Mean Compound Muscle Action Potential Research Articles

Radial motor nerve conduction studies recorded from triceps brachii and extensor carpi radialis longus: Techniques and reference values.

Optimal timing of nerve transfer surgery in cervical spinal cord injury (SCI) depends upon the integrity of lower motor neurons (LMNs) in recipient nerves, which is best predicted by compound muscle action potential (CMAP) amplitude. There are no established techniques for obtaining the CMAP in two recipient muscles: triceps brachii and extensor carpi radialis longus (ECRL). This study aimed to develop recording techniques for radial motor studies to triceps and ECRL, and to determine reference values for CMAP amplitudes in healthy volunteers. This was a prospective observational study of healthy adults aged 18 years and older. Motor nerve conduction studies were performed, stimulating the radial nerve in the axilla, over the axillary pulse at the pectoralis major insertion. Recording was from triceps (long head) and ECRL. CMAP amplitude, area, latency, and stimulus intensity were recorded. Reference values (RV) were calculated for CMAP amplitudes using a value 2 standard deviations below the mean. Cube root or logarithmic transformations were used to correct for non-normal distributions. Twenty-five healthy subjects participated. Triceps mean CMAP amplitude was 15.5mV (SD 4.19), with an RV of 8.1mV. ECRL mean CMAP amplitude was 11.5mV (SD 3.54), with an RV of 6.2mV. CMAP amplitude at ECRL was 75% (95% confidence interval 50%-100%) of that at triceps. We describe a technique for recording radial motor NCS from triceps and ECRL. Knowledge of normal CMAP amplitudes will help identify LMN injury in patients with cervical SCI being considered for nerve transfers.

3,4-diaminopyridine treatment for Lambert-Eaton myasthenic syndrome in adults: a meta-analysis of randomized controlled trials

BackgroundLambert-Eaton myasthenic syndrome (LEMS) is a rare autoimmune disorder of neuromuscular transmission. The objective was to examine the efficacy and safety of 3,4-diaminopyridine (3,4-DAP) in patients with LEMS.MethodsWe searched several databases to identify relevant studies, including PubMed, EMBASE, Web of Science, MEDLINE, Cochrane Neuromuscular Disease Group Specialized Register and the Cochrane Central Register of Controlled Trials(CENTRAL). The primary outcome, quantitative myasthenia gravis (QMG) score and the secondary outcome, compound muscle action potentials (CMAP) amplitude were pooled by meta-analysis.ResultsSix randomised controlled trials (RCTs) involving 115 patients with LEMS were included. QMG score showed a significant decrease (improvement) of 2.76 points (95 % CI, -4.08 to -1.45, p < 0.001) after treatment with 3, 4-DAP. Moreover, the overall mean CMAP amplitude improved significantly in LEMS patients with 3, 4-DAP treatment, compared with placebo treatment (mean difference 1.34 mV, 95 % CI, 0.98 to 1.70, p < 0.001). The overall assessment of all included trials showed a low risk of bias and low heterogeneity.ConclusionsThe pooled results of RCTs demonsrated with moderate to high evidence that 3,4-DAP has a significant effect on LEMS treatment, with improvements in muscle strength score and CMAP amplitude.

Nerve Ultrasound Comparison Between Transthyretin Familial Amyloid Polyneuropathy and Chronic Inflammatory Demyelinating Polyneuropathy.

Backgrounds: Transthyretin familial amyloid polyneuropathy (TTR-FAP) is frequently misdiagnosed as chronic inflammatory demyelinating polyneuropathy (CIDP) because of similar phenotypes in the two diseases. This study was intended to identify the role of nerve ultrasonography in evaluating TTR-FAP and CIDP.Methods: Eighteen patients with TTR-FAP, 13 patients with CIDP, and 14 healthy controls (HC) were enrolled in this study. Consecutive ultrasonography scanning was performed in six pairs of nerves of bilateral limbs with 30 sites. The cross-sectional areas (CSAs) and CSA variability data of different groups were calculated and compared.Results: Both TTR-FAP and CIDP showed larger CSAs at most sites of both upper and lower limbs than in HC groups. CIDP patients had larger CSAs than TTR-FAP patients at 8/15 of these sites, especially at U1-3, Sci2 sites (p < 0.01). However, the CSAs at above sites were not a credible index to differentiate TTR-FAP from CIDP with a low area under the curve (<0.8). The CSA variability of median nerves was significantly higher in CIDP than in TTR-FAP and HC groups, with high sensitivity (0.692) and specificity (0.833) to differentiate CIDP from TTR-FAP. The CSA variability of ulnar nerves was not significantly different between the three groups. For the TTR-FAP group, mean CSAs at each site were not correlated with different Coutinho stages, modified polyneuropathy disability, course of sensory motor peripheral neuropathy, Neuropathy Impairment Score, or Norfolk Quality of life-diabetic neuropathy score. The mean compound muscle action potential of ulnar nerves was negatively correlated with the mean CSAs of ulnar nerves.Interpretation: TTR-FAP patients had milder nerve enlargement with less variability in CSAs of median nerves than those with CIDP, suggesting that nerve ultrasound can be a potential useful auxiliary tool to help differentiate the two neuropathies.

Prolonged Exercise Test in Patients With History of Thyrotoxicosis.

Thyrotoxic periodic paralysis is characterized by recurrent episodes of reversible, severe proximal muscle weakness associated with hypokalemia and hyperthyroidism. Prolonged exercise test is an easy, noninvasive method of demonstrating abnormal muscle membrane excitability in periodic paralyses. Although abnormal in thyrotoxic periodic paralysis patients, the effects thyroid hormone levels in non-thyrotoxic periodic paralysis thyrotoxicosis patients have not been well studied. The study aims to evaluate thyrotoxicosis patients (regardless of thyrotoxic periodic paralysis history) with prolonged exercise test and correlate it with their thyroid status. This is a prospective, cross-sectional study of consecutive thyrotoxicosis patients seen at the endocrine clinic of a tertiary medical center. Thyroid status was determined biochemically before prolonged exercise test. Compound muscle action potential (CMAP) amplitudes postexercise were compared against pre-exercise amplitudes and recorded as percentage of mean baseline CMAP amplitude. Comparisons of time-dependent postexercise CMAP amplitudes and mean CMAP amplitude decrement were made between hyperthyroid and nonhyperthyroid groups. Seventy-four patients were recruited, 23 (31%) men, 30 (41%) Chinese, and the mean age was 48.5 ± 16.8 years. Of 74 patients, 32 (43%) were hyperthyroid and 42 (57%) were nonhyperthyroid viz. euthyroid and hypothyroid. Time-dependent CMAP amplitudes from 10 to 45 minutes after exercise were significantly lower in hyperthyroid patients compared with nonhyperthyroid patients (P < 0.01). Mean CMAP amplitude decrement postexercise was significantly greater in hyperthyroid than nonhyperthyroid patients (23.4% ± 11.4% vs. 17.3% ± 10.5%; P = 0.02). Compound muscle action potential amplitude declines on prolonged exercise test were significantly greater in hyperthyroid patients compared with nonhyperthyroid patients. Muscle membrane excitability is highly influenced by thyroid hormone level. Thyrotoxic periodic paralysis occurs from increased levels of thyroid hormone activity in susceptible patients.

Correlations Between Median Nerve Sonography and Conduction Study Results and Functional Scales in Amyotrophic Lateral Sclerosis

We aimed to compare the sonographic measurement of median nerve cross-section area (CSA) in patients with Amyotrophic Lateral Sclerosis (ALS) and healthy individuals. The effect of duration of the disease on correlations between paraclinical findings and ALS functional rating scale (ALSFRS) were secondarily aimed to be evaluated. The cross-sectional study was approved by the Ethical Committee of Iran University of Medical Sciences and conducted between January 2017 and December 2018. We evaluated the median nerve surface area by means of sonography in 35 ALS patients and 35 healthy controls. Compound muscle action potential (CMAP) amplitudes during nerve conduction study and ALSFRS were recorded by the same trained specialist. Data were analyzed using SPSS software version 18. We did not find a significant difference between CSA in ALS patients and the normal population (P&gt;0.05). Comparing to normal individuals, the mean CMAP decreased significantly in ALS patients (6.6±3.07 mV versus 10.25±2.2 mV, P&lt;0.001). ALSFRS correlated with both CSA of the median nerve at the wrist (P:&lt;0.001, r:0.78) and the CMAP (P:&lt;0.001, r:0.74) that were confirmed by regression models designed to consider the effect of disease duration on these correlations. CSA was not different between ALS patients and the normal population, but CMAP decreased in ALS patients. ALSFRS correlated with both CSA and CMAP of the median nerve.

Stem Cells from Human Exfoliated Deciduous Teeth (SHED) Differentiate in vivo and Promote Facial Nerve Regeneration

Post-traumatic lesions with transection of the facial nerve present limited functional outcome even after repair by gold-standard microsurgical techniques. Stem cell engraftment combined with surgical repair has been reported as a beneficial alternative. However, the best association between the source of stem cell and the nature of conduit, as well as the long-term postoperative cell viability are still matters of debate. We aimed to assess the functional and morphological effects of stem cells from human exfoliated deciduous teeth (SHED) in polyglycolic acid tube (PGAt) combined with autografting of rat facial nerve on repair after neurotmesis. The mandibular branch of rat facial nerve submitted to neurotmesis was repaired by autograft and PGAt filled with purified basement membrane matrix with or without SHED. Outcome variables were compound muscle action potential (CMAP) and axon morphometric. Animals from the SHED group had mean CMAP amplitudes and mean axonal diameters significantly higher than the control group (p < 0.001). Mean axonal densities were significantly higher in the control group (p = 0.004). The engrafted nerve segment resected 6 weeks after surgery presented cells of human origin that were positive for the Schwann cell marker (S100), indicating viability of transplanted SHED and a Schwann cell-like phenotype. We conclude that regeneration of the mandibular branch of the rat facial nerve was improved by SHED within PGAt. The stem cells integrated and remained viable in the neural tissue for 6 weeks since transplantation, and positive labeling for S100 Schwann-cell marker suggests cells initiated in vivo differentiation.

Long-term outcomes in patients with ulnar neuropathy at the elbow treated according to the presumed aetiology

ObjectivesUlnar neuropathy at the elbow (UNE) consists mainly of two conditions: entrapment under the humeroulnar aponeurosis (HUA) and extrinsic compression in the retrocondylar (RTC) groove. These in our opinion need different treatment: surgical HUA release and avoidance of inappropriate arm positioning, respectively. We treated our UNE patients accordingly, and studied their long-term outcomes. MethodsWe invited our cohort of UNE patients to a follow-up examination consisting of history, neurological, electrodiagnostic (EDx) and ultrasonographic (US) examinations performed by four blinded investigators. ResultsAt a mean follow-up time of 881 days, we performed a complete evaluation in 117 of 165 (65%) patients, with 96 (90%; 35 HUA and 61 RTC) treated according to our recommendations. An improvement was reported by 83% of HUA and 84% of RTC patients. In both groups the ulnar nerve mean compound muscle action potential (CMAP) amplitude, and the minimal motor nerve conduction velocity increased, while the maximal ulnar nerve cross-sectional area (CSA) decreased. ConclusionAfter 2.5 years similar proportions of HUA and RTC patients reported clinical improvement that was supported by improvement in EDx and US findings. SignificanceThese results suggest that patients with UNE improve following both surgical decompression and non-operative treatment. A clinical trial comparing treatment approaches in neuropathy localised to the HUA and RTC will be needed to possibly confirm our opinion that the therapeutic approach should be tailored according to the presumed aetiology of UNE.

T38. Altered axonal excitability in spinal and bulbar muscular atrophy

Spinal and bulbar muscular atrophy (SBMA) is an inherited motor neuron disease characterized with prominent fasciculations. Fasciculations suggest motor nerve hyperexcitability and potentially result in a burden to motor neuron. Axonal excitability and nerve conduction studies were performed in 31 patients with SBMA and 140 with amyotrophic lateral sclerosis (ALS). These results were compared with those of 16 healthy males (HM). In SBMA, correlations between neurophysiological studies and clinical profiles were examined. Patient backgrounds in SBMA were as follows; mean age; 58 years, mean disease duration; 152 months, mean ALS functional rating scale (ALSFRS-R); 41, mean CAG repeat expansion; 46, mean compound muscle action potential (CMAP) amplitude on abductor pollicis brevis muscle was 6.0 mV. Compared with HM, SBMA patients had longer strength-duration time constant (SDTC), greater threshold change in depolarizing threshold electrotonus (TEd) and greater supernormality (all p < 0.05). ALS patients had similar findings and smaller late subexcitability (all p < 0.05). In SBMA, TEd (90–100 ms) was related to ALSFRS-R (R = 0.42, p < 0.05), and CAG repeat was related to CMAP amplitude (R = −0.52, p < 0.05) and superexcitability (R = −0.46, p < 0.05). Patients were divided into two groups according to CMAP amplitude (over and under 5 mV). Compared with HM, SBMA patients with over 5 mV had greater TEd (10–20 ms) and greater superexcitability (all p < 0.05). SBMA patients with under 5 mV had longer SDTC, greater TEd and greater superexcitability (all p < 0.05). ALS patients with over 5 mV had greater TEd (90–100 ms) and greater superexcitability (all p < 0.05). ALS patients with under 5 mV had longer SDTC, greater TEd, greater superexcitability and smaller subexcitability (all p < 0.05). A previous study investigated axonal excitabilities in 7 patients with SBMA and revealed increased sodium currents. Our findings suggest that SBMA patients have increased sodium and decreased fast potassium currents. Similar findings and decreased slow potassium currents were found in ALS. This difference may suggest that ALS patients have more hyperexcitable motor nerve. Moreover, our findings suggest that decreased fast potassium currents are related to CAG repeat expansion in SBMA. It is already reported that SBMA patients have disruption of axonal transport. CAG repeat expansion may bring about axonal hyperexcitability and result in a burden to motor neuron.

P335 Comparison of median nerve distal motor responses in patients with chronic inflammatory demyelinating polyneuropathy and carpal tunnel syndrome

Objective Dispersion of distal compound muscle action potential (CMAP) is a useful finding for showing demyelination. In this study, we aimed to compare the duration and area of CMAP of median nerve between cases with Chronic Inflammatory Demyelinating Polyneuropathy (CIDP) and Carpal Tunnel Syndrome (CTS). Material and methods Ninety-two participants (thirty patients with CDIP, 32 patients with CTS and 30 participants of normal control group) who were evaluated. The CMAP duration was measured from the onset of the initial negative potential to the terminal negative deflection back to baseline. The CMAP area calculation was performed by computerized EMG machine. Results A significant difference was not found between groups as for mean age of the groups, and distribution of genders (CIDP: 52,73 ± 12,34 years, 18 (%40) women, 12 (%60) men; CTS: 52,38 ± 11,83 years, 25 (%78,1) women, 7 (%21,9) men; control: 48,5 ± 14,41 years,22 (%79,3) women, and 8 (%26,7) men). The mean CMAP duration of patients with CIDP was significantly higher than patients with CTS (p: 0.003) and control group (p: 0.001), however there was not any significant difference between the patients with CTS and control group (p > 0.05). The mean CMAP area of patients with CIDP was significantly lower than patients with CTS (p: 0.003) and control group (p: 0.001), however there was not any significant difference between the patients with CTS and control group (p > 0.05). Conclusion These findings suggest that the duration and area of distal CMAP is a useful parameter for the differentiation of patients with CIDPand CTS.

Compound muscle action potential duration in critical illness neuromyopathy.

We sought to determine the specificity of compound muscle action potential (CMAP) durations and amplitudes in a large critical illness neuromyopathy (CINM) cohort relative to controls with other neuromuscular conditions. Fifty-eight patients with CINM who had been seen over a 17-year period were retrospectively studied. Electrodiagnostic findings of the CINM cohort were compared with patients with axonal peripheral neuropathy and myopathy due to other causes. Mean CMAP durations were prolonged, and mean CMAP amplitudes were severely reduced both proximally and distally in all nerves studied in the CINM cohort relative to the control groups. The specificity of prolonged CMAP durations for CINM approached 100% if they were encountered in more than 1 nerve. Prolonged, low-amplitude CMAPs occur more frequently and with greater severity in CINM patients than in neuromuscular controls with myopathy and axonal neuropathy and are highly specific for the diagnosis of CINM. Muscle Nerve 57: 395-400, 2018.

Electrophysiological Study of Femoral Nerve Function After a Continuous Femoral Nerve Block for Anterior Cruciate Ligament Reconstruction: A Randomized, Controlled Single-Blind Trial

Background: A continuous femoral nerve block (CFNB) is an effective analgesic treatment after anterior cruciate ligament (ACL) reconstruction but may result in transient femoral nerve injuries and quadriceps muscle weakness, which in turn contribute to worsened functional outcomes. Purpose: To compare electrophysiological criteria of a femoral nerve injury as well as functional and pain-related outcomes after ACL reconstruction when analgesia was provided by a CFNB or intravenous patient-controlled analgesic of morphine (IV PCA). Study Design: Randomized controlled clinical trial; Level of evidence, 1. Methods: A total of 74 patients scheduled for ACL reconstruction were randomized to receive a CFNB before surgery, followed by a ropivacaine infusion for 2 days and oxycodone, or IV PCA. The primary outcome was the rate of femoral nerve injuries at 4 weeks postoperatively, defined as a reduction of the compound muscle action potential (CMAP) area from the vastus medialis muscle after supramaximal femoral nerve stimulation at the groin, associated with an absent H-reflex of the femoral nerve and signs of vastus medialis muscle denervation. Secondary functional outcomes were quadriceps muscle strength, active flexion range, and distance walked, as measured on postoperative days 1 and 2. Secondary pain-related outcomes were IV morphine consumption and pain scores at rest and on movement in phase 1 recovery and on postoperative days 1 and 2. Results: No patients met the electrophysiological criteria of a femoral nerve injury. The mean CMAP area at 4 weeks was equivalent in both the CFNB and IV PCA groups (47 ± 16 mV·ms and 51 ± 13 mV·ms, respectively; P = .50). While no differences were detected in functional outcomes or pain scores, the consumption of an IV morphine equivalent was reduced by the administration of a CFNB in phase 1 recovery (6 ± 5 mg and 13 ± 7 mg, respectively; P = .0003), on postoperative day 1 (6 ± 7 mg and 19 ± 17 mg, respectively; P = .0005), and on postoperative day 2 (11 ± 10 mg and 19 ± 17 mg, respectively; P = .03) compared with an IV PCA. Conclusion: Despite prior contrary reports, a CFNB did not result in femoral nerve injuries or worsened functional outcomes after ACL reconstruction. The improvement of analgesia with a CFNB was only marginal and not clinically relevant beyond 24 hours. Registration: NCT01321138 (ClinicalTrials.gov identifier).

Correlation between muscle electrophysiology and strength after fibular nerve injury.

Muscle strength measurement is important when evaluating the degree of impairment in patients with nerve injury. However, accurate and objective evaluation may be difficult in patients with severe pain or those who intentionally try to avoid full exertion. We investigated the usefulness of the affected-to-unaffected side electrophysiological parameter ratios as a measure of objective ankle dorsiflexion (ADF) strength in patients with unilateral fibular nerve injury (FNI). ADF strength was measured in patients with FNI via handheld dynamometer and manual muscle test (MMT). Fibular nerve compound muscle action potential (CMAP) amplitude and latency and ADF strength of the affected side were presented as ratios to the corresponding measurements of the unaffected side. We analysed the correlation of the CMAP ratio with the ADF strength ratio using a dynamometer and compared the CMAP ratios according to MMT grade. Fifty-two patients with FNI were enrolled. The mean CMAP latency ratio did not differ between MMT groups (p=0.573). The CMAP amplitude ratio proportionally increased with the quantified ADF strength ratio via dynamometer increase (ρ=0.790; p<0.001), but the CMAP latency ratio and the quantified ADF strength ratio did not significantly correlate (ρ=0.052; p=0.713). The average CMAP amplitude ratio significantly differed between MMT groups (p<0.001), and post hoc tests showed significant differences in all paired comparisons except of Fair and Good grades (p=0.064). Electrophysiological parameter ratio, such as the affected-to-unaffected side CMAP amplitude ratio, might be sensitive parameters for ADF power estimation after FNI.

Fibular motor nerve conduction studies: Investigating the mechanism for compound muscle action potential amplitude drop with proximal stimulation.

The compound muscle action potential (CMAP) amplitude of extensor digitorum brevis can show a drop with proximal stimulation in normal fibular nerves. We assessed the contribution of the far-field potential recorded by the reference electrode (R-CMAP) to the fibular CMAP. Negative R-CMAP amplitude, peak-to-peak amplitude, and negative area were measured and correlated with the amplitude decrease. Fibular motor nerves from 14 healthy participants were studied. The mean CMAP amplitude drop with proximal stimulation was 14.0 ± 9.3%, including a >30% reduction in 1 study. All measured R-CMAP parameters correlated with the degree of amplitude drop. A greater R-CMAP contribution to the fibular CMAP leads to greater phase cancellation and temporal dispersion. The resulting amplitude drop seen in the proximal CMAP can be large enough to be classified incorrectly as "probable conduction block" by several different diagnostic criteria.

Axillary nerve conduction changes in hemiplegia

AimTo prove the possibility of axillary nerve conduction changes following shoulder subluxation due to hemiplegia, in order to investigate the usefulness of screening nerve conduction studies in patients with hemiplegia for finding peripheral neuropathy.MethodsForty-four shoulders of twenty-two patients with a first-time stroke having flaccid hemiplegia were tested, 43 ± 12 days after stroke onset. Wasting and weakness of the deltoid were present in the involved side. Motor nerve conduction latency and compound muscle action potential (CMAP) amplitude were measured along the axillary nerve, comparing the paralyzed to the sound shoulder. The stimulation was done at the Erb's point whilst the recording needle electrode was inserted into the deltoid muscle 4 cm directly beneath the lateral border of the acromion. Wilcoxon signed rank test was used to compare the motor conduction between the sound and the paralytic shoulder. Mann-Whitney test was used to compare between plegic and sound shoulder in each side.ResultsMean motor nerve conduction latency time to the deltoid muscle was 8.49, SD 4.36 ms in the paralyzed shoulder and 5.17, SD 1.35 ms in the sound shoulder (p < 0.001).Mean compound muscle action potential (CMAP) amplitude was 2.83, SD 2.50 mV in the paralyzed shoulder and was 7.44, SD 5.47 mV in the sound shoulder (p < 0.001). Patients with right paralyzed shoulder compared to patients with right sound shoulder (p < 0.001, 1-sided for latency; p = 0.003, 1-sided for amplitude), and patients with left paralyzed shoulder compared to patients with left sound shoulder (p = 0.011, 1-sided for latency, p = 0.001, 1-sided for amplitude), support the same outcomes. The electro-physiological changes in the axillary nerve may appear during the first six weeks after stroke breakout.ConclusionContinuous traction of the axillary nerve, as in hypotonic shoulder, may affect the electro-physiological properties of the nerve. It most probably results from subluxation of the head of the humerus, causing demyelinization and even axonopathy. Slowing of the conduction velocities of the axillary nerve in the paralyzed shoulders may be related also to the lowering of the skin temperature and muscular atrophy in the same limb. The usefulness of routine screening nerve conduction studies in the shoulder of hemiplegic patients seems to be advocated.

Stem Cells within PGAt Observed In Vivo after 6 Weeks Enhance Facial Nerve Regeneration

Objectives: Autografting, the gold-standard method for facial nerve repair with tissue loss, in association with high quality scaffolds and cell implants, has disclosed distinct experimental outcomes. The aim of the study was to evaluate the functional and histological effects of bone marrow stem cells (BMSC) combined with polyglycolic acid tube (PGAt) in autografted rat facial nerves. Methods: After neurotmesis of the mandibular branch of the rat facial nerve, surgical repair consisted of nerve autografting (groups A-E), contained in PGAt (groups B-E), filled with basement membrane matrix (groups C-E), with undifferentiated BMSC (group D) or Schwann-like cells that had differentiated from BMSC (group E). Axon morphometrics and an objective compound muscle action potentials (CMAP) analysis were conducted. Immunofluorescence assays were carried out with Schwann cell marker S100 and anti-B-galactosidase to label exogenous cells. Results: Six weeks after surgery, animals from either cell-containing group had mean CMAP amplitudes significantly higher than control groups. Differently from other groups, facial nerves with Schwann-like cells implants had mean axonal densities within reference values. This same group had the highest mean axonal diameter in distal segments. We observed expression of the reporter gene LacZ in nerve cells in the graft and distally from it in groups D and E. Group E cells had LacZ coexpressed with S100. Conclusions: Regeneration of the facial nerve was improved by BMSC within PGAt in rats, yet Schwann-like cells were associated with superior effects. Accordingly, groups D and E had BMSC integrated in neural tissue with maintenance of former cell phenotype for 6 weeks.

Anconeus motor unit number estimates using decomposition‐based quantitative electromyography

Motor unit number estimates (MUNEs) provide important information in health, aging, and disease, and can be determined using decomposition-enhanced spike-triggered averaging (DE-STA). Discrimination of surface-detected motor unit potentials (S-MUPs) has been limited to contractile forces of ∽30% maximum voluntary contraction (MVC), which is insufficient to recruit a representative sample of the entire MU pool in most muscles. Unique features of the anconeus may permit MUNEs at high muscle activation levels. In 10 men (25 ± 3 years), anconeus MUNEs were performed using DE-STA at 10%, 30%, and 50% root-mean-square of MVC (RMS(MVC)). The mean compound muscle action potential of the anconeus was ∽6 mV, and average S-MUP amplitudes were ∽100 μV, 145 μV, and 235 μV at 10%, 30%, and 50% RMS(MVC), resulting in low average MUNEs of 58, 38, and 25, respectively. Elbow extensor force-EMG relationships suggest full recruitment of the anconeus MU pool at 50% RMS(MVC), thus providing a representative sample for MUNE.

Impact of Aortic Cross-Clamping Time on Peripheral Nerves: Experimental Model

The present study investigated the correlation between extend aortic cross-clamping time and peripheral nerve injury on rats. 24 male, Sprague Dawley rats were divided into 3 groups; (a) control group: abdomen was directly closed after reached aorta, and followed by 72 hours, (b) short-term ischaemia-reperfusion group: peripheral nerve ischemia was induced in rats by supraceliac aortic occlusion for 20 min followed by 72 h of reperfusion, (c) long-term ischaemia-reperfusion group: peripheral nerve ischemia was induced for 30 min followed by 72 h of reperfusion. Preoperative and postoperative, electromyography (EMG) recordings were done. End of 72 h, the sciatic nerves were harvested from each animal for histopathological and biochemical analysis. The mean compound muscle action potential (CMAP) amplitude of long-term ischaemia-reperfusion group was statically significant reduced when compared to the control group (p <0.01). However, the mean distal latency value of long-term ischaemia-reperfusion group was statically significant increased (p <0.01). On the other hand, there were statically significant differences between the results of malondialdehyde, edema and ischemia fiber degeneration grades on control and long-term ischaemia-reperfusion group (p <0.001). This study demonstrated that the extending cross clamping time directly harms the peripheral nerve of rats.

Preoperative diagnosis of the responsible level in CCM using CMAPs: comparison with SCEPs

A retrospective study. To elucidate the correlation between compound muscle action potentials (CMAPs) amplitudes and responsible level of compressive cervical myelopathy (CCM), and the accuracy of level diagnosis by using CMAPs. This study was conducted at the Department of Orthopedic surgery, Yamaguchi University Graduate School of Medicine, Japan. A total of 28 patients with CCM were investigated in this study. Erb's point-stimulated CMAPs were measured from deltoid, biceps, triceps in all patients as compared with 88 healthy subjects. We performed a level diagnosis on the basis of CMAPs amplitudes. We performed a level diagnosis on the basis of CMAPs amplitudes and using an index that measures the deviation of CMAPs amplitudes between triceps and deltoid or biceps. Significant correlations between the mean CMAPs amplitudes and responsible level were showed for deltoid (6.82±2.33 mV) at C3/4 (P<0.01) and biceps (8.75±4.42 mV) at C4/5 (P=0.015). Despite considerable individual variability in CMAP amplitudes, there were correlations among CMAPs amplitudes for deltoid, biceps and triceps in the same individual. The sensitivity was 75.0%, specificity 75.0% in the index for diagnosis of C3/4. The sensitivity was 75.0%, specificity 66.7% in the index for diagnosis of C4/5. This study showed small CMAPs amplitudes in the deltoid indicated a C3/4 level of myelopathy and in biceps at the C4/5 level and could help exclude clinically silent cord compression and determine the surgical procedure to the suitable level of concern.

Mesenchymal bone marrow stem cells within polyglycolic acid tube observed in vivo after six weeks enhance facial nerve regeneration

Autografting is the gold-standard method for facial nerve repair with tissue loss. Its association with high-quality scaffolds and cell implants has disclosed distinct experimental outcomes. The aim of this study was to evaluate the functional and histological effects of bone marrow stem cells (BMSC) combined with polyglycolic acid tube (PGAt) in autografted rat facial nerves. After neurotmesis of the mandibular branch of the rat facial nerve, surgical repair consisted of nerve autografting (groups A–E) contained in pGAT (groups B–E), filled with basement membrane matrix (groups C–E) with undifferentiated BMSC (group D) or Schwann-like cells that had differentiated from BMSC (group E). Axon morphometrics and an objective compound muscle action potentials (CMAP) analysis were conducted. Immunofluorescence assays were carried out with Schwann cell marker S100 and anti-β-galactosidase to label exogenous cells. Six weeks after surgery, animals from either cell-containing group had mean CMAP amplitudes significantly higher than control groups. Differently from other groups, facial nerves with Schwann-like cell implants had mean axonal densities within reference values. This same group had the highest mean axonal diameter in distal segments. We observed expression of the reporter gene lacZ in nerve cells in the graft and distally from it in groups D and E. Group-E cells had lacZ coexpressed with S100. In conclusion, regeneration of the facial nerve was improved by BMSC within PGAt in rats, yet Schwann-like cells were associated with superior effects. Accordingly, groups D and E had BMSC integrated in neural tissue with maintenance of former cell phenotype for six weeks.

Botulinum toxin has an increased effect when targeted toward the muscle’s endplate zone: A high-density surface EMG guided study

Objectives To compare the effect of endplate-targeted injections of a low Botulinum neurotoxin type A (BoNT-A) dose with that of injections at defined distances from the motor endplate zone. Methods In eight healthy volunteers, the main endplate zones of the right and left extensor digitorum brevis (EDB) muscles were localized using high-density surface EMG. On the study side BoNT-A was injected at fixed distances from the endplate zone. On the control side, BoNT-A was administered into the endplate zone. Compound muscle action potential (CMAP) prior to the injection and 2, 12, and 24 weeks later were recorded. Results On the control side, the mean CMAP reduction 2 weeks after BoNT-A injection was 79.3%. The difference in CMAP reduction between both EDB muscles was significantly related to the injection distance from the endplate zone. Increasing the injection distance by 1 cm reduced the effect of BoNT-A by 46%. Conclusions Guided injection of a reduced BoNT-A dose into the muscle’s endplate zone(s) is a promising strategy for optimizing the therapeutic effectiveness of BoNT-A and for minimizing side-effects such as unwanted weakness of adjacent muscles. Significance Precise endplate-targeted injections increase the effect of BoNT-A and may thus prove to reduce required dosage and treatment costs.