Distribution Of Nerve Conduction Velocities Research Articles

Protective vs. Therapeutic Effects of Mitochondria-Targeted Antioxidant MitoTEMPO on Rat Sciatic Nerve Crush Injury: A Comprehensive Electrophysiological Analysis.

Protective vs. Therapeutic Effects of Mitochondria-Targeted Antioxidant MitoTEMPO on Rat Sciatic Nerve Crush Injury: A Comprehensive Electrophysiological Analysis. Peripheral nerve injuries often result in long-lasting functional deficits, prompting the need for effective interventions. MitoTEMPO (2-(2,2,6,6-tetramethylpiperidin-1-oxyl-4-ylamino)-2-oxoethyl) triphenylphosphonium chloride) is a mitochondria-targeted antioxidant that has shown protective and therapeutic effects against pathologies associated with reactive oxygen species. This study explores the utilization of MitoTEMPO as a therapeutic and protective agent for sciatic nerve crush injuries. By employing advanced mathematical approaches, the study seeks to comprehensively analyze nerve conduction parameters, nerve excitability, and the distribution of nerve conduction velocities to gauge the potential. Forty Wistar-Albino rats were randomly divided into following groups: (I) SHAM-animals subjected to sham operation and treated intraperitoneally (i.p.) with vehicle (bidistilled water) for 14 days; (II) CI (crush injury)-animals subjected to CI and treated with vehicle 14 days; (III) MiP-animals subjected to 7 days i.p. MitoTEMPO treatment before CI (0.7 mg/kg/day dissolved in vehicle) and, only vehicle for 7 days after CI, protective MitoTEMPO; and (IV) MiT-animals i.p. treated with only vehicle for 7 days before CI and 7 days with MitoTEMPO (0.7 mg/kg/day dissolved in vehicle) after CI, therapeutic MitoTEMPO. Nerve excitability parameters were measured, including rheobase and chronaxie, along with compound action potential (CAP) recordings. Advanced mathematical analyses were applied to CAP recordings to determine nerve conduction velocities and distribution patterns. The study revealed significant differences in nerve excitability parameters between groups. Nerve conduction velocity was notably reduced in the MiP and CI groups, whereas CAP area values were diminished in the MiP and CI groups compared to the MiT group. Furthermore, CAP velocity was lower in the MiP and CI groups, and maximum depolarization values were markedly lower in the MiP and CI groups compared to the SHAM group. The distribution of nerve conduction velocities indicated alterations in the composition of nerve fiber groups following crush injuries. In conclusion, postoperative MitoTEMPO administration demonstrated promising results in mitigating the detrimental effects of nerve crush injuries.

Comparison of nerve conduction velocity distribution methods by cold exposure and ischemia

Purpose Non-invasive estimation of the conduction velocity distribution (CVD) of a peripheral nerve has the potential to both improve clinical diagnoses of pathology and to observe the progress of the disease or the efficacy of treatments. Comparisons were made of the performance of three non-invasive CVD estimation methods proposed by independent research groups on peripheral nerve bundles under different conditions. Methods The first method (Cummins) uses a nerve compound action potential (CAP) with temporal dispersion and a mathematical single fiber action potential (SFAP). The second method (Barker) uses two CAPs and a non-mathematical SFAP waveform. The third method (Hirose) uses two CAPs recorded from distal and proximal sites. The Cummins and Barker methods have iterative solutions in the time domain while the Hirose method is a deconvolution estimator in the frequency domain. In order to compare these methods, we used cold exposure to affect primarily motor fibers and ischemia to affect primarily sensory fibers on rat caudal nerve bundles. Results The Cummins method is sensitive to changes in motor and sensory fiber percentages in CVD if it is used with the volume conductor model. The Barker and Hirose methods are sensitive to motor fiber percentages in CVD but they cannot detect changes in sensory fiber percentages accurately. Conclusions Estimation of the CVD using a priori SFAP created with a volume conductor model can non-invasively supply accurate and precise information about fiber groups in a peripheral nerve bundle.

Dexmedetomidine augments the effect of lidocaine: power spectrum and nerve conduction velocity distribution study.

BackgroundIn this study, the individual and combined inhibitory effects of dexmedetomidine and lidocaine on the conduction group of isolated nerve were investigated by determining conduction velocity distribution (CVD) and power spectrum.MethodsElectrophysiological compound action potential (CAP) recordings were conducted on isolated rat sciatic nerve before (Con) and 20 minutes after exposure to 1 mM lidocaine (Lido), 21pM dexmedetomidine (Dex) and their combination (Lido + Dex). Then for CVD, mathematical model and for power spectrum Fast Fourier analysis were conducted.ResultsDexmedetomidine alone made no significant difference in shape and duration of CAPs as compared to Con, on the other hand lidocaine depresses amplitude and prolongs the duration of CAPs, but not more than combination of dexmedetomidine and lidocaine can do.Lidocaine caused a shift in the CVD histogram to relatively slower conducting group significantly while dexmedetomidine did not cause any significant change as compared to Control. Lidocaine, when combined with dexmedetomidine revealed a remarkable effect on the whole CVD histogram by causing almost complete blockage of fast conducting nerve fibers. The relative number of fibers in CVD is conserved for separate applications of anesthetics, but not for their combination.As in CVD, power spectrum shifted from higher to lower frequency region by lidocaine and significantly for lidocaine combined with dexmedetomidine application. Shifts for dexmedetomidine applied group were seen beggarly.ConclusionsWe have concluded that dexmedetomidine alone did not influence nerve conduction, but when it is used with lidocaine it augments neural conduction blockage effect, especially on fast conducting nerve fibers.

Effects of melatonin supplementation on exercise-induced changes in conduction velocity distributions

The mammalian nervous system processes complex information to control complex behaviors. Since the speed of transport of information can be a life-saving phenomenon, it is extremely important to stabilize the rate of these processes. This study aims to investigate the protective effects of melatonin supplementation on acute heavy exercise-induced changes in the nerve conduction velocity distributions (CVD). Remodeling of the sciatic nerve due to heavy exercise demonstrates not only an increase in some parameters (rheobase and chronaxie), but also decreases in maximum depolarization, total area under the compound action potential (CAP), fall-down phase of CAP kinetics and speed of the intermediately conducting group. Acute heavy exercise-induced decreases in the contribution of nerve fibers were mainly found between 1.0 and 1.7 interstimulus interval (ISI) values (46-52 m/s). Presupplementation with melatonin, a powerful antioxidant for nervous tissues, protects the sciatic nerve against all of the aforementioned changes. Presupplementation not only protects the nerve cells from exercise-induced damage, but also increases the contribution of nerve fibers with conduction velocities of 46-52 m/s.

The recruitment order of electrically activated motor neurons investigated with a novel collision technique

ObjectiveThe development of a novel collision technique for assessment of the activation order of electrically activated nerve fibers, which is an important question in functional electrical therapy or for interpretation of results of motor unit number estimates. MethodsCompound muscle action potentials were recorded with the belly-tendon configuration from the abductor digiti minimi. A novel modified Hopf’s collision technique was applied on ten healthy male subjects to determine the distributions of conduction velocities (DCV) of all ulnar nerve fibers and of the fibers activated by electrical stimuli eliciting 20%, 50%, and 80% of the maximal muscle response. ResultsThe maximum nerve conduction velocity was (means±SE) 64.1±0.85m/s. The median conduction velocity of estimated DCV was 58.9±0.97m/s (stimulus at 20%), 58.0±0.98m/s (50%), 57.2±0.91m/s (80%), and 56.5±0.84m/s (whole nerve) (all different between each other, P<0.001). ConclusionsThe proposed collision technique allows the assessment of nerve conduction velocity distributions at maximal and sub-maximal stimulation levels and provided evidence for an inverse activation order of nerve fibers with electrical stimulation. SignificanceThe excessive fatigue seen with nerve electrical stimulation can be explained by a preferential activation of large diameter nerve fibers. The motor units first activated with electrical stimulation are likely not representative of the motor unit pool in the muscle, which poses limitations in the reliability of some of the proposed methods for motor unit counting.

Motor Unit Conduction Velocity Distribution Estimation From Evoked Motor Responses

Action potentials travel along the muscle fibers with a specific conduction velocity that depends on their structural and functional properties. Only the estimation of muscle conduction velocity distribution (MCVD) may be able to depict this propagation heterogeneity. Based on the method proposed by Cummins et al. (Electroenceph Clin Neurophysiol, 46:647-658, 1979) to estimate nerve conduction velocity distribution (NCVD), the present paper proposes a method that modifies the Cummins' approach to make it suitable for MCVD estimation from electrically evoked motor responses. The MCVD estimation algorithm was first assessed by means of simulated signals in order to control all signal features during the optimization process. Simulations showed that estimated distributions were very close to the true ones when taking into account the specificities of the muscle action potential, due to its generation and extinction (MSE divided by 5 on distribution standard deviation). This method was then applied to real signals. Elicited motor responses were recorded on the biceps brachii of healthy subjects either during repeated maximal stimulations at 20 Hz or during increasing intensity stimulations at 1 Hz. MCVD estimates were used to analyze fatigue and motor unit recruitment processes, respectively.

Does the conduction velocity distribution change along the nerve?

Nerve conduction velocity distribution (CVD) is a very useful tool to examine the state and function of nerves. Only one record of compound action potential (CAP) may be sufficient to determine the CVD if the shape functions of the single fiber action potentials (SFAP) of fibers are known. Otherwise, CAP recordings from different locations are necessary to determine CVD. In this case, we confront the problem of whether the shape of the CVD changes along the nerve, because many methods that attempt to determine the CVD are based on the assumption that the CVD is invariant along the nerve. There is not a complete solution to this problem, but there are many suggestions allied with the recording conditions to minimise this effect. The other effect that may influence both shapes of CAP and CVD along the nerve is the volume conductor effect. If a suitable model could isolate and eliminate the volume conductor effect, then the spatial variation of CVD may be attributed to the natural conditions of the nerve. In this study, we followed a procedure to eliminate volume conductor effect and then applied our previously published model to examine the spatial variations in CVD. The results show that CVDs estimated at discrete points along the nerve trunk have significantly different patterns. Consequently, it may be concluded that CVD is not uniform along an isolated nerve trunk contrary to the assumptions of the most CVD estimation methods.

磁気刺激による顔面神経伝導速度分布の検討

Objective: The purpose of this study was to evaluate by the collision method the distribution of nerve conduction velocities (DNCVs) of the facial nerve under transcranial magnetic stimulation (TMS), to better understand its neurophysiological characteristics.Materials and Methods: The subjects were 13 normal volunteers and 3 patients with Bell's palsy. The experiments were carried out using Magstim model 200, a large coil measuring 90mm in diameter with a maximal output of 2.0 tesla (T), and a Neuropack 8 (Nikon Kohden, Japan) to control the stimulation and record the electromyographical findings. The labyrinthine segment of the facial nerve within the temporal bone was selected as the site for transcranial magnetic stimulation, and the main trunk of the facial nerve that runs subcutaneously in the parotid region was selected as the site for electric stimulation. The reference electrode of the bipolar lead was placed over the mentalis muscle. The amplitude of compound muscle action potentials (CMAP) to the mentalis muscle was studied by the collision method.Measurement and Results: The peak of DNCV was detected at 22 to 24m/sec in 13 normal volunteers. The data showed a decrease in the number of thicker fibers, which tended to show faster conduction velocities, in Bell's palsy patients.Conclusions: We were able to investigate the DNCVs of the facial nerve by TMS. Thicker myelinated fibers may be more susceptible to compression damage. From this finding it can be said that the compression of the nerve results in a state comparable with Bell's palsy.

Subclinical neurophysiological effects of lead: A review on peripheral, central, and autonomic nervous system effects in lead workers

Background The peripheral nerve conduction velocity (NCV), distribution of nerve conduction velocities (DCV), somatosensory, visual, and brainstem auditory evoked potentials (SEP, VEP, and BAEP, respectively), event-related potential (P300), computerized static posturography with spectral analysis (postural balance), and electrocardiographic R–R interval variability (CVRR) with spectral analysis appear to be promising techniques for assessing subclinical effects of lead on the peripheral, central and autonomic nervous systems. This article presents an overview of research addressing subclinical neurophysiological effects of lead in workers exposed to lead. Methods We reviewed 102 articles to examine the effects and dose–effects relationships of lead on peripheral, central, and autonomic nervous system function together with reversibility of the effects, interaction between lead and other metals, and relative sensitivity and specificity of each technique. Background and methodology were also reviewed. Results and Conclusion Available data suggest that, on a group basis, the reduction in the NCV, together with the effects on the P300 latency, postural balance, and CVRR, occurs at a mean blood lead concentration (BPb) as low as 30–40 μg/dL; the effects on the latencies of the short-latency SEP, VEP, and BAEP, as well as the DCV, start at a BPb as low as 40–50 μg/dL. Further cross-sectional and preferably prospective studies by using each of those methods are needed to establish more precise dose–effects (and response) relationships of lead. Am. J. Ind. Med. 37:193–204, 2000. © 2000 Wiley-Liss, Inc.

Subclinical neurophysiological effects of lead: A review on peripheral, central, and autonomic nervous system effects in lead workers.

The peripheral nerve conduction velocity (NCV), distribution of nerve conduction velocities (DCV), somatosensory, visual, and brainstem auditory evoked potentials (SEP, VEP, and BAEP, respectively), event-related potential (P300), computerized static posturography with spectral analysis (postural balance), and electrocardiographic R-R interval variability (CV(RR)) with spectral analysis appear to be promising techniques for assessing subclinical effects of lead on the peripheral, central and autonomic nervous systems. This article presents an overview of research addressing subclinical neurophysiological effects of lead in workers exposed to lead. We reviewed 102 articles to examine the effects and dose-effects relationships of lead on peripheral, central, and autonomic nervous system function together with reversibility of the effects, interaction between lead and other metals, and relative sensitivity and specificity of each technique. Background and methodology were also reviewed. Available data suggest that, on a group basis, the reduction in the NCV, together with the effects on the P300 latency, postural balance, and CV(RR), occurs at a mean blood lead concentration (BPb) as low as 30-40 microg/dL; the effects on the latencies of the short-latency SEP, VEP, and BAEP, as well as the DCV, start at a BPb as low as 40-50 microg/dL. Further cross-sectional and preferably prospective studies by using each of those methods are needed to establish more precise dose-effects (and response) relationships of lead.

Bispectral de-noising of the compound action potential for estimation of the nerve conduction velocity distribution

The distribution of the conduction velocities (DCV) of a peripheral nerve is a powerful diagnostic tool for the assessment of neuromuscular disorders. Its efficient calculation depends on the signal-to-noise ratio (SNR) of the acquired electroneurograms (ENGs), thus, time averaging is solely used. An alternative way of improving the SNR is based on averaging in the bispectrum domain and it is proposed in this work. The compound action potential (CAP) is a linear summation of the single fiber action potentials (SFAPs) propagating along the nerve fibers and can be expressed, in the discrete time, as the circular convolution of a delay sequence (DS) and the sampled SFAP. In the proposed method, averaging of low SNR CAP measurements is done in third order spectrum domain so no time alignment is required. Averaged bispectra are introduced in modified Hirose's method, to estimate the delay sequence for a conduction distance l 1. The lost linear phase is recovered by using the delay phase cepstrum. Finally, the DCV can be calculated from the estimated DS, according to the formulation of the forward problem. Comparison between time and bispectrum averaging is performed using simulated data, proving the more efficient performance of the proposed method, especially in the case of noisy ENGs.

Estimation of the nerve conduction velocity distribution by peeling sampled compound action potentials

The nerve conduction velocity distribution is estimated by a "peeling" concept method. The compound action potential is a linear summation of the single fiber action potentials propagating along the nerve fibers and can be expressed as the convolution of a delay sequence and the single fiber action potential wavelet. An algorithm based on the comparison of the front part of a continuously deconstructed compound action potential signal to a single fiber action potential wavelet is developed (i) to separate the delay sequence from the sampled compound action potential signal, and (ii) to estimate the distribution of the conduction velocities.

Computer simulation of post-spike facilitation in spike-triggered averages of rectified EMG.

When the spikes of a motor cortical cell are used to compile a spike-triggered average (STA) of rectified electromyographic (EMG) activity, a post-spike facilitation (PSF) is sometimes seen. This is generally thought to be indicative of direct corticomotoneuronal (CM) connections. However, it has been claimed that a PSF could be caused by synchronization between CM and non-CM cells. This study investigates the generation of PSF using a computer model. A population of cortical cells was simulated, some of which made CM connections to a pool of 103 motoneurons. Motoneurons were simulated using a biophysically realistic model. A subpopulation of the cortical cells was synchronized together. After a motoneuron discharge, a motor unit action potential was generated; these were summed to produce an EMG output. Realistic values were used for the corticospinal and peripheral nerve conduction velocity distribution, for slowing of impulse conduction in CM terminal axons, and for the amount of cortical synchrony. STA of the rectified EMG from all cortical neurons showed PSF; however, these were qualitatively different for CM versus non-CM cells. Using an epoch analysis to determine reliability in a quantitative manner, it was shown that the onset latency of PSF did not distinguish the two classes of cells after 10,000 spikes because of high noise in the averages. The time of the PSF peak and the peak width at half-maximum (PWHM) could separate CM from synchrony effects. However, only PWHM was robust against changes in motor unit action-potential shape and duration and against changes in the width of cortical synchrony. The amplitude of PSF from a CM cell could be doubled by the presence of synchrony. It is proposed that, if a PSF has PWHM < 7 ms, this reliably indicates that the trigger is a CM cell projecting to the muscle whose EMG is averaged. In an analysis of experimental data where macaque motor cortical cells facilitated hand and forearm muscle EMG, 74% of PSFs fulfilled this criterion. The PWHM criterion could be applied to other STA studies in which it is important to exclude the effects of synchrony.

Effects of occupational use of vibrating tools in the autonomic, central and peripheral nervous system.

The objective of this study was to clarify the autonomic, central and peripheral nervous effects of vibrating-tool operation. The ECG R-R interval variability (CVRR), including the C-CVHF, C-CVLF (two component CVs of the CVRR reflecting parasympathetic and sympathetic activities, respectively) and the power spectral densities (PSDHF and PSDLF) after autoregressive analysis, short-latency somatosensory evoked potentials (SSEP), distribution of nerve conduction velocities (DCV), and median and radial nerve conduction velocities (NCVs) were measured in 17 vibrating-tool operators and the same number of age-matched control subjects. Some of the operators complained of white finger even in summer as soon as they arrived at the cold workplace. The significance of the differences in neurophysiological data between the exposed and unexposed groups and the associations between these data in the former were investigated. The CVRR, C-CVHF and PSDHF were significantly lower in the vibrating-tool operators than in the matched controls. The N9-N13 interpeak latency of the SSEP, i.e., conduction time of the cervico-spinobulbar pathway, in the operators was significantly prolonged as compared with the controls; the faster velocities of the DCV and the NCVs were significantly slowed in the operators. The N9-N13 interpeak latency in the operators was significantly correlated with the C-CVHF. Complex stressors of local vibration, cold, noise and heavy work, seem to affect the cervico-spinobulbar, parasympathetic and peripheral nerve functions. Also, parasympathetic hypofunction may imply a consequence in brainstem pathology induced by cold exposure in addition to vibration.

Determination of nerve conduction velocity distribution from sampled compound action potential signals.

The sampled compound action potential (CAP) data sequence was expressed as the circular convolution of the delay sequence and the sampled single fiber action potential (SFAP) data sequence. An algorithm, based on Hirose's method [1], was then developed to separate the delay sequence from the sampled CAP data sequence, and the nerve conduction velocity distribution (NCVD) was consequently calculated from the delay sequence. The NCVD was found to be the product of the amplitude of the SFAP and the number of fibers. Simulations show that the estimated results were in good agreement with the calculated results. Experiments were performed on ten sciatic nerves from five bullfrogs (Rana pipens) using two independent variables: interelectrode distance and stimulus current strength. The results estimated from CAP's recorded under each condition reflect the corresponding feature of NCVD of the condition. The advantage of the technique is to provide detailed information about both slow and fast conducting fibers. This technique also offers the possibility to directly calculate the nerve fiber diameter distribution from the sampled CAP data sequences.

Subclinical impairment in the median nerve across the carpal tunnel among female VDT operators

Sensory nerve conduction velocities in the palm-to-finger (SCV-pf), wrist-to-finger (SCV-wf), wrist-to-palm (SCV-wp), and wrist-to-elbow (SCV-we) segments and the distribution of nerve conduction velocities in the right median nerve were determined among 27 female operators aged 19-37 and 19 healthy women (controls) aged 19-31 to estimate the prevalence of subclinical carpal tunnel syndrome (CTS). Also, the WF/PF ratio, dividing the SCV-wf by the SCV-pf, was calculated to assess abnormalities of nerve conduction within the carpal tunnel. The operators were engaged in data entry in front of a visual display terminal (VDT) for about 6 h/day, and their working duration was between 1 and 17 (mean 6) years. The SCV-wf, SCV-wp, and WF/PF ratio in the operators were significantly lower than those in the controls. The rate of persons with the WF/PF ratio of less than 90%, i.e., below normal limits in the 19 controls, was significantly higher in the operator group (37%) than in the control group (0%). The operators complained of more symptoms related to CTS than did the controls, but any symptoms were not associated with slowing of nerve conduction velocities in the operators. In the controls, the WF/PF ratio was not closely correlated with skin temperature or age despite the presence of significant relations between skin temperature and the SCV-wf, SCV-pf, and SCV-wp; the interpersonal variability of the WF/PF ratio was much smaller than that of all SCVs. In the light of the present and previous studies, the rate of VDT operators with subclinical CTS seems to be high, independent of its symptoms. Also, the WF/PF ratio will be a useful and reliable screening method for the early detection of CTS due to repetitive wrist and finger movements involved in work.

PS-53-4 Distribution of motor nerve conduction velocities in patients in idiopathic carpal tunnel syndrome and undergoing hemodialysis

PS-53-4 Distribution of motor nerve conduction velocities in patients in idiopathic carpal tunnel syndrome and undergoing hemodialysis

PS-3-12 An abnormality of facial nerve conduction velocity distribution in patients with Bell's palsy

PS-3-12 An abnormality of facial nerve conduction velocity distribution in patients with Bell's palsy

Subclinical neuro-psychobehavioral effects in occupational, environmental and community health: methodology and recent findings

Evoked potentials (short-latency somatosensory, visual and brainstem auditory evoked potentials), event-related potential (P300), electrocardiographic R-R interval variability, peripheral nerve conduction velocity, distribution of nerve conduction velocities, postural balance, neurobehavioral test batteries, and questionnaires and psychiatric interview methods appear to be promising techniques for assessment of subclinical neuro-psychobehavioral effects in occupational, environmental and community health. In this paper, an overview of recent methodology and findings is provided. The available data indicate that these techniques are valid, reliable and standardized, and are easily applied in field studies.

Distribution of facial nerve conduction velocities in patients with Bell's palsy.

The etiology of Bell’s palsy remains unclear. Generally speaking, the thicker the myelinated nerve fibers, the faster the conduction velocity. Thick fibers with fast conduction velocity are considered susceptible to damage due to compression. Compression of the nerve in the fallopian canal may possible be the cause of Bell’s palsy. To determine the distribution of facial nerve diameter in normal subjects, and to investigate the electrophysiological pathology of Bell’s palsy, we developed a method for determining the distribution of nerve conduction velocities (DNCV) in facial nerve using the collision method of Hopf [1].