Interosseous Muscle Research Articles

Hypochlorous acid exposure impairs skeletal muscle function and Ca2+ signalling: implications for Duchenne muscular dystrophy pathology.

Duchenne muscular dystrophy (DMD) is a fatal X-linked disease characterised by severe muscle wasting. The mechanisms underlying the DMD pathology likely involve the interaction between inflammation, oxidative stress and impaired Ca2+ signalling. Hypochlorous acid (HOCl) is a highly reactive oxidant produced endogenously via myeloperoxidase; an enzyme secreted by neutrophils that is significantly elevated in dystrophic muscle. Oxidation of Ca2+ -handling proteins by HOCl may impair Ca2+ signalling. This study aimed to determine the effects of HOCl on skeletal muscle function and its potential contribution to the dystrophic pathology. Extensor digitorum longus (EDL), soleus and interosseous muscles were surgically isolated from anaesthetised C57 (wild-type) and mdx (dystrophic) mice for measurement of ex vivo force production and intracellular Ca2+ concentration. In whole EDL muscle, HOCl (200μM) significantly decreased maximal force and increased resting muscle tension which was only partially reversible by dithiothreitol. The effects of HOCl (200μM) on maximal force in slow-twitch soleus were lower than found in the fast-twitch EDL muscle. In single interosseous myofibres, HOCl (10μM) significantly increased resting intracellular Ca2+ concentration and decreased Ca2+ transient amplitude. These effects of HOCl were reduced by the application of tetracaine, Gd3+ or streptomycin, implicating involvement of ryanodine receptors and transient receptor potential channels. These results demonstrate the potent effects of HOCl on skeletal muscle function potentially mediated by HOCl-induced oxidation to Ca2+ signalling proteins. Hence, HOCl may provide a link between chronic inflammation, oxidative stress and impaired Ca2+ handling that is characteristic of DMD and presents a potential therapeutic target for DMD. KEY POINTS: Duchenne muscular dystrophy is a fatal genetic disease with pathological mechanisms which involve the complex interaction of chronic inflammation, increased reactive oxygen species production and increased cytosolic Ca2+ concentrations. Hypochlorous acid can be endogenously produced by neutrophils via the enzyme myeloperoxidase. Both neutrophil and myeloperoxidase activity are increased in dystrophic mice. This study found that hypochlorous acid decreased muscle force production and increased cytosolic Ca2+ concentrations in isolated muscles from wild-type and dystrophic mice at relatively low concentrations of hypochlorous acid. These results indicate that hypochlorous acid may be key in the Duchenne muscular dystrophy disease pathology and may provide a unifying link between the chronic inflammation, increased reactive oxygen species production and increased cytosolic Ca2+ concentrations observed in Duchenne muscular dystrophy. Hypochlorous acid production may be a potential target for therapeutic treatments of Duchenne muscular dystrophy.

Neurophysiological Grading of Ulnar Nerve Entrapment Across wrist and Across Elbow

Ulnar nerve entrapment across the elbow (UNEAE) and across the wrist (UNEAW) is the second most common entrapment of the hand after carpal tunnel syndrome. There are few grading available for UNEAE and fewer in UNEAW. None of those gradings compares the involvements of both (wrist and elbow). None of the literature looks at the involvement of sensory axonal neuropathy in different stages. The aim of this research are;1. To see the relation of sensory nerve involvement across the wrist with the entrapment across the elbow and to evaluate its effectiveness in each level without going for any invasive tests like needle EMG examination. 2. To identify the lesion below and across the wrist in terms of support, the clinical Physiologist (CP) grades them properly and helps the consultant decide to treat with conservative or surgical treatment.3. To compare the recording from the first dorsal interosseous (FDI) muscles with the abductor digiti minimi (ADM) muscle to see which muscle is more sensitive and shows early changes in ulnar nerve entrapment. 4. To differentiate the grading of Guyon’s canal with sensory entrapment below the wrist.5. To analyse the severity of entrapment in both areas (below/across wrist and elbow).The proposed revised grading system is based on more nuanced, descriptive categories, ranging from "early”, "mild”, "moderate” and "severe”. To create a full grading system of UNEAW and UNEAE some additional clinical grading is proposed.Method: Data was collected based on the extensive and detailed grading system previously described by Padua. The tests were performed by a qualified clinical physiologist (neurophysiology) using a Key Point 9033A07 machine, used in line with the departmental protocol (peripheral protocol 1, 2022). The Association of Neurophysiological Scientists (ANS) and British Society of Clinical Neurophysiology (BSCN) (2014) guidelines and minimum standards for the practice of clinical neurophysiology in the United Kingdom were followed. All data was recorded numerically to ensure methodological reliability.Result: The data was collected over one year six months from January 2022 till June 2023. A total of 313 abnormal hands and 200 normal hands were included in this study. Martin Gruber anomalies, which are normal variant, are not included in this study. Out of 313 abnormal hands, 149 hands were right hands and 164 were left hands. 46 hand shows lesion below the wrist and 56 hands shows lesion around Guyon’s canal. Across the elbow shows more mild cases as compared to early, moderate, and severe cases. Moderate ulnar nerve lesion across the elbow are more associated with sensory axonal and double crush cases, which were seen more in mild and moderate cases compared to early and severe cases. Conclusion: Findings show that FDI is more sensitive compared to ADM to recording early changes in ulnar nerve entrapment across the elbow. Additionally, the results show that sensory axonal involvement and double crush syndrome need to be included in the grading system which is not accounted for in any present research publication.

Examining the Intra-rater Reliability of Transcranial Magnetic Stimulation (TMS)-Induced Motor Evoked Potentials (MEPs) Within and Between Sessions: A Step Towards Ensuring Accuracy of Observed MEP Changes in Repeated Measures Studies conducted by Newly Trained TMS Operators

Background: An essential factor in the validity of motor evoked potential (MEP)s recorded by transcranial magnetic stimulation (TMS) over multiple times is their test-retest reliability which to a large extent depends on the accuracy and competence of the assessor (intra-rater reliability). However, intra-rater reliability is infrequently reported in TMS studies suggesting that this is rarely done. Objectives: This study was conducted to determine the intra-rater within and between-session reliability of a newly trained TMS assessor prior to a main TMS study and report on the methodology used to encourage similar practice. Methods: Fourteen (10 males, 4 females; mean age: 32 ± 5.8 years) participants took part in the study. Motor evoked potentials were elicited from a relaxed, right first dorsal interosseous (FDI) muscle three times (T1, T2 and T3) across two testing sessions at least 48 hours apart. During the first session, MEPs were recorded twice (T1 and T2) within an interval of 20 minutes to determine the within (intra) session reliability of the assessor. During the second session, a single measurement was carried out (T3) which was compared to T1 to determine the inter-session reliability. Results: Repeated measure analysis of variance (ANOVA) did not reveal significant difference in the amplitude of the MEPs obtained across the three time periods (P = 0.196) demonstrating agreement in the MEPs and hence the reliability of the assessor. Additionally, the intraclass correlation coefficient (ICC) between T1 and T2; and T1 and T3 were 0.952 (P < 0.001) and 0.833 (P = 0.001) respectively further indicating the within and between sessions reliability of the assessor. Conclusions: The agreement between the three measured MEPs amplitude and the significant ICC demonstrates the reliability of the assessor in this study to use TMS for research. We suggest that the intra-rater reliability of new TMS operators should be established using the methodology in this report prior to main TMS studies.

An assessment of Martin-Gruber anastomosis discrepancies between healthy individuals and patients with carpal tunnel syndrome in motor nerve conduction studies.

Background: The Martin-Gruber anastomosis (MGA) represents a nerve innervation anomaly in the upper extremity, potentially leading to misinterpretation during standard nerve conduction studies (NCSs). This study aims to characterize the electrophysiological attributes of MGA in both healthy subjects and individuals diagnosed with carpal tunnel syndrome (CTS). Methods: This case-control study involved the electrophysiological assessment of 506 forearms, segregated into two distinct groups: a CTS positive (+) case group and a CTS negative (-) control group. The evaluations were conducted over an average period of 8 months in the neurophysiology laboratory. The study encompassed 294 forearms from 147 healthy individuals without CTS and 212 forearms from 106 patients diagnosed with CTS, both clinically and electrodiagnostically. Results: The relationship between the presence of type I MGA and the CTS (+) group was statistically significant (P = 0.002). Similarly, the relationship between the presence of type II MGA and the CTS (+) group was statistically significant (P = 0.013). On the other hand, the relationship between the presence of type III MGA and the CTS (+) group was not statistically significant (P = 0.208). Likewise, the relationship between the presence of type IV MGA and the CTS (+) group was not statistically significant (P = 0.807). The correlation between the side of type I MGA and the groups did not reach statistical significance (P = 0.770). The relationship between the side of type II MGA and the groups also did not attain statistical significance (P = 0.990). Similarly, the side of type III MGA and its association with the groups did not yield statistical significance (P = 0.402). Finally, the relationship between the side of type IV MGA and the groups was not statistically significant (P = 0.166). Conclusion: The MGA represents a relatively frequent anatomical variation observed in the upper extremity. Notably, its presence demonstrated significance in the first dorsal interosseous (FDI) muscle (type II) and the abductor digiti minimi (ADM) muscle (type I) among patients with CTS. The present study emphasizes the importance of recognizing this variation during upper extremity NCSs for a correct diagnostic approach and treatment plan to avoid misdiagnosis of median-ulnar peripheral neuropathy.

Association of Interosseous Tendon Inflammation in the Hand With Different Early Arthritides in a 10-Year Magnetic Resonance Imaging Study.

Inflammation around the tendons of the hand interosseous muscles (interosseous tendon inflammation [ITI]) was recently identified on magnetic resonance imaging (MRI) in a set of patients with rheumatoid arthritis (RA) and arthralgia. We conducted a large MRI study to assess the prevalence of ITI at diagnosis of RA and of other arthritides, as well as its relationship with clinical signs. A total of 1,205 patients presenting with various types of early arthritis between 2010 and 2020 underwent contrast-enhanced hand MRI as part of the prospective Leiden Early Arthritis Cohort. MRI was evaluated with blinding for clinical data, for ITI lateral of metacarpophalangeal (MCP) joints 2-5, and for synovitis/tenosynovitis/osteitis. We assessed ITI presence at baseline per diagnosis and its relationship with clinical characteristics (ie, presence of hand arthritis, increased acute phase reactants, and local joint swelling and tenderness). Logistic regression and generalized estimating equations were used with adjustment for age and established local inflammation features (synovitis/tenosynovitis/osteitis). A total of 36% of patients with early RA (n=532) had ITI; this was similar in patients with anti-citrullinated protein antibody (ACPA)-negative RA (37%) and those with ACPA-positive RA (34%; P = 0.53). ITI occurred regularly in remitting seronegative symmetrical synovitis with pitting edema (60%) and connective tissue diseases (44%) and less frequently in undifferentiated arthritis (14%), psoriatic arthritis (14%), inflammatory osteoarthritis (8%), reactive arthritis (7%), crystal arthritis (7%), and peripheral spondylarthritis (4%). ITI occurred more often in diagnoses with frequent arthritis of the hands (P < 0.001) and increased acute-phase reactants (P < 0.001). Within RA, ITI occurred together with local MCP joint synovitis (odds ratio [OR] 2.4, 95% confidence interval [95% CI] 1.7-3.4), tenosynovitis (OR 2.4, 95% CI 1.8-3.3), and osteitis (OR 2.2, 95% CI 1.6-3.1) on MRI. Moreover, ITI presence was associated with local MCP joint tenderness (OR 1.6, 95% CI 1.2-2.1) and swelling (OR 1.8, 95% CI 1.3-2.6), independent of age and MRI-detected synovitis/tenosynovitis/osteitis. ITI occurs regularly in RA and other arthritides with preferential involvement of hand joints and increased acute-phase reactants. At the MCP joint level, ITI associates independently with joint tenderness and swelling. Hence, ITI is a newly identified inflamed tissue mainly found in arthritides with particularly extensive and symptomatic inflammation.

Transcutaneous cervical vagus nerve stimulation improved motor cortex excitability in healthy adults: a randomized, single-blind, self-crossover design study.

To investigate the effect of transcutaneous cervical vagus nerve stimulation (tcVNS) on motor cortex excitability in healthy adults. Twenty eight healthy subjects were assigned to receive real and sham tcVNS for 30 min. The interval between the real and sham conditions was more than 24 h, and the sequence was random. The central and peripheral motor-evoked potential (MEP) of the right first dorsal interosseous (FDI) muscle was measured by transcranial magnetic stimulation (TMS) before and after stimulation. MEP latency, MEP amplitude and rest motor threshold (rMT) were analyzed before and after stimulation. MEP amplitude, MEP latency and rMT had significant interaction effect between time points and conditions (p < 0.05). After real stimulation, the MEP amplitude was significantly increased (p < 0.001). MEP latency (p < 0.001) and rMT (p = 0.006) was decreased than that of baseline. The MEP amplitude on real condition was higher than that of sham stimulation after stimulation (p = 0.027). The latency after the real stimulation was significantly shorter than that after sham stimulation (p = 0.005). No significantly difference was found in rMT after stimulation between real and sham conditions (p > 0.05). tcVNS could improve motor cortex excitability in healthy adults.

Sensitivity Analysis of CMAP Scan Step Index to Different Stimulation Parameters and Examination of Muscles Affected by Spinal Cord Injury.

Step index (STEPIX) is a recently developed compound muscle action potential (CMAP) scan method for evaluating motor unit loss and remodeling changes. This study investigates the influence of different stimulation parameters during CMAP scan on STEPIX and its examination of muscles affected by spinal cord injury (SCI). CMAP scan of the first dorsal interosseous (FDI) muscle was performed using different stimulus pulse widths (0.1 ms, 0.2 ms) and different numbers of stimuli (500, 1000) in 12 neurologically intact subjects. STEPIX was derived from each CMAP scan of all subjects. A significantly higher STEPIX was obtained using 1000 stimuli than 500 stimuli, while no significant difference in STEPIX was observed using 0.1 and 0.2 ms stimulus pulse widths. STEPIX was further applied to process CMAP scans of the FDI muscle from 13 tetraplegia and 13 healthy control subjects using the same stimulation parameter setting (0.1 ms, 500 stimuli), along with other methods including MScanFit motor unit number estimation (MUNE) and D50. STEPIX was significantly lower for the SCI subjects compared with the healthy control subjects. STEPIX was significantly correlated with MscanFit MUNE and D50, but had a smaller relative width of the overlapping zone (WOZ%) between tetraplegic and healthy control groups compared with MScanFit MUNE and D50. The findings of the study highlight the importance of maintaining a consistent stimulation parameter setting in CMAP scan studies and confirm the usefulness of STEPIX as a convenient CMAP scan parameter for examination of motor unit number changes.

In-Plane Ultrasound-Guided Botulinum Toxin Injection to Lumbrical and Interosseus Upper Limb Muscles: Technical Report.

This technical report presents an innovative approach utilizing in-plane ultrasound-guided injections to precisely target the lumbrical and interosseous muscles within the upper limb. The report also elucidates the rationale and advantages of incorporating ultrasound guidance in the administration of Botulinum toxin (BTX) injections, encompassing the real-time visualization of needle trajectory and accurate localization of the target muscle groups while delving into the pertinent anatomical details of these muscles and their significance in diverse neuromuscular conditions. The step-by-step procedure for conducting in-plane ultrasound-guided BTX injections to the lumbrical and interosseous muscles is delineated, emphasizing critical technical considerations and potential pitfalls to be vigilant of during the procedure. Furthermore, the article addresses the significance of selecting appropriate BTX dosages and injection sites based on individual patient presentations and clinical indications. Overall, the in-plane ultrasound-guided BTX injection technique presents a promising approach for providing precise and targeted treatment to the lumbrical and interosseous muscles in the upper limb. It offers clinicians an alternative to injections performed without guidance or out-of-plane ultrasound-guided injections, potentially decreasing the likelihood of complications and enhancing treatment outcomes for patients with a range of neuromuscular conditions. However, further research and comparative studies are necessary to establish the long-term efficacy and safety of this technique, thus confirming its role in clinical practice.

Study on after-effect of electroacupuncture with different time intervals on corticospinal excitability in primary motor cortex.

To compare the effects of electroacupuncture (EA) with different time intervals on corticospinal excitability of the primary motor cortex (M1) and the upper limb motor function in healthy subjects and observe the after-effect rule of acupuncture. Self-comparison before and after intervention design was adopted. Fifteen healthy subjects were included and all of them received three stages of trial observation, namely EA0 group (received one session of EA), EA6h group (received two sessions of EA within 1 day, with an interval of 6 h) and EA48h group (received two sessions of EA within 3 days, with an interval of 48 h). The washout period among stages was 1 week. In each group, the needles were inserted perpendicularly at Hegu (LI 4) on the left side, 23 mm in depth and at a non-acupoint, 0.5 cm nearby to the left side of Hegu (LI 4), separately. Han's acupoint nerve stimulator (HANS-200A) was attached to these two needles, with continuous wave and the frequency of 2 Hz. The stimulation intensity was exerted higher than the exercise threshold (local muscle twitching was visible, and pain was tolerable by healthy subjects, 1-2 mA ). The needles were retained for 30 min. Using the single pulse mode of transcranial magnetic stimulation (TMS) technique, before the first session of EA (T0) and at the moment (T1), in 2 h (T2) and 24 h (T3) after the end of the last session of EA, on the left first dorsal interosseous muscle, the amplitude, latency (LAT), resting motor threshold (rMT) of motor evoked potentials (MEPs) and the completion time of grooved pegboard test (GPT) were detected. Besides, in the EA6h group, TMS was adopted to detect the excitability of M1 (amplitude, LAT and rMT of MEPs) before the last session of EA (T0*). The amplitude of MEPs at T1 and T2 in the EA0 group, at T0* in the EA6h group and at T1, T2 and T3 in the EA48h group was higher when compared with the value at T0 in each group separately (P<0.001). At T1, the amplitude of MEPs in the EA0 group and the EA48h group was higher than that in the EA6h group (P<0.001, P<0.01); at T2, it was higher in the EA0 group when compared with that in the EA6h group (P<0.01); at T3, the amplitude in the EA0 group and the EA6h group was lower than that of the EA48h group (P<0.001). The LAT at T1 was shorter than that at T0 in the three groups (P<0.05), and the changes were not obvious at the rest time points compared with that at T0 (P > 0.05). The GPT completion time of healthy subjects in the EA0 group and the EA48h group at T1, T2 and T3 was reduced in comparison with that at T0 (P<0.001). The completion time at T3 was shorter than that at T0 in the EA6h group (P<0.05); at T2, it was reduced in the EA48h group when compared with that of the EA6h group (P<0.05). There were no significant differences in rMT among the three groups and within each group (P>0.05). Under physiological conditions, EA has obvious after-effect on corticospinal excitability and upper limb motor function. The short-term interval protocol (6 h) blocks the after-effect of EA to a certain extent, while the long-term interval protocol (48 h) prolongs the after-effect of EA.

Corticospinal excitability changes during muscle relaxation and contraction in motor imagery.

To enhance smooth muscle contraction and relaxation during rehabilitation and sports activities, a comprehensive understanding of the motor control mechanisms within the central nervous system is necessary. However, current knowledge on these aspects is insufficient. Therefore, this study aimed to deepen our understanding of motor controls, by investigating the alterations in corticospinal excitability within cortical motor areas related to muscle contraction and relaxation using motor imagery with a reaction time task paradigm. Transcranial magnetic stimulation was used to measure the motor-evoked potentials in the first dorsal interosseous muscle of the right hand after the 'go' signal. Static weak muscle contraction (Experiment 1: 18 healthy participants) and resting state (Experiment 2: 16 healthy participants) were applied as background factors, and a trial without motor imagery was performed as a control. Muscle contraction was maintained in the background in the contraction motor imagery. A decrease in excitability in the relaxation motor imagery task occurred compared with the control. When the muscles were at rest, an increase in excitability in the contraction motor imagery and a transient increase in excitability in the relaxation motor imagery occurred compared with the control condition. Hence, the excitability of contraction and relaxation motor imagery is characterized by a continuous increase in excitability, transient increase and subsequent decrease in excitability, respectively. These results suggest that muscle contraction sensory information in the background condition may be necessary for muscle relaxation. Matching the background conditions may be crucial when utilizing motor imagery for rehabilitation or sports training.

Increased corticospinal inhibition following brief maximal and submaximal contractions in humans.

A potentiating conditioning contraction (CC) has been shown to increase silent period duration, an index of corticospinal inhibition; however, it is unknown if the CC must induce potentiation for corticospinal inhibition to increase. Ten healthy, young adults (four females) completed this study to assess potentiation and silent period (SP) duration before and after four types of CCs: voluntary and electrically evoked maximal CCs to optimize potentiation, and voluntary and electrically evoked submaximal CCs (∼40% of maximal voluntary force) that induced minimal potentiation. Stimulation was applied to the ulnar nerve to evoke twitches for the assessment of potentiation and to evoke tetanic CCs of the first dorsal interosseous muscle. The SP was elicited by applying transcranial magnetic stimulation to the motor cortex during brief contractions at 25% of maximal voluntary force. Changes to twitch force and SP duration were not different for voluntary and tetanic contractions, so data were pooled. Twitch force increased by 81.2 ± 35.7% (P < 0.001) and 3.2 ± 6.5% (P = 0.039) following maximal and submaximal CCs, respectively. The SP was prolonged following maximal (12.6 ± 6.3%; P < 0.001) and submaximal (4.8 ± 4.9%; P < 0.001) CCs. Correlations between post-CC twitch force and SP duration were not significant for maximal or submaximal conditions (r = -0.068; r = 0.067; P ≥ 0.780, respectively). Duration of the SP increased not only following maximal-intensity CCs but also after submaximal-intensity CCs that induced virtually no potentiation (∼3%). Thus, we suggest that corticospinal inhibition is not directly related to mechanisms of muscle potentiation per se, but, rather, the level of muscle contraction likely mediates feedback from large diameter afferents that affect the SP.NEW & NOTEWORTHY The transcranial magnetic stimulation-induced silent period reflects a transient state of corticospinal inhibition that is influenced by recent history of muscle activation, which may include an effect of potentiation. We demonstrate that silent period duration increases following both voluntary and electrically evoked maximal and submaximal conditioning contractions, even though the latter intensity produced virtually no muscle potentiation. Feedback from group Ia and Ib muscle afferents is proposed as the cause of the increased corticospinal inhibition.

Reconstructing Pinch Strength after Ulnar Nerve Injury by Transferring the Opponens Pollicis Motor Branch.

With ulnar nerve injuries, paralysis of the first dorsal interosseous and adductor pollicis muscle weakens the patient's pinch. In the palm, we transferred the opponens pollicis motor branch to the deep terminal division of the ulnar nerve for pinch reconstruction. Sixteen patients with ulnar nerve injuries around the elbow underwent reconstruction and were followed up postoperatively for a minimum of 14 months. Their mean age was 41 ± 16 years, and the mean interval between injury and surgery was 134 ± 126 days (range, 2 to 390 days). Preoperatively and postoperatively, grasp, key, and subterminal key pinch strength were measured using dynamometers. Reinnervation of the first dorsal interosseous muscle was observed in 15 of the 16 patients. Mean grasp strength improved from 15.5 ± 8.5 kg preoperatively to 24 ± 10 kg postoperatively, achieving 57% ± 16% of contralateral hand strength. Preoperatively, terminal key pinch averaged 3 ± 1 kg, which improved postoperatively to 5.5 ± 2 kg, achieving 71 ± 24% of the strength measured contralaterally. Preoperatively to postoperatively, subterminal key pinch force increased from 0 to 2.4 ± 1.3 kg, achieving 61% ± 27% that of the unaffected side. Patients who underwent surgery within 6 months of their injury showed a mean subterminal key pinch strength recovery of 63% ± 27% of the normal side, whereas those who underwent surgery between 7 and 13 months after injury showed a mean subterminal key pinch strength recovery of 51% ± 29%. Transferring the opponens pollicis motor branch to the deep terminal division of the ulnar nerve improved pinch and grasp strength without jeopardizing thumb function. Therapeutic, IV.

The severity of acute hypoxaemia determines distinct changes in intracortical and spinal neural circuits.

The purpose of this study was to examine how two common methods of continuous hypoxaemia impact the activity of intracortical circuits responsible for inhibition and facilitation of motor output, and spinal excitability. Ten participants were exposed to 2h of hypoxaemia at 0.13 fraction of inspired oxygen ( clamping protocol) and 80% of peripheral capillary oxygen saturation ( clamping protocol) using a simulating altitude device on two visits separated by a week. Using transcranial magnetic and peripheral nerve stimulation, unconditioned motor evoked potential (MEP) area, short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF), and F-wave persistence and area were assessed in the first dorsal interosseous (FDI) muscle before titration, after 1 and 2h of hypoxic exposure, and at reoxygenation. The clamping protocols resulted in differing reductions in by 2h ( clamping protocol: 81.9±1.3%, clamping protocol: 90.6±2.5%). Although unconditioned MEP peak to peak amplitude and area did not differ between the protocols, SICI during clamping was significantly lower at 2h compared to clamping (P=0.011) and baseline (P<0.001), whereas ICF was higher throughout the clamping compared to clamping (P=0.005). Furthermore, a negative correlation between SICI and (rrm =-0.56, P=0.002) and a positive correlation between ICF and (rrm =0.69, P=0.001) were determined, where greater reductions in correlated with less inhibition and less facilitation of MEP responses. Although F-wave area progressively increased similarly throughout the protocols (P=0.037), persistence of responses was reduced at 2h and reoxygenation (P<0.01) during the clamping protocol compared to the clamping protocol. After 2h of hypoxic exposure, there is a reduction in the activity of intracortical circuits responsible for inhibiting motor output, as well as excitability of spinal motoneurones. However, these effects can be influenced by other physiological responses to hypoxia (i.e., hyperventilation and hypocapnia). NEW FINDINGS: What is the central question of this study? How do two common methods of acute hypoxic exposure influence the excitability of intracortical networks and spinal circuits responsible for motor output? What is the main finding and its importance? The excitability of spinal circuits and intracortical networks responsible for inhibition of motor output was reduced during severe acute exposure to hypoxia at 2 h, but this was not seen during less severe exposure. This provides insight into the potential cause of variance seen in motor evoked potential responses to transcranial magnetic stimulation (corticospinal excitability measures) when exposed to hypoxia.

Measurement of the lumbrical muscle activity of the hand using electromyography supported by the ultrasound imaging technique with string navigation

Although placing surface electrodes on small muscles by palpation is difficult, ultrasound guidance may enable electrode placement on the small muscles. This study aimed to examine whether ultrasound guidance is helpful for placement of electrodes on a small muscle, such as the hand lumbrical muscle. Twelve dominant hands of 12 healthy right-handed adults were included in this study. The first lumbrical muscle belly of the hands was identified using ultrasound guidance with a string navigation technique for placing surface electrodes. This technique was designed to identify the location of the center of the muscle belly under ultrasound imaging using a string. After the electrodes were placed on the muscle belly using this technique, the surface electromyographic signals of the first lumbrical, first dorsal interosseous, and adductor pollicis muscles were recorded. The activity of the lumbrical muscle could be separately measured of the first dorsal interosseous and adductor pollicis muscles. This technique has the potential to enable surface electromyography of small muscles for which placement of surface electrodes by palpation is challenging.

Prior elicitation for Gaussian spatial process: An application to TMS brain mapping.

The power and commensurate prior distributions are informative prior distributions that incorporate historical data as prior knowledge in Bayesian analysis to improve inference about a phenomenon under study. Although these distributions have been developed for analyzing non-spatial data, little or no attention has been given to spatial geostatistical data. In this study, we extend these informative prior distributions to a Gaussian spatial process, which enables the elicitation of prior knowledge from historical geostatistical data for Bayesian analysis. Three informative prior distributions were developed for spatial modeling, and an efficient Markov Chain Monte Carlo algorithm was developed for performing Bayesian analysis. Simulation studies were used to assess the adequacy of the informative prior distributions. Hierarchical models combined with the developed informative prior distributions were applied to analyze transcranial magnetic stimulation (TMS) brain mapping data to gain insights into the spatial pattern of a patient's response to motor cortex stimulation. The study quantified the uncertainty in motor response and found that the primary motor cortex of the hand is responsible for most of the movement of the right first dorsal interosseous muscle. The findings provide a deeper understanding of the neural mechanisms underlying motor function and ultimately aid the improvement of treatment options for individuals with health issues.

Interosseous tendon inflammation in the hands of patients with clinically suspect arthralgia: analysis of MRI data from a prospective cohort study.

Inflammation around the tendons of interosseous muscles of the hand (interosseous tendon inflammation) was recently observed with MRI for the first time in patients with rheumatoid arthritis and in at-risk individuals with detectable anti-citrullinated protein antibodies, generating the hypothesis that interosseous tendon inflammation precedes clinical arthritis. To better understand the role of interosseous tendon inflammation during the development of rheumatoid arthritis, we studied the frequency of interosseous tendon inflammation in healthy individuals and in those with arthralgia that was suspected of progressing to rheumatoid arthritis (ie, clinically suspect arthralgia) and the association of interosseous tendon inflammation with other symptoms of inflamed joint tissues and with clinical arthritis development. Adult (age ≥18 years) patients who presented with clinically suspect arthralgia and symptom-free (control) individuals underwent contrast-enhanced hand MRI. MRIs were evaluated for interosseous tendon inflammation on the radial and ulnar sides of the second to fifth metacarpophalangeal joints, and for synovitis, tenosynovitis, and osteitis using the rheumatoid arthritis MRI scoring system. Patients with clinically suspect arthralgia were followed up for clinical arthritis development. The presence of local tenosynovium was examined using immunohistochemistry for anti-CD55 and anti-CD68 on tissue from the hands of three embalmed bodies donated for scientific research. The primary outcome for the cross-sectional part of the study was the presence of interosseous tendon inflammation on MRI. The primary outcome for the longitudinal part of the study was development of clinical arthritis. Between April 3, 2012, and May 20, 2020, 667 patients with clinically suspect arthralgia (mean age 44 years [SD 13], 504 [76%] were women and 163 [24%] were men) underwent contrast-enhanced hand MRI. Between Nov 1, 2013, and Nov 30, 2014, 193 symptom-free controls were recruited (mean age 50 years [SD 16], 136 [70%] were women and 57 [30%] were men). Two (1%) of 193 symptom-free controls had interosseous tendon inflammation. Immunohistochemistry of cadaveric hand tissues showed no tenosynovium surrounding interosseous tendons. At inclusion, 67 (10%) of 667 patients with clinically suspect arthralgia had interosseous tendon inflammation (p<0·0001 vs symptom-free controls). Interosseous tendon inflammation occurred more frequently if synovitis (odds ratio [OR] 2·2 [95% CI 1·2-4·2]), or tenosynovitis (OR 9·7 [5·5-17·0]), was present at metacarpophalangeal joints. A three-dimensional MRI reconstruction suggested confluency of interosseous tendon inflammation with metacarpophalangeal-flexor-tenosynovitis. 91 (16%) of 558 patients with clinically suspect arthralgia developed clinical arthritis during follow-up (median total follow-up 25·3 months [95% CI 25·1-25·5]). Patients with clinically suspect arthralgia with interosseous tendon inflammation had a higher risk of developing clinical arthritis (hazard ratio [HR] 4·5 [2·8-7·2]), which was attenuated but still significant after adjusting for concomitant synovitis, tenosynovitis, or osteitis (HR 1·7 [1·02-2·8]). Interosseous tendon inflammation is almost absent in symptom-free individuals but occurs in people with clinically suspect arthralgia, in whom it correlates with symptoms and is associated with the development of clinical arthritis. The absence of local tenosynovium suggests that interosseous tendon inflammation arises from expanding local subclinical inflammation in the pre-arthritis phase of rheumatoid arthritis. European Research Council and the Dutch Arthritis Society.

Bifurcation of the Brachial Artery into Brachioradial and Brachioulnar Arteries in the Proximal Arm: Case Report and Clinical Significance

During anatomical dissection of fifty donors in the 2020 undergraduate first-year anatomy course at the Uniformed Services University of the Health Sciences, a high origin of the radial and ulnar arteries, also known as a brachioradial artery and a brachioulnar artery, was observed on the left arm of a 90 year-old White female donor. The bifurcation of the brachial artery occurred in the proximal third of the arm. Both the left brachioradial and left brachioulnar arteries ran superficial and medial to the biceps brachii muscle. The brachioulnar artery continues as the UA in the forearm, ran superficial and lateral to the flexor carpi ulnaris muscle, traversed the flexor retinaculum, and continued to form the superficial arterial palmar arch. The brachioradial artery ran deep to the pronator teres muscle and continued as the RA in the forearm. It presented with an atypical branching pattern and was tortuous until it reached the hand. On the dorsum of the hand, the radial artery runs superficial to the first dorsal interosseous muscle, parallel to the first metacarpal bone. It also reached the palmar side of the hand in an unusual manner. Medical professionals, especially radiologists, orthopedic and vascular surgeons, need to be aware of these variations to avoid iatrogenic injuries during normal procedures, such as venipuncture and intravenous injections. Knowledge of these variations is also important during invasive procedures, such as elbow reconstructive surgery, percutaneous brachial catheterization, and when creating an arteriovenous fistula using the radial artery. When such variations are suspected, Doppler and angiogram studies are necessary.

Anterior interosseous nerve syndrome following infection with COVID-19: a case report

BackgroundVarious neurological manifestations associated with coronavirus disease 2019 have been increasingly reported. Herein, we report a rare case of anterior interosseous nerve syndrome, which occurred 5 days after the onset of coronavirus disease 2019.Case presentationA 62-year-old Asian woman with a history of coronavirus disease 2019 who developed a complete motor deficit in the left flexor pollicis longus and pronator quadratus without sensory deficits. The symptoms appeared as a sudden onset fatigue and severe pain of the left arm, 5 days after the onset of coronavirus disease 2019. She noticed paralysis of the left thumb at 2 weeks after the onset of coronavirus disease 2019. Electromyography assessment of the anterior interosseous nerve-dominated muscles revealed neurogenic changes such as positive sharp wave and fibrillation in flexor pollicis longus and pronator quadratus, confirming the diagnosis of anterior interosseous nerve syndrome. There were no other diseases that could have resulted in peripheral nerve palsy. We performed a functional reconstruction surgery of the thumb by tendon transfer from the extensor carpi radialis longus to the flexor pollicis longus. The patient reported a good patient-reported outcome (2.27 points in QuickDASH Disability/Symptom scoring and 5 points in Hand20 scoring) at final follow-up (1 year after the surgery).ConclusionThis case highlights the need for vigilance regarding the possible development of anterior interosseous nerve syndrome in patients with coronavirus disease 2019. Tendon transfer from extensor carpi radialis longus to flexor pollicis longus can provide good functional recovery for unrecovered motor paralysis after anterior interosseous nerve syndrome.

Sex-specific reference values for total, central, and peripheral latency of motor evoked potentials from a large cohort.

Differentiating between physiologic and altered motor evoked potentials (MEPs) to transcranial magnetic stimulation (TMS) is crucial in clinical practice. Some physical characteristics, such as height and age, introduce sources of variability unrelated to neural dysfunction. We provided new age- and height-adjusted normal values for cortical latency, central motor conduction time (CMCT), and peripheral motor conduction time (PMCT) from a large cohort of healthy subjects. Previously reported data from 587 participants were re-analyzed. Nervous system disorders were ruled out by clinical examination and magnetic resonance imaging. MEP latency was determined as stimulus-to-response latency through stimulation with a circular coil over the "hot spot" of the First Dorsal Interosseous and Tibialis Anterior muscles, during mild tonic contraction. CMCT was estimated as the difference between MEP cortical latency and PMCT by radicular magnetic stimulation. Additionally, right-to-left differences were calculated. For each parameter, multiple linear regression models of increasing complexity were fitted using height, age, and sex as regressors. Motor evoked potential cortical latency, PMCT, and CMCT were shown to be age- and height-dependent, although age had only a small effect on CMCT. Relying on Bayesian information criterion for model selection, MEP cortical latency and PMCT were explained best by linear models indicating a positive correlation with both height and age. Also, CMCT to lower limbs positively correlated with height and age. CMCT to upper limbs positively correlated to height, but slightly inversely correlated to age, as supported by non-parametric bootstrap analysis. Males had longer cortical latencies and CMCT to lower limbs, as well as longer PMCT and cortical latencies to upper limbs, even when accounting for differences in body height. Right-to-left-differences were independent of height, age, and sex. Based on the selected regression models, sex-specific reference values were obtained for all TMS-related latencies and inter-side differences, with adjustments for height and age, where warranted. A significant relationship was observed between height and age and all MEP latency values, in both upper and lower limbs. These set of reference values facilitate the evaluation of MEPs in clinical studies and research settings. Unlike previous reports, we also highlighted the contribution of sex.

Compound muscle action potential (CMAP) scan examination of paretic and contralateral muscles reveals motor unit alterations after stroke

This study presents a novel compound muscle action potential (CMAP) examination of motor unit changes in paretic muscle post stroke. CMAP scan of the first dorsal interosseous (FDI) muscle was performed bilaterally in 16 chronic stroke subjects. Various parameters were derived from the CMAP scan to examine paretic muscle changes, including CMAP amplitude, D50, step index (STEPIX) and amplitude index (AMPIX). A significant decrease in CMAP amplitude and STEPIX was observed in paretic muscles compared with contralateral muscles (CMAP amplitude: paretic (9.0±0.5) mV, contralateral (11.3±0.9) mV, P=0.024; STEPIX: paretic 101.2±7.6, contralateral 121.9±6.5, P=0.020). No significant difference in D50 and AMPIX was observed between the paretic and contralateral sides (P>0.05). The findings revealed complex paretic muscle changes including motor unit degeneration, muscle fiber denervation, reinnervation and atrophy, providing useful insights to help understand neuromuscular mechanisms associated with weakness and other functional deterioration post stroke. The CMAP scan experimental protocols and the applied processing methods are noninvasive, convenient, and automated, offering practical benefits for clinical application.