Subcutaneous Needle Electrodes Research Articles

Use of NEedle Versus suRFACE Recording Electrodes for Detection of Intraoperative Motor Warnings: A Non-Inferiority Trial. The NERFACE Study Part II

In the NERFACE study part I, the characteristics of muscle transcranial electrical stimulation motor evoked potentials (mTc-MEPs) recorded from the tibialis anterior (TA) muscles with surface and subcutaneous needle electrodes were compared. The aim of this study (NERFACE part II) was to investigate whether the use of surface electrodes was non-inferior to the use of subcutaneous needle electrodes in detecting mTc-MEP warnings during spinal cord monitoring. mTc-MEPs were simultaneously recorded from TA muscles with surface and subcutaneous needle electrodes. Monitoring outcomes (no warning, reversible warning, irreversible warning, complete loss of mTc-MEP amplitude) and neurological outcomes (no, transient, or permanent new motor deficits) were collected. The non-inferiority margin was 5%. In total, 210 (86.8%) out of 242 consecutive patients were included. There was a perfect agreement between both recording electrode types for the detection of mTc-MEP warnings. For both electrode types, the proportion of patients with a warning was 0.12 (25/210) (difference, 0.0% (one-sided 95% CI, 0.014)), indicating non-inferiority of the surface electrode. Moreover, reversible warnings for both electrode types were never followed by permanent new motor deficits, whereas among the 10 patients with irreversible warnings or complete loss of amplitude, more than half developed transient or permanent new motor deficits. In conclusion, the use of surface electrodes was non-inferior to the use of subcutaneous needle electrodes for the detection of mTc-MEP warnings recorded over the TA muscles.

Comparing Motor-Evoked Potential Characteristics of NEedle versus suRFACE Recording Electrodes during Spinal Cord Monitoring-The NERFACE Study Part I.

Muscle-recorded transcranial electrical stimulation motor-evoked potentials (mTc-MEPs) are used to assess the spinal cord integrity. They are commonly recorded with subcutaneous needle or surface electrodes, but the different characteristics of mTc-MEP signals recorded with the two types of electrodes have not been formally compared yet. In this study, mTc-MEPs were simultaneously recorded from the tibialis anterior (TA) muscles using surface and subcutaneous needle electrodes in 242 consecutive patients. Elicitability, motor thresholds, amplitude, area under the curve (AUC), signal-to-noise ratio (SNR), and the variability between mTc-MEP amplitudes were compared. Whereas amplitude and AUC were significantly higher in subcutaneous needle recordings (p < 0.01), motor thresholds and elicitability were similar for surface and subcutaneous needle recordings. Moreover, the SNRs were >2 in more than 99.5% of the surface and subcutaneous needle recordings, and the variability between consecutive amplitudes was not significantly different between the two recording electrode types (p = 0.34). Surface electrodes appear to be a good alternative to needle electrodes for spinal cord monitoring. They are non-invasive, can record signals at similar threshold intensities, have adequately high SNRs, and record signals with equivalent variability. Whether surface electrodes are non-inferior to subcutaneous needle electrodes in detecting motor warnings is investigated in part II of the NERFACE study.

Topographic and widespread auditory modulation of the somatosensory cortex: potential for bimodal sound and body stimulation for pain treatment

Objective. There has been growing interest in understanding multisensory integration in the cortex through activation of multiple sensory and motor pathways to treat brain disorders, such as tinnitus or essential tremors. For tinnitus, previous studies show that combined sound and body stimulation can modulate the auditory pathway and lead to significant improvements in tinnitus symptoms. Considering that tinnitus is a type of chronic auditory pain, bimodal stimulation could potentially alter activity in the somatosensory pathway relevant for treating chronic pain. As an initial step towards that goal, we mapped and characterized neuromodulation effects in the somatosensory cortex (SC) in response to sound and/or electrical stimulation of the body. Approach. We first mapped the topographic organization of activity across the SC of ketamine-anesthetized guinea pigs through electrical stimulation of different body locations using subcutaneous needle electrodes or with broadband acoustic stimulation. We then characterized how neural activity in different parts of the SC could be facilitated or suppressed with bimodal stimulation. Main results. The topography in the SC of guinea pigs in response to electrical stimulation of the body aligns consistently to that shown in previous rodent studies. Interestingly, auditory broadband noise stimulation primarily excited SC areas that typically respond to stimulation of lower body locations. Although there was only a small subset of SC locations that were excited by acoustic stimulation alone, all SC recording sites could be altered (facilitated or suppressed) with bimodal stimulation. Furthermore, specific regions of the SC could be modulated by stimulating an appropriate body region combined with broadband noise. Significance. These findings show that bimodal stimulation can excite or modulate firing across a widespread yet targeted population of SC neurons. This approach may provide a non-invasive method for altering or disrupting abnormal firing patterns within certain parts of the SC for chronic pain treatment.

SY5.4. Monitoring for peripheral nerve surgery

Injuries or diseases of peripheral nerves can have severe impact on function, severe disability (inability to work), social and psychological effects or chronic pain. The main reason to perform Intraoperative monitoring (IOM) during peripheral nerve surgery are to prevent nerve injuries during surgery, to identify peripheral nerves or fascicles in cases of variable anatomy, scar tissue or tumors, to determine axon continuity across a lesion, and to guide surgical decisions regarding the type of neural reconstruction to perform. Nerve action potential (NAP) recording is considered a standard method for peripheral nerve monitoring given its ability to determine the presence or absence of functional axons in a segment of nerve, it also localizes functional and non-functional nerve segments. A NAP recording requires 4.000 to 5.000 intact or regenerating axons to be obtained and its preferred to compound muscle action potential (CMAP) recordings. The presence or absence of a NAP is more important than its latency, amplitude or shape. If a NAP is recorded in a nerve or fascicle, neurolysis is performed, and nerve grafts are required in no-responding fascicles. Some technical difficulties of NAP recording are related to very short stimulation/recording distances, stimulus artifact, volume conduction from another nerve, low temperature, use of tourniquet and use of local anesthetics. CMAP recording is like that used in triggered EMG, surface or subcutaneous needle electrodes are placed over desired muscles and the exposed peripheral nerve is stimulated. Free EMG is useful to detect, in real time, trains or bursts of abnormal discharges that indicate possible nerve damage. It́s easy to use, not affected by anesthesia and has high sensitivity but low specificity. Bipolar intramuscular electrodes are preferred for EMG recordings.

Extramuscular Recording of Spontaneous EMG Activity and Transcranial Electrical Elicited Motor Potentials in Horses: Characteristics of Different Subcutaneous and Surface Electrode Types and Practical Guidelines.

IntroductionAdhesive surface electrodes are worthwhile to explore in detail as alternative to subcutaneous needle electrodes to assess myogenic evoked potentials (MEP) in human and horses. Extramuscular characteristics of both electrode types and different brands are compared in simultaneous recordings by also considering electrode impedances and background noise under not mechanically secured (not taped) and taped conditions.MethodsIn five ataxic and one non-ataxic horses, transcranial electrical MEPs, myographic activity, and noise were simultaneously recorded from subcutaneous needle (three brands) together with pre-gelled surface electrodes (five brands) on four extremities. In three horses, the impedances of four adjacent-placed surface-electrode pairs of different brands were measured and compared. The similarity between needle and surface EMGs was assessed by cross-correlation functions, pairwise comparison of motor latency times (MLT), and amplitudes. The influence of electrode noise and impedance on the signal quality was assessed by a failure rate (FR) function. Geometric means and impedance ranges under not taped and taped conditions were derived for each brand.ResultsHigh coherencies between EMGs of needle-surface pairs degraded to 0.7 at moderate and disappeared at strong noise. MLTs showed sub-millisecond simultaneous differences while sequential variations were several milliseconds. Subcutaneous MEP amplitudes were somewhat lower than epidermal. The impedances of subcutaneous needle electrodes were below 900 Ω and FR = 0. For four brands, the FR for surface electrodes was between 0 and 80% and declined to below 25% after taping. A remaining brand (27G DSN2260 Medtronic) revealed impedances over 100 kΩ and FR = 100% under not taped and taped conditions.ConclusionSubcutaneous needle and surface electrodes yield highly coherent EMGs and TES–MEP signals. When taped and allowing sufficient settling time, adhesive surface-electrode signals may approach the signal quality of subcutaneous needle electrodes but still depend on unpredictable conditions of the skin. The study provides a new valuable practical guidance for selection of extramuscular EMG electrodes. This study on horses shares common principles for the choice of adhesive surface or sc needle electrodes in human applications such as in intraoperative neurophysiological monitoring of motor functions of the brain and spinal cord.

A Novel Plug and Play Robotic Dynamometer to Assess Skeletal Muscle Contractile Function and Perform Plyometric Exercise in Live Mice

OBJECTIVEOur goal was to develop a user‐friendly, all in one instrument, which can be used in longitudinal studies of mice, to assess contractile torque produced by the ankle dorsiflexor muscles and perform forced plyometric exercise on this muscle group.METHODSWe repurposed a commercial, STEM Education robotics kit, which contains a microcontroller, stepper motors and modular parts, to build a robotic dynamometer. We connected two stepper motors in parallel for optimal driving torque. The axle that connected the motors was linked in series to a torque cell and footplate. Through a commercial plug and play data acquisition device connected to a PC through a USB port, we were able to visualize real‐time data from the torque cell, and record data as needed. We wrote custom routines in the programming language of the robotics kit to perform four sets of ten stretch‐shortening plyometric contractions of the ankle dorsiflexors, at an angular velocity of 300 degrees/s, through a range of 90–160 degrees of plantar flexion and dorsiflexion. During ankle movement produced by the robotic dynamometer, the dorsiflexor muscles were tetanized with subcutaneous needle electrodes connected to an electrical stimulator. To test our rig, we studied four, healthy, 1‐yr old, male, C57BL/6J mice. We performed all testing and training of live animals under general anesthesia induced and maintained by inhaled isoflurane (2–5% to effect).RESULTSWe found that plyometric exercise performed on our dynamometer induced a significant loss of contractile torque immediately after exercise (2816 ± 222 mNmm before exercise versus 2046 ± 87 mNmm after exercise; *, p &lt; 0.001). At 3 days post‐exercise, contractile torque was still lower than pre‐exercise levels (2322 ± 143 mNmm at Day 3; *, p = 0.002), but was significantly greater than immediate post‐exercise levels (#, p = 0.038). Histological studies (hematoxylin and eosin staining) of cross sections of the injured tibialis anterior muscle revealed that 9.6 ± 4 % of the cross sectional area was damaged (pale and disrupted cytoplasmic staining of muscle fibers).CONCLUSIONOur novel robotic dynamometer is suitable for assessing contractile function and performing forced plyometric exercise on living mice. Since our rig is made from a commercial STEM Education robotics kit, a plug and play data acquisition system, and other standard parts, it is not only user‐friendly, but is also modular in nature and therefore helps reduce machine to machine variability.Support or Funding InformationNIH R03HD091648 from NICHD and a FRAP award from EACPHS Wayne State University to JARContractile Torque and Histological DataFigure 1

大鼠视觉诱发电位记录方法比较研究

目的：比较不同F-VEP检测电极设置方法的差异，为大鼠F-VEP检测探索更优的电极放置方法。方法：SD大鼠18只，随机均分三组，分别予以植入式颅骨电极、传统皮下式针状电极、改良皮下式针状电极记录。检测指标为F-VEP的N1波、P1波的潜伏期和N1-P1波振幅，对结果进行统计学分析。结果：植入式颅骨电极记录组P1波潜伏期较传统皮下式针状电极记录组提前(P = 0.002)，改良皮下式针状电极记录组P1波潜伏期较传统皮下式针状电极记录组提前(P = 0.025)，而植入式颅骨电极组与改良皮下式针状电极组P1波潜伏期无差异(P > 0.05)；植入式颅骨电极记录组N1-P1振幅较皮下式针状电极组均更大(P = 0.028/P = 0.011)，两组皮下式针状电极组振幅无差异(P > 0.05)；安全性方面仅植入式颅骨电极组出现不良事件，皮下针状电极组无一例出现。结论：植入式颅骨电极其敏感性、重复性较优，传统皮下式针状电极安全性较优，而改良皮下式针状电极保留了安全性的优势，同时增强了敏感性和重复性，是对F-VEP检测的有效改良。 Objective: To explore a better electrode setting method for F-VEP detection in rats, the difference of different F-VEP recording methods was compared. Methods: 18 SD-rats were randomly divided into three groups. The skull implanted electrode, the traditional hypodermic needle electrode and the modified hypodermic needle electrode were respectively recorded in each group. The recording results are the latency of N1 wave and P1 wave and the amplitude of N1-P1 wave, and were statistically analyzed by SPSS software. Results: The latency of P1 wave in the skull implanted electrode group was significantly advanced than the traditional subcutaneous needle electrode group (P = 0.002); the latency of P1 wave in modified subcutaneous needle electrode group was significantly advanced than the traditional subcutaneous needle electrode group (P = 0.025); and no significantly difference was found between the skull implanted electrode group and the modified subcutaneous needle electrode (P > 0.05). The amplitude of the N1-P1 wave in the skull implanted electrode group were significantly larger than two subcutaneous needle electrode groups (P = 0.028/P = 0.011); and no difference was showed between the two subcutaneous needle electrode group in amplitude of the N1-P1 wave (P > 0.05). Only the skull implanted electrode group had adverse events, while subcutaneous needle electrode groups were all well. Conclusion: The skull implanted electrode recording method has excellent sensitivity and repeatability, and the traditional subcutaneous needle electrode recording method is well in animal’s safety, but the modified subcutaneous needle electrode recording method retains the security advantage and simultaneously enhances the sensitivity and repeatability. So the modified subcutaneous needle electrode recording method is effective in F-VEP recording in rats.

Influence of Clonidine on Antihypertensive Selective Afferent Vagal Nerve Stimulation in Rats

Selective-afferent vagal nerve stimulation (sVNS) may be a treatment option for therapy-resistant hypertension, as it lowers blood pressure (BP) in rats without causing significant side effects. Alpha-2-agonists are widely used for the treatment of withdrawal, chronic pain and other disorders, and even if sVNS becomes a treatment option for therapy resistant hypertension, in some patients it might be necessary to combine sVNS with an alpha-2-agonist like clonidine. Alpha-2-agonists exhibit a central and peripheral mechanism of action. This study investigated the influence of the commonly used alpha-2-agonist clonidine on sVNS. A polyimide multichannel-cuff-electrode was placed around the left vagal nerve bundle including the aortic depressor nerve (ADN) in eight male Wistar rats for the focused stimulation of baroreceptive fibers of the ADN. Stimulation parameters were adapted to the thresholds of the individual animals and ranged from frequencies between 30 and 50 Hz, amplitudes of 0.5-0.9 mA and pulse widths between 0.4 and 0.8 ms. BP was recorded using a microtip transducer in the left carotid artery, and electrocardiography was registered using subcutaneous needle electrodes. Before clonidine, we found a frequency-dependent drop of BP with maximum at 40 Hz. The animals' mean arterial blood pressures and respiration rate dropped after intravenous clonidine administration (10 µg/kg bodyweight), and sVNS still decreased in BP, but they did so to a lesser extent. Unwanted bradycardia, which was expected by the superimposition of sVNS and clonidine, did not occur. Left-sided vagotomy abolished the respiratory depressant effect of clonidine and blunted the BP reducing effect of sVNS while sVNS hardly affected heart rate anymore. The effect of sVNS on BP is dampened by clonidine, but sVNS can still lower the BP in clonidine treated rats without causing significant bradycardia.

Prevalence of Complications in Intraoperative Magnetic Resonance Imaging Combined with Neurophysiologic Monitoring

High-field intraoperative magnetic resonance imaging (ioMRI) is becoming increasingly available in neurosurgery centers, where it has to be combined with intraoperative neurophysiologic monitoring (IONM). IONM needle electrodes remain on the patient during ioMRI and may cause image distortions and burns. We tested magnetic resonance (MR) -heating experimentally and investigated the prevalence of complications. We studied electrodes that are certified for IONM, but not "MR conditional." They consist of copper cables (length, 1.5 m) and needles made of either stainless steel (ferromagnetic) or paramagnetic platinum/iridium alloy. We simulated an ioMRI session with gel and measured the temperature increase with optical fibers. We measured the force that an electrode experiences in the magnetic field. Between 2013 and 2016, we prospectively documented subcutaneous needle electrodes that remained in the patient during intraoperative 3 Tesla ioMRI scans. The invitro testing of the electrodes produced a maximum heating (ΔT= 3.9°C) and force of 0.026 N. We placed 1237 subcutaneous needles in 57 surgical procedures with combined IONM and ioMRI, where needles remained in place during ioMRI. One patient suffered a skin burn on the shoulder. All other electrodes had no side effects. We have corroborated the history of safe use for electrodes with 1.5 m cable in a 3T MRI scanner and demonstrated their use. Nevertheless, heating cannot be excluded, as it depends on location and cable placement. When leaving electrodes in place during ioMRI, risks and benefits have to be carefully evaluated for each patient.

Effect of Cardiac-Cycle-Synchronized Selective Vagal Stimulation on Heart Rate and Blood Pressure in Rats.

Activation of the baroreflex system through the selective vagal nerve stimulation (sVNS) may become a treatment option for therapy-resistant hypertension, which is a frequently observed problem in the antihypertensive therapy. In previous studies, we used continuous sVNS to lower blood pressure (BP) without major side effects in a rat model. As continuous stimulation is energy consuming and sVNS could be implemented in an antihypertensive stimulator, it was the aim of this study to investigate the efficacy of pulsatile, cardiac-cycle-synchronized sVNS (cssVNS) on the reduction of BP. A multichannel cuff electrode was wrapped around the left vagal nerve in six male Wistar rats under Isoflurane anesthesia. BP was recorded in the left carotid artery. An electrocardiogram (ECG) was obtained via subcutaneous needle electrodes. The aortic depressor nerve fibers in the vagal nerve bundle were selectively stimulated with 18 parameter settings within a window of 15-30ms after the R-peak in the ECG. The stimulation paradigm included every heartbeat, every second heart beat, and every third heart beat. BP and heart rate were initially recorded over 10min. Using cssVNS, BP could be significantly reduced over 30min and maintained at this level. While the highest BP reduction was seen during cssVNS at every heartbeat with minimal bradycardia, less-yet significant-BP reduction was seen during cssVNS at every second or third heartbeat without causing detectable bradycardia. cssVNS can chronically reduce BP in rats avoiding measurable bradycardic side effects. This energy-efficient technique might allow the implementation of sVNS using an implantable device to permanently lower BP in patients. The study was funded by Bundesministerium fur Bildung und Forschung/German Federal Ministry of Education and Research among the call "Individualisierte Medizintechnik" under the grant number FKZ 13GW0120B.

Integrative action of axonal membrane explored by trains of subthreshold stimuli applied to the peripheral nerve

ObjectiveThe objective of this study was to provide evidence on the integrative action of axonal membrane in humans and its ability to integrate multipulse subthreshold stimuli and generate action potential. MethodsThe median nerve was stimulated at the wrist in six healthy subjects and 17 patients who underwent low spine surgery by means of percutaneous electrodes, with trains of one to nine near-threshold constant-current stimuli of 500-μs duration. The interstimulus interval between stimuli was 2 or 4ms. The compound muscle action potential (CMAP) was recorded from the abductor pollicis brevis muscle using subcutaneous needle electrodes in patients and surface electrodes in healthy subjects. Total intravenous anesthesia (TIVA) without a muscle relaxant was used in all patients, and measurements were performed at the end of surgery. ResultA single near-threshold stimulus did not generate CMAP either in the healthy subjects or in the patients. However, when the number of near-threshold stimuli was increased to two to nine stimuli, and packed into a short train with interstimulus intervals of 2 or 4ms, a CMAP of varying amplitude from 100 to 200μV was successfully elicited. ConclusionWe concluded that the described phenomenon might be explained by the integrative action of the axonal membrane, which is able to summate the trains of subthreshold stimuli, increasing the resting potential to the firing level, and consequently generating CMAP. This is because the subthreshold stimuli make the axonal membrane hyperexcitable. SignificanceThis phenomenon is not very well explored in clinical neurophysiology, and it needs to be studied further. This can explain some neurophysiologic phenomena during intraoperative monitoring.

Transcranial Electrical Stimulation (TES) as a Possible Novel Alternative to Transcranial Magnetic Stimulation (TMS) to Assess the Motor Function of the Spinal Cord for Clinical Diagnosis in Horses

Reasons for performing studyTo introduce and assess the feasibility of multipulse transcranial electrical stimulation (TES) in horses.ObjectivesTo assess latency times of muscular motor evoked potentials (MEP) in the m. extensor carpi radialis (ECR) and the m. tibialis cranialis (TC), elicited by transcranially applied multipulse stimulation in 12 healthy horses.Study designProspective observational study applied in 12 healthy horses.MethodsHorses with a mean age of 11.0 (range 3.6–20.5) years and a height of 160 (s.d. ± 10.0) cm were studied. Horses were sedated with detomidin (1.5 μg/kg bwt) and butorphanol (1.5 μg/kg bwt) i.v. A subcutaneous ring block with lidocaine 2% + adrenaline was placed on the forehead. TES was performed using biphasic high frequency multipulse voltage trains (pulse width: 0.1 ms, interpulse interval: 1.3 ms, 3 pulses/train) applied to 2 subcutaneous needle electrodes bilateral from the centre of the forehead. Latency times (30 V above motor threshold (MT) and amplitude of MEP were recorded bilaterally at the ECR and the TC muscles. Motor latency times are expressed as mean ± 2 s.d.ResultsMean latency times (at MT + 30 V) for the ECR muscles were respectively 20.18 ± 1.85 ms (left side) and 19.7 ± 1.69 ms (right side) and for the TC muscles respectively: 34.6 ± 2.01 ms (left) and 34.9 ± 2.43 ms (right).ConclusionsTES is well tolerated. Interestingly, recorded motor latency times at the level of front and hind legs appear to be shorter for TES when compared to TMS from literature data [1].Ethical animal research: Ethical approval was granted by the animal ethics committee of the Groningen University. Sources of funding: JS Center and Wolvega Equine Clinic. Competing interests: None.

Superiority of tympanic ball electrodes over mastoid needle electrodes for intraoperative monitoring of hearing function

Recording the auditory brainstem response (ABR) is a common method for monitoring the integrity of auditory pathways during surgery in the cerebellopontine angle. Electrocochleography (ECochG) is an alternative means of intraoperative neuromonitoring. In the present study the authors compared the practicability and prognostic significance of these two methods by performing simultaneous recordings in the operating room. Between 2006 and 2011, 125 patients (mean age 55 years) underwent surgery in the cerebellopontine angle. Seventy-one percent of the patients presented with a hearing deficit, and 37% had useful hearing but with slight functional impairment. Auditory brainstem response was recorded with a subdermal needle electrode at the mastoid. For ECochG recording, a noninvasive ball electrode was attached to the tympanic membrane. Amplitudes obtained from both ECochG and ABR audiometry were compared and correlated to pre- and postoperative hearing deficits. Simultaneous intraoperative monitoring via ABR and ECochG was possible in 114 cases (91%). Postoperatively, 42% of patients showed some degree of new hearing deficit, whereas 4% had improvement. The mean amplitudes in ECochG monitoring were significantly higher (0.18 ± 0.04 μV) than the ABR potentials (0.08 ± 0.006 μV; p < 0.05). All waves recorded at the mastoid needle electrode could be recognized in the potentials of the tympanic ball electrode. Hearing outcome correlated more reliably with the relative amplitude changes in Waves III and V in ECochG (III: p = 0.0008, V: p = 0.0015) than in ABR monitoring (III: p = 0.2075, V: p = 0.0398). Intraoperative monitoring of the auditory system by recording with noninvasive tympanic ball electrodes is more practicable than with subcutaneous needle electrodes at the tragus. Since there is also a reliable correlation between ECochG and clinical outcome, the method can replace common ABR recording during surgery in the cerebellopontine angle.

In vivo 31P NMR spectroscopy assessment of skeletal muscle bioenergetics after spinal cord contusion in rats

Muscle paralysis after spinal cord injury leads to muscle atrophy, enhanced muscle fatigue, and increased energy demands for functional activities. Phosphorus magnetic resonance spectroscopy ((31)P-MRS) offers a unique non-invasive alternative of measuring energy metabolism in skeletal muscle and is especially suitable for longitudinal investigations. We determined the impact of spinal cord contusion on in vivo muscle bioenergetics of the rat hind limb muscle using (31)P-MRS. A moderate spinal cord contusion injury (cSCI) was induced at the T8-T10 thoracic spinal segments. (31)P-MRS measurements were performed weekly in the rat hind limb muscles for 3 weeks. Spectra were acquired in a Bruker 11 T/470 MHz spectrometer using a 31P surface coil. The sciatic nerve was electrically stimulated by subcutaneous needle electrodes. Spectra were acquired at rest (5 min), during stimulation (6 min), and recovery (20 min). Phosphocreatine (PCr) depletion rates and the pseudo first-order rate constant for PCr recovery (k PCr) were determined. The maximal rate of PCr resynthesis, the in vivo maximum oxidative capacity (V max) and oxidative adenosine triphosphate (ATP) synthesis rate (Q max) were subsequently calculated. One week after cSCI, there was a decline in the resting total creatine of the paralyzed muscle. There was a significant reduction (~24 %) in k PCr measures of the paralyzed muscle, maximum in vivo mitochondrial capacity (V max) and the maximum oxidative ATP synthesis rate (Q max) at 1 week post-cSCI. During exercise, the PCr depletion rates in the paralyzed muscle one week after injury were rapid and to a greater extent than in a healthy muscle. Using in vivo MRS assessments, we reveal an acute oxidative metabolic defect in the paralyzed hind limb muscle. These altered muscle bioenergetics might contribute to the host of motor dysfunctions seen after cSCI.

CONTINUOUS COMPRESSION WITHOUT DEFIBRILLATION FAVOURED NO SHORT-TERM SURVIVAL IN PROLONGED VENTRICULAR FIBRILLATION

CONTINUOUS COMPRESSION WITHOUT DEFIBRILLATION FAVOURED NO SHORT-TERM SURVIVAL IN PROLONGED VENTRICULAR FIBRILLATION

Intra-Operative Computed–Tomography-Like Real-Time Three-Dimensional Ultrasound in Neurosurgery

High-field intraoperative magnetic resonance imaging (ioMRI) is becoming increasingly available in neurosurgery centers, where it has to be combined with intraoperative neurophysiologic monitoring (IONM). IONM needle electrodes remain on the patient during ioMRI and may cause image distortions and burns. We tested magnetic resonance (MR) -heating experimentally and investigated the prevalence of complications.We studied electrodes that are certified for IONM, but not “MR conditional.” They consist of copper cables (length, 1.5 m) and needles made of either stainless steel (ferromagnetic) or paramagnetic platinum/iridium alloy. We simulated an ioMRI session with gel and measured the temperature increase with optical fibers. We measured the force that an electrode experiences in the magnetic field. Between 2013 and 2016, we prospectively documented subcutaneous needle electrodes that remained in the patient during intraoperative 3 Tesla ioMRI scans.The in vitro testing of the electrodes produced a maximum heating (ΔT = 3.9°C) and force of 0.026 N. We placed 1237 subcutaneous needles in 57 surgical procedures with combined IONM and ioMRI, where needles remained in place during ioMRI. One patient suffered a skin burn on the shoulder. All other electrodes had no side effects.We have corroborated the history of safe use for electrodes with 1.5 m cable in a 3T MRI scanner and demonstrated their use. Nevertheless, heating cannot be excluded, as it depends on location and cable placement. When leaving electrodes in place during ioMRI, risks and benefits have to be carefully evaluated for each patient.

Chronic imaging of cortical sensory map dynamics using a genetically encoded calcium indicator

In vivo optical imaging can reveal the dynamics of large-scale cortical activity, but methods for chronic recording are limited. Here we present a technique for long-term investigation of cortical map dynamics using wide-field ratiometric fluorescence imaging of the genetically encoded calcium indicator (GECI) Yellow Cameleon 3.60. We find that wide-field GECI signals report sensory-evoked activity in anaesthetized mouse somatosensory cortex with high sensitivity and spatiotemporal precision, and furthermore, can be measured repeatedly in separate imaging sessions over multiple weeks. This method opens new possibilities for the longitudinal study of stability and plasticity of cortical sensory representations.

Preliminary investigation of somatosensory evoked potentials in equine headshaking

The aim of this study was to develop a technique for recording electrical activity of the equine cerebral cortex following application of a noxious electrical stimulus to the maxillary branch...

Establishment and Characterization of an Experimental Model of Coronary Thrombotic Microembolism in Rats

To establish a model of coronary thrombotic microembolism in rats, either automicrothrombotic particulates (CM group) or saline control (SHAM group) was injected into temporarily clamped aortas of male Sprague-Dawley rats. After automicrothrombotic particulate injection, serum c-troponin I and von Willebrand factor levels, the no-flow area as evaluated by Thioflavin S, myocardial leukocyte infiltration levels, myocardial expressions of tumor necrosis factor alpha and interleukin-6, the percentage of arterioles obstructed by thrombosis, and myocardial fibrosis were all significantly increased whereas cardiac function as evaluated by echocardiography and hemodynamic measurements were significantly reduced compared with the sham group. Thus, aortic automicrothrombotic particulate injection could induce coronary microembolism in rats, and this model could be of value in improving the understanding of pathophysiology of coronary microembolism.

Does Electrode Placement Influence Quality of Intraoperative Monitoring in Vestibular Schwannoma Surgery?

Continuous recording of electromyographic signals (EMG) is a standard method for intraoperative monitoring of facial nerve function in cerebello-pontine angle surgery. Subcutaneous needle electrodes in the facial muscles are used in different setups. The goal of this study was to compare two commonly used electrode setups concering sensitivity for pathological EMG activity. A group of 10 patients undergoing vestibular schwannoma surgery were examined. Continuous EMG from facial muscles was recorded using needle electrodes in setups according to Kartush or Møller, with narrow or wide interelectrode distances, respectively. Quantity of pathological A-train activity and signal-to-noise ratios were compared between setups. A-train activity was seen in all patients. On average, 37% of A-train activity was seen in the Kartush setup alone, 4% in Møller setups alone and 59% in both setups synchronously (p<0.05; ratio of median train time--Kartush:Møller 3:2). The wide interelectrode distance of the Møller setup was found to be significantly more susceptible to artefacts, especially to low frequency and power line noise. Artefacts were the main reason for the Møller setup to fail detecting A-train activity. For continuous intraoperative monitoring of facial nerve function, narrow interelectrode distance should be used.