Abductor Digiti Minimi Muscle Research Articles

Descending motor command to prime mover of dependent finger induces tactile gating in target and distant non-target finger

This study examined whether tactile gating induced by the descending motor command to one finger spreads out to the other fingers to which the command is not delivered and whether this gating is dependent on the target finger to which the command is delivered. The change in perceptual threshold to the digital nerve stimulation of one finger induced by tonic contraction of the first dorsal interosseous or abductor digiti minimi muscle was examined. The perceptual threshold to the digital nerve stimulation of the thumb or little finger was increased by tonic contraction of the abductor digiti minimi muscle. This finding indicates that the descending motor command to the prime mover of the little finger abduction induces tactile gating not only in the finger to which the command is delivered but also in the other finger to which the command is not delivered. Tonic contraction of the first dorsal interosseous muscle did not change the perceptual threshold to the digital nerve stimulation in any finger. This finding means that tactile gating occurs particularly when the descending motor command is delivered to the dependent finger. Spreading out of tactile gating of one finger, to which the descending motor command is not delivered, is likely mediated by surround inhibition.

Factors associated with adherence to noninvasive positive pressure ventilation in amyotrophic lateral sclerosis.

This cohort study aimed to investigate the factors associated with noninvasive positive pressure ventilation adherence and assess the long-term effects of noninvasive positive pressure ventilation adherence in patients with amyotrophic lateral sclerosis (ALS). The medical records of patients with ALS admitted to a tertiary hospital for noninvasive positive pressure ventilation initiation were retrospectively reviewed. Pulmonary function parameters, variables of blood gas analysis, the site of symptom onset, the time from onset and diagnosis to noninvasive positive pressure ventilation application, ALS Functional Rating Scale-Revised, neurophysiological index, and the length of hospital stay were evaluated. The adherence to noninvasive positive pressure ventilation was defined as the use of noninvasive positive pressure ventilation for ≥ 2 h/day or ≥ 4 h/day. The correlations between noninvasive positive pressure ventilation adherence or length of hospital stay and other clinical parameters were analyzed. Fifty-one patients with ALS were included in the study. The time from onset and diagnosis to NIPPV application was reduced by 16 months in the adherent group than that in the non-adherent group; however, the parameters of blood gas analysis and pulmonary function tests did not differ significantly between the groups. Furthermore, the neurophysiological index of the abductor digiti minimi muscle was higher by 4.05 in the adherent group than that in the non-adherent group. The adherence to noninvasive positive pressure ventilation prolonged tracheostomy-free survival compared to that of non-adherence. Desaturation events, lower forced vital capacity, last pCO2, bicarbonate, and base excess, and higher differences in pCO2, were associated with an increase in the length of hospital stay. Noninvasive positive pressure ventilation application shortly after symptom onset and ALS diagnosis in patients with CO2 retention and reduced forced vital capacity can be considered for successful adherence. Adherence to noninvasive positive pressure ventilation may result in reduced tracheostomy conversion rates and prolonged tracheostomy-free survival.

Nonenhancing motor eloquent gliomas: navigated transcranial magnetic stimulation oncobiological signature.

Preoperative grading of nonenhancing motor eloquent gliomas is hampered by a lack of specific imaging surrogates. Tumor grading is crucial for the informed consent discussion before tumor resection. In this paper, the authors hypothesized that navigated transcranial magnetic stimulation (nTMS)-derived metrics could provide significant information to distinguish between high- and low-grade motor eloquent gliomas that present as nonenhancing tumors and therefore contribute to improving patient counseling, timing of treatment, preoperative planning, and intraoperative strategies. The authors conducted a retrospective single-center cohort study of patients admitted for tumor surgery between January 2018 and April 2022 with a nonenhancing motor eloquent glioma and preoperative bilateral nTMS mapping. nTMS data including resting motor threshold (RMT), interhemispheric RMT ratio (iRMTr), Cortical Excitability Score (CES), area and volume of cortical activation, and motor evoked potential (MEP) characteristics were obtained and integrated with demographic and clinical data. Thirty patients met the inclusion criteria, and 10 healthy participants were recruited for comparison. Seizures were the most common presenting symptom (25 patients) and WHO grade 3 the most common tumor grade (21 patients). The area and volume of functional cortical activation of both the abductor pollicis brevis and first dorsal interosseous muscles were decreased in healthy participants compared with patients with WHO grade 3 glioma (p < 0.05). An abnormal iRMTr for the lower limbs (16.7% [1/6] WHO grade 2, 76.2% [16/21] WHO grade 3, 100% [3/3] WHO grade 4; p = 0.015) and a higher CES (maximal abnormal CES: 0% [0/6] WHO grade 2, 38% [8/21] WHO grade 3, 66.7% [2/3] WHO grade 4; p = 0.010) were associated with the prediction of high-grade lesions. A total of 7280 MEPs were analyzed. A significant increase in the amplitude and a significant decrease in latency in the MEPs for the first dorsal interosseous and abductor digiti minimi muscles (p < 0.0001) were identified in healthy participants compared with WHO grade 3 glioma patients. Nonenhancing motor eloquent gliomas have a different impact on both anatomical and functional reorganization of motor areas according to their WHO grading.

Uncommon Anatomical Causes of Ulnar Compression: A Narrative Review.

Some patients develop ulnar nerve compression due to rare anatomical variations or malformations. The aims of this review are to provide a comprehensive overview of anatomical structures and variations that can cause ulnar nerve compression and to evaluate treatment options. Case reports and case series about rare cases of unusual ulnar nerve compression published from January 2000 until April 2022 were obtained from databases Embase, MEDLINE, and Web of Science. A total of 48 studies describing 64 patients were included in our study. The following structures have proven to cause ulnar nerve compression: anconeus epitrochlearis, accessory abductor digiti minimi, vascular anomalies, palmaris longus, fibrous bands, and flexor carpi ulnaris. All cases except one have had a surgical release of the ulnar nerve resulting in diminished symptoms or complete recovery at follow-up. In addition to considering common compression points, it is important to be aware that proximal compression symptoms, such as pain and a positive Tinel sign at the medial elbow, may be attributed to a hypertrophic AE or vascular anomaly. Distal compression symptoms encompass swelling, along with pain and a positive Tinel sign at the distal forearm. Various structures contributing to distal compression include an accessory abductor digiti minimi muscle, an accessory or anomalous palmaris longus muscle, or an accessory or hypertrophic flexor carpi ulnaris muscle. The occurrence of fibrous bands exhibits variability, manifesting in diverse locations across the arm.Level of Evidence: IV.

Unveiling Myasthenia Gravis: A Comprehensive Analysis of Diagnostic Tools and Clinical Insights

Objective: This research offers a comprehensive analysis of Myasthenia Gravis (MG), uncovering the remarkable accuracy of spinal accessory, ulnar, and facial nerve repetitive nerve stimulation (RNS), along with the precision of single fiber electromyography (SF-EMG) in MG diagnosis. We also embark on an exploration of clinical features and autoantibody test results in generalized MG patients.&#x0D; Methods: In this prospective study, we welcomed 31 individuals definitively diagnosed with generalized MG into our quest. The categorization of patients was conducted in accordance with the criteria set by the Myasthenia Gravis Foundation of America (MGFA). We examined patients' trapezius, nasalis, and abductor digiti minimi (ADM) muscles using RNS. We meticulously recorded the presence of MG autoantibodies, clinical subtypes based on affected muscle groups, and SF-EMG jitter rates.&#x0D; Results: The mean age of the 31 patients of whom 19 (61.3%) were male, was 64 ± 13.9 years. Among them, 20 showed positivity in the Anti-AChR antibody test. In 28 patients, accounting for 90.3% of the study group, single fiber electromyography (EMG) displayed increased jitter. There were 4 (12.9%), 24 (77.4%) and 12 (38.7%) patients featuring a decremental response of exceeding 10% in ADM, trapezius and nasalis muscles, respectivelyOur investigation revealed notable findings, such as the absence of substantial correlations between decremental response rates and age, gender, duration of complaints, antibody test results, thymus abnormalities, affected muscle types, familial history, or increased jitter rates in SF-EMG (p&gt;0.05).&#x0D; Conclusion: As our findings clearly show, we can confidently attest to the remarkable sensitivity of RNS in MG diagnosis when muscle selection is precise. A gem discovered on our study is the high sensitivity of the spinal accessory nerve, a revelation that should guide the course of routine RNS studies, particularly for those facing ocular-onset myasthenia.

Normative parameters of motor nerve conduction studies in infants

Introduction. Electromyography (EMG) is a modern method of instrumental neurophysiological diagnostics, which includes two main techniques as nerve conduction studies and needle EMG. Parameters of motor nerve conduction studies have been used in a number of clinical studies to evaluate the effectiveness of treatment in children with spinal muscular atrophy (SMA) during the use of pathogenetic therapy (nusinersen). Now, in our country there are no verified normative parameters of motor nerve conduction studies in infants. It is also worth saying that neonatal screening for identifying SMA patients started in 2023 in our country, and currently gene therapy for this disease is increasingly used, so improving methods for instrumental assessment of the dynamics of the condition during treatment, including using EMG, is relevant. &#x0D; Objective: to determine the normative parameters of motor nerve conduction studies in 1–6 months, 7–12 months, and 13–24 months infants without neurological pathology.&#x0D; Materials and methods: The motor nerve conduction studies were carried out using a 2-channel electromyograph Neuro-MVP-Micro (Russia) with electrical stimulation of the ulnar nerve and registration of the compound muscle action potential (CMAP) from the abductor digiti minimi muscle. This made it possible to determine the main parameters of the negative peak of the CMAP — distal latency, amplitude and area, and calculate the motor nerve conduction velocity (MNCV) along the distal part of the ulnar nerve. The obtained data for each parameter were subject to normal distribution and presented in the form of mean and standard deviation (M±SD), minimum and maximum values (min – max).&#x0D; Results: In the age range of 1–6 months, the amplitude of the CMAP (mV) was 5.0±1.0 (3.0–8.0); CMAP area (ms∙mV) — 9.1 ± 2.1 (5.5–12.9); distal latency (ms) — 2.2 ± 0.2 (1.6–2.5), MNCV (m/s) — 37.5 ± 5.4 (27.5–48.9).&#x0D; In the age range of 7–12 months, the amplitude of the CMAP (mV) was 6.2 ± 1.3 (3.8-9.3); CMAP area (ms∙mV) — 11.7 ± 3.0 (6.5–18.6); distal latency (ms) — 2.0 ± 0.2 (1.4–2.4), MNCV (m/s) – 48.4 ± 4.1 (42.1–55.2).&#x0D; In the age range of 13-24 months, the amplitude of the CMAP (mV) was 6.4 ± 0.6 (5.0-7.3); CMAP area (ms∙mV) — 13.3 ± 2.8 (9.8–18.2); distal latency (ms) — 2.2 ± 0.2 (1.8–2.5), MNCV (m/s) – 52.6 ± 3.8 (41.8–57.3).&#x0D; Conclusion. For the first time, normative parameters of motor nerve conduction studies were obtained in 1–6, 7–12, and 13–24 months infants without neurological pathology. This will make it possible to objectify neurophysiological parameters in neuromuscular diseases in infants.

Modulation of motor surround inhibition during motor tasks.

Surround inhibition (SI) in the motor system is important in individuation of actions, but is sometimes difficult to demonstrate. It has also not been evaluated in real life tasks. In this study, we use real life tasks and a new method where excitability of the surround muscle is assessed with respect to its current activity level rather than when it is at rest. Motor evoked potential (MEP) amplitudes were measured in the abductor digiti minimi (ADM) muscle while participants performed several motor tasks: "writing" on paper, "holding a pen" precisely and, "holding a water bottle" against gravity. These MEPs were compared to ADM MEPs amplitudes measured during a fifth finger abduction (ADM being the center muscle). SI was also measured in the traditional way, by comparing ADM MEPs during an index finger flexion and at rest. For the "writing" and "holding a pen" tasks, but not the "holding bottle" task, the MEP amplitudes were significantly smaller when compared to MEP amplitudes when the ADM was the center muscle with the same level of activation. The ADM MEP amplitudes were not different between rest and during index finger flexion. The new method employed here shows, that motor SI can be measured during tonic movements. The findings also show motor SI during two real-life motor tasks: "writing" and "holding a pen". The lack of modulation of MEP amplitude during "holding bottle" task seems to indicate that SI is action specific rather than muscle specific.

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.

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.

Corticospinal excitability during observation of basketball free-throw movement: Effects of video playback speed and stimulus timing.

Transcranial magnetic stimulation studies have indicated that action observation (AO) modulates corticospinal excitability. Although a few previous studies have shown that the AO of simple motor movements at a slow playback speed facilitates corticospinal excitability more than that at normal playback speed, it is unclear if this effect occurs during the AO of sport-related complex movements. Therefore, we investigated the changes in the motor evoked potential (MEP) amplitudes of the flexor carpi radialis (FCR) and abductor digiti minimi (ADM) muscles during the AO of a basketball free-throw movement at three different playback speeds (100%, 75%, and 50% speeds). Additionally, we evaluated the effects of stimulus timing (holding the ball vs. releasing the ball for shooting) and motor expertise (expert basketball players vs. novices) on the MEP amplitude during the AO. Our results demonstrated that regardless of motor expertise, the MEP amplitude of the FCR muscle was significantly smaller in the 50% speed condition than in the 100% condition. In the ADM muscle, the MEP amplitude was significantly larger when the ball was held after dribbling than when the ball was released. Therefore, it is suggested that corticospinal excitability in specific muscles during the observation of complex whole-body movements is influenced by video playback speed and stimulus timing.

Fully automated F-wave corridor extraction and analysis algorithm for F-wave analyses and MUNE studies

F-waves are used in motor unit number estimation (MUNE) studies, which require rapid dedicated software to perform calculations. The aim of this study is to define a mathematical method for a fully automated F-wave extraction algorithm to perform F-wave and MUNE studies while performing baseline corrections without distorting traces. Ten recordings from each class, such as healthy controls, polio patients and ALS patients, were included. Submaximal stimuli were applied to the median and ulnar nerves to record 300 traces from the abductor pollicis brevis and abductor digiti minimi muscles. The autocorrelation function and the signal of sum of all traces were used to find the location for the maximum amplitude of the F-waves. F-waves were revealed by using a cutting window. Linear line estimation was preferred for baseline corrections because it did not cause any distortion in the traces. The algorithm automatically revealed F-waves from all 30 recordings in accordance with the locations marked by a neurophysiologist. The execution of the algorithm was less than 2 (usually < 1) minutes when 300 traces were analyzed. Mean sMUP amplitudes and MUNE values are important for differentiating healthy controls from patients. Moreover, F-wave parameters belonging to polio patients on whom there was a relatively low number of studies conducted were also evaluated.

No Major Nerve Regeneration Seems to Occur during Recovery of Ulnar Neuropathy at the Elbow.

Introduction: There are three main potential mechanisms of recovery after nerve lesion: (1) resolution of conduction block, (2) collateral reinnervation, and (3) nerve regeneration. Their relative contributions in recovery after focal neuropathies are not well established. Methods: In a group of previously reported prospective cohort of patients with ulnar neuropathy at the elbow (UNE), I performed a post-hoc analysis of their clinical and electrodiagnostic findings. I compared amplitudes of the compound muscle action potential (CMAP) and sensory nerve action potential (SNAP) on ulnar nerve stimulation, as well as qualitative concentric needle electromyography (EMG) findings in the abductor digiti minimi muscle on the initial and follow-up examinations several years later. Results: Altogether, 111 UNE patients (114 arms) were studied. During median follow-up period of 880 days (range: 385-1545 days), CMAP amplitude increased (p = 0.02), and conduction block in the elbow segment recovered (from median 17% to 7%; p < 0.001). By contrast, SNAP amplitude did not change (p = 0.89). On needle EMG, spontaneous denervation activity diminished (p < 0.001), motor unit potential (MUP) amplitude increased (p < 0.001), and MUP recruitment remained unchanged (p = 0.43). Conclusions: Findings of the present study indicate that nerve function in chronic focal compression/entrapment neuropathies seems to improve mainly due to the resolution of the conduction block and collateral reinnervation. Contribution of nerve regeneration seems to be minor; the majority of axons lost in chronic focal neuropathies probably never recover. Further studies using quantitative methods are needed to validate present findings.

Estimating motor unit numbers from a CMAP scan: Repeatability study on three muscles at 15 centres

ObjectiveTo assess the repeatability and suitability for multicentre studies of MScanFit motor unit number estimation (MUNE), which involves modelling compound muscle action potential (CMAP) scans. MethodsFifteen groups in 9 countries recorded CMAP scans twice, 1–2 weeks apart in healthy subjects from abductor pollicis brevis (APB), abductor digiti minimi (ADM) and tibialis anterior (TA) muscles. The original MScanFit program (MScanFit-1) was compared with a revised version (MScanFit-2), designed to accommodate different muscles and recording conditions by setting the minimal motor unit size as a function of maximum CMAP. ResultsComplete sets of 6 recordings were obtained from 148 subjects. CMAP amplitudes differed significantly between centres for all muscles, and the same was true for MScanFit-1 MUNE. With MScanFit-2, MUNE differed less between centres but remained significantly different for APB. Coefficients of variation between repeats were 18.0% for ADM, 16.8% for APB, and 12.1% for TA. ConclusionsIt is recommended for multicentre studies to use MScanFit-2 for analysis. TA provided the least variable MUNE values between subjects and the most repeatable within subjects. SignificanceMScanFit was primarily devised to model the discontinuities in CMAP scans in patients and is less suitable for healthy subjects with smooth scans.

Neurophysiological grading tool of ulnar nerve entrapment across the elbow

Ulnar nerve entrapment across the elbow (UNEAE) is the second most common entrapment of the hand after carpal tunnel syndrome. There are few grades available for UNEAE with their limitations. The aim of this research is to establish, using the best available evidence, a clinically appropriate revision of the current ulnar nerve conduction grading tool and to evaluate its effectiveness in terms of acceptability, without any invasive tests. 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. The revised scale is designed from a clinical physiologist’s perspective and is based on the numerical values of nerve conduction findings. It could also assist surgeons to use this as a tool for interventional prediction. The proposed revised grading system is based on more nuanced, descriptive categories, ranging from “normal, “early, “mild, “moderate, “severe,” and “complete” absence. An additional category of clinical grading is therefore 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 Keypoint 9033A07 machine, used in line with the departmental protocol (peripheral protocol 1, 2015). 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 the course of one year (2017). A total of 190 patients were involved in this study. A collection of 278 consecutive symptomatic hands was tested for conduction block across the elbow while recording from the first dorsal interosseous FDI muscles. Out of the 278 samples, 201 hands were graded as having normal conduction velocity: 9 hands showed early changes, 51 hands showed mild changes, 14 hands showed moderate changes, 2 hands showed severe changes, and 1 hand showed complete absence or no response from the wrist and across the elbow. Additional studies were carried out from the abductor digiti minimi (ADM) muscles for those patients who showed conduction block across the elbow while recording from the FDI muscles. Only 57 patients underwent a nerve conduction study for ADM. 77 symptomatic hands were tested for conduction block in the ADM muscle. 18 hands were graded as normal; 48 hands showed mild changes; 10 hands showed moderate changes; and 1 hand showed complete absence or no response from the wrist and across the elbow. Out of 278 hands, 266 hands were graded as having normal amplitude across the elbow while recording from FDI muscles; 7 hands showed early changes in amplitude; 1 hand showed moderate amplitude change; 4 hands showed severe amplitude changes; and 1 hand showed complete absence or no response from the wrist and across the elbow. Out of 77 hands, 73 hands showed normal amplitude across the elbow while recording from ADM muscles; 2 hands showed mild changes; 1 hand showed a moderate change; and 1 hand showed complete absence or no response from the wrist and across the elbow. Conclusion: Finding show that FDI is more sensitive in comparison to ADM to record early changes in ulnar nerve entrapment across the elbow. In addition, it shows that a drop in amplitude is not as significant when compared to a conduction block across the elbow.

Differentiating Neurodegenerative Disease From Compressive Cervical Myelopathy Using Motor-Evoked Potentials.

A retrospective case-control study. To differentiate neurodegenerative diseases from compressive cervical myelopathy (CCM) using motor-evoked potentials (MEPs). When considering surgery for CCM, it may be necessary to differentiate the condition from a neurodegenerative disease. A total of 30 healthy volunteers, 52 typical CCM patients with single-level compression of the spinal cord at C4-5 or C5-6, 7 patients with amyotrophic lateral sclerosis (ALS), and 12 patients with demyelinating disease of the central nervous system, including 11 patients with multiple sclerosis and 1 patient with neuromyelitis optica spectrum disorder, formed our study population. MEPs were recorded from the bilateral abductor digiti minimi (ADM) and abductor hallucis (AH) muscles using transcranial magnetic stimulation and electrical stimulation of the ulnar and tibial nerves. Central motor conduction time, peripheral conduction time, amplitude of MEPs, and frequency of F waves were evaluated. Receiver operating characteristic curve analysis was used to determine the cutoff value for distinguishing between CCM and ALS. Significant differences were observed in the amplitude of MEPs and frequency of F waves evoked by peripheral nerve stimulation between patients with CCM and ALS. The MEP amplitude of AH was more accurate in differentiating between the two diseases compared with ADM (cutoff value, 11.2 mV, sensitivity, 87.5%; specificity, 85.7%). All 7 patients with ALS showed reduced frequency of F waves from ADM or AH, but none of the healthy volunteers or patients with other diseases demonstrated this finding. Moreover, there were no significant differences between CCM and demyelinating disease of the central nervous system in any of the assessments. The amplitude of MEPs and frequency of F waves evoked by peripheral nerve stimulation could be helpful in differentiating ALS from CCM.

Mirror movements – A simple algorithm for mirror activity signal processing and normative values

Mirror activity is an involuntary activation of a muscle when the respective contralateral muscle is contracting. This phenomenon has been described primarily in children and in disease states, and, more recently, also in healthy adults. Different ways of assessing mirror activity have been described.In this work we propose a simple protocol for quantifying the amount of mirror activity during a brief isolated full force isometric contraction of a given muscle. The signal was analyzed by a custom-built algorithm that detects the beginning and the end of muscle contraction. The amount of EMG signal on the mirror muscle in relation to the amount of EMG signal of the active muscle is then calculated.We studied 57 right-handed healthy subjects. Mirror activity was evaluated in the Abductor digiti minimi (ADM) and Tibialis anterior (TA) muscles during a 2–3 s full force isometric contraction. The intensity of mirror movement was represented as a percentage of the signal from maximal voluntary contraction.The performance of the algorithm for the detection of the beginning of muscle contraction was very good, when compared to 2 human operators. Intraclass correlation coefficient was excellent (0.998). The Bland-Altman plots showed similar performances of the algorithm and the human operators.We found a significant correlation of mirror activity with intensity and age. There was significantly more intense mirror activity in the left limbs (non-dominant) when compared to the right limbs.The upper limits of normality for mirror EMG signal was 27.4% for right ADM, 15.4% for left ADM, 10.4% for right TA and 2.1% for left TA.This simple protocol allows for an objective measurement of the amount of mirror activity. We propose this technique for investigation of neurological disorders.

Effects of high resistance muscle training on corticospinal output during motor fatigue assessed by transcranial magnetic stimulation.

Introduction: Central fatigue refers to a reduced drive of motor cortical output during exercise, and performance can be enhanced after training. However, the effects of training on central fatigue remain unclear. Changes in cortical output can be addressed non-invasively using transcranial magnetic stimulation (TMS). The aim of the study was to compare responses to TMS during a fatiguing exercise before and after a 3weeks lasting resistance training, in healthy subjects. Methods: The triple stimulation technique (TST) was used to quantify a central conduction index (CCI = amplitude ratio of central conduction response and peripheral nerve response) to the abductor digiti minimi muscle (ADM) in 15 subjects. The training consisted of repetitive isometric maximal voluntary contractions (MVC) of ADM for 2mintwice a day. Before and after this training, TST recordings were obtained every 15s during an 2minexercise of MVC of the ADM, where subjects performed repetitive contractions of the ADM, and repeatedly during a recovery period of 7min. Results: There was a consistent decrease of force to approximately 40% of MVC in all experiments and in all subjects, both before and after training. In all subjects, CCI decreased during exercise. While before training, theCCI decreased to 49% (SD 23.7%) after 2minof exercise, it decreased after training onlyto 79% (SD 26.4%) after exercise (p < 0.01). Discussion: The training regimen increased the proportion of target motor units that could be activated by TMS during a fatiguing exercise. The results point to a reduced intracortical inhibition, which may be a transient physiological response to facilitate the motor task. Possible underlying mechanisms at spinal and supraspinal sites are discussed.

Differentiation Between Compressive Cervical and Thoracic Myelopathy Using the Central Motor Conduction Time Ratio.

Thoracic myelopathy is a rare condition whose diagnosis is often missed or delayed. This study aimed to differentiate between cervical and thoracic myelopathy using motor-evoked potential testing. The authors included 835 patients with compressive cervical myelopathy and 94 patients with compressive thoracic myelopathy. Myelopathy using motor-evoked potentials were recorded from the bilateral abductor digiti minimi and abductor hallucis muscles through transcranial magnetic stimulation. The peripheral conduction time was measured through electrical stimulation of the ulnar and tibial nerves; moreover, the central motor conduction time (CMCT) was calculated by subtracting the peripheral conduction time from the myelopathy using motor-evoked potential latency. The most accurate differentiation between compressive cervical myelopathy and compressive thoracic myelopathy was achieved by the CMCT ratios (CMCT-ADM:CMCT-AH; cutoff value of 0.490, sensitivity of 83.0%, and specificity of 80.5%). After excluding patients with compressive cervical myelopathy who had spinal cord compression at C6-7, the cutoff value was 0.490, with a sensitivity of 83.0% and specificity of 87.3%. Determining the CMCT ratio (cutoff value of 0.490) through motor-evoked potential testing could facilitate differentiation between compressive cervical myelopathy and compressive thoracic myelopathy.

Presence of accessory abductor digiti minimi muscle in two cadavers.

During routine cadaveric dissection, accessory hypothenar muscles were incidentally discovered in two cadavers, both males, aged 86 and 92. Both muscles originated from the palmaris longus tendon in the distal portion of the forearm and were identified as accessory abductor digiti minimi (AADM) muscles, based on their association with abductor digiti minimi. While AADM is a common variant in the antebrachium, it is less typical for them to originate from the palmaris longus tendon. The presence of such an AADM could complicate surgical procedures requiring resection of the palmaris longus tendon. Moreover, the surrounding neurovasculature - namely the ulnar nerve as it passes through the ulnar canal between the pisiform and hook of the hamate - could be compressed by contractions of an AADM with such a proximal origin. This can manifest as ulnar neuropathies resulting in pain, weakness, or protracted flexion of the fourth and fifth digits (ulnar claw). Our description of these muscles adds to previous accounts of variation of the palmaris longus and abductor digiti minimi muscles while considering potential clinical implications.

Promising application of a new ulnar nerve compound muscle action potential measurement montage in amyotrophic lateral sclerosis: a prospective cross-sectional study.

Previous studies have shown that ulnar nerve compound muscle action potential recorded by the conventional "belly-tendon" montage does not accurately and completely reflect the action potential of the ulnar nerve dominating the abductor digiti minimi muscle due to the effects of far-field potentials of intrinsic hand muscles. A new method of ulnar nerve compound muscle action potential measurement was developed in 2020, which adjusts the E2 electrode from the distal tendon of the abductor digitorum to the middle of the back of the proximal wrist. This new method may reduce the influence of the reference electrode and better reflect the actual ulnar nerve compound muscle action potential. In this prospective cross-sectional study, we included 64 patients with amyotrophic lateral sclerosis and 64 age- and sex-matched controls who underwent conventional and novel ulnar nerve compound muscle action potential measurement between April 2020 and May 2021 in Peking University Third Hospital. The compound muscle action potential waveforms recorded by the new montage were unimodal and more uniform than those recorded by traditional montage. In the controls, no significant difference in the compound muscle action potential waveforms was found between the traditional montage and new montage recordings. In amyotrophic lateral sclerosis patients presenting with abductor digiti minimi spontaneous activity and muscular atrophy, the amplitude of compound muscle action potential-pE2 was significantly lower than that of compound muscle action potential-dE2 (P < 0.01). Using the new method, damaged axons were more likely to exhibit more severe amplitude decreases than those measured with the traditional method, in particular for patients in early stage amyotrophic lateral sclerosis. In addition, the decline in compound muscle action potential amplitude measured by the new method was correlated with a decrease in Revised Amyotrophic Lateral Sclerosis Functional Rating Scale scores. These findings suggest that the new ulnar nerve compound muscle action potential measurement montage reduces the effects of the reference electrode through altering the E2 electrode position, and that this method is more suitable for monitoring disease progression than the traditional montage. This method may be useful as a biomarker for longitudinal follow-up and clinical trials in amyotrophic lateral sclerosis.