Quality Control of Motor Unit Number Index (MUNIX) Measurements in 6 Muscles in a Single-Subject "Round-Robin" Setup

Background

Motor Unit Number Index (MUNIX) is a neurophysiological measure that provides an index of the number of lower motor neurons in a muscle. Its performance across centres in healthy subjects and patients with Amyotrophic Lateral Sclerosis (ALS) has been established, but inter-rater variability between multiple raters in one single subject has not been investigated.

Objective

To assess reliability in a set of 6 muscles in a single subject among 12 examiners (6 experienced with MUNIX, 6 less experienced) and to determine variables associated with variability of measurements.

Methods

Twelve raters applied MUNIX in six different muscles (abductor pollicis brevis (APB), abductor digiti minimi (ADM), biceps brachii (BB), tibialis anterior (TA), extensor dig. brevis (EDB), abductor hallucis (AH)) twice in one single volunteer on consecutive days. All raters visited at least one training course prior to measurements. Intra- and inter-rater variability as determined by the coefficient of variation (COV) between different raters and their levels of experience with MUNIX were compared.

Results

Mean intra-rater COV of MUNIX was 14.0% (±6.4) ranging from 5.8 (APB) to 30.3% (EDB). Mean inter-rater COV was 18.1 (±5.4) ranging from 8.0 (BB) to 31.7 (AH). No significant differences of variability between experienced and less experienced raters were detected.

Conclusion

We provide evidence that quality control for neurophysiological methods can be performed with similar standards as in laboratory medicine. Intra- and inter-rater variability of MUNIX is muscle-dependent and mainly below 20%. Experienced neurophysiologists can easily adopt MUNIX and adequate teaching ensures reliable utilization of this method.

Instruments for the evaluation of motor abilities for children with severe multiple disabilities: A systematic review of the literature

Based on a systematic review, psychometric characteristics of currently available instruments on motor abilities of children with disabilities were evaluated, with the aim to identify candidates for use in children with severe multiple (intellectual and motor) disabilities. In addition, motor abilities are essential for independent functioning, but are severely compromised in these children. The methodological quality of all studies was evaluated with the Consensus Based Standards for the Selection of Health Status Measurement Instruments (COSMIN) Checklist; overall levels of evidence per instrument were based on the Cochrane Back Review Group strategy. As a result, 18 studies with a total of eight instruments, developed for children with cerebral palsy (CLA, GMFM-88 and LE85), spinal muscular atrophy (MHFMS), neuromuscular diseases (MFM), disabilities 0-6 years (VAB, WeeFIM), and one developed specifically for children with severe multiple disabilities (TDMMT) were found. Strong levels of evidence were found for construct validity of LE85 and MFM and for responsiveness of WeeFIM, but reliability studies of these instruments had a limited methodological quality. Up to now studies of the TDMMT resulted in limited and unknown evidence for structural validity due to the poor methodological quality of reliability studies. In a next step, the clinical suitability of the instruments for children with severe multiple disabilities will be evaluate.

[The threat of snake and scorpion venoms]

Venoms of snakes and scorpions pose a significant threat to the health and life of humans. The speed and range of their actions causes damage of the organ responsible for the maintenance of vital signs. Venomous snake venoms cause blood clotting disorders, tissue necrosis and hemolysis, and the release of a number of proinflammatory cytokines and impair antibody synthesis. Availability of antitoxins is limited and in the most cases supportive treatment is recommended. In turn, the venom of scorpions beside intestinal symptoms cause significant impairment of neuromuscular conduction, causing severe respiratory disorders. Action venom poses a particular threat to sensitive patients. The degree of threat to life caused by the venom of snakes and scorpions authorizes the treatment of these substances as a potential biological weapon.

Single-Channel EMG Classification With Ensemble-Empirical-Mode-Decomposition-Based ICA for Diagnosing Neuromuscular Disorders

An accurate and computationally efficient quantitative analysis of electromyography (EMG) signals plays an inevitable role in the diagnosis of neuromuscular disorders, prosthesis, and several related applications. Since it is often the case that the measured signals are the mixtures of electric potentials that emanate from surrounding muscles (sources), many EMG signal processing approaches rely on linear source separation techniques such as the independent component analysis (ICA). Nevertheless, naive implementations of ICA algorithms do not comply with the task of extracting the underlying sources from a single-channel EMG measurement. In this respect, the present work focuses on a classification method for neuromuscular disorders that deals with the data recorded using a single-channel EMG sensor. The ensemble empirical mode decomposition algorithm decomposes the single-channel EMG signal into a set of noise-canceled intrinsic mode functions, which in turn are separated by the FastICA algorithm. A reduced set of five time domain features extracted from the separated components are classified using the linear discriminant analysis, and the classification results are fine-tuned with a majority voting scheme. The performance of the proposed method has been validated with a clinical EMG database, which reports a higher classification accuracy (98%). The outcome of this study encourages possible extension of this approach to real settings to assist the clinicians in making correct diagnosis of neuromuscular disorders.

Neuromuscular Scoliosis: Current Concepts

Scoliosis is a common deformity in neuromuscular disorders. This spinal deformity usually presents at an early age, rapidly progresses during growth, and continues to progress even after skeletal maturity. Neuromuscular scoliosis classically involves the entire thoracolumbar spine, often extending to the pelvis and causing pelvic obliquity. Physical examination can be challenging, but it is important to assess the flexibility of the spinal curve and associated joint contractures. Upright anteroposterior and lateral radiographs are the preferred imaging. When formulating a treatment plan, it is important to take into account not only the degree of curvature, but also each patient's needs and quality of life, the potentially high perioperative complication rates, and the natural history of the underlying neuromuscular disorder. Different neuromuscular conditions behave differently and should therefore be treated differently. With the exception of steroids for Duchenne muscular dystrophy, bracing remains the only reliable nonoperative intervention available. Preoperative optimization of medical comorbidities is crucial given the relatively high complication rate. Posterior segmental instrumentation has revolutionized the surgical management of neuromuscular scoliosis and is the most commonly used technique today. Despite reported improvement in postoperative quality of life, there are several limitations with currently used outcome measures that prevent a well-informed discussion on the outcomes after surgery.

Early stages of building a rare disease registry, methods and 2010 data from the Belgian Neuromuscular Disease Registry (BNMDR)

The Belgian Neuromuscular Disease Registry, commissioned in 2008, aims to collect data to improve knowledge on neuromuscular diseases and enhance quality health services for neuromuscular disease patients. This paper presents a clear outline of the strategy to launch a global national registry. All patients diagnosed with one of the predefined 62 neuromuscular disease groups and living in Belgium may be included in the yearly updated Registry. Basic core data is harvested through a newly designed web application by the six accredited neuromuscular reference centres. In 2010, 3,424 patients with a neuromuscular disorder were registered. The most prevalent disease group in the Registry is Hereditary Motor and Sensory Neuropathy, as similarly stated by other studies, albeit the prevalence in Belgium is five times lower: 6.5 per 100,000 in the north of Belgium, versus 17.0-41.0 per 100,000 in other areas of Europe. Very few patients were captured in the south of the country. With the aim to collect valuable epidemiological data, the registry targets to gather high quality data, that the sample to be representative of the population and that it be complete. The past 5 years of building the registry have improved its quality, albeit the consistent gap in data from the south of the country prevails, influencing the estimated prevalence of these diseases. To this day, the true burden of neuromuscular diseases in Belgium is not known but actions have been undertaken to address these issues.

Neuromuscular comorbidity, heart failure, and atrial fibrillation as prognostic factors in left ventricular hypertrabeculation/noncompaction

BACKGROUND

There is some controversy concerning the prognosis of patients with left ventricular hypertrabeculation/noncompaction (LVHT). LVHT is frequently associated with neuromuscular disorders (NMDs). The aim of this study was to assess cardiac and neurological findings as predictors of mortality in patients with LVHT.

PATIENTS AND METHODS

The study included patients with LVHT diagnosed between June 1995 and January 2014 in one echocardiographic laboratory. They underwent a baseline cardiologic examination and were invited for a neurological examination. Between January and February 2014, their survival status was assessed.

RESULTS

LVHT was diagnosed in 220 patients (68 female, aged 52 ± 17 years) with a prevalence of 0.35 %/year. During a follow-up of 72 ± 61 months, 65 patients died. The mortality was 5 %/year. A neurological investigation was performed on 173 patients (79 %) and revealed specific NMDs in 31 (14 %), NMD of unknown etiology in 103 (47 %), and normal findings in 39 (18 %) patients. In multivariate analysis, the predictors of mortality were increased age (p = 0.0001), presence of a specific NMD (p = 0.0062) or NMD of unknown etiology (p = 0.0062), heart failure NYHA III (p = 0.0396), atrial fibrillation (p = 0.0022), and sinus tachycardia (p = 0.0395).

CONCLUSIONS

LVHT patients should undergo systematic neurological examinations. Whether an optimal therapy of heart failure and atrial fibrillation will improve the prognosis of LVHT patients needs to be addressed in further studies.

Origin, Incidence, and Management of Nongynecologic Pelvic Masses Seen on Cross-sectional Imaging

OBJECTIVE

To characterize the origin of nongynecologic pelvic masses.

STUDY DESIGN

Using a radiology database, women who underwent transvaginal ultrasound, CT scan, or MRI for the indication of pelvic mass or pelvic fullness were identified. Demographic information, radiologic data, and outcomes were reviewed.

RESULTS

A total of 450 women underwent imaging for the above indications been 2002 and 2012. Of those women, 347 had at least 1 pelvic mass; 3 women had both gynecologic and nongynecologic masses, and 13 women had 2 gynecologic masses. Forty women (12%) had nongynecologic pathology. Of the nongynecologic masses 13 were gastrointestinal in origin, 9 were urologic, and 9 were neuromuscular. Other etiologies included metastatic cancers, iatrogenic masses, and hematologic masses. Seventy-four women had malignant pathology (21%): 17/40 (43%) of nongynecologic pelvic masses and 57/320 (18%) of gynecologic masses (p < 0.05).

CONCLUSION

Compared to pelvic masses of gynecologic origin, nongynecologic pelvic masses are more likely to be malignant.

Proper Performance and Interpretation of Electrodiagnostic Studies. [Corrected]

The AANEM strongly recommends that EDX procedures be performed by physicians with comprehensive knowledge of neurological and musculoskeletal disorders to assure accurate interpretation and diagnosis. Individuals without a medical education in neuromuscular disorders and without special training in EDX procedures typically are not qualified to interpret the waveforms generated by NCSs and needle EMGs or to correlate the findings with other clinical information to reach a diagnosis. It is also the AANEM's position that the same physician should directly supervise and interpret the NCSs including those performed by an EDX technician. The AANEM believes that interpreting NCS without performing a focused history and physical and having oversight over the design and performance is inappropriate. Nerve conduction studies performed independent of needle EMG studies may only provide a portion of the information needed to diagnose muscle, nerve root, and most nerve disorders. For this reason, it is the position of the AANEM that, except in unique situations, NCSs and needle EMG should be performed together in a study design determined by a trained neuromuscular physician. There are common diagnoses that depend on performing a needle EMG and combining the needle EMG data with the NCS data. Needle EMG studies are a necessary part of the evaluation in the diagnosis of myopathy, radiculopathy, plexopathy, disorders of the motor neuron, peripheral neuropathies and most disorders of the individual peripheral motor nerves. When the NCS is used on its own without integrating needle EMG findings or when an individual relies solely on a review of NCS data, the results can often be misleading, and important diagnoses will likely be missed. Patients may thus be subjected to incorrect, unnecessary, and potentially harmful treatment interventions. The AANEM is concerned that utilizing only NCSs to make health care decisions provides incomplete diagnostic information, leading to inadequate or inappropriate therapy for some patients and may increase health care costs.

Ophthalmoplegia in congenital neuromuscular disease with uniform type 1 fiber

Congenital neuromuscular disease with uniform type 1 fiber (CNMDU1) is a rare type of congenital myopathy. It is characterized by early onset of symptoms, mild proximal muscle weakness, hyporeflexia or areflexia, normal serum creatine kinase (CK) levels and myopathic electromyography finding, uniform type 1 fibers, and nonprogression. We report a 2-year-old boy who presented with congenital hypotonia, breathing and feeding difficulty, myopathic facies, proximal muscle weakness, ptosis, total external ophthalmoplegia and delayed motor developmental milestones. Normal serum muscle enzyme and short duration of motor unit potentials on electromyography were noted. Muscle biopsy showed uniformity of type 1 fibers (greater than 99%) and moderate variation in fiber size without specific structural abnormality. Total external ophthalmoplegia may be one of the important clinical manifestations of CNMDU1. It is important to recognize this disorder because it is nonprogressive in nature.

Who presents to our electroneurophysiology laboratory?

OBJECTIVE

To determine the distribution rate of Electroneuromyography diagnosis and correspondence between the preliminary diagnosis and final outcome.

METHODS

The retrospective study was conducted at the Department of Neurology, Harran University, Sanliurfa, Turkey, and comprised record of patients diagnosed with Electroneuromyography during a 24-month period from April 2011 to April 2013. SPSS 11.5 was used for data analysis.

RESULTS

Of the 4,230 cases reviewed, 1,946 (46%) showed normal Electroneuromyography findings despite pathological Electroneuromyography findings in 2,284(54%) cases. The most common diagnosis was carpal tunnel syndrome in 721(17%) patients, followed by polyneuropathy 312(7.4%), peripheral nerve injury 238(5.6%), brachial plexus lesion 180(4.3%), myopathy 114(2.7%), lumbar radiculopathy 108(2.6%), poliomyelitis 62(1.5%) and injection neuropathy 62(1.5%).

CONCLUSIONS

Off-label use of Electroneuromyography may be reduced by using electroneurophysiological laboratory rotation as well as adequate and comprehensive clinical evaluation of patients.

Unsupervised discrimination of motor unit action potentials using spectrograms

Single motor unit activity study is a major research interest because changes of MUAP morphology, MU activation, and MU recruitment provide the most informative part in diagnosis and treatment of neuromuscular disorders. Intramuscular recordings often provide a more than one motor unit activities, thus MUAP discrimination is a crucial task to study single unit activities. Most neurology laboratories worldwide still need specialists who spend hours to classify MUAPs. In this study, we present a new real-time unsupervised method for MUAP discrimination. After automatically detect MUAPs, we extract features of spectrogram images from the wavelet coefficients of MUAPs. Unlike benchmark methods, we do not calculate Euclidean distances which assumes a spherical distribution of data. Instead, we measure correlation between spectrogram images. Then MUAPs are automatically discriminated without any prior knowledge of the number of clusters as in previous works. MUAP were detected on a real data set with a precision PPV of 94% (tolerance of 2 ms). We obtained a similar result in MUAP classification to the reference. The difference in percentages of MU proportions between our method and the reference were 3% for MU1, 0.4% for MU2, and 12% for MU3. In contrast, F1-score for MU3 reached the highest level at 91% (PPV at the highest of 96.64% as well).

Recognition and management of motor delay and muscle weakness in children

Diagnosis of neuromuscular disorders in young children is often delayed for years after symptoms emerge, resulting in missed opportunities for therapy and genetic counseling. Identification of the weak child begins with careful attention to caregiver concerns and developmental surveillance at well-child visits. Family and medical histories can differentiate inherited from acquired causes of weakness. Physical examination should include observation of ageappropriate motor skills such as pull-to-sit, sitting, rising to stand, and walking/running. Serum creatine kinase levels should always be measured in children exhibiting neuromuscular weakness. Referrals to early intervention programs should not be postponed pending definitive diagnosis. If motor delay does not improve with early intervention, referral to a pediatric neurologist for diagnostic assessment is recommended. Tongue fasciculations, loss of motor milestones, or creatine kinase level greater than three times the normal limit should prompt immediate neurology referral. Once a neuromuscular disorder is diagnosed, the primary care clinician can help the family navigate subspecialty visits and consultations, advocate for services in the school and home, and help them cope with the emotional stresses of caring for a child with special needs.

Critical illness associated neuromuscular disorders -- keep them in mind

Neuromuscular disorders complicating sepsis and critical illness are not new and scarce phenomena yet they receive little attention in daily clinical practice. Critical illness polyneuropathy and myopathy affect nearly half of the patients with sepsis. The difficult weaning from the ventilator, the prolonged intensive care unit and hospital stay, the larger complication and mortality rate these disorders predispose to, put a large burden on the patient and the health care system. The aim of this review is to give an insight into the pathophysiological background, diagnostic possibilities and potential preventive and therapeutic measures in connection with these disorders to draw attention to their significance and underline the importance of preventive approach.

The value of cough peak flow in the assessment of cough efficacy in neuromuscular patients. A cross sectional study

BACKGROUND

Cough efficacy assessment is of clinical relevance in neuromuscular patients. Tests of varying complexity and invasiveness, such as cough peak flow (CPF), maximal expiratory pressure (PEmax) and gastric pressure during cough (Cough Pgas) are routinely available.

AIM

To assess the value of CPF, PEmax and Cough Pgas in the detection of ineffective cough in patients suffering from neuromuscular diseases.

DESIGN

Prospective observational study.

SETTING

Outpatient laboratory for respiratory muscle function assessment.

POPULATION

Forty-nine patients with neuromuscular diseases (25 F, age 50 ± 15 years).

METHODS

Each patient performed spirometry, CPF, PEmax, Cough Pgas and maximal inspiratory pressure (PImax). Normal values for each test were determined from published and in-house lab data.

RESULTS

In all patients, vital capacity ranged from 46 to 119% of pred. Twenty seven percent of patients resulted under the lower normal limit of CPF and this percentage was significantly lower as compared to that of PEmax and Cough Pgas (51% and 53% respectively, P=0.013). Combining all three tests, the percentage of patients resulting below normal was 22% (P=0.638, as compared to CPF results alone). Additionally, CPF correlated significantly with PImax, PEmax, and Cough Pgas (P<0.01 for each correlation) and by multiple regression analysis PImax and PEmax contributed 65% of CPF variance.

CONCLUSION

Our study shows that in neuromuscular patients, PEmax and Cough Pgas values may overdiagnose an ineffective cough. CPF, a non invasive and easy to perform test, is a global measure of voluntary cough. CLINICAL REHABILITATION SETTING:CPF may be relevant in the routine evaluation of patients with neuromuscular diseases, both in research and in rehabilitation settings.

Detecting within- and between-day manifestations of neuromuscular fatigue at work: an exploratory study

Cumulative neuromuscular fatigue may result from exposure to physically demanding work, such as repetitive and/or sustained work with insufficient recovery. The aims of this exploratory study were to develop a battery of field usable fatigue measures and to document hand/arm fatigue in physically demanding work over multiple workdays and after a weekend break. Sixteen plumbers were observed for five days and measures of handgrip force, variability, tremor and discomfort were obtained pre-, mid- and post-shift. This exploratory study demonstrated increasing fatigue of the hand/arm over the day and persistent fatigue from Tuesday to Friday, and that a number of the measures did not return to baseline values following a weekend break. The findings provide preliminary evidence of cumulative fatigue in residential plumbing and insight into neuromuscular fatigue measurement. However, further work is needed to develop and refine a set of fatigue measures to detect neuromuscular fatigue at the workplace.

PRACTITIONER SUMMARY

Cumulative fatigue has been linked to long-term health outcomes, including work-related musculoskeletal disorders. This paper presents findings from a physically demanding job (i.e. plumbing) revealing persistent fatigue over the work shift(s) and insufficient recovery after a weekend break, and provides insight into fatigue measurement at the workplace.

Consistency between referral diagnosis and post-ENMG diagnosis in children

OBJECTIVE

To evaluate the degree of consistency between the referral diagnosis and that based on electroneuromyography.

METHODS

The retrospective study was conducted at the Paediatric Neurology Laboratory of Mersin University School of Medicine, Turkey, and comprised all electroneuromyographies carried out between January 2005 and December 2010. Demographic data, referral diagnosis and post-procedure diagnosis were recorded for each patient, and were classified into groups. Consistency between the two groups was compared using SPSS 13.

RESULTS

Of the total 294 patients, polyneuropathy was the reason for referral in 104 (35.4%), peripheral nerve injury in 54 (18.4%), brachial plexus injury in 52 (17.7%), myopathy in 52 (17.7%), hypotonia in 23 (7.8%), and facial paralysis in 9 (3.0%) patients. There was consistency between the two diagnoses in 179 (60.9%) patients.

CONCLUSION

Electroneuromyography is an uneasy, painful and stressfull procedure for children, and, therefore, it should be recommended only in cases where the result may be beneficial in the diagnosis treatment and follow-up of a patient.