Motor Unit Potential Amplitude Research Articles

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.

Quantitative facial electromyography monitoring after hypoglossal-facial jump nerve suture.

Objectives/HypothesisThe time course of the reinnervation of the paralyzed face after hypoglossal‐facial jump nerve suture using electromyography (EMG) was assessed. The relation to the clinical outcome was analyzed.Study DesignRetrospective single‐center cohort studyMethodsReestablishment of motor units was studied by quantitative EMG and motor unit potential (MUP) analysis in 11 patients after hypoglossal‐facial jump nerve suture. Functional recovery was evaluated using the Stennert index (0 = normal; 10 = maximal palsy).ResultsClinically, first movements were seen between 6 and >10 months after surgery in individual patients. Maximal improvement was achieved at 18 months. The Stennert index decreased from 7.9 ± 2.0 preoperatively to a final postoperative score of 5.8 ± 2.4. EMG monitoring performed for 2.8 to 60 months after surgery revealed that pathological spontaneous activity disappeared within 2 weeks. MUPs were first recorded after the 2nd month and present in all 11 patients 8–10 months post‐surgery. Polyphasic regeneration potentials first appeared at 4–10 months post‐surgery. The MUP amplitudes increased between the 3rd and 15th months after surgery to values of control muscles. The MUP duration was significantly increased above normal values between the 3rd and 24th months after surgery.ConclusionReinnervation can be detected at least 2 months earlier by EMG than by clinical evaluation. Changes should be followed for at least 18 months to assess outcome. EMG changes reflected the remodeling of motor units due to axonal regeneration and collateral sprouting by hypoglossal nerve fibers into the reinnervated facial muscle fibers.Level of Evidence3b.

Template-operated MUP analysis is not accurate in the diagnosis of myopathic or neuropathic changes in the diaphragm

The aim of this study was to evaluate the quantitative motor unit potential (MUP) analysis in the diagnosis of myopathy and neuropathy of the diaphragm. Diaphragm template-operated quantitative EMG were performed in 30 patients with myotonic dystrophy type 1 (DM1), 17 with myotonic dystrophy type 2 (DM2) and 40 with amyotrophic lateral sclerosis (ALS). Low MUP amplitude precluded MUP analysis in 21% of DM1 patients. Only a single DM1 patient had EMG findings consistent with myopathy. In this patient, and another 4 DM1 and 3 DM2 patients, findings were consistent with neuropathy. Neuropathic MUP changes were found in 92% of ALS patients, but due to motor neuron cell loss in only 60% MUPs analyses could be done. Phrenic nerve conduction studies correlated with respiratory function tests, whereas MUP parameters did not. Quantitative MUP analysis was not able to adequately sample diaphragm MUPs in patients with chronic myopathy or motor neuronopathy.

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.

Motor unit potentials of the erector spinae muscle by concentric needle electromyography.

IntroductionThe needle electromyography (EMG) serves to supply additional information in patients with suspected neuromuscular disorders. We aimed to provide motor unit potential (MUP) data by concentric needle EMG in the erector spinae (ES) in comparison with biceps brachii (BB) and lateral vastus (LV).MethodsElectromyography MUP data (n) were obtained in ES (517), BB (539), and LV (627) in 32 healthy volunteers (16f).ResultsMotor unit potential data: amplitude (μV) 393 ± 174 (ES), 375 ± 162 (BB), and 577 ± 304 (LV); duration (ms) 10.4 ± 2.4 (ES), 10.1 ± 2.1 (BB), and 11.1 ± 2.3 (LV), area (μV × ms) 585 ± 327 (ES), 538 ± 267 (BB), and 881 ± 492 (LV); phase number 3.23 ± 0.94 (ES), 2.98 ± 0.76 (BB), and 3.19 ± 0.81 (LV); size index 0.60 ± 0.56 (ES), 0.51 ± 0.53 (BB), and 0.96 ± 0.55 (LV). LV displayed higher values (p at least <.001) for MUP amplitude, duration, area, and size index as compared to both, BB and ES.ConclusionConcentric needle EMG investigations in healthy adult human subjects revealed similar MUP parameters in the ES and BB muscles, while in the LV muscle MUP amplitude, duration, area, and size index were significantly larger. Different neuromuscular disorders display a predominant involvement of proximally located muscles such as truncal muscles. The present results given here may facilitate the diagnosis of neuromuscular disorders.

Needle electromyography features and values of paraspinal muscle parameters in assessment of respiratory function of patients with amyotrophic lateral sclerosis

Objective: To analyze the features of needle electromyography (EMG) in patients with amyotrophic lateral sclerosis (ALS), and explore the correlation between EMG parameters of the tenth thoracic paraspinal muscle and disease duration, rate of disease progression, forced vital capacity (FVC) and revised Amyotrophic Lateral Sclerosis Functional Rating Scale (ALSFRS-R). Methods: Standard EMG was recorded from unilateral sternocleidomastoid muscle and/or tongue muscles, upper and lower limbs muscles and the tenth thoracic paraspinal muscle in 112 patients with definite ALS between March 2012 and June 2013 in the Department of Neurology at Chinese PLA General Hospital. Parameters studies included spontaneous potentials, duration and amplitude of motor unit potentials (MUP), pattern of recruitment. Results: EMG revealed diffuse neurogenic changes in each case. Fibrillation potential or positive sharp waves were found in some muscles in all of patients, and both of them were found in most of the cases. Fasciculation potentials (FPs) were found in 8 patients and accompanied with fibrillation potential and positive sharp waves in 5 of them. Complex repetitive discharges (CRDs) were found in only 1 patient. Duration and amplitude of MUP was prolonged and increased in ALS patients, and the rate of high amplitude and decreased recruitment pattern were 35.71% and 72.32%, respectively. Logistic regression analysis revealed an association of the FVC loss with the drop of ALSFRS-R and peak amplitude of the tenth thoracic paraspinal muscle. Conclusions: The abnormal spontaneous activity with high frequency are fibrillation potentials and/or positive sharp waves. However, FPs is observed in a small number of patients and CRDs is rarely seen in ALS. The ALSFRS-R and peak amplitude of thetenth thoracic paraspinal muscle may be of certain clinical value in estimating the severity of disease especially the respiratory dysfunction in ALS patients.

ID 311 – Do the motor unite potentials properties change with recording from near tendon?

Objectives Purpose is to compare the properties of motor unit potentials (MUP) voluntarily recorded from neuromuscular junction (NMJ) and 5 cm distally from NMJ (near tendon) of the biceps muscle. Methods We recorded MUPs in voluntarily activated biceps muscle from 5 healthy controls and 6 patients with motor neuron disease (MND), 7 patients with myopathy. We evaluated amplitudes and durations from neuromuscular junction and near tendon with concentric needle electrodes. Results The mean duration from NMJ and tendon were 6.37 and 7.4 ms in healthy controls; 4.94 and 4.35 ms in patients with myopathy; 8.52 and 11.2 ms in patients with MND respectively. The mean amplitudes from NMJ and tendon were 456 and 474 μV in healthy controls, 508 and 421 μV in patients with myopathy; 1169 and 1032 μV in patients with MND respectively. Conclusions Amplitudes of MUPs decrease with recording from near tendon in myopathy and neuropathy. Duration of MUPs do not change significantly in myopathy and healthy controls, but increase in neuropathy.

Electrostimulation to Increase Peroneal Muscle Strength in Pediatric Patients With Postsurgical Clubfoot

Background: Idiopathic congenital clubfoot is a deformity with various components. Its treatment can be conservative and or surgical in order to eliminate the deformity and to obtain a pain-free foot allowing for adequate mobility. Objectives: Our objective was to evaluate whether neuromuscular electrostimulation is useful for improving peroneal muscle strength in post-operative congenital clubfoot in children. Patients and Methods: An experimental, prospective, longitudinal, and comparative study was carried out on 10 patients with congenital clubfoot in the experimental group, and on 10 for historical controls. Initial and post-treatment clinical evaluations were conducted on patients in both groups. Surface electromyography (SEMG) was used for the experimental group; each patient received 30 sessions of treatment with neuromuscular electrostimulation in order to obtain muscular contraction. Results: In both groups, there were more males with the average age or 5.5 years (ranging from 3 to 8 years of age). Peroneal muscular strength evaluated through the Daniels and Worthingham’s test increased post-treatment only in the experimental group, and comparing these results to those of the historical group, a significance level of P = 0.001 was obtained. The motor unit potential amplitude in the SEMG increased in the experimental group with a significance level of P < 0.05. Conclusions: Neuromuscular electrostimulation can be used to increase muscle strength, and it is a safe and painless treatment.

Clinical-physiological characteristics of diabetic polyneuropathy in pregnancy

Materials and methods. The study included 22 pregnant women suffering from diabetic neuropathy. 14 women were diagnosed with type 1 diabetes, and 8 - type 2 diabetes. The average duration of the diabetes in women with type 1 diabetes was 14,6±6,4 years, in women with type 2 diabetes 6,6±3,1 years. Authors applied the scales NSS, NDS, electroneuromyography for diagnostic of diabetic neuropathy. Complex neurological and instrumental examination was carried out on terms 15 and 32 weeks of pregnancy. Results. During pregnancy showed deterioration of subjective symptoms, an increase of neurological deficit, which was manifested increase in the average score of NSS, NDS in the 3rd trimester of pregnancy (p0,05). Analyzing the electroneuromyography characteristics was detected a significant decrease the amplitude of motor unit potential of n. peroneus and sensor unit potential of n. suralis in pregnant women suffering from type 1 diabetes mellitus (p0,05). Conclusions. Pregnancy is a risk factor for the progression of diabetic neuropathy and leads to a more rapid damage of axons of peripheral nerves.

The use of electromyography interference pattern analysis to determine muscle force of the deep digital flexor muscle in healthy and laminitic horses

ABSTRACTBackground: In equine laminitis, the deep digital flexor muscle (DDFM) appears to have increased muscle force, but evidence-based confirmation is lacking.Objectives: The purpose of this study was to test if the DDFM of laminitic equines has an increased muscle force detectable by needle electromyography interference pattern analysis (IPA).Animals and Methods: The control group included six Royal Dutch Sport horses, three Shetland ponies and one Welsh pony [10 healthy, sound adults weighing 411 ± 217 kg (mean ± SD) and aged 10 ± 5 years]. The laminitic group included three Royal Dutch Sport horses, one Friesian, one Haflinger, one Icelandic horse, one Welsh pony, one miniature Appaloosa and six Shetland ponies (14 adults, weight 310 ± 178 kg, aged 13 ± 6 years) with acute/chronic laminitis. The electromyography IPA measurements included firing rate, turns/second (T), amplitude/turn (M) and M/T ratio. Statistical analysis used a general linear model with outcomes transformed to geometric means.Results: The firing rate of the total laminitic group was higher than the total control group. This difference was smaller for the ponies compared to the horses; in the horses, the geometric mean difference of the laminitic group was 1.73 [geometric 95% confidence interval (CI) 1.29–2.32], and in the ponies this value was 1.09 (geometric 95% CI 0.82–1.45).Conclusion and clinical relevance: In human medicine, an increased firing rate is characteristic of increased muscle force. Thus, the increased firing rate of the DDFM in the context of laminitis suggests an elevated muscle force. However, this seems to be only a partial effect as in this study, the unchanged turns/second and amplitude/turn failed to prove the recruitment of larger motor units with larger amplitude motor unit potentials in laminitic equids.

Multi-Motor Unit Potential Analysis and Other Quantitative Techniques for Laryngeal Electromyogram.

Reference values for motor unit potentials of laryngeal muscles, the thyroarytenoid (TA) and cricothyroid (CT) muscles, have been collected using multi-motor unit potential quantitative electromyogram analysis technique with concentric quantitative electromyogram-needle electrode type in 40 healthy volunteers. The method is well tolerated, easy to perform, and examination of one muscle takes usually around 5 minutes. The mean motor unit potential amplitude of both muscles was significantly larger in men than in women. The method can safely be used in clinical routine. Other quantitative electromyogram methods are also shortly reviewed.

Influence of needle electrode depth on DE‐STA motor unit number estimation

To assess a potential source of technique-associated error, we evaluated the influence of needle electrode depth on decomposition-enhanced spike-triggered averaging (DE-STA) motor unit number estimation (MUNE) and quantitative motor unit analysis in the upper trapezius (UT). The DE-STA MUNE protocol was performed at superficial, intermediate, and deep needle electrode depths in 18 control subjects. Mean surface-detected motor unit potential amplitudes were significantly smaller for intermediate versus superficial (P<0.05), deep versus superficial (P<0.001), and deep versus intermediate (P<0.05). MUNE was significantly larger for deep versus superficial (P<0.001), with statistical trends toward larger MUNE values at greater depths for the remaining comparisons. No significant differences were found among needle electrode depths for quantitative motor unit potential parameters. These results demonstrate the important influence of needle electrode depth on DE-STA MUNE in the UT. Suggestions are made for improved standardization of the protocol.

Electrophysiological and Clinical Examination of Polymyositis: A Retrospective Analysis

BackgroundWe retrospectively analyzed electromyogram (EMG), laboratory and clinical data of 93 patients with polymyositis (PM) to help improve early diagnostic accuracy. MethodsData were collected from hospitalized patients who were diagnosed with PM between January 1, 2006 and April 1, 2010 at Chinese People’s Liberation Army General Hospital. ResultsEighty-six (92.47%) patients exhibited an isolated myopathic EMG pattern, 3 (3.23%) showed myopathy combined with neuropathy and 1 (1.08%) had diabetes mellitus. Among the 4 without myopathic EMG, 1 had inflammatory myopathy, and 3 had prior corticosteroid treatment with clinical improvement before EMG examination. Muscle biopsy, performed in 40 cases, inclusive of the 7 cases that did not show an isolated myopathic EMG patterns, revealed that 80% exhibited typical pathological features of PM, 17.5% showed nonspecific muscle fiber necrosis and 2.5% were normal. EMG showed that tibialis anterior and biceps brachii exhibited more abnormal EMG results than abductor pollicis brevis. Patients with disease duration >3 months had significantly higher alanine aminotransferase and reduced motor unit potential (MUP) amplitudes compared to patients with shorter disease duration. statistical analysis revealed a significant association between disease duration and MUP amplitude reduction. Patients without interstitial lung disease showed significantly longer disease duration and higher creatine kinase and lactate dehydrogenase levels than patients with interstitial lung disease. Conclusionsour results show that MUP is a sensitive yardstick for diagnosis of PM and is inversely related to disease duration. our study also highlights that selecting specific muscles for EMG may improve diagnostic accuracy in PM.

P588: Are the electrophysiological tests helpful in differentiating diagnosis between myotonic dystrophies (DM1 and DM2)?

Rochester, MN, USA over 5 years (2009-2013). EMG was performed under conscious sedation in most of the children. Nerve conduction studies were performed in at least 2 nerves (one motor and sensory) and EMG performed in at least 2 muscles in ipsilateral upper and lower limb. 224 patients with the following referral diagnoses (myopathy, muscle weakness, neuromuscular disorders, myositis, myalgia, myoglobinuria, myasthenia, myotonia, cramps, periodic paralysis, hypotonia, and developmental delay) were reviewed. Myotonic discharges were defined as train of spontaneous myofiber action potentials, with waxing and waning amplitudes and frequencies. Myopathic EMG was defined as short duration, low amplitude motor unit potentials with rapid recruitment. Results: Eight children were identified with myotonic discharges during the study period (less than 0.5%). The age range was 3 to 16 years; 6 were males. Two children had isolated myotonic discharges without myopathic changes on EMG while the rest had myopathic EMG in addition to the myotonic discharges. The final diagnoses were: myotonia congenita in 2 (autosomal dominant inheritance in 1 and lack of definite family history in another), congenital myopathy in 3 (centronuclear myopathy-1, congenital fiber type disproportion-1 and congenital myopathy, indeterminate type -1), muscular dystrophy in 2 (facioscapulohumeral muscular dystrophy -1 and muscular dystrophy of indeterminate type-1), and inflammatory myopathy in 1. Two patients with myotonia congenita had clinical myotonia while the rest had only electrical myotonia. Myotonic discharges were diffuse in patients with myotonia congenita while patchy in other patients. Conclusions: Electrical myotonia is a rare electrophysiological finding encountered in our study similar to that reported in the published literature. Though rare, identification of myotonic discharges help to narrow the differential in children with suspected muscle disorders. Diffuse myotonic discharges without myopathic EMG are characteristic of non-dystrophic myotonic disorders.

Pilot study: quantification of motor unit stability, or “jiggle”, in amyotrophic lateral sclerosis (731.11)

Loss of motor units (MUs) have been found in aging, neuropathies, and motor neuron diseases. With MU loss, subsequent collateral reinnervation results in unstable motor unit potentials (MUPs) with variability in firing times and generation of muscle fiber action potentials. Jiggle is a measure of MUP stability, which can be calculated using Decomposition‐based Quantitative Electromyography (DQEMG). Two previous studies have attempted to measure jiggle, but both studies were limited by the EMG decomposition algorithms used. The purpose of this study is to measure jiggle in the upper trapezius muscle of 11 amyotrophic lateral sclerosis (ALS) patients compared to age‐matched healthy controls. Jiggle will be calculated using the normalized value of the median consecutive amplitude difference (CAD). Jiggle will also be compared to other MUP parameters including motor unit number estimation (MUNE), mean surface MUP (S‐MUP) size, MUP amplitude, and near fiber count. As a result of denervation and incomplete reinnervation, we expect to see significantly higher jiggle values in patients with ALS relative to controls. We also expect jiggle to be negatively correlated with MUNE, and positively correlated with mean S‐MUP size, MUP amplitude, and near fiber count. If successful, jiggle may be a valuable diagnostic parameter or outcome measure in age‐related sarcopenia, neuropathies, or motor neuron diseases such as ALS.

Effects of muscle fibre shortening on the characteristics of surface motor unit potentials

Traditionally, studies dealing with muscle shortening have concentrated on assessing its impact on conduction velocity, and to this end, electrodes have been located between the end-plate and tendon regions. Possible morphologic changes in surface motor unit potentials (MUPs) as a result of muscle shortening have not, as yet, been evaluated or characterized. Using a convolutional MUP model, we investigated the effects of muscle shortening on the shape, amplitude, and duration characteristics of MUPs for different electrode positions relative to the fibre-tendon junction and for different depths of the MU in the muscle (MU-to-electrode distance). It was found that the effects of muscle shortening on MUP morphology depended not only on whether the electrodes were between the end-plate and the tendon junction or beyond the tendon junction, but also on the specific distance to this junction. When the electrodes lie between the end-plate and tendon junction, it was found that (1) the muscle shortening effect is not important for superficial MUs, (2) the sensitivity of MUP amplitude to muscle shortening increases with MU-to-electrode distance, and (3) the amplitude of the MUP negative phase is not affected by muscle shortening. This study provides a basis for the interpretation of the changes in MUP characteristics in experiments where both physiological and geometrical aspects of the muscle are varied.

The standard concentric needle cannula cannot replace the Macro EMG electrode

ObjectiveTo establish the usefulness of the single use and affordable standard concentric EMG electrode as a substitute for the expensive standard macro electrode. MethodsMacro EMG performed with macro electrode is compared with recordings from the uninsulated cannula of a standard EMG electrode at two different recording depths in the tibialis anterior muscle. This was performed both in muscles with signs of collateral reinnervation and without. ResultsThe amplitude of the motor units recorded with the uninsulated concentric needle cannula were lower for the deeply recorded motor units compared to motor unit potential (MUP) amplitudes recorded with the standard macro electrode. The deeply recorded concentric needle (CN) cannula recorded MUPs amplitudes were also lower than superficially recorded CN cannula MUPs. The standard Macro EMG signals show no difference between deeply and superficially recorded motor units. ConclusionThe uninsulated cannula of the concentric needle electrode cannot replace the standard Macro EMG electrode due to technical reasons, probably from different effects of shunting of the bare cannula in deep vs. superficially recorded motor units. SignificanceThe standard CN electrode could not be used as substitute for the standard Macro EMG needle.

Spatial distribution of surface action potentials generated by individual motor units in the human biceps brachii muscle

This study analyses the spatial distribution of individual motor unit potentials (MUPs) over the skin surface and the influence of motor unit depth and recording configuration on this distribution. Multichannel surface (13×5 electrode grid) and intramuscular (wire electrodes inserted with needles of lengths 15 and 25mm) electromyographic (EMG) signals were concurrently recorded with monopolar derivations from the biceps brachii muscle of 10 healthy subjects during 60-s isometric contractions at 20% of the maximum torque. Multichannel monopolar MUPs of the target motor unit were obtained by spike-triggered averaging of the surface EMG. Amplitude and frequency characteristics of monopolar and bipolar MUPs were calculated for locations along the fibers’ direction (longitudinal), and along the direction perpendicular (transverse) to the fibers. In the longitudinal direction, monopolar and bipolar MUPs exhibited marked amplitude changes that extended for 16–32mm and 16–24mm over the innervation and tendon zones, respectively. The variation of monopolar and bipolar MUP characteristics was not symmetrical about the innervation zone. Motor unit depth had a considerable influence on the relative longitudinal variation of amplitude for monopolar MUPs, but not for bipolar MUPs. The transverse extension of bipolar MUPs ranged between 24 and 32mm, whereas that of monopolar MUPs ranged between 72 and 96mm. The mean power spectral frequency of surface MUPs was highly dependent on the transverse electrode location but not on depth. This study provides a basis for the interpretation of the contribution of individual motor units to the interference surface EMG signal.

Diagnosis of Zygomaticus Muscle Paralysis Using Needle Electromyography With Ultrasonography

A 22-year-old woman visited our clinic with a history of radiofrequency volumetric reduction for bilateral masseter muscles at a local medical clinic. Six days after the radiofrequency procedure, she noticed a facial asymmetry during smiling. Physical examination revealed immobility of the mouth drawing upward and laterally on the left. Routine nerve conduction studies and needle electromyography (EMG) in facial muscles did not suggest electrodiagnostic abnormalities. We assumed that the cause of facial asymmetry could be due to an injury of zygomaticus muscles, however, since defining the muscles through surface anatomy was difficult and it was not possible to identify the muscles with conventional electromyographic methods. Sono-guided needle EMG for zygomaticus muscle revealed spontaneous activities at rest and small amplitude motor unit potentials with reduced recruitment patterns on volition. Sono-guided needle EMG may be an optimal approach in focal facial nerve branch injury for the specific localization of the injury lesion.

Somatic mosaicism in TPM2-related myopathy with nemaline rods and cap structures

The TPM2 gene encodes for beta-tropomyosin. Dominant mutations in TPM2 are associated with different congenital myopathies, including nemaline and cap myopathy [8]. In one family, a TPM2 mutation (p.Glu41Lys) has been reported to cause a myopathy with nemaline rods in the mother and cap structures in the daughter [7]. We describe a family with two siblings affected by congenital myopathy showing both rods and cap-like structures caused by a TPM2 mutation. Their clinically asymptomatic father was a somatic mosaic for the mutation. The proband, a 15-year-old girl, presented with slowly progressing muscle weakness in the first decade. At age 13, she developed rapidly progressing scoliosis and respiratory failure, leading to hypercapnic coma, with subsequent tracheostomy. On examination, she had moderate diffuse weakness more pronounced in ankle extensors, long narrow face, scoliosis and rigid spine. CK level and cardiological examinations were normal. Her 14-year-old brother displayed a similar, although milder, phenotype. He had elongated face, high arched palate, rigid spine and mild scoliosis. Ankle extensors, neck flexors, supra and infraspinatus muscles were weak. Forced vital capacity was 60 % of predicted value. Their parents were reported to be healthy. Muscle MRI features are shown in Fig. 1. Given the clinical and radiological phenotype and the possibly recessive pattern of inheritance, SEPN1 mutations were ruled out. Muscle biopsy disclosed in both patients the presence of nemaline rods, cap structures (Fig. 1d–i) and type 1 fiber predominance. These findings prompted us to examine the TPM2 gene, and a heterozygous deletion, c.412_414delGAG (p.E138del) in exon 4, was found (Fig. 1k). When their parents were examined, the 47-year-old father, who did not complain of any neuromuscular symptom and routinely practiced mountaineering, did not show any obvious weakness or contractures but had mild scoliosis and high arched palate. EMG displayed some polyphasic, short amplitude motor unit potentials. Muscle MRI showed features consistent with those of the siblings (Fig. 1c). Muscle biopsy showed mild myopathic features, with cap structures in rare fibers (Fig. 1j) and no nemaline rods. The electropherogram of the TPM2 gene revealed a relatively low level of the mutation in blood DNA suggesting a somatic mosaicism. SNaPshot analysis [1] confirmed the presence of mosaicism (Fig. 1k). The p.E138del pathogenic deletion found in the family has been previously reported only in pure cap disease [3, 5]. Our findings further substantiate the concept that nemaline rods and cap structures belong to the same spectrum of pathological alterations [4] and, although both nemaline myopathy and cap disease are genetically heterogeneous entities, the coexistence of both features should suggest investigating TPM2 first [7]. In the family, the proband’s father had the mildest phenotype so far reported in association with TPM2 G. Tasca G. Silvestri Don Carlo Gnocchi Onlus Foundation, Milan, Italy