Muscle & Nerve最新文献

Introduction/aims: The hypoglossal nerve is primarily responsible for tongue movement, but studies on its conduction are scarce. The F-wave, generated by antidromic depolarization of spinal motor neurons, serves as an indicator of proximal motor nerve conduction and is commonly used to assess proximal segments, particularly in distal limb nerves. Our aim was to investigate the F-wave of the hypoglossal nerve in healthy subjects.

Methods: Healthy adult volunteers underwent bilateral hypoglossal nerve F-wave testing. Recordings were obtained from the genioglossus muscles using paired monopolar needle electrodes placed 5 mm from the midline on the internal concave surface of the jaw, adjacent to the mental spines. Superficial stimulation was performed with a bipolar electrical stimulator applied to the hypoglossal nerve in the neck, one fingerbreadth below the middle third of the mandibular body. Compound muscle action potentials (CMAPs) and F-waves were recorded, with 10 to 20 stimuli applied to obtain 10 F-waves, using the shortest response for analysis.

Results: A total of 20 participants with 40 hypoglossal nerves were studied. F-waves were successfully recorded in 39 out of 40 hypoglossal nerves, with a mean latency of 11.19 ms (IQR 8.7-20.6; SD 1.7). No significant differences in latency or amplitude were found between sides.

Discussion: This study found reproducible F-waves, enabling exploration of the proximal segments of the hypoglossal nerve. These findings could be valuable for diagnostic purposes in various pathological conditions.

Introduction/aims: Surviving motor units in neurogenic diseases demonstrate collateral reinnervation. Scanning electromyography (EMG) reveals normal motor unit corridor length, but with "silent regions," suggesting that reinnervation does not result in increased motor unit size but may increase motor unit complexity. Motor unit magnetic resonance imaging (MUMRI) pairs MR imaging with electrical nerve stimulation to visualize individual motor units. This study aimed to assess the motor unit dimensions and complexity in patients with previous poliomyelitis compared to healthy controls.

Methods: Patients with a history of polio were recruited from the British Polio Fellowship, compared to a retrospective cohort of healthy controls. They underwent medical history and examination of lower limb power, fatigue assessment (fatigue severity score, FSS), and a 3 T MUMRI scan of the less-affected lower limb. The cross-sectional area, maximum, and minimum Feret diameter of the motor unit territories in tibialis anterior were calculated. Motor unit complexity was computed using the Hausdorff box-counting method.

Results: Of 12 polio survivors, n = 8 (6 female) were suitable for analysis and were compared to 19 controls. The mean motor unit maximum Feret diameter was 10.3 ± 3.1 mm compared to 8.4 ± 5.2 mm in controls (p = 0.34). The mean shape complexity was 0.59 ± 0.12 compared to 0.45 ± 0.2 in controls (p = 0.03).

Discussion: Polio survivors demonstrate motor units with normal dimensions but increased shape complexity, indicating nonuniform collateral reinnervation largely limited to existing territories. The size and shape of motor units could help in understanding the physiological processes behind reinnervation, both in polio and other neurogenic diseases such as amyotrophic lateral sclerosis.

Introduction/aims: Management of myasthenia gravis (MG) includes reduction of pathogenic IgG autoantibodies by intravenous immunoglobulin (IVIg), B-cell depletion, therapeutic plasma exchange (TPE), and neonatal Fc receptor (FcRn) blockers. Concerns exist that chronic IgG reduction could lead to more frequent infections. We assessed the frequency and severity of infection with associated serum IgG levels during infections in MG patients treated with chronic TPE in both inpatient and outpatient settings.

Methods: MG patients treated with chronic TPE at a single center from April 2014 through December 2022 were included. All serum IgG levels from this cohort were recorded. Reported infections were limited to those who had clinically reported symptoms, supportive laboratory findings, necessitated inpatient admission for infection, or were treated with antibiotics/antivirals.

Results: Twenty-three patients were included. Ninety-seven infections were identified, with the majority of these being respiratory (36%) or urinary (22%). There were no differences in median serum IgG levels found during active infection versus periods of non-infection (657.3 [IQR: 459.5-823.1] and 518 [IQR: 472.9-672.5] mg/dL, respectively, Wilcoxon's p = 0.47). Infections necessitating inpatient admission did not have reduced median serum IgG compared with less severe infections or periods of non-infection (515.75 [IQR: 457.0-799.1], 660.5 [IQR: 472.9-808.4], and 518 [IQR: 467.8-672.5] mg/dL, respectively, pairwise Wilcoxon's p = 0.84). No correlation was identified between the number of reported infections per patient and their median serum IgG levels throughout the study period (Spearman's p = 0.26, p = 0.23).

Discussion: In this small retrospective study, there was no association between IgG levels and infections in patients with MG treated with chronic TPE.

Introduction/aim: Variants in the EMD gene cause Emery-Dreifuss muscular dystrophy type 1 (EDMD1). While the pattern of fat replacement in the legs of patients with EDMD1 is known, the involvement of the trunk and arms remains unclear. This study aimed to characterize the whole-body distribution of fatty replacement in EDMD1 and clarify its relationship with clinical symptoms.

Methods: Imaging data from eight Japanese EDMD1 patients was analyzed. Fatty replacement in 47 skeletal muscles was scored using the modified Mercuri score (mMS). Hierarchical clustering classified patients according to mMS, and intercluster differences were assessed.

Results: Fatty replacement was observed in the soleus and paraspinal muscles in all patients, as well as in the medial gastrocnemius, semimembranosus (Sm), biceps femoris long head (BFL), serratus anterior (SA), and biceps brachii (BB) in seven patients. A significant difference in mMS was observed between the low- and high-score groups in the SA (p = 0.0042), BB (p = 0.0031), semitendinosus (p = 0.0015), Sm (p < 0.0005), and BFL (p = 0.0031). Elbow flexion strength on manual muscle testing strongly correlated with BB mMS (p = 0.03, r = -0.75). The patient with a missense variant had a lower mMS than those with truncating variants.

Discussion: Elbow flexion strength is a potential marker of disease severity. The finding that the patient with a missense variant had a lower mMS supports previous reports that missense variants are associated with milder phenotypes. Genetic variant type should be considered in biomarker development for EDMD1.

Introduction/aims: Quantitative MRI (qMRI) of gluteal muscle groups for Duchenne muscular dystrophy (DMD) progression requires sensitive biomarkers and stage-specific validation. This 12-month study investigates qMRI responsiveness across disease stages and identifies early-stage damage markers.

Methods: A total of 137 DMD patients (9.1 ± 1.8 years) and 32 controls (9.5 ± 2.0 years) were prospectively enrolled and underwent 3 T MRI (T1 mapping, 3-point Dixon) assessing fat fraction (FF) and T1 in gluteal muscle groups (flexors, extensors, adductors, and abductors). Patients underwent North Star Ambulatory Assessment (NSAA) and timed functional tests and were classified by baseline NSAA scores into mild (76-100), moderate (51-75), and severe (0-50) groups. Standardized response mean (SRM) was used as a measure of disease progression responsiveness.

Results: Over 12 months, the severe group showed greater T1 and FF changes (except adductors) than mild/moderate groups, while FF changes of the adductors were only higher than the mild group. The moderate group had greater FF changes than the mild group (p < 0.05). qMRI responsiveness to disease progression varied by disease stage, with FF of the abductors in the mild functional stable/decline group (SRM = 1.016/1.445) and adductors in moderate/severe groups (SRM = 1.606/1.633) showing the highest responsiveness. SRM for function scales remained below 0.8 in all DMD subgroups. qMRI biomarkers demonstrated potential for identifying early-stage patients with or without functional decline.

Discussion: qMRI of the gluteal muscle group demonstrates higher responsiveness to DMD progression than function scales, with sensitivity varying by disease stage. qMRI biomarkers appear to be useful for assessing subclinical progression detection.

Introduction/aims: Scapular winging occurs as an abnormal protrusion of the scapula due to nerve injury, muscle weakness, bone, or joint pathology. The main muscular stabilizers of the scapula include the serratus anterior, trapezius, rhomboid major and minor, levator scapulae, and pectoralis minor. Needle electromyography (EMG) has historically been used as one of the primary diagnostic tests for evaluating this finding. However, sampling of these muscles can be technically difficult and carries risks for complications. Muscle ultrasound (MUS) can also reliably identify abnormalities in the muscles involved in scapular stabilization while offering the benefit of rapid side-to-side comparison and improved patient comfort. This study aims to highlight the concordance of ultrasound and EMG findings using our published MUS protocol in patients with scapular winging.

Methods: A retrospective analysis was performed of 13 patients who presented to an electrodiagnostic (EDX) laboratory with the referral diagnosis of "scapular winging" or "scapular dyskinesis." All patients underwent MUS testing of scapular muscles according to a previously published protocol followed by EMG of muscles deemed relevant by the clinician.

Results: Seven patients were found to have a neurogenic cause of their scapular winging and in those patients, all had both EMG and MUS abnormalities. MUS was found to have a sensitivity of 87.5%, specificity of 95.7%, and individual muscle concordance with EMG of 90.6%.

Discussion: There is high concordance between EMG and MUS in patients with scapular winging. This combined with potential advantages of the MUS modality supports their concurrent use in patients with scapular winging.

Introduction/aims: With implementation of newborn screening (NBS) for Duchenne muscular dystrophy (DMD), creatine kinase-muscle (CK) values will be reported on newborns. Maternal, labor, delivery, and newborn factors may elevate CK levels, raising concern for DMD. Predictive modeling could aid hyperCKemia interpretation while awaiting diagnostic confirmation.

Methods: In this single-center, prospective cohort study, parents of 8365 newborns were offered DMD-NBS. Electronic health records provided data on candidate predictors of hyperCKemia defined by values > 97th or 99th percentiles, or 2000 ng/mL in babies with normal DMD sequences. Exposures included maternal, newborn and perinatal factors. Associations between predictors and hyperCKemia were evaluated using univariate logistic regression. A multivariable prediction model for the 97th percentile was derived using backward stepwise logistic regression and externally validated in a cohort of 2672 newborns.

Results: HyperCKemia > 97th percentile was the main outcome. Univariate analyses revealed associations between hyperCKemia and maternal ethnicity, primiparity, labor and delivery complications, oxytocin induction or augmentation, duration of ruptured membranes, forceps or vacuum-assisted delivery, neonatal resuscitation, sex, gestational age, birth weight, and Apgar scores. Lower odds of hyperCKemia were associated with later hour-of-life at sample collection and birth by cesarean section. The final model included parity, shoulder dystocia, forceps or vacuum-assisted delivery, gestational age, neonatal resuscitation, Apgar score (1 min), and time of sample collection.

Discussion: Elevated CK levels may be used for DMD-NBS. Multiple perinatal factors are associated with transient non-DMD hyperCKemia. Our model considers the potential combined impact of such factors and generates a non-disease likelihood for preliminary hyperCKemia interpretation.

Introduction/aims: Radial mononeuropathy is a common peripheral nerve disorder, but comprehensive clinical or electrodiagnostic (EDX) studies remain limited. This study aims to analyze the clinical features, etiologies, and EDX characteristics of radial mononeuropathy.

Methods: A retrospective cohort study was conducted on 177 patients (178 lesions) with motor-involved radial mononeuropathy. Lesions were classified by location and etiology into four subgroups: traumatic and nontraumatic, in arm or forearm. Demographics, clinical presentations, and etiologies were compared across subgroups. EDX findings were analyzed, particularly comparing traumatic and nontraumatic arm lesions. Motor nerve fiber involvement was assessed in traumatic and nontraumatic compressive arm lesions.

Results: Most patients had radial mononeuropathy at the arm level, presenting with hyperacute/acute weakness and sensory loss. Common causes included nerve compression (40%) and humeral fractures (18%), while etiologies such as multifocal motor neuropathy and neuralgic amyotrophy were rare. EDX showed motor conduction block (CB) mostly across the spiral groove (67%) but sometimes distally (28%). Preserved sensory responses and demyelinating EDX findings dominated in nontraumatic arm lesions. Extensor indicis proprius (EIP), extensor digitorum communis (EDC), and brachioradialis muscles were most frequently affected. Triceps involvement occurred in 22%-49% of arm lesions. Twenty percent of nontraumatic compressive arm lesions with motor conduction block demonstrated triceps involvement.

Discussion: Radial mononeuropathy is most commonly caused by nerve compression and humeral fracture. Demyelinating features are strongly associated with nontraumatic lesions. Recording radial motor responses from EIP and EDC improves motor CB detection and localization. Triceps involvement does not always exclude compressive lesions at the spiral groove.

Small fiber neuropathy (SFN) presents with neuropathic pain, dysesthesia, and autonomic symptoms in the context of normal nerve conduction studies, necessitating specialized diagnostic approaches. This evidence-based review by the AANEM SFN Task Force evaluates the diagnostic utility of ancillary tests and appropriate screening laboratory investigations in the assessment of SFN. A comprehensive literature review was conducted using OVID MEDLINE and EMBASE from 1966 to January 2023. Studies were selected based on prespecified inclusion criteria requiring clinical symptoms consistent with SFN and normal large fiber conduction studies. Articles were independently reviewed and graded for evidence quality by multiple raters. Thirteen diagnostic and two laboratory screening studies met criteria. Skin punch biopsy assessing intraepidermal nerve fiber density showed Class II evidence (sensitivity 74%-78%, specificity 65%-80%). Additional metrics included intraepidermal fiber length and inter-fiber distance. Corneal confocal microscopy (CCM) showed potential (Class III) but lacked validation in isolated SFN. Indirect tests (laser/contact heat evoked potentials, cutaneous silent period) had variable sensitivity and high specificity. Lab screening identified metabolic/immune etiologies in up to 64%, though most evidence was Class III. Skin biopsy is the most validated direct diagnostic tool for SFN, though CCM and indirect assessments can aid in diagnosis. No test offers enough sensitivity or specificity to serve as a stand-alone gold standard. Despite limited high-level evidence, screening for metabolic and immune conditions may help identify etiologies. Standardized methods and population studies are needed to improve accuracy.