Needle Electromyography Research Articles

Differentiation between single fiber potentials from one muscle fiber or contaminated by other fibers using discriminating function

ObjectivesThe aim was to improve the identification of potentials recorded using single fiber electromyography (SFEMG) contaminated by potentials from other muscle fibers, which might affect measured jitter value, by defining more selective criteria of single fiber potential (SFP) discrimination. We were looking for solutions suitable for automatization. MethodsStandard parameters characterizing SFP and their combinations were analyzed to define an analytical discriminating function able to verify if potentials recorded using SFEMG are due to single fiber or due to two (or more) fibers. ResultsThe discriminating function is based on combination of standard SFP parameters. The procedure was tested on a set of simulated i.e., known data and on samples of clinical data. The tests on simulated data confirmed assumed properties of discriminating function. Preliminary results of pilot studies using patient data suggest its ability for differentiation between potentials of one fiber and contaminated ones. The procedure is suitable for automatization. ConclusionResults suggest that proposed discriminating function when supplementing standard criteria would help to promote SFP recordings and enable to improve relevancy of jitter measurements and of jitter value norms.

The Utility of Concentric Needle Single Fiber Electromyography in Diagnosing Myasthenia Gravis

The Utility of Concentric Needle Single Fiber Electromyography in Diagnosing Myasthenia Gravis

P038 Is it all in the eyes?

Abstract Background/Aims The ocular manifestations of giant cell arteritis (GCA) and ocular myasthenia gravis (OMG) have significant overlap, which can lead to clinical uncertainty in the absence of awareness and routine diagnostic testing. Methods We present the case of a 63-year-old male patient with a strong family history of autoimmune disease. He presented to the Rheumatology department in 2009 with symptoms of polymyalgia rheumatica (PMR) and was treated successfully with a reducing regime of Prednisolone. In 2013, he presented to the Ophthalmology department with blurred vision and diplopia. Giant cell arteritis was suspected and a high dose of Prednisolone was started. His temporal artery biopsy was normal and inflammatory markers were not raised, but there was a complete resolution of his symptoms since starting steroids. Under the care of the Rheumatology department, reducing regimes of Prednisolone were attempted and a steroid sparing agent, Methotrexate was introduced. Unfortunately, he continued to have recurring symptoms of blurred vision and diplopia, particularly at Prednisolone doses less than 20mg. Over the course of a few years, there was a progression of his ocular symptoms. He developed a horizontal diplopia, monocular ptosis and a 4th nerve palsy. He was referred back to the Ophthalmology department, where alternate diagnoses were investigated. Anti-acetylcholine receptor antibodies (AChR) were strongly positive at 35 mU/L (normal <0.44 mU/L). MRI head was normal, and CT chest showed no thymoma. Single fibre EMG confirmed severe OMG. Our patient was subsequently commenced on Pyridostigmine, with which symptoms improved. Results The literature on OMG mimicking GCA is sparse. The prevalence of an exclusively ophthalmic presentation in patients with GCA is 1 in 5. Ocular signs and symptoms in GCA can vary drastically due to the propensity of the disease to affect different structures within the eye. Transient and permanent visual loss, affects 10-30% of GCA patients due to anterior ischemic optic neuropathy. Diplopia affects 5% of GCA patients. In comparison, OMG can be the only presenting feature in 15% of patients with Myasthenia Gravis, and is characterised by unilateral ptosis, oculomotor paresis and binocular diplopia. Conclusion This case highlights the clinical similarities of OMG and GCA, and that OMG should be considered as a differential diagnosis when the clinical picture of GCA does not truly fit. In patients presenting with GCA with ocular symptoms, normal inflammatory markers and no systemic features, OMG should be considered and AChR antibody testing be performed. More awareness of OMG is needed. We also propose that OMG should be included as a differential diagnosis, in the British Society of Rheumatology guidelines for GCA. Disclosure A. Gharatya: None. J. Wajed: None. N. Cernovschi: None. D. Christidis: None.

Profiling age-related muscle weakness and wasting: neuromuscular junction transmission as a driver of age-related physical decline.

Pathological age-related loss of skeletal muscle strength and mass contribute to impaired physical function in older adults. Factors that promote the development of these conditions remain incompletely understood, impeding development of effective and specific diagnostic and therapeutic approaches. Inconclusive evidence across species suggests disruption of action potential signal transmission at the neuromuscular junction (NMJ), the crucial connection between the nervous and muscular systems, as a possible contributor to age-related muscle dysfunction. Here we investigated age-related loss of NMJ function using clinically relevant, electrophysiological measures (single-fiber electromyography (SFEMG) and repetitive nerve stimulation (RNS)) in aged (26 months) versus young (6 months) F344 rats. Measures of muscle function (e.g., grip strength, peak plantarflexion contractility torque) and mass were assessed for correlations with physiological measures (e.g., indices of NMJ transmission). Other outcomes also included plantarflexion muscle contractility tetanic torque fade during 1-s trains of stimulation as well as gastrocnemius motor unit size and number. Profiling NMJ function in aged rats identified significant declines in NMJ transmission stability and reliability. Further, NMJ deficits were tightly correlated with hindlimb grip strength, gastrocnemius muscle weight, loss of peak contractility torque, degree of tetanic fade, and motor unit loss. Thus, these findings provide direct evidence for NMJ dysfunction as a potential mechanism of age-related muscle dysfunction pathogenesis and severity. These findings also suggest that NMJ transmission modulation may serve as a target for therapeutic development for age-related loss of physical function.

Electrophysiological Study of the Tibial Nerve Across the Tarsal Tunnel in Distal Symmetric Diabetic Polyneuropathy.

The aim of the study was to demonstrate abnormalities of motor conduction of the tibial nerve across the tarsal tunnel in type 2 diabetes. One hundred twenty-four consecutive patients (mean age = 66.6 yrs, 62.1% male) with distal symmetric diabetic polyneuropathy clinically diagnosed were prospectively enrolled. Nerve conduction studies of deep peroneal, tibial, superficial peroneal, medial plantar, and sural nerves and standard needle electromyography in the lower limbs were performed. Demographic, anthropometric, and clinical findings were collected. Motor conduction velocity of the tibial nerve across tarsal tunnel was slowed in 60.5% of patients; another 4% showed conduction block across tarsal tunnel without reduction of motor conduction velocity. Overall percentage of abnormalities across tarsal tunnel (64.5%) exceeds that of the sensory conduction velocities of proximal sural and superficial peroneal nerves. Abnormal tibial motor conduction velocity across tarsal tunnel represents the most common abnormality among all motor nerve conduction study parameters and significantly correlates with hemoglobin level, diabetic neuropathic index score, and diabetic complications frequency. Tibial conduction abnormalities across tarsal tunnel are the most sensitive motor parameter in distal symmetric diabetic polyneuropathy, second only to conduction abnormalities of sensory/mixed distal nerves of the feet. The use of nerve conduction studies across tarsal tunnel of the tibial nerve may be useful in the electrophysiological protocol to confirm the diagnosis of distal symmetric diabetic polyneuropathy.

Thymic Neoplasm: A Rare Disease With Unusual Neurologic Manifestations

Thymoma is a rare tumor that is commonly associated with autoimmune diseases. Of these, myasthenia gravis (MG) is widely considered as the most common paraneoplastic condition. On the other hand, dermatomyositis (DM) has been rarely reported as the first presentation of non-invasive thymoma. Hereby, we describe a patient with non-invasive thymoma who initially presented with painful symmetric proximal muscle weakness with no signs of ptosis or diplopia. The needle electromyography (EMG) revealed spontaneous/insertional activity in proximal muscles. The patient was finally diagnosed with DM by muscle biopsy. Spiral chest computed tomography (CT) scan coupled with pathological assessment confirmed a non-invasive thymoma with diffuse reaction for P63 and pancytokeratin (Panck). Corticosteroids pulse therapy was initiated and the patient was referred for thymectomy. A few months later, patient began to display other neurological symptoms such as ptosis and diplopia with fluctuating pattern. As coexistence of MG was presumed, nerve conduction study (NCS) study was performed and slow repetitive nerve stimulation in proximal muscles showed more than 10% decrement in compound muscle action potential (CMAP) amplitude in repetitive nerve stimulation (RNS). Further workup revealed a positive anti-acetylcholine receptor antibody with high titer. Thus, MG was confirmed. No more treatment options were planned. Low dose corticosteroids were continued and azathioprine and pyridostigmine were prescribed. During follow-ups, symptoms were fully controlled. J Neurol Res. 2021;11(1-2):32-36 doi: https://doi.org/10.14740/jnr625

Neuromuscular urethral function and urethral urodynamic parameters between urgency and stress incontinence do not differ.

To describe and compare urethral neuromuscular function using concentric needle electromyography (CNEMG) and urodynamic (UDS) parameters between stress incontinent (SUI) and urge incontinent (UUI) women. Incontinent women were recruited from a urogynecology clinic if they answered "sometimes" or "always" to one of the items on the Medical, Epidemiologic, and Social Aspects of Aging questionnaire. Participants were categorized by MESA scores into stress (SUI) or urgency (UUI) incontinence groups. Participants underwent CNEMG of the striated urethral sphincter at three insertion sites using Medtronic multiple motor unit action potential analysis. UDS was performed with Laborie microtip catheters: urethral pressure profiles were obtained at baseline and 300ml. Data were analyzed in SPSS. Continuous variables were compared with independent t-test or Mann-Whitney U, categorical variables with chi-square test. A logistic regression was performed to control for variables found to be significant on univariate analysis. Fifty-six women (37 SUI, 19 UUI) with mean ± SD age of 53 ± 13years participated. At baseline, patients with SUI were younger, more likely to be premenopausal and had lower BMIs. There were no differences in urethral EMG or UDS parameters between UUI and SUI women except lower maximum cystometric capacity in women with UUI. When controlling for age, BMI and MCC on logistic regression, there remained no differences between SUI and UUI groups on EMG or UDS parameters. Women with UUI and DO show similar evidence of denervation-reinnervation injury to the striated urethral sphincter muscle as women with SUI.

In memoriam: Robert T. Leshner, MD

In memoriam: <scp>Robert T. Leshner</scp>, <scp>MD</scp>

Direct Cortical Stimulation in Neurosurgical Emergencies: Single-Center Experience in 2 Patients

Intraoperative neuromonitoring (IONM) is widely used for elective resection of eloquently located brain tumors to increase safety and extent of resection. Owing to the need for specially trained personnel for IONM and the sophisticated, time-consuming technical setup, standard IONM is usually not suitable for emergency situations. We report the use of a device that can be operated by the neurosurgeon autonomously for monopolar brain mapping in 2 emergency cases. Both patients were initially scheduled for elective neurosurgery under IONM. Acute neurological deterioration in both cases led to emergency surgery. For monopolar cortical/subcortical stimulation, a standard monopolar probe was connected to a new device enabling electromyography real-time tracking of 8 muscles. Preoperative application of subdermal electromyography needles and intraoperative handling of the device were performed by the neurosurgeons independently. Cortical mapping of the motor cortex was performed in both patients with a threshold of 4 mA in case 1 and 14 mA in case 2. Gross total resection with residual tumor volume of <2 mL in case 1 and subtotal resection with residual tumor volume of 4.2 mL in case 2 were achieved under use of the new device without any new neurological deficit. Grade IV glioblastoma was diagnosed in both patients. We demonstrate the feasibility of monopolar stimulation in 2 patients undergoing emergency neurosurgery using a device autonomously operated by the surgeon. Owing to fast setup and nondemanding handling, monopolar stimulation could be used during emergency neurosurgery to extend resection with preservation of neurological function in both cases.

Risk factors and diagnostic methods of intensive care unit-acquired weakness

To explore the risk factors of intensive care unit-acquired weakness (ICU-AW) and the characteristics of Medical Research Council (MRC) score and electromyogram. A case control study was conducted. Patients with mechanical ventilation ≥ 7 days and MRC score admitted to department of respiratory and critical care medicine of China-Japan Friendship Hospital from September 2018 to January 2020 were enrolled, and they were divided into ICU-AW group (MRC score < 48) and non-ICU-AW group (MRC score ≥ 48) according to MRC score. The general situation, past medical history, related risk factors, MRC score, respiratory support mode, laboratory examination results, electromyogram examination results, ICU-AW related treatment, outcome and length of ICU stay were collected, and the differences between the two groups were compared. The risk factors of ICU-AW were analyzed by binary multivariate Logistic regression, and the characteristics of MRC score and electromyogram were analyzed. A total of 60 patients were enrolled in the analysis, including 17 patients in ICU-AW group and 43 patients in non-ICU-AW group. Univariate analysis showed that there were significant differences in acute physiology and chronic health evaluation II (APACHE II) score, sequential organ failure assessment (SOFA) score, brain natriuretic peptide (BNP), blood urea nitrogen (BUN) on the first day of ICU admission and the ratio of invasive mechanical ventilation between ICU-AW group and non-ICU-AW group [APACHE II score: 21 (18, 25) vs. 18 (15, 22), SOFA score: 7 (5, 12) vs. 5 (3, 8), BNP (ng/L): 364.3 (210.1, 551.2) vs. 160.1 (66.8, 357.8), BUN (mmol/L): 9.9 (6.2, 17.0) vs. 6.0 (4.8, 9.8), invasive mechanical ventilation ratio: 88.2% vs. 46.5%, all P < 0.05]. Binary multivariate Logistic regression analysis showed no independent risk factor for ICU-AW. The average MRC score of 17 ICU-AW patients was 33±11. The limb weakness was symmetrical, and the proximal limb weakness was the main manifestation. Electromyography examination showed that the results of nerve conduction examination in ICU-AW patients mainly revealed that the amplitude of compound muscle action potential (CMAP) and sensory nerve action potentials (SNAP) were decreased, and the conduction velocity was slowed down; needle electromyography showed increased area of motor unit potential (MUP), prolonged time limit and a large number of spontaneous potentials. Prognosis evaluation showed that compared with non-ICU-AW group, patients in ICU-AW group underwent more tracheotomy (70.6% vs. 11.6%), longer length of ICU stay (days: 57±52 vs. 16±8), and more rehabilitation treatment (58.8% vs. 14.0%), and the differences were statistically significant (all P < 0.01). The occurrence of ICU-AW may be related to high APACHE II score and SOFA score, high levels of BNP and BUN on the first day of ICU admission and the proportion of invasive mechanical ventilation, but the above factors are not independent risk factors for ICU-AW. The MRC score of ICU-AW patients was characterized by symmetrical limb weakness, mainly proximal limb weakness; in electromyography examination, the nerve conduction examination results mainly showed that CMAP and SNAP amplitude were decreased, and conduction velocity was slowed down; needle electromyography examination showed increased MUP area, prolonged duration and a large number of spontaneous potentials.

Thymic Neoplasm: A Rare Disease With Unusual Neurologic Manifestations

Thymoma is a rare tumor that is commonly associated with autoimmune diseases. Of these, myasthenia gravis (MG) is widely considered as the most common paraneoplastic condition. On the other hand, dermatomyositis (DM) has been rarely reported as the first presentation of non-invasive thymoma. Hereby, we describe a patient with non-invasive thymoma who initially presented with painful symmetric proximal muscle weakness with no signs of ptosis or diplopia. The needle electromyography (EMG) revealed spontaneous/insertional activity in proximal muscles. The patient was finally diagnosed with DM by muscle biopsy. Spiral chest computed tomography (CT) scan coupled with pathological assessment confirmed a non-invasive thymoma with diffuse reaction for P63 and pancytokeratin (Panck). Corticosteroids pulse therapy was initiated and the patient was referred for thymectomy. A few months later, patient began to display other neurological symptoms such as ptosis and diplopia with fluctuating pattern. As coexistence of MG was presumed, nerve conduction study (NCS) study was performed and slow repetitive nerve stimulation in proximal muscles showed more than 10% decrement in compound muscle action potential (CMAP) amplitude in repetitive nerve stimulation (RNS). Further workup revealed a positive anti-acetylcholine receptor antibody with high titer. Thus, MG was confirmed. No more treatment options were planned. Low dose corticosteroids were continued and azathioprine and pyridostigmine were prescribed. During follow-ups, symptoms were fully controlled. J Neurol Res. 2021;11(1-2):32-36 doi: https://doi.org/10.14740/jnr625

Peripheral nerve reconstruction - diagnostics as a basis for decision-making: report of the Consensus Workshop at the 35th Meeting of the DAM

In the early stage of nerve lesions, the clinical differentiation between neurapraxia, axonotmesis and neurotmesis often presents a big challenge. Especially in the early stage, however, it is crucial to correctly classify the type of damage because this is what essentially determines the therapeutic concept, in particular the surgical approach and, therefore, the prognosis. A precise diagnosis not only requires detailed clinical assessment and medical history taking, but also the use of additional electrophysiological (functional) and/or imaging examinations. Electrophysiological diagnostic tests may provide information ion localization, severity, course, type of damage and incipient or past reinnervation. Preoperative functional diagnostic measures should include neurography, needle electromyography (EMG) and, if needed, evoked potentials (EP), while imaging procedures should include neural sonography and magnetic resonance imaging (MRI). As a complimentary procedure, EMG may also be performed during surgery.

Lower Motor Neuron Abnormality in Chronic Cervical Spinal Cord Injury: Implications for Nerve Transfer Surgery.

Nerve transfer surgery (NT) constitutes an exciting option to improve upper limb functions in chronic spinal cord injury (SCI), but requires intact sublesional lower motor neuron (LMN) health. The purpose of this study was to characterize patterns of LMN abnormality in nerve-muscle groups that are the potential recipients of NT, using a standardized electrodiagnostic examination, in individuals with chronic SCI (injury duration >2 years, injury levels C4-T1). The LMN abnormality was determined using a semihierarchical approach, combining the amplitude compound muscle action potential (CMAP) and abnormal spontaneous activity on needle electromyography (EMG). Ten participants (46 potential recipient muscles) were included (median age, 42.5 years; six males and four females; median duration from injury, 15.5 years). A high frequency of LMN abnormality was observed (87%), although there was substantial variation within and between individuals. No statistically significant discordance was observed between LMN abnormality on CMAP and EMG (p = 0.24), however, 50% of muscles with normal CMAP demonstrated abnormal spontaneous activity. The high frequency of LMN abnormality in recipient nerve-muscle groups has implications to candidate selection for NT surgery in chronic SCI and supports the important role of the pre-operative electrodiagnostic examination. Our results further support the inclusion of both CMAP and needle EMG parameters for characterization of LMN health. Although the number of nerve-muscle groups with normal LMN health was small (13%), this underscores the neurophysiological potential of some patients with chronic injuries to benefit from NT surgery.

Long-term outcomes of dual innervation in functional muscle transfers for facial palsy

This study describes a different approach with a 2-stage facial reanimation in patients with long-standing unilateral facial paralysis using free gracilis muscle transfer, innervated by both cross-facial nerve graft and masseteric nerve. The authors present their rationale, surgical technique, and long-term outcomes. Between August 2012 and March 2016, 11 patients (6 female and 5 male patients) underwent a 2-staged dually innervated gracilis muscle transfer. Patients were evaluated with physical examination and needle electromyography. A standardized assessment of preoperative and postoperative photographs and videos was performed using Terzis' smile functional grading system at 48 months following surgery and the Emotrics software to assess improvement in symmetry over a 36-month postoperative period. Voluntary contraction of the gracilis muscle was observed in all patients at a mean of 4 months and 4 days following muscle transfer. A spontaneous smile produced without teeth clenching was developed in all patients by 18 months postoperatively. Six patients achieved excellent and 5 good results. The difference between the averaged pre- and postoperative scores was statistically significant. With Emotrics, there were significant improvements in the smile angle, upper lip elevation, commissural excursion, and commissural height, with continuous improvement over 36 months. The postoperative electromyography (EMG) confirmed dual innervation of the gracilis muscle by the facial and masseteric donor motor neural sources. We present our results at minimum 48 months postoperatively. Dual innervated two-stage gracilis transfer is an effective method for reanimation in long-standing unilateral facial paralysis, providing both rapid reinnervation of the transferred muscle, together with a powerful, synchronous smile.

Fasciculation score: a sensitive biomarker in amyotrophic lateral sclerosis.

The aim of our study was to elucidate the characteristic of fasciculation distributions in amyotrophic lateral sclerosis (ALS) using a fasciculation score (FS) of muscle ultrasound (MUS) and to compare the diagnostic values of three MUS fasciculation parameters in patients. Thirty ALS patients, 16 ALS mimics, and 10 healthy subjects were involved. MUS of unilateral 10 muscles in each patient and needle electromyography (EMG) of total 204 muscles were performed to detect fasciculations and spontaneous activity respectively in ALS. Control groups underwent only MUS. Fasciculation was graded semiquantitatively with FS. Three hundred fifty muscles in ALS and 260 in controls were examined. The fasciculation detection rates, total FS, the number of muscles with fasciculation, and the total number of fasciculations in ALS were all significantly higher than those of controls (P < 0.001). ALS patients exhibited a multifocal continuous pattern of fasciculation in limbs, whereas there were few fasciculations in controls. Compared with other parameters, total FS had the largest area under the curve (AUC) (AUC = 0.899, P < 0.001) in ALS diagnosis. The detection rates of lower motor neuron (LMN) acute lesions by MUS (70.6%) and EMG (72.1%) were nearly the same, and a positive correlation between the FS and spontaneous activity grades (P < 0.001, r = 0.359) was proved. ALS patients exhibited the multifocal continuous pattern of fasciculation in limbs. FS showed high sensitivity and specificity in differentiating ALS from non-ALS patients, and the optimal cut-off value was determined as 4. The combination of MUS and EMG can provide additional information about specific muscles.

Combined Muscle Biopsy and Comprehensive Electrophysiology in General Anesthesia is Valuable in Diagnosis of Neuromuscular Disease in Children.

The diagnostic workup in patients with delayed motor milestones suspected of having either myopathy or a congenital myasthenic syndrome is complex. Our hypothesis was that performance of a muscle biopsy and neurophysiology including stimulated single-fiber electromyography during an anesthetic procedure, combined with genetic testing has a high diagnostic quality. Clinical and paraclinical data were retrospectively collected from 24 patients aged from 1 month to 10 years (median: 5.2 years). Neurophysiology examination was performed in all patients and was abnormal in 11 of 24. No patients had findings suggestive of a myasthenic syndrome. Muscle biopsy was performed in 21 of 24 and was normal in 16. Diagnostic findings included nemaline rods, inclusion bodies, fiber size variability, and type-II fiber atrophy. Genetic testing with either a gene panel or exome sequencing was performed in 18 of 24 patients, with pathogenic variants detected in ACTA1, NEB, SELENON, GRIN2B, SCN8A, and COMP genes. Results supporting a neuromuscular abnormality were found in 15 of 24. In six patients (25%), we confirmed a genetic diagnosis and 12 had a clinical neuromuscular diagnosis. The study suggests that combined use of neurophysiology and muscle biopsy in cases where genetic testing does not provide a diagnosis can be useful in children with delayed motor milestones and clinical evidence of a neuromuscular disease.

A Novel Pathogenic HSPG2 Mutation in Schwartz-Jampel Syndrome.

Schwartz–Jampel syndrome is a rare autosomal recessive disease caused by mutation in the heparan sulfate proteoglycan 2 (HSPG2) gene. Its cardinal symptoms are skeletal dysplasia and neuromuscular hyperactivity. Herein, we identified a new pathogenic mutation site (NM_005529.6:c.1125C>G; p.Cys375Trp) of HSPG2 leading to Schwartz–Jampel syndrome by whole-exome sequencing. This mutation carried by the asymptomatic parents was previously registered in a single-nucleotide polymorphism database of the National Institutes of Health as a coding sequence variant rs543805444. The pathogenic nature of this missense mutation was demonstrated by in silico pathogenicity assessment, clinical presentations, and cellular function of primary fibroblast derived from patients. Various in silico software applications predicted the mutation to be pathogenic [Sorting Intolerant From Tolerant (SIFT), 0; Polyphen-2, 1; CADD (Combined Annotation Dependent Depletion), 23.7; MutationTaster, 1; DANN (deleterious annotation of genetic variants using neural networks); 0.9]. Needle electromyography revealed extensive complex repetitive discharges and multiple polyphasic motor unit action potentials in axial and limb muscles at rest. Short exercise test for myotonia showed Fournier pattern I. At cellular levels, mutant primary fibroblasts had reduced levels of secreted perlecan and impaired migration ability but normal capability of proliferation. Patients with this mutation showed more neuromuscular instability and relatively mild skeletal abnormality comparing with previously reported cases.

The eccentric mechanotransduction, neuro-muscular transmission, and structural reversibility of muscle fatty infiltration. An experimental advanced disuse muscle-wasting model of rabbit supraspinatus.

IntroductionFull-thickness rotator cuff tear is present in almost 50% of patients over age 65 years, and its degree is known to be a good predictor of the severity of muscle-wasting (MW) sarcopaenia, also known as fatty degeneration (FD). A FD CT grade > 2° is recognized as a borderline of its reversibility. A disuse model of supraspinatus FD (grade 2) in rabbits provides clinically relevant data. Therefore, the present study evaluates the correlation between eccentric mechanotransduction, neuromuscular transmission (NT), and reversibility of muscle fatty infiltration (MFI) in rabbit supraspinatus FD > 2°.Material and methodsThe supraspinatus tendon was detached from the greater tubercle, infraspinatus, and subscapularis in 16 rabbits. The tendon was reinserted after 12 weeks, and the animals were euthanized 24 weeks after reconstruction. MFI was measured in the middle part of the supraspinatus. Single-fibre EMG (SFEMG) examination of the supraspinatus NT was performed on 4 animals.ResultsThe power of analysis was 99%. Significant differences in MFI volume were found between the operated (4.6 ±1.1%) and the opposite control sides (2.91 ±0.61%) (p < 0.001). SFEMG revealed no significant differences between the disuse and the control supraspinatus muscles (p > 0.05); however, 6.5% of the examined muscle fibres exhibited NT disorders combined with blockade of conduction in 2.5% of muscle fibres.ConclusionsCritical MFI in a disuse model of rabbit supraspinatus FD, CT grade > 2°, is substantially reversible by eccentric training despite subclinical impairment of neuromuscular transmission. In addition, 0.63% reversal of MFI is correlated with 1% hypertrophy of type I and II muscle fibre diameter.

Scapular winging secondary to serratus anterior dysfunction: analysis of clinical presentations and etiology in a consecutive series of 96 patients.

This study aimed to establish the relative incidence of etiologies causing serratus anterior (SA) dysfunction in patients with proven abnormality on needle electromyography. This was a retrospective review of patients with scapular winging secondary to SA dysfunction. Each patient underwent a detailed clinical, radiological, and neurophysiological assessment to arrive at the precise etiological diagnosis. Patients with atypical clinical features were referred for a neurologist's assessment. Hematological and genetic testing were requested at the discretion of the neurologist. A scapular winging severity score based on clinical signs was devised to aid clinical grading. Between 2014 and 2020, a consecutive series of 108 patients with suspected SA dysfunction were assessed, of whom 96 met the inclusion criteria. There were 34 females and 62 males, with a mean age of 38 years (range, 15-77 years). Winging affected the right scapulae in 69 patients, the left scapulae in 17 patients, and was bilateral in 10 patients. This was caused by a myopathic disorder in 12 (12%) patients. Eighty-four (88%) patients had a long thoracic nerve lesion, caused by cervical pathology (2), iatrogenic injury (2), trauma (33), and neuralgic amyotrophy (NA) (47). Among those with NA, winging resolved spontaneously within 3 years of onset in 22 patients (mean duration, 16 months; range, 3-36 months). No patients recovered fully if their duration of winging lasted longer than 3 years. Patients with palsy secondary to NA tended to have a worse severity of winging than those due to a traumatic cause (P = .04). NA accounted for approximately half of the patients with SA dysfunction; therefore, it is essential to also consider the differentials of myopathy, trauma, iatrogenic injury, and spinal pathology. We recommend the judicious employment of ancillary tests and a low threshold of referral to a neurologist, in order to arrive at the exact diagnosis to accurately guide patient treatment.

Preoperative electrophysiologic assessment of C5-innervated muscles in predicting C5 palsy after posterior cervical decompression.

To investigate the feasibility of both needle electromyography (EMG) and proximal nerve conduction studies (NCS) in predicting C5 palsy after posterior cervical decompression. This study included 192 patients with cervical myelopathy undergoing laminoplasty or laminectomy. Preoperatively, all patients accepted bilateral needle EMG detection and proximal NCS that consisted of supramaximally stimulating Erb's point and recording compound muscle action potential (CMAP) from bilateral deltoid. In the present study, 11 (11/192, 5.7%) patients developed unilateral C5 palsy after operation, and more patients with C5 palsy showed abnormal spontaneous activity in C5-innervated muscles compared to those without C5 palsy (8/11 vs. 16/181, p < 0.05). The sensitivity and specificity of spontaneous activity in C5-innervated muscles in predicting postoperative C5 palsy were 72.7% and 91.2%, respectively. Furthermore, there were significant left-to-right differences of deltoid CMAP amplitudes between the patients with and without C5 palsy (p < 0.05), and this measurement was also demonstrated to be useful for distinguishing patients with C5 palsy from cases without C5 palsy by receiver operating characteristic (ROC) curve analysis (cut-off value: 2.1mV, sensitivity: 63.6%; specificity: 95.0%). In addition, the sensitivity and specificity of a series application of these two measurements were 63.6% and 100.0%, respectively. The findings of this study support the hypothesis that pre-existing progressive C5 root injury may be a risk factor for C5 palsy after posterior cervical decompression. Clinically, the estimation of NCS and needle EMG in C5-innervated muscles may provide additional useful information for predicting C5 palsy after cervical spinal surgery. Diagnostic: individual cross-sectional studies with the consistently applied reference standard and blinding.