Concentric Needle Electrode Research Articles

Behavior of jittering potential before and after impulse blockings: a preliminary study in myasthenia gravis

Neuromuscular junction disorders lead to secession of bioelectrical activity transmission between motor nerve endings and muscle fibers. In diseases that are severe enough, impulse blockings are observed. This study aims to reveal the behavior of neuromuscular junction before and after impulse blockings. Fourteen recordings harboring impulse blockings from nine myasthenia gravis (MG) patients were included. Recordings were made from frontalis muscle by using concentric needle electrode during voluntary contraction. One hundred traces were acquired in each session. In addition to well-known jitter parameters, new parameters were calculated such as number of consecutive impulse blocking groups, number of impulse blockings in each group, ratio of maximum number of consecutive impulse blockings to all number of blockings. Graphics were composed to show location change behavior of jittering potential in all traces. For jittering potential, before or after a single impulse blocking the amount of getting further away from trigger peak was greater than getting closer to trigger peak. However, after consecutive impulse blockings the amount of getting closer to trigger peak was greater than the amount of getting further away. The behavior of neuromuscular junction before and after impulse blockings was demonstrated in MG patients. Moreover, new features were extracted for jitter studies. Building models for different diseases according to their impulse blockings may be possible with the developed algorithm.Graphical abstract

Sensory nerve conduction stimulus threshold measurements of the infraorbital nerve and its applicability as a diagnostic tool in horses with trigeminal-mediated headshaking

BackgroundTo determine whether sensory nerve conduction stimulus threshold measurements of the infraorbital nerve are able to differentiate horses with idiopathic trigeminal-mediated headshaking (i-TMHS) from healthy horses and from horses with secondary trigeminal-mediated headshaking (s-TMHS). In a prospective trial, headshaking horses were examined using a standardized diagnostic protocol, including advanced diagnostics such as computed tomography and 3-Tesla-magnetic resonance imaging (MRI), to differentiate s-TMHS from i-TMHS. Clinically healthy horses served as controls. Within this process, patients underwent general anesthesia, and the minimal sensory nerve conduction stimulus threshold (SNCT) of the infraorbital nerve was measured using a bipolar concentric needle electrode. Sensory nerve action potentials (SNAP) were assessed in 2.5–5 mA intervals. Minimal SNCT as well as additional measurements were calculated.ResultsIn 60 horses, SNAP could be recorded, of which 43 horses had i-TMHS, six had suspected s-TMHS, three horses had non-facial headshaking, and eight healthy horses served as controls. Controls had a minimal SNCT ≥ 15 mA, whereas 14/43 horses with i-TMHS and 2/6 horses with s-TMHS showed a minimal SNCT ≤ 10 mA. Minimal SNCT ≤ 10 mA showed 100% specificity to distinguish TMHS from controls, but the sensitivity was only 41%.ConclusionA minimal SNCT of the infraorbital nerve ≤ 10 mA was able to differentiate healthy horses from horses with TMHS. Nevertheless, a higher minimal SNCT did not exclude i-TMHS or s-TMHS and minimal SNCT does not distinguish s-TMHS from i-TMHS.

Concentric needle jitter analysis of the genioglossus muscle in patients with motor neuron disease

ABSTRACT Objectives Difficulty relaxing the genioglossus muscle makes the evaluation of spontaneous activity problematic in patients with motor neuron disease (MND). We performed jitter analysis using conventional disposable concentric needle electrodes (CNEs) of the voluntarily activated genioglossus muscle in patients with and without MND to detect the denervation-reinnervation process. Methods CNE jitter analysis was performed at the genioglossus muscle in 21 MND(+) patients and 22 MND(–) subjects. The jitter analysis was considered abnormal if the jitter values exceeded these limits for the mean consecutive difference (MCD) or the individual MCD in more than 10% of readings. Results Seventeen MND(+) patients (81%) had at least three abnormal individual jitter values whereas denervation findings were obtained in eleven of them during the needle electromyographic examination at genioglossus muscle. None of the MND(–) subjects showed CNE jitter abnormality. Conclusion CNE jitter analysis of genioglossus muscle may provide an useful information that may be suggestive of a diagnosis of MND/ALS.

Using jitter analysis with concentric needle electrodes to assess disease status and treatment responses in myasthenia gravis

ObjectiveThis study assesses the utility of jitter analysis with concentric needles to evaluate disease severity in myasthenia gravis (MG), correlate changes in jitter with clinical status as well as identify reasons for any discordance. MethodsWe performed a retrospective chart review of 82 MG patients and extracted data on demographics, MG subtype, antibody status, clinical scales, electrophysiology, and interventions at baseline and follow-up. ResultsBaseline MGII scores correlated with jitter (r = 0.25, p = 0.024) and abnormal pairs (r = 0.24, p = 0.03). After 28 months, MGII scores correlated with jitter (r = 0.31, p = 0.006), abnormal pairs (r = 0.29, p = 0.009), and pairs with blocks (r = 0.35, p = 0.001). Changes in MGII scores correlated with changes in jitter (r = 0.35, p = 0.002), abnormal pairs (r = 0.27, p = 0.014), and pairs with blocks (r = 0.36, p = 0.001). ConclusionsConcentric needle jitter analysis may have the potential to evaluate baseline and sequential disease severity in MG. SignificanceThis study highlights the potential for improved MG patient care through precise assessment and management using concentric needle jitter analysis to improve the accuracy of MG diagnosis and monitoring of disease activity.

The neural control of movement: a century of in vivo motor unit recordings is the legacy of Adrian and Bronk.

In two papers dated 1928 to 1929 in The Journal of Physiology, Edgar Adrian and Detlev Bronk described recordings from motor nerve and muscle fibres. The recordings from motor nerve fibres required progressive dissection of the nerve until a few fibres remained, from which isolated single fibre activity could be detected. The muscle fibre recordings were performed in humans during voluntary contractions with an intramuscular electrode - the concentric needle electrode - that they describe for the first time in the second paper. They recognised that muscle fibres would respond to each impulse sent by the innervating motor neurone and that therefore muscle fibre recordings provided information on the times of activation of the motor nerve fibres which were as accurate as a direct record from the nerve. These observations and the description of the concentric needle electrode opened the era of motor unit recordings in humans, which have continued for almost a century and have provided a comprehensive view of the neural control of movement at the motor unit level. Despite important advances in technology, many of the principles of motor unit behaviour that would be investigated in the subsequent decades were canvassed in the two papers by Adrian and Bronk. For example, they described the concomitant motor neurones' recruitment and rate coding for force modulation, synchronisation of motor unit discharges, and the dependence of discharge rate on motor unit recruitment threshold. Here, we summarise their observations and discuss the impact of their work. We highlight the advent of the concentric needle, and its subsequent influence on motor control research.

Computed tomography in measuring electrode insertion angle and depth for cricopharyngeal muscle electromyography.

Electromyography of the cricopharyngeal muscle (CP-EMG) is one of many assessment tools for dysphagia. The key to performing EMG and BTX injections is to precisely locate the cricopharyngeal muscle with an electrode. One of the main difficulties of electrode insertion is the fact that the CP muscle is located deep within the neck. Since a neck computed tomography (CT) can clearly display the CP muscle, thyroid, and blood vessels in the neck, we speculate that a safe concentric needle electrode insertion path to the cricopharyngeal muscle can be simulated with the assistance of the patient's neck CT which clearly marks the angle and depth of concentric needle electrode insertion. The purpose of this study was to explore simulated electrode insertion angles and insertion depths for cricopharyngeal electromyography based on retrospective CT data and present a method of percutaneous localization of the cricopharyngeal muscle based on CT images of the neck. One hundred and forty-three neck CT scans performed between January 2019 and November 2020 were included in this study. With the assistance of the angle and straight-line tools found in the Advantage Workstation 4.4 (GE, HealthCare), simulated insertion angles and depths from the anterior border of the sternocleidomastoid muscle to the cricopharyngeal muscle were obtained. The 143 CT images originated from participants that included 63 males (44.1%) with an average age of 46.2±13.9 years old. The insertion angle, insertion depth, and neck thickness measured on the CT images were 53.2±10.7˚, 24.2±4.1 mm, and 130.1±17.7 mm, respectively. The insertion angle and depth were significantly greater in males than in females (P<0.05), and the insertion angle increased with the age of participants (P<0.05). A generalized linear model (GLM) showed that insertion angle was positively correlated with neck thickness (β=0.14; 95% CI: 0.03 to 0.25) and gender (β=5.08; 95% CI: 1.31 to 8.85), and negatively correlated with age (β=-5.88; 95% CI: -9.54 to -1.62). Insertion depth was only positively correlated with the neck thickness (β=0.11; 95% CI: 0.07 to 0.15). This study indicates that age, gender, and neck thickness are influencing factors for insertion angle, while neck thickness is the influencing factor for insertion depth. The simulated concentric needle electrode insertion method based on CT can assist clinical operation to ensure safety and effectiveness of cricopharyngeal electromyography.

Automatic jitter measurement in needle-detected motor unit potential trains

In an active motor unit (MU), the time intervals between the firings of its muscle fibers vary across successive MU activations. This variability is called jitter and is increased in pathological processes that affect the neuromuscular junctions or terminal axonal segments of MUs. Traditionally, jitter has been measured using single fiber electrodes (SFEs) and a difficult and subjective manual technique. SFEs are expensive and reused, implying a potential risk of patient infection; so, they are being gradually substituted by safer, disposable, concentric needle electrodes (CNEs). As CNEs are larger, voltage contributions from individual fibers of a MU are more difficult to detect, making jitter measurement more difficult. This paper presents an automatic method to estimate jitter from trains of motor unit potentials (MUPs), for both SFE and CNE records. For a MUP train, segments of MUPs generated by single muscle fibers (SF MUP segments) are found and jitter is measured between pairs of these segments. Segments whose estimated jitter values are not reliable, according to several SF MUP segment characteristics, are excluded. The method has been tested in several simulation studies that use mathematical models of muscle fiber potentials. The results are very satisfactory in terms of jitter estimation error (less than 10% in most of the cases studied) and mean number of valid jitter estimates obtained per simulated train (greater than 1.0 in many of the cases and less than 0.5 only in the most complicated). A preliminary study with real signals was also performed, using 19 MUP trains from 3 neuropathic patients. Jitter measurements obtained by the automatic method were compared with those extracted from a commercial system (Keypoint) and the edition and supervision of an expert electromyographer. From these measurements 63% were taken from equivalent interval pair sites within the time span of the MUP trains and, as such, were considered as compatible measurements. Differences in jitter of these compatible measurements were very low (mean value of 1.3 μs, mean of absolute differences of 2.97 μs, 25% and 75% percentile intervals of −0.85 and 3.82 μs, respectively). Although new tests with larger number of real recordings are still required, the method seems promising for clinical practice.

Single fiber electromyography and measuring jitter with concentric needle electrodes.

This monograph contains descriptions of the single fiber electromyography (SFEMG) method and of the more recently implemented method of recording jitter with concentric needle electrodes (CNEs). SFEMG records action potentials from single muscle fibers (SFAPs), which permits measuring fiber density (FD), a sensitive measure of reinnervation, and jitter, a sensitive measure of abnormal neuromuscular transmission (NMT). With voluntary activation, jitter is measured between two SFAPs with acceptable amplitude and rise time. With activation by axon stimulation, jitter is measured between the stimulus and individual SFAPs. Pitfalls due to unstable triggers and inconstant firing rates during voluntary activation and subliminal stimulation during axon stimulation should be identified and avoided. In CNE recordings, spikes with shoulders or rising phases that are not parallel are produced by summation of SFAPS; these should be excluded and reference values for CNE jitter should be used. CNE and SFEMG have similar and very high sensitivity in detecting increased jitter, as in myasthenia gravis and other myasthenic conditions. However, jitter is also seen in ongoing reinnervation and some myopathic conditions. With SFEMG, these can be identified by increased FD; however, FD cannot be measured with CNE, and conventional electromyography should be performed in muscles with increased jitter to detect neurogenic or myogenic abnormalities. Jitter is abnormal after injections of botulinum toxin, even in muscles remote from the injection site, and can persist for 6mo or more. This can complicate the detection or exclusion of abnormal NMT.

Single fiber EMG and measuring jitter with concentric needle electrodes.

This monograph contains descriptions of the single-fiber electromyography (SFEMG) method and of the more recently implemented method of recording jitter with concentric needle electrodes (CNE). SFEMG records action potentials from single muscle fibers (SFAPs), which permits measuring fiber density (FD), a sensitive measure of reinnervation, and jitter, a sensitive measure of abnormal neuromuscular transmission (NMT). With voluntary activation, jitter is measured between two SFAPs with acceptable amplitude and rise time. With activation by axon stimulation, jitter is measured between the stimulus and individual SFAPs. Pitfalls due to unstable triggers and inconstant firing rates during voluntary activation and subliminal stimulation during axon stimulation should be identified and avoided. In CNE recordings, spikes with shoulders or rising phases that are not parallel are produced by summation of SFAPS; these should be excluded and reference values for CNE jitter should be used. CNE and SFEMG have similar and very high sensitivity in detecting increased jitter, as in myasthenia gravis and other myasthenic conditions. However, jitter is also seen in ongoing reinnervation and some myopathic conditions. With SFEMG, these can be identified by increased FD; however, FD cannot be measured with CNE, and conventional EMG should be performed in muscles with increased jitter to detect neurogenic or myogenic abnormalities. Jitter is abnormal after injections of botulinum toxin, even in muscles remote from the injection site, and can persist for 6mo or more. This can complicate the detection or exclusion of abnormal NMT.

Influence of time shifting of single muscle fiber potentials (SFPs) on jitter values measured using concentric needle electrode – a simulation study

ObjectivesThe aim of this simulation study was to evaluate the resulting value of jitter measured from a simulated examination recording and to analyze its dependence on both the number of SFPs contributing either to the triggering peak or the non-triggered peak, and time shifting (delays of triggering at the end-plate) of individual SFPs in these paired potentials. MethodsWe simulated potentials recorded using a concentric needle electrode with two well separated peaks, and performed a simulated examination (consisting of 50 trains of 100 discharges) with an assumed number of fibers forming peaks. For each train, fiber diameters were chosen at random within the allowed ranges. For each discharge the delay of triggering for each fiber at the end-plate was selected at random from an assumed range. The mean jitter values were calculated, together with the median and 95% quantile. ResultsThe results suggest that jitter is related to the mean of the individual SFP shifts. ConclusionThese findings extend the understanding of reduced jitter measurements using a concentric needle electrode. If more than one fiber forms the peak, then jitter decreases due to averaging of individual time shifts of potentials constituting the peak, rather than due to detection of the SFP with the earliest peak.

Electromyography of the muscle spindle

In needle electromyography, there are two spontaneous waveforms, miniature end plate potentials and “end plate spikes”, appearing usually together. Miniature end plate potentials are local, non-propagating postsynaptic waves, caused by spontaneous exocytosis of acetylcholine in the neuromuscular junction. The prevailing hypothesis states that “end plate spikes” are propagated postsynaptic action potentials of muscle fibers, caused by presynaptic irritation of the motor nerve or nerve terminal. Using several small concentric needle electrodes in parallel with the muscle fibers, most “end plate spikes” are strictly local or propagating for 2–4 mm. At the end plate zone, there are miniature end plate potentials without “end plate spikes”. Local “end plate spikes” are junctional potentials of intrafusal gamma neuromuscular junctions of the nuclear bag fibers, and propagated “end plate spikes” are potentials of nuclear chain muscle fibers of muscle spindles. Miniature end plate potentials without “end plate spikes” at the end plate zone derive from alpha neuromuscular junctions. These findings contrast with the prevailing hypothesis. The history of observations and different hypotheses of the origin of end plate spikes are described.

Small nerve fiber selectivity of laser and intraepidermal electrical stimulation: A comparative study between glabrous and hairy skin

ObjectivesIn clinical neurophysiology practice, various methods of stimulation can be used to activate small-diameter nociceptive cutaneous afferents located in the epidermis. These methods include different types of laser and intraepidermal electrical stimulation techniques. The diffusion of the stimulation in the skin, inside or under the epidermis, depends on laser wavelength and electrode design, in particular. The aim of this study was to compare several of these techniques in their ability to selectively stimulate small nerve fibers. MethodsIn 8 healthy subjects, laser stimulation (using a CO2 or Nd:YAP laser) and intraepidermal electrical stimulation (using a micropatterned, concentric planar, or concentric needle electrode), were applied at increasing energy or intensity on the dorsal or volar aspect of the right hand or foot. The subjects were asked to define the perceived sensation (warm, pinprick, or electric shock sensation, corresponding to the activation of C fibers, Aδ fibers, or Aβ fibers, respectively) after each stimulation. Depending on the difference in the sensations perceived between dorsal (hairy skin with thin stratum corneum) and volar (glabrous skin with thick stratum corneum) stimulations, the diffusion of the stimulation inside or under the epidermis and the nature of the activated afferents were determined. ResultsRegarding laser stimulation, the perceived sensations turned from warm to pinprick with increasing energies of stimulation, in particular with the Nd:YAP laser, of which pulse could penetrate deep in the skin according to its short wavelength. In contrast, CO2 laser stimulation produced only warm sensations and no pricking sensation when applied to the glabrous skin, perhaps due to a thicker stratum corneum and the shallow penetration of the CO2 laser pulse. Regarding intraepidermal electrical stimulation using concentric electrodes, the perceived sensations turned from pinprick to a combination of pinprick and electrical shocks with increasing intensities. Using the concentric planar electrode, the sensations perceived at high stimulation intensity even consisted of electric shocks without concomitant pinprick. In contrast, using the micropatterned electrode, only pinprick sensations were produced by the stimulation of the hairy skin, while the stimulation of the glabrous skin produced no sensation at all within the limits of stimulation intensities used in this study. ConclusionsUsing the CO2 laser or the micropatterned electrode, pinprick sensations were selectively produced by the stimulation of hairy skin, while only warm sensation or no sensation at all were produced by the stimulation of glabrous skin. These two techniques appear to be more selective with a limited diffusion of the stimulation into the skin, restricting the activation of sensory afferents to the most superficial and smallest intraepidermal nerve fibers.

WS6.3. Measuring jitter with concentric needle electrodes

Although it is preferable to use single fiber electrodes (SFEs) to measure jitter, concentric needle electrodes (CNEs) are increasingly used instead because of concern about transmissible diseases and the cost of SFEs. Increasing the low frequency filter to 1 kHz or higher produces CNE signals that appear identical to SF action potentials (APs), but such CNE signals frequently represent summation of many SFAPs – to emphasize this, simple spikes recorded with CNEs that resemble SFAPs have been called “apparent single fiber action potentials” (ASFAPs). Jitter in summated signals recorded with CNEs is somewhat less than the jitter in SFAPs. Thus, although increased jitter in CNE studies indicates abnormal neuromuscular transmission, mild abnormalities may not be detected as well as with SFEs unless appropriate reference values are used. Note – fiber density measurements can only be made with SFEs. The following precepts should be followed if CNEs are used for jitter measurements: • Use the CNE with the smallest recording surface. Currently this is the DCF 25 electrode, which is available from several vendors. Note – because of their large pickup area, monopolar needle electrodes are even more likely to record superimposed APs and should not be used for jitter analysis. • Use a high pass filter setting of 1 kHz. Because this will reduce the amplitude of recorded signals, spikes with amplitude as low as 50 μV are acceptable for jitter measurement if they have a rise time less than 300 μsec. • Measure jitter only from simple spikes that resemble SFAPs (ASFAPs). Do not measure jitter from spikes with a notch or “shoulder,” as these are definitely produced by more than one AP. • Use reference values for the specific CNE that you are using. We recommend that each laboratory obtain results from a small group of control subjects and compare these to published reference values, using the same techniques that were used to acquire those reference values, i.e., the specific type of electrode, filter settings, and criteria of acceptable APs.

Workshop 6: Single-Fiber EMG WS6.1. Voluntary SFEMG: Principles and Parameters

SFEMG is a selective recording technique that identifies action potentials (APs) from individual muscle fibers. Selectivity results from the 25 µm diameter recording surface that exits on the side of the electrode, 3 mm from the tip, and is further enhanced by using a 500Hz high pass filter. SFEMG measures fiber density and neuromuscular jitter. Fiber density is measured during slight voluntary muscle activation. Position the electrode to record with maximum amplitude the AP from one muscle fiber, which triggers the display, and count the number of time-locked acceptable APs (amplitude >200 μV, rise time <300 μs). The FD is the mean number of APs, including the triggering AP, counted at 20 sites throughout the muscle. The FD differs among different muscles and increases with age, especially after age 70 and in distal limb muscles. Jitter is measured either during axonal stimulation or voluntary activation. Stimulate facial nerve branches proximal to their entry into the muscle or anterior to the ear. In limb muscles, stimulate intramuscular axons via a monopolar needle electrode inserted near the endplate zone. Stimulate at 2 to 10 Hz (10 Hz is preferred) and adjust the stimulus intensity to produce a slight twitch. Measure jitter between the stimulus and individual APs. Analyze at least 50 stimuli for each AP and aim to measure at least 30 APs at different sites throughout the muscle. Jitter measured during voluntary activation is less subject to technical problems. Position the electrode to record at least two time-locked acceptable APs. Aim to measure jitter from 20 AP pairs from different sites throughout the muscle. Calculate jitter as the Mean value of Consecutive Differences (MCD) of successive interpotential intervals. A study is abnormal if the mean MCD exceeds the muscle upper limit, or if more than 10% of AP pairs or endplates have increased jitter. With more pronounced disturbances, individual muscle fibers fail to respond to nerve activation, blocking. Jitter can be measured with small concentric needle electrodes if careful attention is given to signal quality and appropriate reference values are used. Fiber density can only be measured with SFEMG electrodes.

Impact of obstructive sleep apnea on neuromuscular transmission- a descriptive study

ABSTRACT Objective: Obstructive sleep apnea (OSA) is a sleep disorder accompanied by intermittent hypoxia. Neuromuscular transmission (NT) is known to be disturbed under chronic hypoxia. In this descriptive study, it has been aimed to test NT under intermittent hypoxia in OSA. Methods: Thirty-nine newly diagnosed OSA patients without any comorbidities or conditions that alter NT were included in the study. Jitter analysis was performed using a concentric needle electrode. Results: The mean jitter value of 39 OSA patients was 25.9 ± 3.7 μs. When compared to the mean reference jitter values, patients in the present study had significantly higher jitter (p < 0.001). Seven (17.9%) patients met the electrophysiological criteria for NT failure. Conclusion: The authors propose that intermittent hypoxia can be the trigger for NT failure in OSA. The interaction between increased oxidative stress and disturbed mitochondrial functions may also contribute.

Investigating the Prevalence of Peripheral Neuropathy in Chemical Burns

Background: With the growing number and variety of chemical agents used in industry and for home purposes, chemical burns and their consequences have drawn physicians’ attention. Involvement of the nervous system that is a major consequence of systemic chemical exposure can be problematic in local chemical burns, as well. This study was designed to evaluate the peripheral nervous system in chemical burn victims. Objectives: Investigating the peripheral neuropathy prevalence in patients with chemical burn in a Burn Hospital, Shiraz. performing electrodiagnostic (EDX) study for all patients both on tibial and median nerve based on the reference data and in order to rule out polyneuropathy. Examining Motor nerve conduction velocities using standard procedures with concentric needle electrodes among all samples. Defining Peripheral neuropathies scored as mono- or polyneuropathy compared with the number of involved nerves. Methods: In this cross-sectional study, 59 patients with chemical burns were recruited from those referring to Shiraz Central Burn Hospital. The patients underwent a nerve conducting study besides electromyography in order to evaluate the tibial and median nerves after filling the informed consent. Also, a questionnaire covering the demographic data, the chemical agent responsible for the burn, and some other relevant information was given to each patient. The incidence of peripheral neuropathy and distance was calculated with a 95% incidence. Results: Twenty-three patients (38.9%) had peripheral neuropathy, of whom 19 cases (32.2%) had mono-neuropathy and 4 cases (6.78%) had poly-neuropathy. Axonotmesis was frequently found in patients with mono-neuropathy. The most frequent chemical agent responsible for burn was acid (56.4%). Hands were the most common site of burn (n=22 35.4%). We also evaluated the mean of total body burned surface area as 2.24±1.03% (1-9%). Conclusion: Based on our results, peripheral neuropathy has a high prevalence in localized chemical burns.

Intravenous lidocaine and magnesium on responses of A-δ and A-β nerve fibers at non-affected and affected areas in three cases of neuralgias

Intravenous magnesium and lidocaine have been used for the management of intractable pain individually or in combination. A study reported on the positive effects when used in combination on neuralgia when antiepileptic drugs failed, but nobody has clarified how the combination works. The aim of the present case report is to see how a combination of intravenous magnesium and lidocaine influenced electrically-evoked responses of peripheral A-δ and A-β nerve fibers at non-affected and affected areas in three patients with neuralgia. For nociceptive stimulation, a method of intraepidermal electrical stimulation (IES) was used for the selective activation of cutaneous A-δ fibers, using a stainless steel concentric bipolar needle electrode. For tactile stimulation, similar cutaneous sites were stimulated for cutaneous A-β fibers using the same electrode. Three patients with intractable trigeminal neuralgia or intercostal neuralgia were treated using an intravenous infusion of a combination of 1.2g of magnesium and 100mg of lidocaine for one hour. Although all patients experienced sound pain relief after the combined intravenous infusion therapy, the combination had a different effect on electrically-evoked responses of peripheral A-δ and A-β nerve fibers at non-affected and affected areas in each patient.

Concentric Needle Jitter in 97 Myasthenia Gravis Patients.

Objectives: To estimate the jitter parameters (single-fiber electromyography) in myasthenia gravis patients mostly by electrical activation in Frontalis, Orbicularis Oculi, and Extensor Digitorum muscles using a concentric needle electrode.Methods: Between 2009 and 2019, a total of 97 myasthenia gravis patients, 52 male, and mean age 54 years were included.Results: Any abnormal jitter parameter in individual muscles was 90.5% (Frontalis), 88.5% (Orbicularis Oculi), and 86.6% (Extensor Digitorum). Any jitter parameter combining Orbicularis Oculi and Frontalis muscle was abnormal in 100% for the ocular, and in 92.9% for the generalized myasthenia gravis. The most abnormal muscle was Orbicularis Oculi for the generalized, and Frontalis for the ocular myasthenia gravis. The decrement was abnormal in 78.4%, 85.9% for the generalized, and 25% for the ocular myasthenia gravis. The mean jitter ranged from 14.2 to 86 μs (mean 33.3 μs) for the ocular myasthenia gravis and from 14.4 to 220.4 μs (mean 66.3 μs) for the generalized myasthenia gravis. The antibody titers tested positive in 86.6%, 91.8% for the generalized, and 50% for the ocular myasthenia gravis. Thymectomy was done in 48.5%, thymoma was found in 19.6%, and myasthenic crisis occurred by 21.6%.Conclusion: The jitter parameters achieved a 100% abnormality in ocular myasthenia gravis if both the Orbicularis Oculi and Frontalis muscles were tested. There was a high jitter abnormality in generalized myasthenia gravis cases with one muscle tested, with about a 2% increase in sensitivity when a second is added. Concentric needle electrode jitter had high sensitivity similar to the single fiber electrode (93.8%), followed by antibody titers (86.6%), and abnormal decrement (78.4%).

Reference jitter values for the sternocleidomastoid muscle with concentric needle electrodes.

The aim of this study was to establish reference jitter values for the voluntary activated sternocleidomastoid (SCM) muscle using a concentric needle electrode (CNE). The study included 39 healthy participants (20 female and 19 male) aged 18-77 y. Jitter was expressed as the mean consecutive difference (MCD) of 80-100 consecutive discharges. Filters were set at 1 and 10 kHz. The mean MCDs for all participants were pooled, and the mean value +2.5 SD was accepted as the upper limit for the mean MCD. The upper limit for individual MCD was calculated using +2.5 SD of the upper 10th percentile MCD for individual participants. Mean age of the participants was 45 ± 14.5 y. Mean MCD was 16.20 ± 2.23 μs (range: 12-21 μs), and the upper limit of normal for mean MCD was 21.8 μs. The mean value for 823 individual jitters was 23.3 ± 4.61 μs (range: 6.6-36.9 μs), and the upper limit of normal for each individual jitter was 34.6 μs. The present findings indicate that upper normal limit for mean MCD is 22 μs and for individual data it is 35 μs.

Electrophysiological study of neuromuscular junction in congenital myasthenic syndromes, congenital myopathies, and chronic progressive external ophthalmoplegia

This study was designed to analyze the sensitivity, specificity, and accuracy of jitter parameters combined with repetitive nerve stimulation (RNS) in congenital myasthenic syndrome (CMS), chronic progressive external ophthalmoplegia (CPEO), and congenital myopathies (CM). Jitter was obtained with a concentric needle electrode during voluntary activation of the Orbicularis Oculi muscle in CMS (n = 21), CPEO (n = 20), and CM (n = 18) patients and in controls (n = 14). RNS (3 Hz) was performed in six different muscles for all patients (Abductor Digiti Minimi, Tibialis Anterior, upper Trapezius, Deltoideus, Orbicularis Oculi, and Nasalis). RNS was abnormal in 90.5% of CMS patients and in only one CM patient. Jitter was abnormal in 95.2% of CMS, 20% of CPEO, and 11.1% of CM patients. No patient with CPEO or CM presented a mean jitter higher than 53.6 µs or more than 30% abnormal individual jitter (> 45 µs). No patient with CPEO or CM and mild abnormal jitter values presented an abnormal decrement. Jitter and RNS assessment are valuable tools for diagnosing neuromuscular transmission abnormalities in CMS patients. A mean jitter value above 53.6 µs or the presence of more than 30% abnormal individual jitter (> 45 µs) strongly suggests CMS compared with CPEO and CM.