F-wave acquisition using low-current stimulation

Muscle & Nerve, 2018

Introduction: We sought to obtain normative values for radial nerve F-wave variables, recording with surface electrodes from the anconeus muscle. Methods: We tested 30 healthy participants (17 women, 13 men) and measured the following variables: number of F waves/40 traces (F%); minimum, maximum, and mean F-wave latency (FMIN, FMAX, FMED, respectively); Fwave chronodispersion (FCHR); interside differences of F% and FMIN (DF% and DFMIN, respectively). Results: The mean F % was 41.3%; the normative values of FMIN, FMED, FMAX, and FCHR were < 21.2, <22.1, <23.3, and < 4.0 ms, respectively; and normative values of DF% and DFMIN were < 16.6% and < 1.1 ms, respectively. Height was the sole independent predictor in a regression model of FMIN, FMED, and FMAX; this explained 37%-44% of the variability. Discussion: We identified a feasible and useful technique to record radial nerve F waves from the anconeus muscle and obtained normative values of F-wave variables. Muscle Nerve: XX: 000-000, 2018.

Muscle & Nerve, 2000

The purpose of the study was to examine the time course of neuromuscular fatigue components during a low-frequency electrostimulation (ES) session. Three bouts of 17 trains of stimulation at 30 HZ (4 s on, 6 s off) were used to electrically induce fatigue in the plantar flexor muscles. Before and after every 17-train bout, torque, electromyographic activity [expressed as root mean square (RMS) and median frequency (MF) values], evoked potentials (M-wave and H-reflex), and the level of voluntary activation (LOA, using twitch interpolation technique) were assessed. Torque during maximal voluntary contraction decreased significantly from the very first stimulation bout (À6.6 AE 1.11%, P < 0.001) and throughout the session (À10.32 AE 1.68% and À11.53 AE 1.27%, for the second and third bouts, respectively). The LOA and RMS/Mmax values were significantly decreased during the ES session (À2.9 AE 1.07% and À17.5 AE 6.14%, P < 0.01 and P < 0.001, respectively, at the end of the protocol), while MF showed no changes. The Hmax/Mmax ratio and Mmax were not significantly modified during the session. All twitch parameters were significantly potentiated after the first bout and throughout the session (P < 0.001). The maximal torque decrease was evident from the early phase of a low-frequency ES protocol, with no concomitant inhibition of motoneuron excitability or depression of muscle contractile properties. These results are consistent with an early failure of the central drive to the muscle.

Diagnostics

Neuromuscular electrical stimulation (NMES) is useful for muscle strengthening and for motor restoration of stroke patients. Using a portable ultrasound instrument, we developed an M-mode imaging protocol to visualize contractions elicited by NMES in the quadriceps muscle group. To quantify muscle activation, we performed digital image processing based on the Teager–Kaiser energy operator. The proposed method was applied for 35 voluntary patients (18 women and 17 men), of 63.8 ± 14.1 years and body mass index (BMI) 30.2 ± 6.70 kg/m2 (mean ± standard deviation). Biphasic, rectangular electric pulses of 350 µs duration were applied at two frequencies (60 Hz and 120 Hz), and ultrasound was used to assess the sensory threshold (ST) and motor threshold (MT) amplitude of the NMES signal. The MT was 23.4 ± 4.94 mA, whereas the MT to ST ratio was 2.69 ± 0.57. Linear regression analysis revealed that MT correlates poorly with body mass index (R2 = 0.004) or with the thickness of the subcutan...

Frontiers in Neuroscience

BackgroundUnmodulated high-frequency alternating currents (HFAC) are employed for producing peripheral nerves block. HFAC have been applied in humans with frequencies up to 20 kHz, whether transcutaneously, percutaneously, or via surgically-implanted electrodes. The aim of this study was to assess the effect of percutaneous HFAC, applied with ultrasound-guided needles at 30 kHz, on the sensory-motor nerve conduction of healthy volunteers.MethodsA parallel, double-blind, randomized clinical trial with a placebo control was conducted. Percutaneous HFAC at 30 kHz or sham stimulation was applied via ultrasound-guided needles in 48 healthy volunteers (n = 24 in each group) for 20 min. The assessed outcome variables were pressure pain threshold (PPT), mechanical detection threshold (MDT), maximal finger flexion strength (MFFS), antidromic sensory nerve action potential (SNAP), hand temperature, and subjective sensations by the participants. The measurements were recorded pre-intervention,...

Journal of Clinical Medicine

Former studies investigated the application of high-frequency alternating currents (HFAC) in humans for blocking the peripheral nervous system. The present trial aims to assess the effect of HFAC on the motor response, somatosensory thresholds, and peripheral nerve conduction when applied percutaneously using frequencies of 10 kHz and 20 kHz in healthy volunteers. A parallel, placebo-controlled, double-blind, randomized clinical trial was conducted. Ultrasound-guided HFAC at 10 kHz and 20 kHz and sham stimulation were delivered to the median nerve of 60 healthy volunteers for 20 min. The main assessed variables were the maximum isometric flexion strength (MFFS) of the index finger, myotonometry, pressure pain threshold (PPT), mechanical detection threshold (MDT), and sensory nerve action potential (SNAP). A decrease in the MFFS is observed immediately postintervention compared to baseline, both in the 10 kHz group (−8.5%; 95% CI −14.9 to −2.1) and the 20 kHz group (−12.0%; 95% CI −1...

Muscle & Nerve, 1994

Journal of NeuroEngineering and Rehabilitation, 2018

Background: High-frequency alternating currents of greater than 1 kHz applied on peripheral nerves has been used in animal studies to produce a motor nerve block. It has been evidenced that frequencies higher than 5 kHz are necessary to produce a complete peripheral nerve block in primates, whose nerve thickness is more similar to humans. The aim of the study was to determine the effect on muscle strength after the application of a high-frequency stimulation at 5 and 10 kHz compared to sham stimulation in healthy volunteers. Findings: Transcutaneous stimulation at 5 kHz, 10 kHz and sham stimulation were applied to eleven healthy volunteers over the ulnar and median nerves for 20 min. Maximal handgrip strength was measured before, during, immediately after the intervention, and 10 min after the end of intervention. The 10 kHz stimulation showed a lower handgrip strength during the intervention (28.1 N, SEM 3.9) when compared to 5 kHz (31.1 N, SEM 3.6; p < 0.001) and to sham stimulation (33.7 N, SEM 3.9; p < 0.001). Furthermore, only stimulation at 10 kHz decreased handgrip strength when compared to baseline. Conclusions: These findings suggest high-frequency stimulation has an inhibitory effect over muscle strength. Future studies are required in patients that are characterized by motor hyperactive such as spasticity or tremors. Clinical trial registration: NCT, NCT03169049. Registered on

Neuropsychiatric Disease and Treatment, 2015

Background: F waves are late electrophysiological responses to antidromic activation of motor neurons and are used to evaluate the conduction along the whole length of peripheral nerves. We aimed to determine the diagnostic efficacies of minimum median nerve F-wave latency (FWL) and median-to-ulnar nerve F-wave latency difference (FWLD) on carpal tunnel syndrome (CTS). Materials and methods: The electrophysiological studies consisted of sensory and motor nerve conduction and F-wave studies of the median and ulnar nerves. The best cutoff points of minimum median nerve FWL and FWLD for the diagnosis of CTS were detected for the whole study group and for different height subgroups (Group 1: 150-159 cm, Group 2: 160-169 cm, and Group 3: over 170 cm). The diagnostic efficacies of minimum median nerve FWL and FWLD were calculated for the whole CTS group and for the mild CTS group, separately. Results: The best cutoff point of minimum median nerve FWL on the diagnosis of CTS was determined as 24.60 ms for the whole group. It was 23.90 ms for Group 1, 24.80 ms for Group 2, and 28.40 ms for Group 3. The usage of these stratified cutoff points yielded a higher total diagnostic efficacy rate than single cutoff point usage (79.9% vs 69%, respectively; P=0.02). The best cutoff point of FWLD on the diagnosis of CTS was 0.80 ms for the whole group. It was 0.55 ms for Group 1, 0.30 ms for Group 2, and 0.85 ms for Group 3. Both the single cutoff point usage and the stratified chart usage for FWLD had equal diagnostic efficacy (85.1%). In the mild CTS group, diagnostic efficacy was 55.5% for minimum median nerve FWL and 78.8% for FWLD (P=0.0001). Conclusion: Median-to-ulnar nerve FWLD yields a higher diagnostic efficacy than minimum median nerve FWL on the diagnosis of CTS. However, the sensitivities of both parameters are not satisfactory for the extremities with mild CTS, which compose the main group having diagnostic challenge.

Journal of the Neurological Sciences, 2004

Objective: To examine the utility of repetitive nerve stimulation (RNS) in the evaluation of peripheral nerve hyperexcitability (PNH). Background: PNH describes a group of disorders characterized by muscle cramps, twitching and stiffness. When severe, PNH may be characterized by the presence of continuous muscle fiber activity on routine needle electromyography (EMG). In milder forms of the disease, nerve hyperexcitability may be evidenced by the presence of after-discharges or cramp potentials following RNS. Methods: Fifty-four patients were prospectively recruited and classified into one of three groups-PNH, other neuromuscular disease and controls. We recorded and quantified the after-discharges and cramp potentials following RNS at 1, 5, 10 and 30 Hz. Results: The proportion of nerves with afterdischarges and/or cramp potentials was significantly greater in the PNH group than the control group at both 5 Hz (p = 0.03) and 10 Hz (p = 0.01), as well as in the neuromuscular disease group compared to controls at 5 Hz (p = 0.02). There was also a significant concordance between complaints of muscle cramps and fasciculations and the finding of after-discharges and/or cramp potentials at both 5 Hz (p = 0.005) and 10 Hz (p = 0.004). At a stimulation frequency of 10 Hz, the sensitivity of RNS for the diagnosis of PNH (primary or secondary) was 79% and the specificity was 88%. Conclusion: Our findings suggest that RNS at or below a stimulation frequency of 10 Hz (when positive) is a useful test for the diagnosis of PNH, whether it is primary or secondary.

European Journal of Applied Physiology, 2011

The use of electrical stimulation (ES) can contribute to our knowledge of how our neuromuscular system can adapt to physical stress or unloading. Although it has been recently challenged, the standard technique used to explore central modiWcations is the twitch interpolated method which consists in superimposing single twitches or high-frequency doublets on a maximal voluntary contraction (MVC) and to compare the superimposed response to the potentiated response obtained from the relaxed muscle. Alternative methods consist in (1) superimposing a train of stimuli (central activation ratio), (2) comparing the MVC response to the force evoked by a high-frequency tetanus or (3) examining the change in maximal EMG response during voluntary contractions, if this variable is normalized to the maximal M wave, i.e. EMG response to a single stimulus. ES is less used to examine supraspinal factors but it is useful for investigating changes at the spinal level, either by using H reXexes, F waves or cervicomedullary motor-evoked potentials. Peripheral changes can be examined with ES, usually by stimulating the muscle in the relaxed state. Neuromuscular propagation of action potentials on the sarcolemma (M wave, high-frequency fatigue), excitation-contraction coupling (e.g. low-frequency fatigue) and intrinsic force (high-frequency stimulation at supramaximal intensity) can all be used to non-invasively explore muscular function with ES. As for all indirect methods, there are limitations and these are discussed in this review. Finally, (1) ES as a method to measure respiratory muscle function and (2) the comparison between electrical and magnetic stimulation will also be considered.