostic value of MEPs and offer suggestions for further research.

Data Interpretation, Statistical↗

PubMed2002

Motor recovery after stroke: a systematic review of the literature.

OBJECTIVE: To collect and integrate existing data concerning the occurrence, extent, time course, and prognostic determinants of motor recovery after stroke using a systematic methodologic approach. DATA SOURCES: A computer-aided search in bibliographic databases was done of longitudinal cohort studies, original prognostic studies, and randomized controlled trials published in the period 1966 to November 2001, which was expanded by references from retrieved articles and narrative reviews. STUDY SELECTION: After a preliminary screening, internal, external, and statistical validity was assessed by a priori methodologic criteria, with special emphasis on the internal validity. DATA EXTRACTION: The studies finally selected were discussed, based on the quantitative analysis of the outcome measures and prognostic determinants. Meta-analysis was pursued, but was not possible because of substantial heterogeneity. DATA SYNTHESIS: The search resulted in 174 potentially relevant studies, of which 80 passed the preliminary screening and were subjected to further methodologic assessment; 14 studies were finally selected. Approximately 65% of the hospitalized stroke survivors with initial motor deficits of the lower extremity showed some degree of motor recovery. In the case of paralysis, complete motor recovery occurred in less than 15% of the patients, both for the upper and lower extremities. Hospitalized patients with small lacunar strokes showed relatively good motor recovery. The recovery period in patients with severe stroke was twice as long as in patients with mild stroke. The initial grade of paresis was the most important predictor for motor recovery (odds ratios [OR], >4). Objective analysis of the motor pathways by motor-evoked potentials (MEPs) showed even higher ORs (ORs, >20). CONCLUSIONS: Our knowledge of motor recovery after stroke in more accurate, quantitative, and qualitive terms is still limited. Nevertheless, our data synthesis and quantitative analysis comprises data from many methodologically robust studies, which may support the clinician in the management of stroke patients. With respect to early prognosis of motor recovery, our review confirms clinical experience that the initial grade of paresis (as measured on admission in the hospital) is the most important predictor, although the accuracy of prediction rapidly improves during the first few days after stroke. Initial paralysis implies the worst prognosis for subsequent motor recovery. Remarkably, the prognostic accuracy of MEPs appears much higher than that of clinical examination for different subgroups of patients.

Activities of Daily Living↗

PubMedDate not supplied

Analysis of recovery processes after stroke by means of transcranial magnetic stimulation.

The objective of this study was to use motor evoked potentials (MEPs) to analyze the integrity of fast corticospinal functions as the neurophysiologic basis for motor recovery in stroke patients. This was a cohort study including 44 acute stroke patients with paralysis of the upper or the lower extremity. Motor evoked potentials of the abductor digiti minimi, the biceps brachii, the vastus medialis, and the tibialis anterior were performed within 10 days (mean, 6.9 days; range, 3 to 10 days) and 40 days (mean, 27.8 days; range, 14 to 40 days) after stroke onset. A separate score was defined for proximal and distal motor functions of the upper and lower extremity within the original Fugl-Meyer motor assessment. Motor performance was evaluated simultaneously with the MEP assessments and 26 weeks after stroke. For all the muscles in which a response was present during the first investigation, obvious recovery of the fast corticospinal functions occurred. For the abductor digiti minimi amplitude ratio and the vastus medialis MEP amplitude the differences between the two investigations were significant. An MEP response could be elicited in more cases at the second than on the first MEP assessment. A present MEP response during the first registration indicated nearly always subsequent motor recovery, both for proximal and distal motor functions of the upper and lower extremity. However, motor recovery was also observed in some patients for whom no MEP response could be elicited. Regression analysis showed significant relationships between the abductor digiti minimi (P = 0.020/0.004 [t1/t2])and biceps brachii (P = 0.020/0.004 [t1/t2]) MEP amplitude parameters and the 26-week hand and arm motor scores. No relationship existed between the tibialis anterior and the vastus medialis MEP parameters and the leg motor scores. Motor recovery manifests neurophysiologically often as the recovery of fast corticospinal functions. In many cases, assessment by MEPs is more sensitive than clinical examination to detect residual corticospinal functions, which forms the pathophysiologic basis for the predictive value of MEPs for motor recovery after stroke.

Adult↗