Motor Unit Number Estimation Method Research Articles

Value of MUNE versus compound muscle action potential in assessing motor unit loss in patients with carpal tunnel syndrome

BackgroundThe most prevalent nerve entrapment disorder, known as carpal tunnel syndrome (CTS), is brought on by wrist-based median nerve compression. Focal demyelination progresses to axonal dysfunction as the condition worsens. In order to detect motor unit (MU) loos, this study compares two motor unit number estimation (MUNE) techniques with compound muscle action potential (CMAP) amplitude. The CMAP amplitude and MUNE of the median nerve in 137 hands of 70 neurophysiologically approved CTS patients, aged 40.27 ± 10.06 years were examined. Another 90 hands from 56 healthy volunteers who are age- and gender-matched serve the control group.ResultsIn contrast to 192.5 and 248.5 in controls, the median nerve values of incremental and adapted multipoint stimulation (aMPS) MUNE in CTS patients were, respectively, 111 and 133 (p < 0.0001). Patients with severe CTS compared to those with mild CTS using both methods had significantly lower MUNE. MUNE values are the same regardless of gender or hand dominance. In comparison to MUNE methods (cutoff values of 106.5 and 203, respectively), CMAP amplitude had a sensitivity and specificity of more than 60% in detecting MU loss (cutoff value of 6.85 mV). The CTS grading had no effect on the CMAP amplitude. MUNE values had positive with CMAP amplitude and negative with CTS grading and Phalen test positivity.ConclusionsWhen identifying motor nerve involvement in CTS patients, the MUNE technique is more accurate than a standard motor nerve conduction study (NCS). It was emphasized that MUNE evaluation in determining MU loss in the early stages of CTS may be helpful in diagnosis and treatment. There was no correlation between handedness and the number of MUs as determined by MUNE techniques. Both methods almost equally identify MU loss and have the same sensitivity and specificity.

Subclinical motor involvement in non-systemic vasculitic neuropathy determined by the motor unit number estimation method MScanFit.

Non-systemic vasculitic neuropathy (NSVN) is characterized by a predominant lower-limb involvement in many patients. Motor unit changes in upper extremity muscles have not been investigated in this subgroup, but might be of interest to improve the understanding of the multifocal nature of the disease and counseling of patients on potential future symptoms. We aimed to investigate subclinical motor involvement in upper extremity muscles of patients with lower-limb predominant NSVN using the new motor unit number estimation (MUNE) method MScanFit. In this single center cross-sectional study, 14 patients with biopsy-proven NSVN, with no clinical signs of upper extremity motor involvement, were investigated and compared to 14 age-matched healthy controls. All participants were assessed clinically and by the MUNE method MScanFit to the abductor pollicis brevis muscle. The number of motor units and peak CMAP-amplitudes were significantly reduced in patients with NSVN (p=0.003; p=0.004). Absolute median motor unit amplitudes and CMAP-discontinuities were not significantly different (p=0.246; p=0.1). CMAP-discontinuities were not significantly correlated with motor unit loss (p=0.15, Rho=0.4). The number of motor units did not correlate with clinical scores (p=0.77, Rho 0.082). Both MUNE and CMAP-amplitudes showed motor involvement in upper extremity muscles in lower-limb predominant NSVN. Overall, there was no evidence of significant reinnervation. Investigations of the abductor pollicis brevis muscle did not correlate with the overall functional disability of the patients.

Feasibility and reliability of MScanFit motor unit number estimation in peroneus longus muscle.

Motor unit number estimation (MUNE) methods may be valuable to detect motor involvement earlier than compound muscle action potential (CMAP) amplitude. The most recent MUNE method, MScanFit, has been shown to have advantages compared with previously described methods. However, MScanFit has only been applied in a few lower extremity muscles. In this study we examined the feasibility and reliability of MScanFit in peroneus longus muscle. Twenty healthy controls (16 males and 4 females; mean age, 36.05 ± 2.58 years) were examined twice within a 1- to 2-week interval. Fibular nerve was stimulated at the knee and CMAP scans were recorded from peroneus longus muscle. From this, MScanFit MUNE and size parameters were calculated, as was the CMAP amplitude. The reliability was examined using coefficient of variation (CV) and intraclass correlation coefficient (ICC). MUNE was correlated with CMAP amplitude using linear regression analysis. The CV between sessions was higher for CMAP amplitude (11.63 ± 1.88%) than MScanFit MUNE (3.13 ± 0.78%). Among the size parameters, mean unit amplitude (μV) showed the lowest CV (11.46 ± 1.77%). Using ICC, CMAP amplitude exhibited good reliability (0.787), whereas that of MScanFit MUNE was excellent (0.902). Reliability was good for all size parameters. There was no significant correlation between MScanFit MUNE and CMAP amplitude (R=0.25, P > .05). MScanFit MUNE is feasible in the peroneus longus muscle, with high test-retest reliability in healthy subjects. Studies in patients are needed to examine the sensitivity of this muscle in disease.

Assessing inter-rater reproducibility in MScanFit MUNE in a 6-subject, 12-rater “Round Robin” setup

ObjectiveTo assess the inter-rater reliability of MScanFit MUNE using a “Round Robin” research design. MethodsTwelve raters from different centres examined six healthy study participants over two days. Median, ulnar and common peroneal nerves were stimulated, and compound muscle action potential (CMAP)-scans were recorded from abductor pollicis brevis (APB), abductor digiti minimi (ADM) and anterior tibial (TA) muscles respectively. From this we calculated the Motor Unit Number Estimation (MUNE) and “A50”, a motor unit size parameter. As statistical analysis we used the measures Limits of Agreement (LOA) and Coefficient of Variation (COV). Study participants scored their perception of pain from the examinations on a rating scale from 0 (no pain) to 10 (unbearable pain). ResultsBefore this study, 41.6% of the raters had performed MScanFit less than five times. The mean MUNE-values were: 99.6 (APB), 131.4 (ADM) and 126.2 (TA), with LOA: 19.5 (APB), 29.8 (ADM) and 20.7 (TA), and COV: 13.4 (APB), 6.3 (ADM) and 5.6 (TA). MUNE-values correlated to CMAP max amplitudes (R2-values were: 0.463 (APB) (p<0.001), 0.421 (ADM) (p<0.001) and 0.645 (TA) (p<0.001)). The average perception of pain was 4. DiscussionMScanFit indicates a high level of inter-rater reliability, even with only limited rater experience and is overall reasonably well tolerated by patients. These results may indicate MScanFit as a reliable MUNE method with potential as a biomarker in drug trials.

Fifty Years of Motor Unit Number Estimation.

The objective was to use bibliometric analysis to create an infographic of motor unit number estimation methods over the past 50 years. The original method was published in 1971, but secondary and tertiary waves of research using alternative methods occurred in the early 2000s and a decade later. A metric of influence was used to determine if different methods had clear peaks of use over the past 50 years. While the original method continues to register influence, the MUNIX method introduced in 2004 stands out as the most influential method to estimate the innervation status of skeletal muscles.

Motor neurons loss in Parkinson Disease: An electrophysiological study (MUNE)

The aim of this study was to evaluate the involvement of a peripheral motor neuron in Parkinson Disease (PD) using the motor unit number estimation (MUNE) method, which reflects motor unit loss in motor neuron diseases. Multipoint incremental MUNE method was calculated in abductor pollicis brevis (APB) and abductor digiti minimi (ADM) in forty one (41) patients with PD and forty five (45) healthy volunteers. From the analysis, the MUNE of APB was lower in PD than in the control group, especially in the sub-group aged 60 years or older. MUNE was negatively correlated with the age of patientsfor APB, but not with the duration of the disease and advancement of PD. The loss of motor units in sporadic Parkinson's disease revealed by multipoint incremental MUNE method is considered a sign of lower motor neuron involvement, however, loss of motor neurons is slight and does not manifest equally in all muscles . Thus, the results from this experiment should be treated with concern, as it could be a landmark for further experiments.

Motor unit number estimation in adult patients with spinal muscular atrophy treated with nusinersen.

The aim was to assess the organization and short-term changes of motor units in adult patients with spinal muscular atrophy (SMA) treated with nusinersen. In this single-centre cross-sectional and longitudinal study 15 adult patients with SMA type 3 were assessed and compared to 15 age-matched healthy controls and nine patients with amyotrophic lateral sclerosis. Moreover, 10 patients with SMA were followed up after 4-8months. All patients were investigated clinically and by the motor unit number estimation method MScanFit of the abductor pollicis brevis muscle. The number of motor units (p<0.001) was significantly lower in patients with SMA compared to healthy controls at study entry. Mean unit amplitude, median amplitude and largest unit (p<0.001) were significantly increased in patients with SMA. Patients with amyotrophic lateral sclerosis showed a significant reduction of compound muscle action potential (p=0.005) and number of motor units (p=0.03) compared to patients with SMA, accompanied by a larger median amplitude (p=0.03). A prospective analysis identified patients with the ability to walk to improve the number of motor units (p=0.046) accompanied by a decreased median amplitude (p=0.03). Electrophysiological measures showed a moderate to strong correlation with clinical scores. Patients with SMA show loss of motor units in distal muscles. MScanFit variables indicate that compound muscle action potential amplitudes are maintained by collateral sprouting. Prospective analyses suggest that milder affected adult patients with SMA preferentially benefit from nusinersen treatment through recovery of smaller motor units. Correlations with clinical scores underline the potential of MScanFit as a surrogate marker.

Workshop 4: Advanced Neurophysiology Techniques WS4.1. My Approach to Motor Unit Number Estimation (with Demonstration)

In motor neuron disease such as amyotrophic lateral sclerosis, the motor neurons die from the disease process. They cannot be replaced. The loss of motor units (MUs) is partially compensated by reinnervation. As a result, the number of MUs is reduced and their size is increased. Reinnervation cannot sustain and may not be sufficient as the MU loss continues. This leads to progressive weakness. As we look for treatments, we need a biomarker to track the disease progression. This had led to the methods of “motor unit number estimation (MUNE)” over the last 5 decades. If a treatment is effective, the rate of MU loss should decrease. In this workshop I will review MUNE methods that were based on recording and measuring individual surface recorded motor unit potentials (SMUPs). They are called “incremental stimulation”, “multiple point stimulation”, etc. The methods are time consuming due to low amplitude signals and have been used to study small distal muscles. Furthermore, they are not automated. In the last 15 years we have seen new methods based on mathematical models. Hence the calculation is described as “motor unit number index (MUNIX)”. In MUNIX the compound muscle action potential (CMAP) and surface EMG interference pattern are analyzed. The procedure is automated, requires less than 5 minutes per muscle, and can be used for large muscles such as tibialis anterior. By adding results from several muscles, one can better track the disease progression. The methods also provide a measure for the amplitude of SMUP. The motor unit size index (MUSIX) increases with reinnervation. Another set of methods is based on ‘CMAP scan’. The stimulus intensity is reduced in fine steps from supramaximal level to low intensity where no response is recorded. The amplitude of 500 responses is analyzed using different algorithms. This method is also automated for recording the data. All methods have their advantages and disadvantages. They provide different numerical results. However, each method shows disease progression when serial investigations are performed. Such assessment requires careful measurements of the CMAP regardless of the method.

MScanFit Motor Unit Number Estimation

Motor unit number estimation (MUNE) methods have been found to be better suited than any other electrophysiological test to study the degree and time course of lower motor unit loss. However, MUNE methods have not yet been implemented in clinics and research. This may be because an ideal method has not been developed yet. This review aims to give an overview of the strengths and limitations of the existing MUNE methods, why a new method was necessary and how the novel MScanFit MUNE can overcome some of the limitations that the other methods had. In the end, the existing literature MScanFit applied has been summarised.

Detecting peripheral motor nervous system involvement in chronic spinal cord injury using two novel methods: MScanFit MUNE and muscle velocity recovery cycles

ObjectiveTo examine the peripheral nervous system (PNS) in spinal cord injured (SCI) patients using two novel methods: (1) MScanFit MUNE; a motor unit number estimation method detecting motor unit loss and (2) muscle velocity recovery cycles (MVRCs) measuring muscle membrane properties which has previously shown depolarization of the muscle membrane in denervated muscles. MethodsThirty chronic SCI patients (lesion above Th10) and twenty-five gender –and age matched healthy controls (HC) were examined. MScanFit was recorded from peroneal nerve to anterior tibial muscle (TA) and tibial nerve to abductor hallucis muscle after excluding localized mononeuropathies. MVRCs were recorded from TA. ResultsNerve conduction studies showed mononeuropathy in 8 patients (27%) (sciatic (2), -or peroneal nerve (6)). SCI patients had in average reduced motor unit number compared with HC and prolonged muscle refractory period and reduced supernormality. SignificanceA high prevalence of nerve lesion and a diffuse affection of the PNS following SCI are highly relevant findings that should be accounted for when planning neurorehabilitation for persons living with SCI.

Assessing Rat Forelimb and Hindlimb Motor Unit Connectivity as Objective and Robust Biomarkers of Spinal Motor Neuron Function

Sensitive and objective biomarkers of neuronal injury, degeneration, and regeneration can help facilitate translation of experimental findings into clinical testing. Whereas measures of upper motor neuron connectivity have been readily established, functional assessments of lower motor neuron (LMN) innervation of forelimb muscles are lacking. Compound muscle action potential (CMAP) and motor unit (MU) number estimation (MUNE) are well-established methods that allow longitudinal MU integrity monitoring in patients. In analogy we refined CMAP and MUNE methods for assessing spinal MU input in the rat forelimb and hindlimb. Repeated CMAP and MUNE recordings are robust (coefficients of variability: 4.5–11.3%), and MUNE measurements from forelimb wrist flexor muscles (415 ± 8 [SEM]) align with back-traced anatomical LMN counts (336 ± 16 [SEM]). For disease validation, cross-sectional blinded electrophysiological and muscle contractility measurements were obtained in a cohort of G93A SOD1 mutant overexpressing rats and compared with controls. Longitudinal assessment of mutant animals demonstrated progressive motor unit decline in the hindlimb to a greater extent than the forelimb. Hindlimb CMAP and MUNE demonstrated strong correlations with plantarflexion muscle contractility. Cross-species assessment of upper/fore- limb and lower/hind- limb motor units using objective electrophysiological CMAP and MUNE values as biomarkers will guide and improve bi-directional translation.

Detection of early motor involvement in diabetic polyneuropathy using a novel MUNE method – MScanFit MUNE

ObjectiveDetection of motor involvement in diabetic polyneuropathy (DPN) by nerve conduction studies (NCS) does not occur until there is substantial loss of motor units, because collateral reinnervation maintains compound muscle action potential (CMAP) amplitude. Motor unit number estimation (MUNE) methods may therefore be more sensitive. This study was undertaken to test whether the novel method, MScanFit MUNE (MScan) can detect motor involvement in DPN despite normal NCS. MethodsFifty-two type-2 diabetic patients and 38 healthy controls were included. The median nerve was examined in all participants using standard NCS and a detailed CMAP scan, used for MScan. Additional lower extremity NCS in patients were used for DPN diagnosis. ResultsOf 52 diabetic patients, 21 had NCS-defined DPN while lower extremity NCS were normal in 31 patients. MScan motor unit number and size showed higher sensitivity and incidence of abnormality than motor NCS parameters, and a similar sensitivity to sensory NCS. ConclusionsMScan is able to detect motor axonal damage at times when collateral reinnervation limits NCS changes. SignificanceMScan is a sensitive method to detect motor involvement in DPN, which our data suggests is present as early as sensory.

Motor unit number index and compound muscle action potential amplitude

ObjectivesMUNIX (motor unit number index), derived from the compound muscle action potential (CMAP) and surface EMG interference pattern (SIP) has become popular as a substitute for motor unit number estimation (MUNE). This study was undertaken to determine why, in recent recordings from amyotrophic lateral sclerosis (ALS) patients and healthy controls, we found that MUNIX values resembled CMAP amplitudes more closely than MUNE values. MethodsThe relationship between MUNIX and CMAP and SIP amplitudes was investigated by a theoretical analysis and by reanalysing the data from the previous study. ResultsTheory indicates that when motor unit potentials overlap extensively, information about motor unit size and number is lost, and MUNIX depends only on CMAP area and power. Accordingly, MUNIX values were found to be sensitive to changes in CMAP amplitude but insensitive to changes in SIP amplitude. The reproducibility of MUNIX measurements in healthy controls was found to depend almost entirely on correlation with CMAP properties. ConclusionsMUNIX gives misleading information about motor unit numbers in healthy controls, and provides little information about loss of motor units in ALS patients beyond that given by simple CMAP amplitude measurements. SignificanceMUNIX should not be interpreted as a MUNE method.

Following disease progression in motor neuron disorders with 3 motor unit number estimation methods.

The objective of this study was to evaluate a recently developed motor unit number estimation (MUNE) method, MScanFit MUNE (MScan), as a measure of disease progression in amyotrophic lateral sclerosis (ALS) compared with compound muscle action potential (CMAP) amplitude and 2 traditional MUNE methods. ALS patients were evaluated clinically using the ALS Functional Rating Scale-Revised (ALSFRS-R). MScan, multiple-point stimulation MUNE (MPS), and motor unit number index (MUNIX) were performed in the abductor pollicis brevis (APB) muscle at baseline (27 patients), 4 months (23 patients), and 8 months (16 patients). Of the 5 measures, MScan registered the largest decline (8.7% per month), compared with MPS (3.4%), MUNIX (4.8%), CMAP amplitude (2.0%), and ALSFRS-R (1.9%). Only MScan and ALSFRS-R registered significant decrements over 4 and 8 months. MScan may be useful as a sensitive, objective tool for quantifying motor unit loss in ALS. Muscle Nerve 59:82-87, 2019.

CMAP Scan MUNE (MScan) - A Novel Motor Unit Number Estimation (MUNE) Method.

Like other methods for motor unit number estimation (MUNE), compound muscle action potential (CMAP) scan MUNE (MScan) is a non-invasive electrophysiologic method to estimate the number of functioning motor units in a muscle. MUNE is an important tool for the assessment of neuropathies and neuronopathies. Unlike most MUNE methods in use, MScan assesses all the motor units in a muscle, by fitting a model to a detailed stimulus-response curve, or CMAP scan. It thereby avoids the bias inherent in all MUNE methods based on extrapolating from a small sample of units. Like 'Bayesian MUNE,'MScan analysis works by fitting a model, made up of motor units with different amplitudes, thresholds, and threshold variabilities, but the fitting method is quite different, and completed within five minutes, rather than several hours. The MScan off-line analysis works in two stages: first, a preliminary model is generated based on the slope and variance of the points in the scan, and second, this model is then refined by adjusting all the parameters to improve the fit between the original scan and scans generated by the model. This new method has been tested for reproducibility and recording time on 22 amyotrophic lateral sclerosis (ALS) patients and 20 healthy controls, with each test repeated twice by two blinded physicians. MScan showed excellent intra- and inter-rater reproducibility with ICC values of >0.98 and a coefficient of variation averaging 12.3 ± 1.6%. There was no difference in the intra-rater reproducibility between the two observers. Average recording time was 6.27 ± 0.27 min. This protocol describes how to record a CMAP scan and how to use the MScan software to derive an estimate of the number and sizes of the functioning motor units. MScan is a fast, convenient, and reproducible method, which may be helpful in diagnoses and monitoring disease progression in neuromuscular disorders.

T137. Detection of early motor involvement in diabetic polyneuropathy using a novel MUNE method – MScanFit MUNE

Detection of motor involvement in diabetic polyneuropathy (DPN) with nerve conduction studies (NCS) is delayed by collateral sprouting, resulting in fewer and larger motor units. Our aim is to examine whether a novel Motor Unit Number Estimation (MUNE) method so called MScanFit MUNE (MScan) can detect early motor involvement in DPN. We prospectively included 45 patients with diabetes mellitus type II and 35 healthy subjects (HS), age 59.56 ± 2.05. MScan in abductor pollicis brevis (APB) muscle were done in all participants. Additionally, NCS of three motor (median, peroneal, tibial) and three sensory (bilateral sural and median) nerves was done in all patients. NCS results were compared to laboratory controls. All participants with carpal tunnel syndrome were excluded. DPN diagnosis was given using Dyck’s criteria requiring NCS abnormality in at least two nerves, one must be the sural nerve. Twelve patients (26.6%) had DPN (DPN+), age 61.64 ± 1.83 and 33 patients had normal NCS (DPN−), age 63.5 ± 2.76. There was no significant difference in age between the tree groups. DPN+ patients had a significantly lower number of motor units (78.58 ± 8.01) when comparing with both HS (119.9 ± 5.21) (p = 0.00022) and DPN− patients (113.4 ± 6.44) (p = 0.005). There was no difference between HS and DPN− patients (p = 0.43709). Motor unit size was significantly larger in DPN+ patients (6.343 ± 0.658) compared to HS (3.851 ± 0.241) (p = 0.00083) and DPN− patients (3.84 (3.25, 5.17), p = 0.01384). No difference between HS and DPN− patients (p = 0.12388). Compound muscle action potential amplitude was within normal ranges for all DPN+ patients. MScan abnormality with normal CMAP amplitude in APB muscle suggests that MScan may be a sensitive measure of early motor involvement in DPN. Further studies with larger patient groups and application of MScan in different muscles particularly in lower extremities are needed.

The utility of motor unit number estimation methods versus quantitative motor unit potential analysis in diagnosis of ALS

ObjectiveTo compare the diagnostic utility of motor unit number estimation (MUNE) methods to motor unit potential (MUP) analysis in amyotrophic lateral sclerosis (ALS). MethodsTwenty-five patients (1 definite, 11 probable, 9 possible ALS and 4 progressive muscular atrophy) and 22 healthy controls were prospectively included. Quantitative MUP analysis and three MUNE methods; Multiple Point Stimulation MUNE (MPS), Motor Unit Number Index (MUNIX) and MScanFit MUNE (MScan) were done in abductor pollicis brevis muscle. The sensitivities were compared by McNemar chi-square test. MUNE, MUP and revised ALS Functional Rating Scale (ALSFRS-R) parameters were correlated by regression analysis. ResultsThe sensitivities of MPS (76%) and MScan (68%) were higher than MUP duration (36%) and amplitude (40%) in detecting motor unit loss (p < 0.05). MUNE methods increased the categorical probability from possible to probable ALS in 4 patients (16%). There was only significant correlation between ALSFRS-R and MScan (r = 0.443, p = 0.027) among the electrophysiological tests. MUNE methods did not correlate to MUP parameters. ConclusionsMUNE methods are more sensitive in showing abnormality than MUP analysis. SignificanceMUNE methods, in particular MScan, may have the potential to be implemented in the clinical practice for diagnosis and follow-up of neuromuscular disorders particularly ALS.

S70 Estimating motor unit number from CMAP scans – MScanFIT MUNE

Objectives There is no method that can measure the exact number of motor units, therefore motor unit number estimation (MUNE) methods have been developed. Most MUNE methods are based on estimating the size of an average surface-recorded motor unit potential and dividing that value into maximal compound action potential (CMAP). This makes the estimates strongly influenced by any bias in unit selection. Other limitations of the existing MUNE methods are the presence of subjectivity in the estimation process, the failure to sample enough units or the long time to perform the test or analyse. To overcome these limitations, a new MUNE method was recently developed, so-called ‘MScanFit MUNE‘, (MScan). Methods MScan meets the above-mentioned criticisms by fitting a model to a detailed stimulus-response curve (∼500 stimuli) or ‘CMAP scan’, taking into account the threshold variability of all the units, and avoiding subjectivity. Results The method has been found to be accurate (mean absolute error 7%) for simulated data.The reproducibility and the diagnostic utility of MScan were found to be good in healthy controls and in patients with amyotrophic lateral sclerosis (ALS) and different types of polyneuropathy. Discussion MScan revealed in neurofibromatosis-type-2 patients denervation and reinnervation in peripheral nerves suggesting that it may be used to quantify and monitor disease progression. Conclusions MScan is a novel method with good reproducibility, and may be performed in less than five minutes. Significance Preliminary results suggest MScan as a promising MUNE method with potential to be used in diagnoses and monitoring disease progression, particularly in ALS.

P340 The MUNE method as a complementary test to routine EMG in amyotrophic lateral sclerosis

Electromyographic (EMG) abnormalities that reveal denervation and reinnervation caused by lower motor neuron degeneration do not reflect the number of motor units that determines muscle strength. Consequently, motor unit activity potential (MUAP) parameters do not reflect muscle dysfunction. Objectives The aim of the study was to compare the value of motor unit number estimation (MUNE) and MUAP parameters as indicators of clinical muscle dysfunction in patients with amyotrophic lateral sclerosis (ALS), and to analyze the role of MUNE as a supplement to the EMG criteria for the diagnosis of ALS. Methods In 25 patients with ALS, MUNE by the multipoint incremental method in the abductor digiti minimi (ADM) and quantitative EMG in the first dorsal interosseous (FDI) were obtained. The Medical Research Council (MRC) scale was used to evaluate clinical muscle dysfunction. Results A strong correlation between the number of motor units evaluated by MUNE and ADM clinical function by the MRC scale was found ( P 0.001 ). An increased value of surface-detected single motor action potential was associated with a decreased MRC score for ADM ( P 0.1 ). No relation was found between MUAP parameters in FDIand MRC scores. Conclusion and Significance Our data support the value of the MUNE method for the detection of motor unit loss in ALS, and it could be postulated that MUNE studies may be considered complementary tests for ALS in a future revision of ALS criteria.

O25 Motor unit number estimation methods compared to quantitative motor unit potential analysis in amyotrophic lateral sclerosis

Objectives To compare the sensitivity of MUNE methods to quantitative motor unit potential (MUP) analysis in amyotrophic lateral sclerosis (ALS). Methods Twenty-four patients (1 definite, 11 probable and 8 possible ALS according to awaji criteria as reference standard, and 4 progressive muscular atrophy) were included. Patients were evaluated by revised ALS functional rating scale (ALSFRS-R). In all patients, quantitative MUP analysis and three MUNE methods; MScanFit MUNA (MScan), multiple point stimulation MUNE (MPS), and Motor Unit Number Index (MUNIX) were done in abductor pollicis brevis (APB). MUNE results were compared to 20 age-matched healthy controls and EMG to laboratory controls. The sensitivity of each methods was compared using McNemar chi-square test. MUNE values and MUP parameters were correlated to ALSFRS-R by regression analysis. Results MScan (70%) and MPS (61%) more frequently showed abnormality than MUP duration (35%) whereas only MScan was more often abnormal than MUP amplitude (39%) ( p r = 0.42, p = 0.03) but not MPS ( r = 31), MUNIX ( r = 35), MUP duration ( r = 0.19) or amplitude ( r = 0.09). Discussion MUP analysis gives information about reinnervation, but not about loss of motor units. Therefore MUNE methods may be preferable in ALS electrodiagnosis. Conclusions MUNE methods, particularly MScan, had higher sensitivities than MUP analysis in detection of abnormality in APB and were correlated better to ALSFRS-R. Significance MScan is a promising novel method which should be considered in diagnosis and monitoring disease progression in ALS.