Amplitude, area and duration of the compound muscle action potential change in different ways over the length of the ulnar nerve

Electrophysiological Signal Validation of Regenerative Peripheral Nerve Interface at Nerve Ending: A Preliminary Rat Model Experiment

BACKGROUND

 As the number of extremity amputations continues to rise, so does the demand for prosthetics. Emphasizing the importance of a nerve interface that effectively amplifies and transmits physiological signals through peripheral nerve surgery is crucial for achieving intuitive control. The regenerative peripheral nerve interface (RPNI) is recognized for its potential to provide this technical support. Through animal experiment, we aimed to confirm the actual occurrence of signal amplification.

METHODS

 Rats were divided into three experimental groups: control, common peroneal nerve transection, and RPNI. Nerve surgeries were performed for each group, and electromyography (EMG) and nerve conduction studies (NCS) were conducted at the initial surgery, as well as at 2, 4, and 8 weeks postoperatively.

RESULTS

 All implemented RPNIs exhibited viability and displayed adequate vascularity with the proper color. Clear differences in latency and amplitude were observed before and after 8 weeks of surgery in all groups (p < 0.05). Notably, the RPNI group demonstrated a significantly increased amplitude compared with the control group after 8 weeks (p = 0.031). Latency increased in all groups 8 weeks after surgery. The RPNI group exhibited relatively clear signs of denervation with abnormal spontaneous activities (ASAs) during EMG.

CONCLUSION

 This study is one of few preclinical studies that demonstrate the electrophysiological effects of RPNI and validate the neural signals. It serves as a foundational step for future research in human-machine interaction and nerve interfaces.

Exploring the effect of the nerve conduction distance on the MScanFit method ofmotor unit number estimation (MUNE)

OBJECTIVE

MScanFit motor unit number estimation (MUNE) is a sensitive method for detecting motor unit loss and has demonstrated high reproducibility in various settings. In this study, our aim was to assess the outputs of this method when the nerve conduction distance is increased.

METHODS

MScanFit recordings were obtained from the abductor digiti minimi muscle of 20 healthy volunteers. To evaluate the effect of nerve conduction distance, the ulnar nerve was stimulated from the wrist and elbow respectively. Reproducibility of MUNE, compound muscle action potential (CMAP), and other motor unit parameters were assessed using intraclass correlation coefficients (ICCs).

RESULTS

Motor unit numbers obtained from stimulation at the wrist and elbow did not significantly differ and exhibited strong consistency in the ICC test (120.3 ± 23.7 vs. 118.5 ± 27.9, p > 0.05, ICC: 0.88). Similar repeatability values were noted for other parameters. However, the Largest Unit (%) displayed notable variability between the two regions and exhibited a negative correlation with nerve conduction distance.

CONCLUSION

Our findings indicate that MScanFit can consistently calculate motor unit numbers and most of its outputs without substantial influence from nerve conduction distance. Exploring MScanFit's capabilities in various settings could enhance our understanding of its strengths and limitations for extensive use in clinical practice.

Nerve conductions studies in experimental models of autoimmune neuritis: A meta-analysis and guideline

Nerve conduction studies (NCS) are essential to assess peripheral nerve fiber function in research models of immune-mediated neuritis. However, the current lack of standard protocols and reference values impedes data comparability across models and studies. We performed a systematic review and subsequent meta-analysis of the last 30 years of NCS of immune-mediated neuritis in Lewis-rats. Twenty-six papers met the inclusion criteria for meta-analysis. Extracted data showed considerable heterogeneity of recorded nerve conduction velocity (NCV) and compound muscle action potential (CMAP). Studies also significantly differed in terms of technical, methodical, and data reporting issues. The heterogeneity of the underlying studies emphasizes the need for standardization when conducting and reporting NCS in rats. We provide normative values for NCS of the sciatic nerve of Lewis rats and propose seven items that should be addressed when NCS are performed when studying immune paradigms in Lewis rats.

Diagnostic challenges in chronic inflammatory demyelinating polyradiculoneuropathy

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) consists of a spectrum of autoimmune diseases of the peripheral nerves, causing weakness and sensory symptoms. Diagnosis often is challenging, because of the heterogeneous presentation and both mis- and underdiagnosis are common. Nerve conduction study (NCS) abnormalities suggestive of demyelination are mandatory to fulfil the diagnostic criteria. On the one hand, performance and interpretation of NCS can be difficult and none of these demyelinating findings are specific for CIDP. On the other hand, not all patients will be detected despite the relatively high sensitivity of NCS abnormalities. The electrodiagnostic criteria can be supplemented with additional diagnostic tests such as CSF examination, MRI, nerve biopsy, and somatosensory evoked potentials. However, the evidence for each of these additional diagnostic tests is limited. Studies are often small without the use of a clinically relevant control group. None of the findings are specific for CIDP, meaning that the results of the diagnostic tests should be carefully interpreted. In this update we will discuss the pitfalls in diagnosing CIDP and the value of newly introduced diagnostic tests such as nerve ultrasound and testing for autoantibodies, which are not yet part of the guidelines.

Reference values of upper extremity nerve conduction studies in a Colombian population

•

Reference values for upper extremity nerve conductions studies from a South American population.

•

AANEM task force of nerve conduction reference value establishment recommendations followed.

•

Results in agreement to international studies, correlated with studies in similar populations.

Objective

To establish appropriate reference values of upper extremity nerve conduction studies (NCS) at the Del Valle University Hospital, from Colombia.

Methods

Two hundred and twenty-two (N = 222) healthy volunteers were recruited. Latencies, amplitudes and conduction velocities from the Median, Ulnar, and Radial nerves were performed following recommendations from Buschbacher and Prahlow. Then, according to the American Association of Neuromuscular and Electrodiagnostic Medicine (AANEM) task force for reference value establishment, analyses of variance were run where each electrophysiological parameter from every nerve tested was used as dependent variable, to define which characteristics have to be kept for the model. Percentiles 3 and 97 from each of the parameters were derived. Finally, a multivariate quantile regression analysis model was tested.

Results

Sensory percentiles were 2.8–3.5 ms, 18.9–120.8 μV, and 40.0–50.0 m/s for the Median, 2.1–2.9 ms, 10.4–106.9 μV, and 41.0–58.0 m/s for the Ulnar, while 2.6–3.5 ms, 11.3–69.9 μV, and 39.0–54.0 m/s for the Radial nerve. The same parameters for motor function were 2.8–3.9 ms, 4.6–15.0 mV, and 49.0–68.0 m/s for the Median, while 2.3–3.5 ms, 3.9–11.5 mV and 51.0–70 m/s for the Ulnar nerve.

Conclusions

Values of latency, amplitude, and conduction velocity of sensory and motor functions from upper extremity nerves among Colombians are similar to equal parameters, obtained by comparable studies of populations alike.

Significance

This is the first study to establish reference values for upper extremity NCS carried out following the AANEM recommendations in a South American population.

Use of collision tests to identify physiological differences between the median and ulnar nerves

INTRODUCTION

Median and ulnar nerves are used in comparative electrophysiological studies. We analyzed the conduction values in these hand nerves in healthy volunteers to find any physiological differences between them.

METHODS

We performed standard conduction studies and conduction velocity distribution (CVD) tests with estimation of 3 quartiles in 31 healthy right-handed volunteers (17 women, 14 men) with a mean age of 44.8 ± 15.5 years.

RESULTS

The conduction velocities in all quartiles of CVD tests were statistically faster in the ulnar nerve (P < 0.00001), with no differences in the spread of conduction values and no differences between sides. In the ulnar nerve, CVD velocities in all quartiles were faster in the female group (P < 0.05).

DISCUSSION

The ulnar nerve has more fibers conducting with high velocities than does the median nerve. Electrophysiological comparisons between hand nerves must be performed carefully. Muscle Nerve 59:470-474, 2019.

Compound Motor Action Potential Measures Acute Changes in Laryngeal Innervation

Objective:

Vocal fold paralysis is caused by injury to the recurrent laryngeal nerve (RLN). Current clinical measures of laryngeal innervation are often nonquantitative. Compound motor action potentials (CMAP) measure motor innervation. The goal of this study was to determine whether CMAP can quantify laryngeal innervation following acute nerve injury.

Study Design:

Animal study.

Methods:

Twelve canine hemilaryngeal preparations were used. The RLN was serially stimulated with increasing intensities until the nerve was maximally stimulated. The CMAP amplitude was measured for each intensity stimulation and correlated. Next, the RLN was incompletely transected, and the reduction in CMAP amplitude was correlated to the percentage of transected axons. The percentage of transected axons was determined using horseradish peroxidase (HRP) staining.

Results:

Combining all hemilaryngeal preparations, the submaximal stimulation of the RLN linearly correlated with the resultant CMAP amplitude (r = 0.83; 95% CI, 0.76-0.88). Following partial RLN transection, the percentage of remaining axons linearly correlated with the CMAP amplitude (r = 0.87; 95% CI, 0.34-0.98).

Conclusions:

CMAP amplitude is a quantitative measure that may correlate with the degree of vocal fold innervation in canines. Following RLN injury, CMAP may help clinicians quantify the number of intact axons, assess the likelihood of recovery, and counsel patients on their prognosis.

Neurophysiological localisation of ulnar neuropathy at the elbow: Validation of diagnostic criteria developed by a taskforce of the Danish Society of clinical neurophysiology

OBJECTIVE

This study validates consensus criteria for localisation of ulnar neuropathy at elbow (UNE) developed by a taskforce of the Danish Society of Clinical Neurophysiology and compares them to the existing criteria from the American Association of Neuromuscular and Electrodiagnostic Medicine (AANEM). The Danish criteria are based on combinations of conduction slowing in the segments of the elbow and forearm expressed in Z-scores, and difference between the segments in m/s. Examining fibres to several muscles and sensory fibres can increase the certainty of the localisation.

METHODS

Diagnostic accuracy for UNE was evaluated on 181 neurophysiological studies of the ulnar nerve from 171 peer-reviewed patients from a mixed patient-group. The diagnostic reference standard was the consensus diagnosis based on all available clinical, laboratory, and electrodiagnostic information reached by a group of experienced Danish neurophysiologists.

RESULTS

The Danish criteria had high specificity (98.4%) and positive predictive value (PPV) (95.2%) and fair sensitivity (76.9%). Compared to the AANEM criteria, the Danish criteria had higher specificity (p<0.001) and lower sensitivity (p=0.02).

CONCLUSIONS

The Danish consensus criteria for UNE are very specific and have high PPV.

SIGNIFICANCE

The Danish criteria for UNE are reliable and well suited for use in different centres as they are based on Z-scores.

Interrater Repeatability of Motor Nerve Conduction Velocity of the Ulnar Nerve

OBJECTIVE

The purpose of this study was to obtain data on interrater repeatability of the motor nerve conduction velocity (NCV) of the ulnar nerve of different segments, ulnar distal motor latency (DML), and compound muscle action potential (CMAP) amplitudes.

DESIGN

Twenty-four healthy volunteers were examined in consecutive order. Ulnar motor NCV of different segments, ulnar DML, and CMAP amplitudes were determined. Based on a randomization list of various combinations and sequences, 1 of 3 examiners performed the first measurement. A second examiner repeated the evaluation within half an hour.

RESULTS

There were no significant differences between the first and second measurements for all parameters. For the ulnar motor NCV of the different segments, the intraclass correlation coefficient (ICC) ranged from 0.38 to 0.51, and the coefficient of repeatability (CR) ranged from 8.0 to 11.6 m/s. For the ulnar DML, the ICC was 0.44, and the CR was 0.49 millisecond. For the CMAP amplitudes at the different stimulation sites, the ICC ranged from 0.53 to 0.76, and the CR ranged from 1.5 to 2.3 mV.

CONCLUSIONS

A moderate amount of interrater variability of the ulnar motor NCV must be taken into account. Compared with the CMAP amplitudes, the interrater repeatability of the ulnar motor NCV is poorer.

Comparison of the Nerve Conduction Parameters in Proximally and Distally Located Muscles Innervated by the Bundles of Median and Ulnar Nerves

OBJECTIVE

The aim of this study was to investigate and compare the conduction parameters of nerve bundles of median and ulnar nerves that innervate proximal and distal muscles.

SUBJECTS AND METHODS

Thirty male and 30 female healthy volunteers between 18 and 70 years of age were enrolled in the study. The conduction parameters were recorded from the proximally located flexor carpi ulnaris, pronator teres and the flexor carpi radialis muscles to the distally located abductor digiti minimi and abductor pollicis brevis muscles for the ulnar and median nerves. Each nerve was stimulated at the region above the elbow and at the axillary region separately. The Student t test was used for statistical analysis, and Levene's test was used to assess whether or not the group variances exhibited a uniform distribution.

RESULTS

The conduction velocities were faster (78.27 ± 6.55 vs. 67.83 ± 6.76 m/s, and 74.57 ± 5.66 and 74.23 ± 5.88 vs. 66.38 ± 6.85 m/s) and the durations of compound muscle action potential (CMAP) response were longer (15.65 ± 2.43 vs. 13.55 ± 1.78 ms, and 16.38 ± 2.39 and 16.04 ± 2.34 vs. 13.40 ± 1.79 ms) in proximally located muscles than in distally located muscles that are innervated either by ulnar or median nerves (p < 0.001). However, the CMAP amplitudes were smaller (2.52 ± 1.16 vs. 5.81 ± 3.13 mV, and 2.90 ± 1.20 and 3.59 ± 1.66 vs. 6.88 ± 2.77 mV) in proximal muscles than in distal muscles (p < 0.001). There was no significant difference (p > 0.05) between males and females regarding conduction velocities and CMAP amplitudes recorded from proximal and distal muscles.

CONCLUSION

Proximal muscles innervated by median or ulnar nerves had lower CMAP amplitude values, longer CMAP durations and higher conduction velocities than distal muscles. These findings could reveal a temporal dispersion and phase cancellation due to desynchronized conduction during nerve stimulation.

A novel approach for evaluating nerve function in healthy elderly persons: a pilot study

Background

Motor nerve function decreases with age and can cause abnormalities in motor function. Using newly designed methods, we used evoked electromyograms to evaluate change in motor nerve function.

Material/Methods

Motor function was assessed by grip strength, timed up-and-go test, 5-m normal walk, and 5-m fastest walk. In addition, motor nerve conduction velocity was calculated by measuring latency differences (NCV) in elderly and young subjects. We also investigated motor nerve conduction velocity by correlation coefficient (NCVCC) and the difference between NCV and NCVCC (DNCV).

Results

Significant differences were observed in the motor function of elderly and young persons in grip strength, the timed up-and-go test, and the 5-m fastest walk; however, no difference was observed in the 5-m normal walk test. NCVCC was lower than NCV in both elderly and young. The correlation coefficient peak of the NCVCC calculation was lower in elderly than in young. A negative correlation was observed between correlation coefficient peak and DNCV in elderly subjects.

Conclusions

NCVCC compares the overall shape of compound muscle action potential and reflects not only the fastest motor unit, but also the motor nerve conduction velocity of other motor unit components. A significant negative correlation between DNCV and the correlation coefficient peak was observed only in elderly subjects, suggesting that older individuals, including those that maintain a high level of physical strength, experience a loss of motor nerve function. Thus, changes in motor nerve function among elderly persons can potentially be further examined for clinical use.

Motor evoked potentials and compound muscle action potentials as prognostic tools for neonates with spina bifida

MEPs and CMAPs as prognostic tools for spina bifida.

AIM

The aim of this prospective study was to determine the prognostic value of neurophysiological investigations compared to clinical neurological examination in infants with spina bifida.

METHODS

Thirty-six neonates born with spina bifida between 2002 and 2007 were evaluated and followed for 2 years. Lumbar motor evoked potentials (MEPs) and compound muscle action potentials (CMAPs) were obtained at the median age of 2 days old before surgical closure of the spinal anomaly. MEPs were recorded from the quadriceps femoris, tibialis anterior, and gastrocnemius muscles and CMAPs from the latter two muscles. Areas under the curve and latencies of the MEPs and CMAPs were measured. Clinical neurological outcome at the age of 2 years was described using Muscle Function Classes (MFCs) and ambulation status.

RESULTS

The areas under the curve of MEPs and CMAPs in the legs were associated with lower neonatal levels of motor and sensory impairment. Better muscle function class of the lower limbs at 2 years of age was associated with larger MEP and CMAP areas of the gastrocnemius and tibialis anterior muscles at neonatal age.

DISCUSSION

MEPs and CMAPs of the gastrocnemius and tibialis anterior muscles are of prognostic value for clinical neurological outcome in neonates born with spina bifida.

Pitfalls in using electrophysiological studies to diagnose neuromuscular disorders

Electrodiagnostic testing is used widely for the full characterization of neuromuscular disorders and for providing unique information on the processes underlying the pathology of peripheral nerves and muscles. However, such testing should be considered as an extension of anamnesis and physical examination, not as pathognomonic of a specific disease entity. There are many pitfalls that could lead to erroneous interpretation of electrophysiological study results when the studies are not performed properly or if they are performed in the presence of anatomical aberrations. The diagnostic reliability of electrodiagnostic studies can be improved and the associated pitfalls overcome if the physician is familiar with all of those possible pitfalls. In this article we discuss the most common and important pitfalls associated with electrodiagnostic medicine.

Conduction in ulnar nerve bundles that innervate the proximal and distal muscles: a clinical trial

Background

This study aims to investigate and compare the conduction parameters of nerve bundles in the ulnar nerve that innervates the forearm muscles and hand muscles; routine electromyography study merely evaluates the nerve segment of distal (hand) muscles.

Methods

An electrophysiological evaluation, consisting of velocities, amplitudes, and durations of ulnar nerve bundles to 2 forearm muscles and the hypothenar muscles was performed on the same humeral segment.

Results

The velocities and durations of the compound muscle action potential (CMAP) of the ulnar nerve bundle to the proximal muscles were greater than to distal muscles, but the amplitudes were smaller.

Conclusions

Bundles in the ulnar nerve of proximal muscles have larger neuronal bodies and thicker nerve fibers than those in the same nerve in distal muscles, and their conduction velocities are higher. The CMAPs of proximal muscles also have smaller amplitudes and greater durations. These findings can be attributed to the desynchronization that is caused by a wider range of distribution in nerve fiber diameters.

Conduction parameters of nerve fibers with different diameters in the same peripheral nerve can be estimated.

Compound muscle action potentials in newborn infants with spina bifida

The aim of this study was to investigate the relationship between compound muscle action potentials (CMAPs) and neurological impairment in newborn infants with spina bifida. Thirty-one newborn infants (17 males, 14 females, mean gestational age 39 wks [SD 2]; mean birthweight 3336 g [SD 496]) with spina bifida were investigated at a median age of 2 days (range 1-18 d). Motor and sensory impairment and muscle stretch reflexes were assessed and neuroimaging was performed. CMAPs were recorded from the tibialis anterior muscle and the gastrocnemius muscle after percutaneous electrical nerve stimulation. CMAPs were obtained in almost all infants. The area under the curve of the CMAP (CMAP-area) was associated with motor and sensory impairment and with the presence of muscle stretch reflexes, but not with the morphological level of the spinal anomaly. These associations were stronger for the gastrocnemius muscle than for the tibialis anterior muscle. In conclusion, the CMAP-area correlates with neurological impairment in neonatal spina bifida and provides an estimate of residual motor neuron function in affected spinal segments. The assessment of CMAPs after percutaneous electrical nerve stimulation is recommended as an additional instrument to the clinical neurological examination and imaging studies.