Electromyographs of the flexor digitorum profundus muscle are useful for the diagnosis of inclusion body myositis

Introduction: The frequent observation of high‐amplitude and long‐duration motor unit potentials (MUPs) in inclusion body myositis (IBM) is problematic, because it may lead to a misdiagnosis of amyotrophic lateral sclerosis (ALS). Objective: To document the diagnostic utility of EMG from the flexor digitorum profundus (FDP) muscle for IBM. Methods: Quantitative analyses of MUP parameters were performed in the FDP and biceps brachii (BB) muscles from 7 biopsy‐confirmed IBM patients. Results: In the FDP muscle, all MUP parameters were significantly decreased in IBM patients, which indicated the predominance of low‐amplitude and short‐duration MUPs in this muscle. In the BB muscle, most parameters were increased, suggesting the frequent contamination of high‐amplitude and long‐duration MUPs. Conclusions: Low‐amplitude MUPs in the FDP muscle indicate the presence of an advanced myopathy in this muscle that was extremely weak for all subjects. Examining the FDP muscle would reduce the chance of misdiagnosing IBM as ALS. Muscle Nerve 46: 181–186, 2012     

Assessment of muscle stiffness using a continuously scanning laser‐Doppler vibrometer

Introduction: A stand‐alone and low‐cost elastography technique has been developed using a single continuously scanning laser Doppler vibrometer. Methods: This elastography technique is used to measure the propagation velocity of surface vibrations over superficial skeletal muscles to assess muscle stiffness. Results: Systematic variations in propagation velocity depending on the contraction level and joint position of the biceps brachii were demonstrated in 10 subjects. Conclusions: This technique may assist clinicians in characterizing muscle stiffness (or tone) changes due to neuromuscular disorders. Muscle Nerve 50 : 133–135, 2014     

Quantitative assessment of motor impairment and surgical outcome in Hirayama disease with proximal involvement using motor unit number index

ObjectiveTo assess the feasibility of motor unit number index (MUNIX) in quantitatively evaluating Hirayama disease (HD) with proximal involvement and to identify the effectiveness of anterior cervical fusion (ACF) in treating atypical HD with proximal involvement.MethodsThis study included 28 atypical HD patients with proximal involvement (proximal-distal vs. distal-proximal groups: 5 vs. 23) and 41 healthy controls. All patients underwent pre- and postoperative 1-year MUNIX tests on abductor pollicis brevis (APB), abductor digiti minimi (ADM), biceps brachii (BB) and deltoid (Del). The disabilities of arm, shoulder and hand (DASH) and Medical Research Council (MRC) scales were also performed in these patients before and one year after operation.ResultsPreoperatively, the patients in the distal-proximal group showed reduced compound muscle action potential (CMAP), decreased MUNIX and increased motor unit size index (MUSIX) in bilateral distal muscles and symptomatic-side proximal muscles (P < 0.05), and similar abnormalities were also observed in ADM, BB and Del on the symptomatic side in the proximal-distal groups (P < 0.05). Postoperative follow-up analysis identified increased MUNIX in the symptomatic-side proximal muscles with improved motor function in the proximal-distal groups (P < 0.05), and distal-proximal group patients showed an increase in both CMAP and MUSIX in the symptomatic-side proximal muscles (P < 0.05).ConclusionsMUNIX may serve as an available supplementary test to quantitatively evaluate the motor dysfunction and treatment outcome in HD with proximal involvement. ACF procedures can effectively treat these atypical HD patients, especially for those whose symptoms started in proximal muscles.     

Quantitative ultrasound of the tongue and submental muscles in children and young adults

Introduction: The purpose of this study was to assess the feasibility of quantitative muscle ultrasound (QMUS) to visualize oral muscles and to establish normative data for muscle thickness and echo intensity of submental and tongue muscles in healthy children and young adults. The data were compared with those of 5 patients with Duchenne muscular dystrophy (DMD). Methods: Ultrasound images from the suprahyoid region and from the surface of the tongue were made in 53 healthy subjects aged 5 to 30 years. Results: All measurements were feasible in all subjects and patients with good reproducibility except for the mylohyoid muscle. Muscle thickness depended on height, and echo intensity depended on weight. Our findings suggest gradual involvement of oral muscles in DMD. Conclusions: QMUS in oral muscles is feasible in healthy children, adults and patients with DMD. These data show that it is possible to differentiate between healthy persons and patients with DMD. Muscle Nerve 46:31–37, 2012     

Decomposition-based quantitative electromyography in the evaluation of muscular dystrophy severity

Introduction: Electromyography is useful in the diagnosis of myopathies, but its utility in determining disease severity requires further investigation. In this study we aimed to determine whether decomposition‐based quantitative electromyography (DQEMG) could indicate the severity of involvement in a cohort of patients with muscular dystrophies (MDs). Methods: Fifteen patients with facioscapulohumeral (FSHD), limb‐girdle (LGMD), and Becker (BMD) muscular dystrophy, and 7 healthy controls, participated in this investigation. Knee extensor isometric strength differentiated the “more severe” and “less severe” MD groups. The vastus lateralis (VL), biceps brachii (BB), and tibialis anterior (TA) muscle groups were investigated using DQEMG. Results: All muscles from the MD group showed changes in mean MUP (motor unit potential) AAR (area‐to‐amplitude ratio), and turns, compared with controls (P < 0.05). More severely affected muscles (VL and BB) also had shortened mean MUP durations compared with controls (P < 0.01). Conclusions: DQEMG was capable of indicating the severity of MD involvement, as changes in MUP morphology reflected the progressive nature of the disease. Muscle Nerve, 2012     

Origin of surface motor unit potentials in hypothenar motor unit number estimation

Introduction: Far‐field potentials (FFPs) from muscles other than the abductor digiti minimi (ADM) may interfere with motor unit number estimation (MUNE) from that muscle. Methods: We identified the origin of each surface motor unit potential (SMUP) during hypothenar MUNE using the multiple point stimulation method in 20 control subjects by recording from individual ulnar‐innervated muscles with a common proximal reference (pref). Results: ADM SMUPs comprised 39.0% of the accepted SMUPs, followed by those from the fourth dorsal interosseous muscle (14.0%), the fourth lumbrical muscle (9.2%), and the second and third palmar interosseous muscles (8.8% each). The percentage of ADM SMUPs varied from 18% to 73% of accepted SMUPs among individual subjects. Accepted non‐ADM SMUPs were usually much smaller than ADM SMUPs, and many more non‐ADM SMUPs were excluded due to their small size. Conclusions: A large contribution from non‐ADM or non‐hypothenar SMUPs obscures the meaning of the MUNE value. Muscle Nerve, 48: 185–190, 2013     

Muscle shear modulus measured with ultrasound shear‐wave elastography across a wide range of contraction intensity

Introduction: In this study we examine the repeatability of measuring muscle shear modulus using ultrasound shear‐wave elastography between trials and between days, and the association between shear modulus and contraction intensity over a wide range of intensities. Methods: Shear modulus of the biceps brachii was determined using ultrasound shear‐wave elastography during static elbow flexion (up to 60% of maximal contraction) in healthy young adults. Results: The correspondence of shear modulus was confirmed in phantoms between the manufacturer‐calibrated values and the shear‐wave elastography values. The intraclass correlation coefficient of muscle shear modulus was high: 0.978 between trials and 0.948 between days. Shear modulus increased linearly with elbow flexion torque across contraction intensity, and its slope was associated negatively with muscle strength. Conclusions: Muscle shear modulus measured with ultrasound shear‐wave elastography may be useful for inferring muscle stiffness across a wide range of contraction intensity. In addition, it has high repeatability between trials and between days. Muscle Nerve 50 : 103–113, 2014     

Motor-evoked potentials from multiple target muscles in multiple sclerosis and cervical myelopathy

Motor-evoked potentials (MEP) from abductor digiti minimi (ADM), biceps brachii (BB) and tibialis anterior (TA) muscle were analysed in 101 patients with multiple sclerosis (MS) and in 72 patients with compressive cervical myelopathy (CM). In definite MS the results were abnormal in 82% and in probable or possible MS in 64% of patients. In CM results were abnormal in 56% when the compression site was at the C4/C5 interspace or higher (CM_C1-C4-), and in 100% when the compression fell between the C5 and C7 level (CM_C5-C7). The pattern of normal responses from BB with abnormal responses from ADM was found in 37% of patients with CM_C5-C7, in 10% of patients with MS (p = 0.01) and in 19% of patients with CM_C1-C4+. Abnormal MEP from both ADM and BB were significantly more frequent in MS than in CM (p = 0.002). Although “specific patterns” of MEP abnormality could be significantly correlated with patient groups and anatomical compression sites, they cannot be taken as a reliable diagnostic clue in the individual case. In particular, abnormal responses from BB were frequently also found in CM_C5-C7. These discrepancies cannot be explained on the basis of a localized mechanical mechanism and raise the question of the pathogenesis in CM.     

The relationship between passive stiffness and muscle power output: Influence of muscle cross‐sectional area normalization

Introduction: We examined the relationship between passive stiffness of posterior hip and thigh muscles and muscle power output before and after normalization of passive stiffness to muscle cross‐sectional area (CSA). Methods: Pearson correlation coefficients (r) were used to assess the relationships between the normalized and non‐normalized slopes of the initial (phase 1) and final (phase 2) portions of the angle–torque curve and peak power output (Pmax). Results: A significant positive relationship was observed between the non‐normalized slope of phase 1 and Pmax (r = 0.723; P ≤ 0.001); however, no correlations were observed between the normalized slope of phase 1 and Pmax (r = 0.244; P = 0.299) nor between Pmax and the normalized and non‐normalized slopes of phase 2 (r = ?0.159–0.418; P = 0.067–0.504). Conclusions: The findings suggest that muscle size, rather than stiffness, accounted for a significant portion of the variance in muscle power output. Muscle Nerve 49 : 69–75, 2014     

Dose response with onabotulinumtoxinA for post‐stroke spasticity: A pooled data analysis

Clinical trials demonstrate that onabotulinumtoxinA reduces upper limb post‐stroke spasticity, with therapeutic response influenced by injected dose. Individual studies provide limited insight regarding muscle group‐specific dose–response relationships. Our objective was to characterize dose–response relationships between onabotulinumtoxinA and muscle tone in specific upper limb muscles. Individual patient data from seven multicenter, randomized, double‐blind, placebo‐controlled trials were pooled. Of 544 post‐stroke patients enrolled, 362 received onabotulinumtoxinA and 182 received placebo, injected into the flexor carpi radialis (FCR), flexor carpi ulnaris (FCU), flexor digitorum superficialis (FDS), flexor digitorum profundus (FDP), and/or biceps brachii (BB). Ashworth Scale score change at week 6 (AshworthCBL) was the primary outcome measure for muscle tone. For a broader analysis of response, AshworthCBL/onabotulinumtoxinA dosage relationships were characterized using three techniques: (1) AshworthCBL plotted as a function of onabotulinumtoxinA dose in Units (U) [dose–response curve]; (2) mean AshworthCBL per onabotulinumtoxinA dose depicting the responses seen with specific dose injection clusters/groups for each specific muscle group; and (3) onabotulinumtoxinA dose estimated to produce a mean 1‐point decrease in AshworthCBL as an indicator of clinically meaningful benefit of treatment. Increasing onabotulinumtoxinA doses produced greater AshworthCBLs (muscle tone improvements). The maximal week 6 response (E_max) model indicated a saturating dose–response relationship, with mean E_max AshworthCBL values of ‐1.48, ‐1.48, ‐0.63, ‐0.77, and ‐0.61 in the FCR, FCU, FDS, FDP, and BB, respectively. OnabotulinumtoxinA doses estimated to produce a mean 1‐point decrease in AshworthCBL were: 22.5U, 18.4U, 66.3U, 42.5U in the FCR, FCU, FDS, and FDP, respectively, and not determinable in the BB. These analyses demonstrate a saturating effect of greater muscle tone improvements with increasing onabotulinumtoxinA doses in post‐stroke spasticity patients. These findings suggest potentially effective onabotulinumtoxinA doses in selected muscle groups in this study population. © 2010 Movement Disorder Society.     

Significant CMAP decrement by repetitive nerve stimulation is more frequent in median than ulnar nerves of patients with amyotrophic lateral sclerosis

Introduction: Several studies have shown a significant amplitude decrement in compound muscle action potentials (CMAPs) on repetitive nerve stimulation (RNS) of muscles involved in amyotrophic lateral sclerosis (ALS).In ALS, muscle wasting preferentially affects the thenar muscles (APB) rather than the hypothenar muscles (ADM). Methods: We performed RNS studies in the APB and ADM muscles of 32 ALS patients to determine whether the effect of RNS differs between the median and ulnar nerves. Results: The decremental responses to RNS were greater in the APB than in the ADM. Reduced CMAP amplitude was negatively correlated with CMAP decrement in median but not in ulnar nerves. Conclusions: The greater CMAP decrement in median nerve is attributable to preferential involvement of the APB in the pathophysiology of ALS or some underlying difference in the biology of the two muscles/nerves. Further investigations will better our understanding of the pathophysiology of ALS. Muscle Nerve, 2012     

Magnetic resonance imaging in duchenne muscular dystrophy: Longitudinal assessment of natural history over 18 months

Introduction: In Duchenne muscular dystrophy (DMD), fat replacement of muscle may be a useful endpoint in trials of therapy, although progression in different muscle groups is uneven. In this study we assessed the progression of fat replacement with T₁‐weighted imaging over 2 9‐month periods. Methods: Eight ambulant, corticosteroid‐treated boys with DMD were imaged at 3 Tesla at 3 time‐points (baseline and 9 and 18 months) with T₁‐weighted imaging to measure fat replacement. Results: The greatest increase in fat content was measured in the biceps femoris long head, vastus lateralis, and rectus femoris, whereas the biceps femoris short head and gluteus maximus progressed more slowly. None of the lower leg muscles studied changed significantly. Conclusions: MRI can measure specific changes in fat replacement of muscle over time, demonstrating the variability in rates of natural progression between muscle groups and identifying those muscles suitable for use as biomarkers in clinical trials. Muscle Nerve 48 : 586–588, 2013     

Split‐hand phenomenon in amyotrophic lateral sclerosis: A motor unit number index study

Introduction: The split‐hand phenomenon refers to preferential wasting of the thenar muscles with relative sparing of the hypothenar muscles in amyotrophic lateral sclerosis (ALS). Methods: We compared the split‐hand index (SI) calculated from the compound muscle action potential (CMAP; SI_CMAP) with that calculated from the motor unit number index (MUNIX; SI_MUNIX). We performed MUNIX on the abductor policis brevis (APB), first dorsal interosseous (FDI), and abductor digiti minimi (ADM) muscles of 39 ALS patients and 40 age‐matched, healthy controls. SI is derived by multiplying the CMAP (or MUNIX) recorded over the APB and FDI and dividing by the CMAP (or MUNIX) recorded over the ADM. Results: Receiver‐operating characteristic curve analysis revealed good diagnostic accuracy for both indices, but better performance of SI_MUNIX than SI_CMAP. Conclusion: SI_MUNIX and SI_CMAP were useful in differentiating ALS patients from healthy controls. SI_MUNIX appears to be a better electrophysiological marker than SI_CMAP for the split‐hand sign of ALS. Muscle Nerve 53 : 885–888, 2016     

Muscle ultrasound elastography and MRI in preschool children with Duchenne muscular dystrophy

The aim of this study was to determine muscle tissue elasticity, measured with shear-wave elastography, in selected lower limb muscles of patients affected by Duchenne muscular dystrophy (DMD) and to correlate the values obtained with those recorded in healthy children and with muscle magnetic resonance imaging (MRI) data from the same DMD children, specifically the pattern on T1-weighted (w) and short-tau inversion recovery (STIR) sequences. Five preschool DMD children and five age-matched healthy children were studied with shear-wave elastography. In the DMD children, muscle stiffness was moderately higher compared with the muscle stiffness in HC, in the rectus femoris, vastus lateralis, adductor magnus and gluteus maximus muscles. On muscle MRI T1-w images showed fatty replacement in 3/5 patients at the level of the GM, while thigh and leg muscles were affected in 2/5; hyperintensity on STIR images was identified in 4/5 patients. No significant correlation was observed between stiffness values and MRI scoring. Our study demonstrated that lower limb muscles of preschool DMD patients show fatty replacement and patchy edema on muscle MRI and increased stiffness on shear-wave elastography. In conclusion, although further studies in larger cohorts are needed, shear-wave elastography could be considered a useful non-invasive tool to easily monitor muscle changes in early stages of the disease.     

Different short-term modulation of cortical motor output to distal and proximal upper-limb muscles during painful sensory nerve stimulation

The pattern of upper-limb muscle activation following painful stimulation has not been clarified in detail. We investigated the short-term inhibitory and excitatory effects of painful electrical digital stimulation on the motoneuron pools of distal and proximal upper-limb muscles. Transcranial magnetic stimulation (TMS) was used as test stimulus, and painful digital nerve stimulation as conditioning stimulus for motor evoked potential (MEP) recordings over the abductor digiti minimi (ADM), abductor pollicis brevis (APB), biceps brachii (BB), and deltoid muscles. Inhibition of the conditioned MEP response was most prominent in the distal muscles, whereas BB and deltoid muscles were only weakly inhibited. The mean MEP response over APB decreased with painful cutaneous stimuli, showing maximum inhibition (by 82%) at interstimulus intervals (ISIs) of 50 ms. Inhibition in the ADM was maximal (49%) but less pronounced at an ISI of 40 ms. The BB and deltoid muscles showed inhibition by 25% and 29%, respectively. Significant facilitation was present in BB and deltoid muscles by 43% and 41% at an ISI of 100 ms, but not in the smaller hand muscles. The observed pattern of upper-limb muscle activation corresponds to the protective withdrawal reflex and the neuronal basis of the observed short-term modulation of motor activity is compatible with a spinal or brainstem pathway.     

Pattern difference of dissociated hand muscle atrophy in amyotrophic lateral sclerosis and variants

Introduction: Split hand is considered to be a specific feature of amyotrophic lateral sclerosis (ALS). Methods: We evaluated the pattern difference of intrinsic hand muscles of upper limb‐onset ALS (UL‐ALS), upper limb‐onset progressive muscular atrophy (UL‐PMA), brachial amyotrophic diplegia (BAD), and Hirayama disease (HD) by measuring objective electrophysiological markers. Results: The abductor digiti minimi (ADM)/abductor pollicis brevis (APB) compound muscle action potential (CMAP) amplitude ratio was significantly higher in UL‐ALS than other variants, but a considerable proportion of UL‐ALS cases had an amplitude ratio in the range of other variants. Absent APB CMAP and abnormally high ADM/APB CMAP amplitude ratio (≥4) occurred only with UL‐ALS. Conversely, an absent ADM CMAP was identified only in UL‐PMA and BAD. Conclusions: The absolute ADM/APB CMAP amplitude ratio was not specific for ALS; however, several findings from simple electrophysiological measurements may help predict prognosis in patients with motor neuron diseases and may be early diagnostic markers for ALS. Muscle Nerve 51: 333–337, 2015     

Magnetic resonance imaging of the proximal upper extremity musculature in boys with Duchenne muscular dystrophy

There is a pressing need for biomarkers and outcomes that can be used across disease stages in Duchenne muscular dystrophy (DMD), to facilitate the inclusion of a wider range of participants in clinical trials and to improve our understanding of the natural history of DMD. Quantitative magnetic resonance imaging (qMRI) and spectroscopy (MRS) biomarkers show considerable promise in both the legs and forearms of individuals with DMD, but have not yet been examined in functionally important proximal upper extremity muscles such as the biceps brachii and deltoid. The primary objective of this study was to examine the feasibility of implementing qMRI and MRS biomarkers in the proximal upper extremity musculature, and the secondary objective was to examine the relationship between MR measures of arm muscle pathology and upper extremity functional endpoints. Biomarkers included MRS and MRI measures of fat fraction and transverse relaxation time (T ₂). The MR exam was well tolerated in both ambulatory and non-ambulatory boys. qMR biomarkers differentiated affected and unaffected participants and correlated strongly with upper extremity function (r = 0.91 for biceps brachii T ₂ versus performance of upper limb score). These qMR outcome measures could be highly beneficial to the neuromuscular disease community, allowing measurement of the quality of functionally important muscles across disease stages to understand the natural history of DMD and particularly to broaden the opportunity for clinical trial participation.     

Real‐time visualization of muscle stiffness distribution with ultrasound shear wave imaging during muscle contraction

A stand‐alone ultrasound shear wave imaging technology has been developed to quantify and visualize Young's modulus distribution by remotely applying ultrasound radiation force and tracking the resulting microvibrations in soft tissues with ultrafast ultrasound imaging. We report the first preliminary data that detected the distribution of local muscle stiffness within and between resting and contracting muscles at different muscle lengths with this technology. This technique may assist clinicians in characterizing muscle injuries or neuromuscular disorders. Muscle Nerve, 2010     

Effect of physical training on pain sensitivity and trapezius muscle morphology

The objective of this study was to investigate morphological and physiological characteristics of painful muscles in women with (MYA, n= 42) and without (CON, n = 20) trapezius myalgia, and assess changes in response to a 10‐week, randomized, controlled trial. MYA accomplished: (1) specific strength training (SST); (2) general fitness training (GFT); or (3) reference intervention (REF). Differences in muscle morphology could not be detected by ultrasound imaging. Significantly lower pressure pain threshold (PPT) and shoulder torque were observed for MYA, indicating pain‐related lack of full activation. After 10 weeks, increased shoulder torque and PPT of the painful trapezius were observed in SST solely. The PPT of a pain‐free reference muscle was increased in response to both SST and GFT, indicating a general effect of physical activity on pain perception. This study shows clinically relevant improvement in pain sensitivity and muscle strength capacity in response to SST. Muscle Nerve, 2010