Search

Fibromyalgia (FM) is characterized by widespread muscle pain and central neural deregulation. Previous studies showed increased muscle fiber conduction velocity (CV) in non-painful muscles of FM patients. This study investigates the relationship between central activation and the CV in FM.Twenty-two females with primary FM and 21 controls underwent surface electromyography of the non-painful biceps brachii. Mean CVs were calculated from the motor unit potential velocities (CV-MUPs), and the CV-MUPs' statistical distributions were presented as histograms. The amount of muscle activity (average rectified voltage, ARV) was measured.The CV was higher in the FM-group than in the controls (P = 0.021), with CV-MUPs generally shifted to higher values, indicative of increased muscle membrane propagation speeds. The largest increase in the CV of the FM-group occurred when adopting and maintaining a limb position at only 5% of maximum strength (P 0.001); the CV did not, as normal, increase with greater force. However, the ARV in both groups similarly increased with force.In fibromyalgia patients, the muscle membrane propagation speed increases independently of the force load or amount of muscle activity produced. When adopting a limb position, the patients show an augmented muscle membrane reaction, suggesting deregulation from higher neural centers.These findings contribute to understanding fibromyalgia.

Objective: Chronic fatigue syndrome (CFS) and fibromyalgia (FM) are disorders of unknown etiology and unclear pathophysiology, with overlapping symptoms of – especially muscular –fatigue and pain. Studies have shown increased muscle fiber conduction velocity (CV) in the non-painful muscles of FM patients. We investigated whether CFS patients also show CV abnormalities. Methods: Females with CFS (n = 25), with FM (n = 22), and healthy controls (n = 21) underwent surface electromyography of the biceps brachii, loaded up to 20% of maximum strength, during short static contractions. The mean CV and motor unit potential (MUP) velocities with their statistical distribution were measured. Results: The CV changes with force differed between CFS-group and both FM-group and controls (P = 0.01). The CV of the CFS-group increased excessively with force (P < 0.001), whereas that of the controls increased only slightly and non-significantly, and that of the FM-group did not increase at all. In the CFS-group, the number of MUPs conveying very high conduction velocities increased abundantly with force and the MUPs narrowed. Conclusion: Our results suggest disturbed muscle membrane function in CFS patients, in their motor units involved in low force generation. Central neural deregulation may contribute to this disturbance. Significance: These findings help to detangle the underlying mechanisms of CFS.

Objective Several epidemiological and clinical reports associate fibromyalgia (FM) with seizure disorders, and clinical studies associate FM diagnosis with psychogenic non-epileptic seizures. However, these associations rely on self-reports of being diagnosed with FM or unstandardized clinical diagnosis in combination with small samples. We investigated the association of FM and self-reported seizures using a large rheumatic disease databank and the current established self-reported, symptom-based FM diagnostic criteria. Methods We selected a random observation from 11,378 subjects with rheumatoid arthritis (RA), 2,390 (21.0%) of whom satisfied 2016 revised criteria for FM. Patients were inquired about the presence of any kind of seizures in the previous 6 months, anti-epileptic medications, and patient-reported symptoms and outcomes. Results Seizures were reported by 89 RA patients who met FM criteria (FM+) and by 97 patients who did not (FM-), resulting in an age- and sex-adjusted seizure prevalence of 3.74 (95% CI 2.95 to 4.53) per 100 FM+ subjects and 1.08 (95% CI 0.87 to 1.30) in FM- subjects. The seizure odds ratio of FM+ to FM- cases was 3.54 (95% CI 2.65 to 4.74). Seizures were associated to a very similar degree with symptom reporting (somatic symptom count and comorbidity index) as to FM diagnosis variables. RA patients reporting seizures also reported worse pain, quality of life, and functional status. Seizure patients treated with anti-seizure medication had worse outcomes and more comorbidities than seizure patients with no seizure drugs. Conclusions We found a significant and similar association of both FM diagnostic variables and FM-related symptom variables, including the number of symptoms and comorbidities, with self-reported seizures in people with RA. The observed association was similar to those found in previous studies of symptoms variables and seizures and does not suggest a unique role for fibromyalgia diagnosis. Rather, it suggests that multi-symptom comorbidity is linked to seizures in a complex and not yet clearly understood way. As the current study relied on self-reported seizures and was not able to distinguish between epileptic and psychogenic nonepileptic seizures, future studies are needed to replicate the findings using both validated FM criteria assessments and clinically verified diagnoses of epileptic and psychogenic seizures.

Vibration exercise (VE) has been suggested as an effective training for improving muscle strength and coordination. However, the underlying physiological adaptation processes are not yet fully understood, limiting the development of safe and effective exercise protocols. To better understand the neuromuscular responses elicited by VE, we aimed at investigating the acute effects of superimposed vibration on the Hoffmann reflex (H-reflex), measured after fatiguing exercise. Twenty-five volunteers performed four isometric contractions of the right Flexor Carpi Radialis (FCR) with baseline load at 80% of their maximal voluntary contraction (MVC), both with no vibration and with superimposed vibration at 15, 30, and 45 Hz. Fatigue was estimated by MVC test and estimation of electromyographic spectral compression. H-reflex suppression was estimated as the relative decrease after exercise. Our results show that fatiguing exercise determined a decrease in H-reflex amplitude compared to rest condition while vibration determined a lower H-reflex suppression as compared to no vibration. The superimposition of 30-Hz vibration determined the largest acute reduction in force generating capacity (36 N, p < 0.05) and the lowest H-reflex suppression (20%, p < 0.05). These results suggest VE to be particularly suitable in rehabilitation programs for rapid restoration of muscle form and function after immobilization periods.

Objective Diagnostic value and efficacy of re-interpretation of previous EEGs in 100 patients admitted to a tertiary epilepsy center with EEG results conflicting with the clinical diagnosis after the first visit. Methods EEGs were reclassified. A matched control group was included to assess the efficiency of the re-interpretation process. Efficacy was assessed by questionnaires and costs as number of technician hours needed. Results In 85 patients the previous EEG conclusion was known. In 43 the conclusion was altered. In 23 the epileptic activity changed from positive to negative (17) or the reverse (6). In 15 the focus changed (7 originally classified as generalized epileptic activity). In 5 the syndrome changed. 57% of the re-interpretation group needed no extra EEG afterwards. 96% of the re-interpretations were considered useful by requesting and 72% by not involved neurologists. The average time per EEG technologist per patient was 8,81 h in controls and 5,40 in the re-interpretation group. Conclusions In 43 from the 85 patients (51%) re-interpretation of ‘controversial’ EEGs led to a different opinion. The re-interpretations were useful and less time consuming, compared to new EEGs in controls. Significance Re-interpretation of ‘controversial’ EEGs is useful and cost effective.

To improve the diagnostic accuracy of electroencephalography (EEG) criteria for nonconvulsive status epilepticus (NCSE), external validation of the recently proposed Salzburg criteria is paramount. We performed an external, retrospective, diagnostic accuracy study of the Salzburg criteria, using EEG recordings from patients with and without a clinical suspicion of having NCSE. Of the 191 EEG recordings, 12 (12%) was classified as an NCSE according to the reference standard. In the validation cohort, sensitivity was 67% and specificity was 89%. The positive predictive value was 47% and the negative predictive value was 95%. Ten patients in the control group (n = 93) were false positive, resulting in a specificity of 89.2%. The interrater agreement between the reference standards and between the scorers of the Salzburg criteria was moderate; disagreement occurred mainly in patients with an epileptic encephalopathy. The Salzburg criteria showed a lower diagnostic accuracy in our external validation study than in the original design, suggesting that they cannot replace the current practice of careful weighing of both clinical and EEG information on an individual basis.

Peripheral neuropathy in patients with merosin-negative congenital muscular dystrophy (MN-CMD) has been sporadically investigated and has been considered to be motor and demyelinating in nature on the basis of nerve conduction studies. We performed neurophysiologic studies in 12 children with MN-CMD to establish the spectrum and evolution of peripheral nervous system involvement. In our patients, nerve conduction studies for both motor and sensory nerves were near normal in the children younger than six months and abnormal in the older children. The older children had the relatively slowest nerve conduction velocities suggesting a progressive, age-related dysmyelinating neuropathy. We hypothesize that the findings are due to a myelination arrest as a result of insufficient synthesis and maintenance of the peripheral myelin sheath. (J Pediatr Neurol 2004; 2(4): 213–218).

Introduction: We investigated whether muscle ultrasound can distinguish muscles affected by post-polio syndrome (PPS) from healthy muscles and whether severity of ultrasound abnormalities is associated with muscle strength. Methods: Echo intensity, muscle thickness, and isometric strength of the quadriceps muscles were measured in 48 patients with PPS and 12 healthy controls. Results: Patients with PPS had significantly higher echo intensity and lower muscle thickness than healthy controls. In patients, both echo intensity and muscle thickness were associated independently with muscle strength. A combined measure of echo intensity and muscle thickness was more strongly related to muscle strength than either parameter alone. Conclusions: Quantitative ultrasound distinguishes healthy muscles from those affected by PPS, and measures of muscle quality and quantity are associated with muscle strength. Hence, ultrasound could be a useful tool for assessing disease severity and monitoring changes resulting from disease progression or clinical intervention in patients with PPS. Muscle Nerve 51: 24–29, 2015

OBJECTIVE:To investigate the effect of physical training combined with growth hormone (GH) on muscle thickness and its relationship with muscle strength and motor development in infants with Prader-Willi syndrome (PWS).METHODS:In a randomized controlled trial, 22 infants with PWS (12.9 ± 7.1 months) were followed over 2 years to compare a treatment group (n = 10) with a waiting-list control group (n = 12). Muscle thickness of 4 muscle groups was measured by using ultrasound. Muscle strength was evaluated by using the Infant Muscle Strength meter. Motor performance was measured with the Gross Motor Function Measurement. Analyses of variance were used to evaluate between-group effects of GH on muscle thickness at 6 months and to compare pre- and posttreatment (after 12 months of GH) values. Multilevel analyses were used to evaluate effects of GH on muscle thickness over time, and multilevel bivariate analyses were used to test relationships between muscle thickness, muscle strength, and motor performance.RESULTS:A significant positive effect of GH on muscle thickness (P < .05) was found. Positive relationships were found between muscle thickness and muscle strength (r = 0.61, P < .001), muscle thickness and motor performance (r = 0.81, P < .001), and muscle strength and motor performance (r = 0.76, P < .001).CONCLUSIONS:GH increased muscle thickness, which was related to muscle strength and motor development in infants with PWS. Catch-up growth was faster in muscles that are most frequently used in early development. Because this effect was independent of GH, it suggests a training effect.

Introduction: Excitotoxicity plays an important role in the pathogenesis of the preferential motor neuron death observed in amyotrophic lateral sclerosis (ALS). Continuous theta burst stimulation (cTBS) by transcranial magnetic stimulation has an inhibitory effect on corticospinal excitability (CSE). We characterized the neurophysiological changes induced by cTBS in ALS. Methods: The patients received 5 daily sessions of cTBS. CSE was assessed at baseline and after each session of cTBS. Results: The amplitude of a single pulse motor evoked potential was significantly decreased (34%) over the days. The amplitude returned to baseline a week after the last session. The resting motor threshold increased significantly, whereas intracortical inhibition and facilitation did not change over the sessions. Conclusions: Daily cTBS has a cumulative depressing effect on CSE in patients with ALS. These results suggest that modulation of CSE in ALS is possible, but repetitive sessions are needed to maintain the effect. © 2013 Wiley Periodicals, Inc.

Item does not contain fulltext PURPOSE: Patients suffering from postcancer fatigue have both an inferior physical activity and physical fitness compared to non-fatigued cancer survivors. The aims of this study were (1) to examine the effect of cognitive behavior therapy, an effective treatment for postcancer fatigue, on physical activity and physical fitness and (2) to examine whether the effect of cognitive behavior therapy on postcancer fatigue is mediated by physical activity and/or physical fitness. METHODS: Severely fatigued cancer survivors were randomly assigned to either the intervention (cognitive behavior therapy) or the waiting list condition. After assigning 23 patients in the intervention condition and 14 patients in the waiting list condition, they were assessed both at baseline and 6 months later. Physical activity was assessed via actigraphy and physical fitness was assessed by a maximal exercise test. A nonparametric bootstrap approach was used to test the statistical significance of the mediation effects. RESULTS: A significant increase in physical activity was observed in the intervention group from baseline to follow-up, whereas physical activity did not change from baseline to follow-up in the waiting list group. Physical fitness did not significantly change after cognitive behavior therapy or after 6 months of waiting for therapy. Fatigue decreased more significantly in the intervention group than in the waiting list group. The mediation hypotheses were rejected. CONCLUSIONS: Cognitive behavior therapy effectively reduced postcancer fatigue and increased physical activity but did not change physical fitness. The effect of cognitive behavior therapy on postcancer fatigue is not mediated by a change in physical activity or physical fitness.

Essential to all living creatures is the ability to convey information. In addition motor responses are required, for example running. This all is possible due to the ability of specialized cells to conduct information along the cell membrane by means of action potentials (AP) made possible by the charged cell membrane, which has selective permeability for different ions. Voltage and ligand sensitive ion channels are responsible for sudden changes in selective permeability of the membrane resulting in local depolarization of the membrane. The neuromuscular junction is a highly specialized region of the distal motor axon that is responsible for the transferring of activation from nerve to muscle. All these systems and subsystems can fail and a thorough understanding is necessary in order to understand the changes a clinical neurophysiologist can encounter while recording from the human nervous system in cases of disorders of brain, nerve and muscle.

Introduction: Fibromyalgia (FM) is a disorder of widespread muscular pain. We investigated possible differences in surface electromyography (sEMG) in clinically unaffected muscle between patients with FM and controls. Methods: sEMG was performed on the biceps brachii muscle of 13 women with FM and 14 matched healthy controls during prolonged dynamic exercises, unloaded, and loaded up to 20% of maximum voluntary contraction. The sEMG parameters were: muscle fiber conduction velocity (CV); skewness of motor unit potential (peak) velocities; peak frequency (PF) (number of peaks per second); and average rectified voltage (ARV). Results: There was significantly higher CV in the FM group. Although the FM group performed the tests equally well, their electromyographic fatigue was significantly less expressed compared with controls (in CV, PF, and ARV). Conclusion: In the patients with FM, we clearly showed functional abnormalities of the muscle membrane, which led to high conduction velocity and resistance to fatigue in electromyography

Item does not contain fulltext PURPOSE: The aim of this study is to examine whether physical fitness of severely fatigued and non-fatigued cancer survivors, as measured by maximal exercise performance, is different between both groups and, if so, whether this difference can be explained by differences in physical activity, self-efficacy regarding the exercise test, and/or social support. METHODS: Severely fatigued (n = 20) and sex- and age-matched non-fatigued (n = 20) disease-free cancer survivors, who completed treatment for a malignant, solid tumor at least 1 year earlier, participated in this case-control study. Maximal oxygen consumption was measured during an incremental cycling exercise test. Physical activity was assessed via actigraphy. Self-efficacy regarding the test and social support were assessed via questionnaires to study its relationship with physical fitness. RESULTS: Maximal oxygen consumption was significantly lower in fatigued compared to non-fatigued participants. Actual physical activity, self-efficacy regarding the test, and negative interactions of social support were significantly different between both groups. However, after inclusion of these three variables in linear regression analyses, the difference in physical fitness between fatigued and non-fatigued cancer survivors persisted. CONCLUSIONS: Maximal oxygen consumption, a measure for physical fitness, was reduced in severely fatigued compared to non-fatigued cancer survivors. The inferior maximal exercise performance cannot fully be explained by differences in physical activity, self-efficacy, or social support between both groups. Other currently still unknown factors, such as a disturbance in the cardiopulmonary circuit, may play a role.

Contains fulltext : 96283.pdf (Publisher’s version ) (Closed access) OBJECTIVE: To report on the development and psychometric evaluation of the Radboud Oral Motor Inventory for Parkinson's Disease (ROMP), a newly developed patient-rated assessment of speech, swallowing, and saliva control in patients with Parkinson's disease (PD). DESIGN: Reliability and validity study. SETTING: Tertiary-care Parkinson center for multidisciplinary assessment. PARTICIPANTS: Consecutive community-dwelling patients with PD (n=129) or atypical parkinsonism (AP; n=49; mean +/- SD age, 64+/-9.8y; mean +/- SD disease duration, 7y; median Hoehn and Yahr [HY] stage, 2.5). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: To evaluate reproducibility, 60 patients completed the ROMP twice within a mean of 24+/-12 days. To study validity, another cohort of 118 patients who had completed the ROMP was assessed by both a neurologist (HY stage, Unified Parkinson's Disease Rating Scale III) and speech-language pathologist (severity of dysarthria, dysphagia, drooling) who were blinded to ROMP scores. RESULTS: Confirmatory factor analysis identified the 3 a priori-designed ROMP domains of speech, swallowing, and saliva control. Internal consistency was .95 for the total ROMP and .87 to .94 for the 3 domains or subscales. Intraclass correlation coefficients for reproducibility were .94 and .83 to .92 for the subscales. Construct validity was substantial to good with correlations ranging from .36 to .82. The ROMP differentiated significantly (P

INTRODUCTION: Amyotrophic lateral sclerosis (ALS) is a progressive disease caused by the degeneration of upper and lower motor neurons. The etiology of ALS is unclear, but there is evidence that loss of cortical inhibition could be related to motor neuron degeneration. We sought to determine whether cathodal transcranial direct current stimulation (tDCS) can reduce cortical excitability in patients with ALS. METHODS: Three sessions of cathodal tDCS, lasting 7, 11, or 15 minutes, were performed in 10 patients and 10 healthy controls. Corticospinal excitability was measured before and after the tDCS. RESULTS: Cathodal tDCS induced a consistent decrease in corticospinal excitability in healthy controls, but not in ALS patients. CONCLUSIONS: The failure of tDCS to produce an excitability shift in the patients supports the potential diagnostic value of tDCS as a marker of upper motor neuron involvement. However, variation in corticospinal excitability measurements both inter- and intraindividually will limit its usefulness.

Drooling is an incapacitating feature of Parkinson's disease. Better pathophysiological insights are needed to improve treatment. In this study, we tested the hypothesis that the cause of drooling is multifactorial. We examined 15 patients with Parkinson's disease with distinct diurnal saliva loss ("droolers") and 15 patients with Parkinson's disease without drooling complaints ("nondroolers"). We evaluated all factors that could potentially contribute to drooling: swallowing capacity (maximum volume), functional swallowing (assessed with the dysphagia subscale of the Therapy Outcome Measures for rehabilitation specialists), unintentional mouth opening due to hypomimia (Unified Parkinson's Disease Rating Scale item), posture (quantified from sagittal photographs), and nose-breathing ability. We also quantified the frequency of spontaneous swallowing during 45 minutes of quiet sitting, using polygraphy. Droolers had more advanced Parkinson's disease than nondroolers (Unified Parkinson's Disease Rating Scale motor score 31 vs 22; P=.014). Droolers also scored significantly worse on all recorded variables except for nose breathing. Swallowing frequency tended to be higher, possibly to compensate for less efficient swallowing. Logistic regression with adjustment for age and disease severity showed that hypomimia correlated best with drooling. Linear regression with hypomimia as the dependent variable identified disease severity, dysphagia, and male sex as significant explanatory factors. Drooling in Parkinson's disease results from multiple risk factors, with hypomimia being the most prominent. When monitored, patients appear to compensate by increasing their swallowing frequency, much like the increased cadence that is used to compensate for stepping akinesia. These findings can provide a rationale for behavioral approaches to treat drooling.

Contains fulltext : 98113.pdf (Publisher’s version ) (Closed access) Motor problems in Prader-Willi syndrome (PWS) are presumably related to abnormal body composition and certain neuromuscular abnormalities. The authors reviewed the literature to evaluate the extent to which body composition is affected and gathered all findings on neuromuscular functioning in PWS. A systematic review was conducted in four databases (1956-2010). The methodological quality of each included article was evaluated. Thirty-eight papers were included: body composition (9 studies), neuromuscular functioning (7) and growth hormone (GH) effect studies (23). Increased fat mass and decreased lean body mass are characteristics of PWS. As a result, muscle mass is decreased by 25-37%, which might explain partly the weakness and hypotonia. However, there are also structural and functional muscle abnormalities, and cortical motor areas are hypo-excitable in PWS patients. Moreover, disuse as result of decreased activity in PWS could also contribute. GH treatment positively influences body composition, but does not normalize it. Training could prevent disuse and improves body composition. Therefore GH treatment and training will probably enhance one another.

Item does not contain fulltext This study evaluated the effectiveness of resistance training to preserve submaximal plantar flexor (PF) torque steadiness following 60 days of bed rest (BR). Twenty-two healthy male subjects underwent either BR only (CTR, n=8), or BR plus resistance training (RT, n=14). The magnitude of torque fluctuations during steady submaximal isometric PF contractions (20%, 40%, 60% and 80% of maximum) were assessed before and after BR. Across contraction intensities, torque fluctuations (coefficient of variation, CV) increased more (P

Background: Charcot-Marie-Tooth disease type 1A (CMT1A) is known as a demyelinating hereditary neuropathy. Secondary axonal dysfunction is the most important determinant of disease severity. In adult patients, clinical progression may be because of further axonal deterioration as was shown with compound muscle action potential (CMAP) amplitude reductions over time. The motor unit number estimation (MUNE) technique may be more accurate to determine the number of axons as it is not disturbed by the effect of reinnervation. The purpose of this study was to investigate the number and size of motor units in relation to age in patients and controls. Methods: In a cross-sectional design, we assessed arm and hand strength and performed electrophysiological examinations, including CMAP amplitudes and MUNE of the thenar muscles using high-density surface EMG in 69 adult patients with CMT1A and 55 age-matched healthy controls. Results: In patients, lower CMAP amplitudes and MUNE values were related to hand weakness. The CMAP amplitude and MUNE value of the thenar muscles were significantly lower in patients than in controls. CMAP amplitudes declined with age in controls, but not in patients. MUNE values declined with age in both patients and controls. Conclusions: The age-dependent decrease in the number of motor units was not significantly different between patients with CMT1A and controls, indicating that loss of motor units in adult patients is limited. © 2010 Radboud University Nijmegen Medical Centre. Journal compilation © 2010 EFNS.

Contains fulltext : 89651.pdf (Publisher’s version ) (Closed access) Sandhoff disease is a lipid-storage disorder caused by a defect in ganglioside metabolism. It is caused by a lack of functional N-acetyl-beta-d-glucosaminidase A and B due to mutations in the HEXB gene. Typical, early-onset Sandhoff disease presents before 9 months of age with progressive psychomotor retardation and early death. A late-onset form of Sandhoff disease is rare, and its symptoms are heterogeneous. As drug trials that aim to intervene in the disease mechanism are emerging, the recognition and identification of Sandhoff disease patients-particularly those with atypical phenotypes-are becoming more important. The authors describe six new late-onset Sandhoff cases demonstrating cerebellar ataxia or lower motor neuron (LMN) involvement combined with, mostly subclinical, neuropathy. Two different mutations were found: IVS 12-26 G/A and c.1514G-->A. In patients with either progressive cerebellar ataxia or LMN disease in the setting of a possibly recessive disorder, Sandhoff disease should be suspected, even when the onset age is over 45 years. 01 september 2010

Contains fulltext : 89303.pdf (Publisher’s version ) (Closed access) The Awaji Commission recently proposed a modification of the electrodiagnostic criteria for ALS. We assessed whether the Awaji recommendations improve the sensitivity of the early diagnosis of ALS. In a retrospective study we reviewed clinical and neurophysiological data for 213 patients who visited our motor neuron disease outpatient clinic between October 2006 and December 2008. Using the El Escorial criteria, 51 patients were diagnosed with definite or probable ALS, 14 with probable laboratory-supported ALS, and 28 with possible ALS. An alternative diagnosis was present in 120 patients. Applying the Awaji recommendations, 66 patients were diagnosed with either definite or probable ALS, and 27 with possible ALS. Of the 14 patients diagnosed with probable laboratory-supported ALS, eight switched to probable ALS and six to possible ALS using the Awaji recommendations; none of the patients with an ALS mimic was diagnosed with ALS according to the Awaji recommendations. In conclusion, the new criteria for ALS do not result in a loss of specificity and can potentially improve the sensitivity by 16%. However, this diagnostic improvement appears eliminated if patients with probable laboratory-supported ALS - due to UMN signs in one region - should be categorized as possible ALS. 01 december 2010

Contains fulltext : 89158.pdf (Publisher’s version ) (Closed access) In amyotrophic lateral sclerosis (ALS), progressive motor neuron loss causes severe weakness. Functional measurements tend to underestimate the underlying pathology because of collateral reinnervation. A more direct marker of lower motor neuron loss is of significant importance. We evaluated high-density motor unit number estimation (MUNE), as compared with the ALS Functional Rating Scale (ALSFRS) and maximal compound muscle action potential (CMAP) amplitude, for monitoring and classifying disease progression. MUNE showed good reproducibility (intraclass correlation coefficient = 0.86). MUNE showed a significantly greater decrease than the ALSFRS, the Medical Research Council (MRC) scale, and CMAP amplitude. Patients could be stratified into groups with rapidly or slowly progressive disease based on a decrement in MUNE at 4 months from baseline; ALSFRS score at 8 months was significantly lower in the rapidly progressive group. MUNE was sensitive to motor neuron loss early in the disease course when compared to other clinical measures. Stratification of patients based on a decrease in MUNE seems feasible. 01 augustus 2010

Ultrasonography can detect structural muscle changes caused by neuromuscular disease. Quantitative analysis is the preferred method to determine if ultrasound findings are within normal limits, but normative data are incomplete. The purpose of this study was to provide normative muscle ultrasonography data for muscle thickness and echo intensity for five different muscle groups in adults. Bilateral scans of the sternocleidomastoid, biceps brachii/brachialis, forearm flexor group, quadriceps femoris, and tibialis anterior were made in 95 volunteers, aged 17-90 years. Both muscle thickness and echo intensity showed gender differences and a muscle-specific non-linear correlation with age. The muscles of the upper extremities showed right-left differences. These data demonstrate the effect of age on muscle characteristics and provide normative values that can be used in clinical practice.

Item does not contain fulltext Pathological muscular hypertrophy results from either muscular or neurogenic damage. Rarely, it is caused by a congenital malformation consisting of a unilateral muscular hyperplasia of the upper extremity. We report on a young woman with an enlargement of the right upper extremity. Electromyography showed polyphasic, large motor unit potentials in the affected muscles. MRI and ultrasound assessment demonstrated diffuse enlargement of muscle mass without signs of edema. Muscle biopsy revealed sections with marked variations in fiber size with no signs of inflammation or marked loss of muscle fibers. Factors assumed to be important in the pathophysiology of this phenomenon are discussed.

Contains fulltext : 81084.pdf (Publisher’s version ) (Closed access) Marfan syndrome is a clinically and allelic heterogeneous, heritable connective tissue disorder with infrequently reported neuromuscular features. This study is the first to delineate these symptoms in a non-selected population. Neuromuscular involvement was evaluated in 10 Marfan patients through a standardized questionnaire, physical examination, nerve conduction study (NCS), needle electromyography (EMG), muscle ultrasound, laboratory investigation, and muscle biopsy. Existing neuroimages were screened for dural ectasia and spinal meningeal cysts. Twenty healthy controls with similar age distribution completed the questionnaire. The results showed that various neuromuscular symptoms occur more frequently in the patients. Four older patients reported muscle weakness, five patients had a mild-to-moderate reduction in vibration sense, and all older patients mentioned mild functional impairments. NCS showed axonal polyneuropathy in four and EMG myopathic and neurogenic changes in all patients. Increased echo intensity and atrophy on muscle ultrasound was found in more than half of the patients. Muscle biopsies obtained in two patients showed myopathic changes in the older, female patient. In conclusion, the majority of Marfan patients exhibited neuromuscular symptoms characterized as myopathy or polyneuropathy or both, and signs of lumbosacral radiculopathy, with symptoms being most pronounced in the older patients. Although meriting corroboration, these findings indicate a need to further the awareness of neuromuscular involvement in this population.

Contains fulltext : 81558.pdf (Publisher’s version ) (Closed access) Neuralgic amyotrophy is a painful, episodic peripheral nerve disorder localized to the brachial plexus. Sensory symptoms occur in 80% of the patients. We assessed the frequency of abnormalities in sensory nerve conduction studies of the lateral and medial antebrachial cutaneous, radial sensory, median sensory, and ulnar sensory nerves in 112 patients. Sensory nerve conduction studies showed abnormalities in

Contains fulltext : 70438.pdf (Publisher’s version ) (Closed access) Small surface motor unit potentials (S-MUPs) may have a negative influence on the variability of the motor unit number estimate (MUNE). According to published consensus criteria S-MUPs with a negative peak amplitude smaller than 10 muV should be omitted. The effect of omitting small S-MUPs on the MUNE was evaluated using a simulation model. The model incorporated a healthy and amyotrophic lateral sclerosis (ALS) distribution formed with real S-MUPs. Using a random drawing process the MUNE was calculated with and without small S-MUPs. In the healthy population 27% of all S-MUPs were small. MUNE determined without these S-MUPs was marginally less variable. However, MUNE values dropped about 24% at a sample size of 20. In ALS, only 12% of the total population of 130 S-MUPs were small. MUNE dropped about 12% without the small S-MUPs. By omitting small S-MUPs the differences between the healthy and ALS distributions become smaller. Therefore, incorporating small S-MUPs in the estimate is suggested.

Contains fulltext : 69483.pdf (Publisher’s version ) (Closed access) Fatigue is a multidimensional concept covering both physiological and psychological aspects. Chronic fatigue is a typical symptom of diseases such as cancer, multiple sclerosis (MS), Parkinson's disease (PD) and cerebrovascular disorders but is also presented by people in whom no defined somatic disease has been established. If certain criteria are met, chronic fatigue syndrome can be diagnosed. The 4-item Abbreviated Fatigue Questionnaire allows the extent of the experienced fatigue to be assessed with a high degree of reliability and validity. Physiological fatigue has been well defined and originates in both the peripheral and central nervous system. The condition can be assessed by combining force and surface-EMG measurements (including frequency analyses and muscle-fibre conduction estimations), twitch interpolation, magnetic stimulation of the motor cortex and analysis of changes in the readiness potential. Fatigue is a well-known phenomenon in both central and peripheral neurological disorders. Examples of the former conditions are multiple sclerosis, Parkinson's disease and stroke. Although it seems to be a universal symptom of many brain disorders, the unique characteristics of the concomitant fatigue also point to a specific relationship with several of these syndromes. As regards neuromuscular disorders, fatigue has been reported in patients with post-polio syndrome, myasthenia gravis, Guillain-Barre syndrome, facioscapulohumeral dystrophy, myotonic dystrophy and hereditary motor and sensory neuropathy type-I. More than 60% of all neuromuscular patients suffer from severe fatigue, a prevalence resembling that of patients with MS. Except for several rare myopathies with specific metabolic derangements leading to exercise-induced muscle fatigue, most studies have not identified a prominent peripheral cause for the fatigue in this population. In contrast, the central activation of the diseased neuromuscular system is generally found to be suboptimal. The reliability of the psychological and clinical neurophysiological assessment techniques available today allows a multidisciplinary approach to fatigue in neurological patients, which may contribute to the elucidation of the pathophysiological mechanisms of chronic fatigue, with the ultimate goal to develop tailored treatments for fatigue in neurological patients. The present report discusses the different manifestations of fatigue and the available tools to assess peripheral and central fatigue.

Contains fulltext : 70777.pdf (Publisher’s version ) (Closed access) Muscle ultrasound is a useful tool in the diagnosis of neuromuscular disorders, as these disorders result in muscle atrophy and intramuscular fibrosis and fatty infiltration, which can be visualized with ultrasound. Several prospective studies have reported high sensitivities and specificities in the detection of neuromuscular disorders. Although not investigated in large series of patients, different neuromuscular disorders tend to show specific changes on muscle ultrasound, which can be helpful in differential diagnosis. For example, Duchenne muscular dystrophy results in a severe, homogeneous increase of muscle echo intensity with normal muscle thickness, whereas spinal muscular atrophy shows an inhomogeneous increase of echo intensity with severe atrophy. A major advantage of muscle ultrasound, compared to other imaging techniques, is its ability to visualize muscle movements, such as muscle contractions and fasciculations. This study reviews the possibilities and limitations of ultrasound in muscle imaging and its value as a diagnostic tool in neuromuscular disorders.

Contains fulltext : 71197.pdf (Publisher’s version ) (Closed access) In this study we investigated a family with paramyotonia (PC) congenita caused by a Gly1306Val mutation in the voltage-gated sodium-channel gene SCN4A. A previous study showed that exposure to cold aggravates the muscle stiffness in patients with this mutation. However, the mechanism behind cold sensitivity and the sodium-channel defect remained unclear. In order to gain a better understanding of sarcolemmal propagation in these patients, we measured muscle-fiber conduction velocity (MFCV) invasively. We studied four PC patients and four healthy subjects at room temperature. After the muscle was cooled, MFCV was measured again in the two PC patients and four control subjects. MFCV was significantly lower in the PC patients at room temperature, compatible with dysfunctional sodium channels. After cooling, MFCV was significantly lower in both groups as compared with room temperature. The relative slowing was 1.4% per degrees C for PC patients and 1.5% per degrees C for healthy subjects. These results indicate that, in these PC patients, mutant and wild-type sodium channels respond equally to cold exposure. Thus, MFCV is abnormal in these patients, but the aggravation of muscle stiffness cannot be explained by an abnormal sarcolemmal response to cold.

Contains fulltext : 53011.pdf (Publisher’s version ) (Closed access) The primary goal of this study was to identify secondary functional changes in the peripheral motor units of the paretic upper extremity (UE) in patients with severe ischemic stroke and to determine how these changes develop during the first weeks after stroke. An inception cohort of 27 consecutive patients with an acute ischemic supratentorial stroke and an initial UE paralysis was compared with 10 healthy control subjects. The ulnar nerve was electrically stimulated proximal to the wrist and electromyographic recordings were obtained from the abductor digiti minimi muscle. Hemiparetic side mean values of the compound muscle action potential (CMAP) 1 and 3 weeks after stroke were compared with the nonparetic side and with CMAP values obtained from healthy control subjects. The mean CMAP amplitude in patients was significantly lower on the paretic side compared with the nonparetic side and with control subjects. Decrease in CMAP amplitude was observed in more than half of the stroke patients, sometimes as early as 4 days after stroke, and persisted in most cases. Whenever present, it was accompanied by absence of motor recovery at that specific time after stroke. Decreased CMAP amplitude in the abductor digiti minimi muscle can be seen already in the very acute phases after stroke unrelated to peripheral neuropathy, radiculopathy, or plexopathy, and it is accompanied by absence of UMN recovery. This knowledge is important for interpreting electrophysiological data in stroke patients.

Item does not contain fulltext Behaviour of motor unit potential (MUP) velocities in relation to (low) force and duration was investigated in biceps brachii muscle using a surface electrode array. Short static tests of 3.8 s (41 subjects) and prolonged dynamic tests (prolonged tests) of 4 min (30 subjects) were performed as position tasks, applying forces up to 20% of maximal voluntary contraction (MVC). Four variables, derived from the inter-peak latency technique, were used to describe changes in the surface electromyography signal: the mean muscle fibre conduction velocity (CV), the proportion between slow and fast MUPs expressed as the within-subject skewness of MUP velocities, the within-subject standard deviation of MUP velocities [SD-peak velocity (PV)], and the amount of MUPs per second (peak frequency=PF). In short static tests and the initial phase of prolonged tests, larger forces induced an increase of the CV and PF, accompanied with the shift of MUP velocities towards higher values, whereas the SD-PV did not change. During the first 1.5-2 min of the prolonged lower force levels tests (unloaded, and loaded 5 and 10% MVC) the CV and SD-PV slightly decreased and the MUP velocities shifted towards lower values; then the three variables stabilized. The PF values did not change in these tests. However, during the prolonged higher force (20% MVC) test, the CV decreased and MUP velocities shifted towards lower values without stabilization, while the SD-PV broadened and the PF decreased progressively. It is argued that these combined results reflect changes in both neural regulatory strategies and muscle membrane state.

Contains fulltext : 52159.pdf (Publisher’s version ) (Closed access) Fasciculation potentials (FPs) are observed in healthy individuals, but also in patients with neurogenic disorders. The exact site of origin and the clinical relevance in distinguishing, for example, amyotrophic lateral sclerosis (ALS) from other neurogenic diseases based on specific characteristics of the FPs is still a matter of debate and needs further exploration. This report describes the use of high-density surface EMG (HD-sEMG), with multiple electrodes in a compact grid to noninvasively record FPs. The technique provides both temporal and spatial information of fasciculations. Examples of the FPs of a patient diagnosed with definite ALS are presented. FPs are shown in different electrode montages and the unique spatial characteristics of different FPs are presented. During 30-second recordings, 137 FPs were detected that via a decomposition algorithm could be assigned to 11 different underlying sources. It is concluded that HD-sEMG, both because of its noninvasive character and the unique spatiotemporal information, is very suitable to examine fasciculations. It allows long stable recording times and provides quantitative information. This electrophysiologic tool is expected to expand the existing knowledge of FP properties.

To determine the level of ambulatory disability and the use of walking aids in well-ambulant Hereditary Motor and Sensory Neuropathy type I (HMSN I) patients, and to identify the related demographic, physical and psychological variables.Seventy-five well-ambulant HMSN I patients, aged 20-58 years, were measured in a cross-sectional assessment, addressing disability of ambulation and mobility (Sickness Impact Profile), demographics, muscle strength (Medical Research Council), use of walking aids, physical activity (actometer), fatigue (Checklist Individual Strength), and quality of life (EuroQoL).Seventy-two percent of the patients perceived a significant amount of ambulatory disability. These patients were less active, and more fatigued compared to patients without ambulatory disability, and healthy reference groups. The total patient sample showed marked distal paresis (mean MRC = 3.3), a high level of pain-discomfort (76%), but normal levels of employment (62.7%) and anxiety-depression (20%). Walking aids were used by 49% of the patients. These patients were older, less active, more fatigued, had less muscle strength, and perceived more disabilities of ambulation and mobility than non-users. Of the patients without walking aids, 41% perceived a significant amount of ambulatory disabilities.Ambulatory disability frequently occurred in well-ambulant HMSN I patients. The use of walking aids was not completely in accordance with the perceived ambulatory disability. Therefore prescription requires specific attention as well as complaints about pain and fatigue.

Contains fulltext : 51491.pdf (Publisher’s version ) (Closed access) OBJECTIVE: Fatigue has been described as a typical symptom of neurological diseases. It might be caused both by changes at the peripheral and at the central level. This study measured the level of experienced fatigue and physiological correlates of fatigue in three genetically defined neuromuscular disorders. METHODS: Sixty-five facioscapulohumeral dystrophy (FSHD), 79 classical myotonic dystrophy (DM), 73 hereditary motor and sensory neuropathy type I (HMSN) patients and 24 age-matched healthy controls made a 2-min sustained maximal voluntary contraction of the biceps brachii muscle. Experienced fatigue at the current moment was assessed with the abbreviated fatigue questionnaire just before the physiological measurement. Peripheral fatigue was quantified by comparing the amplitudes of an initial and a final stimulated force response during rest. Muscle fibre conduction velocity was determined from a 5-channel surface EMG recording in order to show peripheral changes during the contraction. Central aspects of fatigue were measured using superimposed electrical endplate stimulation. RESULTS: Patients showed an increased level of experienced fatigue. Total physiological and peripheral fatigue were smaller in patients compared to controls, and central fatigue was normal. The most interesting result of this study was the presence of a large central activation failure (CAF) in all groups of neuromuscular patients; they showed CAF values of 36-41% already directly at the start of sustained contraction, whereas the control group showed only 12%. CAF slightly correlated with the level of experienced fatigue just before the test. CONCLUSIONS: The cause of the large CAF in patients is unclear. Reduced concentration, motivation or effort can lead to lower central activation. In neuromuscular patients especially fear of physical activity or fear to damage the muscle or nerve tissue may contribute. Besides, also physiological feedback mechanisms or changes at the motocortical level may be a cause of reduced central activation. SIGNIFICANCE: For the clinician it is important to know that experienced fatigue is part of the clinical spectrum of neuromuscular patients. Besides, the weakness in these patients is aggravated by reduced central activation. Potentially, both problems could be subject of an intervention.

Contains fulltext : 52925.pdf (Publisher’s version ) (Closed access) Drooling is a well known problem in patients with Parkinson's disease (PD). The aim of this study was to investigate the severity and consequences of drooling in PD. A comprehensive drooling questionnaire was sent to 105 PD outpatients, who had volunteered drooling during a previous questionnaire (n = 216). Among 63 patients who responded and confirmed drooling, 27% experienced severe saliva loss. Social and emotional consequences were reported by 17% to 77% of patients, and significantly more often by those with severe drooling. We conclude that drooling is a frequent, disabling and apparently undertreated symptom of PD. History taking ought to be detailed and specific to understand the full impact of drooling for an individual patient. Therapeutic options should be evaluated more intensively.

Contains fulltext : 51859.pdf (Publisher’s version ) (Open Access) AIM AND METHODS: We prospectively investigated whether early diagnosis of amyotrophic lateral sclerosis (ALS) could be facilitated by demonstrating signs of denervation in a muscle of a clinical and electromyographical unaffected region. Muscle fibre conduction velocity (MFCV) was determined in 18 patients in whom the diagnosis ALS was considered but not established beyond a level of clinically possible ALS according to the revised El Escorial criteria. A muscle biopsy was obtained from the same muscle, to demonstrate neurogenic changes. The study followed the guidelines from the STARD initiative. RESULTS AND CONCLUSION: Results were analysed with respect to the final diagnosis. After a mean follow-up of 16 months, 9 patients developed probable or definite ALS. Sensitivity of abnormal MFCV for developing ALS was 89%. Muscle biopsy confirmed that denervation was the cause of abnormal MFCV. We concluded that MFCV can be used to detect denervation in muscles that show no clinical or electromyographical signs of lower motor neuron disease, and thus may contribute to early diagnosis of probable laboratory-supported ALS.

Item does not contain fulltext Non-dystrophic myotonic syndromes represent a heterogeneous group of clinically quite similar diseases sharing the feature of myotonia. These syndromes can be separated into chloride and sodium channelopathies, with gene-defects in chloride or sodium channel proteins of the sarcolemmal membrane. Myotonia has its basis in an electrical instability of the sarcolemmal membrane. In the present study we examine the discriminative power of the resulting myotonic discharges for these disorders. Needle electromyography was performed by an electromyographer blinded for genetic diagnosis in 66 non-dystrophic myotonia patients (32 chloride and 34 sodium channelopathy). Five muscles in each patient were examined. Individual trains of myotonic discharges were extracted and analyzed with respect to firing characteristics. Myotonic discharge characteristics in the rectus femoris muscle almost perfectly discriminated chloride from sodium channelopathy patients. The first interdischarge interval as a single variable was longer than 30 ms in all but one of the chloride channelopathy patients and shorter than 30 ms in all of the sodium channelopathy patients. This resulted in a detection rate of over 95%. Myotonic discharges of a single muscle can be used to better guide toward a molecular diagnosis in non-dystrophic myotonic syndromes.

Objective To determine the source of an abnormal pattern of latency shifts leading to falsely high jitters in single fibre electromyography (SFEMG). Methods We observed a sudden shortening of the latency to an individual single fibre spike component followed by a gradual return to baseline values during stimulation single fibre electromyography (SFEMG) of the facial muscle. The pattern could be reproduced in healthy controls. Results The sudden decrease in latency proved to follow an additional discharge of the muscle fibre, not due to the external stimulus. This additional discharge was identified as an F-response. Conclusions The mechanism is thought to be a higher muscle fibre conduction velocity resulting from a temporary increase in stimulus frequency, in the form of an extra impulse along the muscle fibre represented by the F-response. Significance The typical abnormal pattern should be recognised because it can falsely increase the mean jitter. We advice to increase the time base to 50 ms if this pattern is observed and to exclude the affected potentials from jitter measurements.

Contains fulltext : 51351.pdf (Publisher’s version ) (Closed access)

Contains fulltext : 50860.pdf (Publisher’s version ) (Open Access) OBJECTIVES: Fatigue is a common symptom experienced by patients with various neuromuscular disorders. The purpose of this study was to assess the influence of relatives on fatigue experienced by patients with various neuromuscular disorders. METHODS: In total, 106 close relatives of patients with facioscapulohumeral dystrophy (FSHD), adult-onset myotonic dystrophy (MD), and hereditary motor and sensory neuropathy type I (HMSN), completed the Checklist Individual Strength for themselves, and how they thought their relatives filled in this questionnaire. We compared the agreement between the two. The reaction of the relative to the fatigue and to the neuromuscular disorder of the patient was assessed by the Family Response Questionnaire. Marital dissatisfaction was also measured. The influence of the relative's response to the patients' fatigue and the relatives' fatigue on the fatigue of the patient was tested in linear regression models. RESULTS: In all 3 patient groups, the responses of the relatives to fatigue and disease were characterized by sympathetic-empathic responses. Low agreement existed between relatives and MD patients (r = 0.26) over the patients' level of fatigue, but higher agreement was found between relatives and FSHD (r = 0.67) and HMSN (r = 0.73) patients. The spouses of MD patients reported less marital satisfaction. The sympathetic-empathic responses of the relatives of FSHD and HMSN patients, and in FSHD also the fatigue experienced by the relative, contributed significantly to higher levels of fatigue experienced by the patients. CONCLUSION: The sympathetic-empathic responses of close relatives to the fatigue of the patient were related to the higher levels of fatigue experienced by FSHD and HMSN patients, but not MD patients.

Contains fulltext : 48457.pdf (Publisher’s version ) (Closed access) OBJECTIVE: To assess the prevalence of severe fatigue and its relation to functional impairment in daily life in patients with relatively common types of neuromuscular disorders. METHODS: 598 patients with a neuromuscular disease were studied (139 with facioscapulohumeral dystrophy, 322 with adult onset myotonic dystrophy, and 137 with hereditary motor and sensory neuropathy type I). Fatigue severity was assessed with Checklist Individual Strength (CIS-fatigue). Functional impairments in daily life were measured with the short form 36 item health questionnaire (SF-36). RESULTS: The three different neuromuscular patient groups were of similar age and sex. Severe experienced fatigue was reported by 61-74% of the patients. Severely fatigued patients had more problems with physical functioning, social functioning, mental health, bodily pain, and general health perception. There were some differences between the three disorders in the effects of fatigue. CONCLUSIONS: Severe fatigue is reported by the majority of patients with relatively common types of neuromuscular disorders. Because experienced fatigue severity is associated with the severity of various functional impairments in daily life, it is a clinically and socially relevant problem in this group of patients.

New surface electromyogram (SEMG) techniques offer the potential to advance knowledge of healthy and diseased motor units. Conduction velocity (CV) estimates, obtained from indwelling electrodes, may provide diagnostic information, but the standard method of CV estimation from SEMG may be of only limited value. We developed a motor unit (MU) tracking algorithm to extract motor unit conduction velocity (MUCV) and motor unit action potential (MUAP) amplitude estimates from SEMG. The technique is designed to provide a noninvasive means of accessing fatigue and recruitment behavior of individual MUs. We have applied this MU tracking algorithm to SEMG data recorded during isometric fatiguing contractions of the tibialis anterior (TA) muscle in nine healthy subjects, at 30%-40% maximum voluntary contraction (MVC). The results reveal that MUCVs and MUAP amplitudes of individual MUs can be estimated and tracked across time. Time-related changes in the MU population may also be monitored. Thus, the SEMG technique employed provides insight into the behavior of the underlying muscle at the MU level by noninvasive means. © 2005 Wiley Periodicals, Inc.

Contains fulltext : 48870.pdf (Publisher’s version ) (Closed access) High-density multichannel electromyography (EMG) recordings add spatial information to the temporal information content of the surface EMG (sEMG) signal. This study explores the potential value of such multichannel information at a single motor unit level, in particular for the improvement of motor unit number estimation (MUNE) techniques. It is shown that multichannel recordings make it easier to distinguish motor unit action potentials (MUAPs) and that MUAP combinations can be better resolved. Furthermore, the spatiotemporal information allows a quantitative assessment of the representativity of the mean of the recorded MUAPs in relation to the maximum CMAP, i.e., for the muscle as a whole. In general, this is practically impossible on the basis of temporal information alone. For these reasons, we expect that high-density sEMG has the potential to address several methodological limitations of single channel surface EMG recordings. This is specifically illustrated in this study for one of the MUNE techniques in use, the F-response method.

Item does not contain fulltext In the study of fatigue, several methods have been used to calculate the development of central activation failure (CAF) and peripheral fatigue (PF) in the course of a sustained maximal voluntary contraction (MVC). This paper presents a model that enables simultaneous determination of CAF and PF during sustained MVC by using only force registration and superimposed electrical stimulation. In the model, we explicitly use the assumption, which is virtually always made implicitly in earlier studies, that a constant relative fraction of maximal possible force is activated by the electrical stimulation. That fraction can be determined at the start and at the end of a sustained MVC. The model shows that in the course of a sustained MVC, CAF can be calculated by merely using 1) this fraction, 2) the amplitudes of the superimposed force responses to stimulation, and 3) the course of voluntary force. After CAF quantification, the development of PF during MVC becomes available as well. The present study first examines the model assumption with data of sustained MVCs of variable durations on six healthy subjects. Subsequently, it shows CAF values in a group of 27 healthy subjects determined with both the model and a method of linear interpolation for PF estimation. Model-based CAF values were significantly higher during, but not at the start and at the end of, a 2-min sustained MVC. Next to a well-justified CAF determination, the model has the advantage of simultaneously quantifying PF, which was not possible with the previous methods.

Contains fulltext : 48137.pdf (Publisher’s version ) (Closed access) The statistical method of motor unit number estimation (MUNE) uses the natural stochastic variation in a muscle's compound response to electrical stimulation to obtain an estimate of the number of recruitable motor units. The current method assumes that this variation follows a Poisson distribution. We present an alternative that instead assumes a binomial distribution. Results of computer simulations and of a pilot study on 19 healthy subjects showed that the binomial MUNE values are considerably higher than those of the Poisson method, and in better agreement with the results of other MUNE techniques. In addition, simulation results predict that the performance in patients with severe motor unit loss will be better for the binomial than Poisson method. The adapted method remains closer to physiology, because it can accommodate the increase in activation probability that results from rising stimulus intensity. It does not need recording windows as used with the Poisson method, and is therefore less user-dependent and more objective and quicker in its operation. For these reasons, we believe that the proposed modifications may lead to significant improvements in the statistical MUNE technique.