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

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

[Recommendations on neurophysiological studies during the COVID-19 pandemic]

At the end of January, the current outbreak of COVID-19 coronavirus disease was declared an important international public health emergency. In Spain, since the government declared the state of alarm on 14 March 2020, doctors responsible for carrying out neurophysiological tests have been performing them without any consensus criterion or clear safety guidelines for doctors, technicians or patients. The following recommendations, based on current knowledge of the disease and therefore liable to change in the future, are proposed when the pandemic appears to have entered a process of decreasing virulence and, with it, the strict containment measures established to date. However, in view of the possibility of a second wave of the pandemic, it seems necessary to establish basic and minimum recommendations to respect the patient's right to appropriate care, similar to that provided prior to the pandemic, and to maintain minimum safety standards for the patients themselves and for the doctors, technicians and health personnel carrying out these tests. These recommendations concern the constitution of a priority based on the reason for consultation, the establishment of calls to check the patient's clinical situation before going to the outpatient department and the rules for carrying out neurophysiological tests, which are generally based on the preservation of hospital circuits, respect for and observation of the known barriers to contagion of this disease, and the use of disposable material. These recommendations are of particular interest, especially given the uncertainty of not knowing the evolution of the SARS-CoV-2 infection in the coming weeks or months.

[Quality and performance in cardiac pacing and electrophysiology. An update to the 2010 Italian Association of Arrhythmology and Cardiac Pacing (AIAC) - Italian Federation of Cardiology (IFC) Document 'Structure and functional organization of Arrhythmology']

In the last decade the field of cardiac pacing and electrophysiology underwent major advancements thanks to both new ways of arrhythmia management and technological innovations. At the same time, the clinical competence and the procedural qualitative level of Cardiac Rhythm Centers have increased significantly. In 2010 an ad hoc Committee of the Italian Association of Arrhythmology and Cardiac Pacing (AIAC) and the Italian Federation of Cardiology (FIC) published a consensus document on the organization of Cardiac Rhythm Centers and on the standards of professional practice in pacing and electrophysiology in Italy. In particular, this document focused on the minimal requirements of a Center to be qualified as suitable to perform first, second and third-level cardiac pacing and electrophysiology activities. However, most of these indicators have been overcome over time. Thus, an update of the previously published organizational model appeared necessary. In this document several new requirements and indicators about the organization and performance of both operators and Cardiac Arrhythmia Centers have been introduced. These include: (i) "structural and procedural requirements" (types of diagnostic and therapeutic procedures performed, logistic structures, healthcare staff and technologies), (ii) "activity indicators" (number of procedures performed); (iii) "appropriateness indicators" (adherence to guideline recommendations); (iv) "outcome indicators" (procedural success and complications); and (v) "quality of care indicators" (management and continuity of care levels). By applying these requirements and indicators, each center can optimize its procedures, increasing its performance and effectiveness. Finally, a new model for the organization of the Italian network of Cardiac Arrhythmia Centers is also suggested.

International Multisite Study of Human-Induced Pluripotent Stem Cell-Derived Cardiomyocytes for Drug Proarrhythmic Potential Assessment

To assess the utility of human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) as an in vitro proarrhythmia model, we evaluated the concentration dependence and sources of variability of electrophysiologic responses to 28 drugs linked to low, intermediate, and high torsades de pointes (TdP) risk categories using two commercial cell lines and standardized protocols in a blinded multisite study using multielectrode array or voltage-sensing optical approaches. Logistical and ordinal linear regression models were constructed using drug responses as predictors and TdP risk categories as outcomes. Three of seven predictors (drug-induced arrhythmia-like events and prolongation of repolarization at either maximum tested or maximal clinical exposures) categorized drugs with reasonable accuracy (area under the curve values of receiver operator curves ~0.8). hiPSC-CM line, test site, and platform had minimal influence on drug categorization. These results demonstrate the utility of hiPSCCMs to detect drug-induced proarrhythmic effects as part of the evolving Comprehensive In Vitro Proarrhythmia Assay paradigm.

Blinova et al. tested human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) for improving torsades de pointes arrhythmia risk prediction of drugs in the Comprehensive In Vitro Proarrhythmia Assay (CiPA) initiative. This validation study confirms their utility based on electrophysiologic responses to 28 blinded drugs, with minimal influence from cell lines, test sites, and electrophysiological platforms.

Nerve Conduction Studies as a Measure of Disease Progression: Objectivity or Illusion?

BACKGROUND

Clinical nerve conduction studies (NCS) are often used as a secondary outcome measure in therapeutic trials, but show a high degree of inter-trial variability even when technical factors known to affect the recorded responses are minimised. This raises the intriguing possibility that some of the observed variability may reflect true changes in nerve activity.

OBJECTIVES

Our aim was determine how much variability these factors might produce, and how this might affect the results of commonly used neuropathy rating scales.

METHODS

A standardised protocol was repeated over forty consecutive trials by the same operators in two healthy subjects. The protocol included recordings that shared either a stimulating or a recording electrode position, such that changes due to electrode position could be excluded, and hand temperature was closely controlled.

RESULTS

Despite controlling for inter-operator differences, electrode position, and hand temperature, the variability in sensory nerve action potential (SNAP) amplitude was extremely high (Range 23 μV, CoV = 10.7-18.8). This variability was greater than the change in amplitude needed to move a subject from point 0 to point 4 on the CMT neuropathy rating scale. Neither temperature or electrode position accounted for all of this variability, suggesting that additional as yet unidentified factors are responsible.

CONCLUSION

Even under closely controlled conditions and sophisticated laboratory methods, test-to-test variability can be significant. The factors responsible for this variability may be difficult to control, limiting the utility of single nerve recordings as a trial outcome measure.

Integration of Organic Electrochemical and Field-Effect Transistors for Ultraflexible, High Temporal Resolution Electrophysiology Arrays

Integration of organic electrochemical transistors and organic field-effect transistors is successfully realized on a 600 nm thick parylene film toward an electrophysiology array. A single cell of an integrated device and a 2 × 2 electrophysiology array succeed in detecting electromyogram with local stimulation of the motor nerve bundle of a transgenic rat by a laser pulse.

Prognostic Value of the Blink Reflex in Acoustic Neuroma Surgery

OBJECTIVE: The study goal was to demonstrate that blink reflex analysis can predict postoperative facial nerve outcome in cerebellopontine angle tumor surgery.

STUDY DESIGN, SETTING, AND PATIENTS: In an open and prospective study conducted at a single tertiary care center over 3 years, 91 subjects with a vestibular schwannoma filling the internal auditory meatus were enrolled and operated on via a translabyrinthine approach. The difference in latency of the early response (δR1) of the blink reflex between the pathologic side and the healthy side was calculated in every patient during a complete electrophysiologic examination of the facial nerve performed on the day before surgery.

MAIN OUTCOME MEASURES: δR1 was compared with the other preoperative data (tumor volume, facial function), with the perioperative observations (difficulties with the dissection of the facial nerve), and especially with the postoperative status after 1 year. The statistical study was conducted using polynomial regression.

RESULTS: Patients with a negative or zero δR1 have normal facial function at 1 year. For those with a positive δR1 the outcome is not favorable unless the tumor is small. For patients presenting with an immediate complete facial paralysis, the value of δR1 is also indicative of facial function outcome.

CONCLUSION: Statistical analysis shows that the blink reflex, through δR1, has an excellent prognostic value in anticipating the difficulties with facial nerve dissection and postoperative facial function after 1 year.

ISCEV standard for clinical visual evoked potentials: (2016 update)

Visual evoked potentials (VEPs) can provide important diagnostic information regarding the functional integrity of the visual system. This document updates the ISCEV standard for clinical VEP testing and supersedes the 2009 standard. The main changes in this revision are the acknowledgment that pattern stimuli can be produced using a variety of technologies with an emphasis on the need for manufacturers to ensure that there is no luminance change during pattern reversal or pattern onset/offset. The document is also edited to bring the VEP standard into closer harmony with other ISCEV standards. The ISCEV standard VEP is based on a subset of stimulus and recording conditions that provide core clinical information and can be performed by most clinical electrophysiology laboratories throughout the world. These are: (1) Pattern-reversal VEPs elicited by checkerboard stimuli with large 1 degree (°) and small 0.25° checks. (2) Pattern onset/offset VEPs elicited by checkerboard stimuli with large 1° and small 0.25° checks. (3) Flash VEPs elicited by a flash (brief luminance increment) which subtends a visual field of at least 20°. The ISCEV standard VEP protocols are defined for a single recording channel with a midline occipital active electrode. These protocols are intended for assessment of the eye and/or optic nerves anterior to the optic chiasm. Extended, multi-channel protocols are required to evaluate postchiasmal lesions.

Machine learning for automatic prediction of the quality of electrophysiological recordings

The quality of electrophysiological recordings varies a lot due to technical and biological variability and neuroscientists inevitably have to select “good” recordings for further analyses. This procedure is time-consuming and prone to selection biases. Here, we investigate replacing human decisions by a machine learning approach. We define 16 features, such as spike height and width, select the most informative ones using a wrapper method and train a classifier to reproduce the judgement of one of our expert electrophysiologists. Generalisation performance is then assessed on unseen data, classified by the same or by another expert. We observe that the learning machine can be equally, if not more, consistent in its judgements as individual experts amongst each other. Best performance is achieved for a limited number of informative features; the optimal feature set being different from one data set to another. With 80–90% of correct judgements, the performance of the system is very promising within the data sets of each expert but judgments are less reliable when it is used across sets of recordings from different experts. We conclude that the proposed approach is relevant to the selection of electrophysiological recordings, provided parameters are adjusted to different types of experiments and to individual experimenters.

DEEP PERONEAL MOTOR NERVE CONDUCTION VELOCITY DISTRIBUTION AND CORRELATION BETWEEN NERVE CONDUCTION GROUPS AND THE NUMBER OF INNERVATED MUSCLE FIBERS

In this study, the distribution of peroneal-nerve conduction velocity was studied in 17 normal subjects, using the collision method. Paired supramaximal stimuli with predetermined interstimulus intervals (ISI) were applied at distal and proximal points of peroneal nerve and the resultant compound muscle action potentials (CMAPs) were recorded. The change in CMAP amplitudes and areas with ISI were deduced, and the relative number of fibers corresponding to each conduction velocity group (CVG) were computed. Conduction velocities of the peroneal motor nerve innervating the Extensor Digitorum Brevis (EDB) muscle were found to be in the range of 28-52 m/s and CVG innervating the greatest number appears to be in 40-48 m/s range, which consists of 70% of all fibers. These results show that, compared with the median motor nerve, deep peroneal motor nerve that innervates the EDB muscle consist of slow fibers.

Threshold determination in sweep VEP and the effects of criterion

In order to develop criteria for the range of data points used for regression line fitting in sweep visually evoked potential (sVEP), which would be objective, clearly specified and give good repeatability and validity, and in order to investigate the effect of luminance on sVEP measurement, visual acuity (VA) and contrast sensitivity (CS) were measured with sVEP in adults aged 17-30 years and children aged 6-8 years. Six to ten participants took part in each experiment. Five criteria (C0-C4) for fitting the regression line were implemented. Test-retest repeatability and validity against psychophysical thresholds at three luminance levels were considered for thresholds and the number of acceptable readings. There were significant effects of criteria (repeated measures ANOVAs, P < 0.05). The criteria, C2 and C3 (based on the range over which the signal-to-noise ratio >or=1), consistently gave better VA and CS, more viable readings, better agreement with psychophysical thresholds in adults and better repeatability than the other criteria. In the case of adults, C2 gave thresholds that were not significantly different from the psychophysical thresholds (P > 0.05). There was little effect of luminance over the 25-100 cd/m(2) range used. Overall, C2 performed the best and would be the criterion of choice, giving better repeatability, better validity and more viable plots.

Construction, calibration, and validation of a simple patch-clamp amplifier for physiology education

A modular patch-clamp amplifier was constructed based on the Strickholm design, which was initially published in 1995. Various parts of the amplifier such as the power supply, input circuit, headstage, feedback circuit, output and nulling circuits were redesigned to use recent software advances and fabricated using the common lithographic printed circuit board fabrication process and commercially available electronic components. The calibration, validation, and regular recording procedures along with the results of an actual recording of inward Ca(2+) currents from PC12 neuronal cells are described in detail. This work describes the construction of a low-cost patch-clamp amplifier and setting up an electrophysiology recording system in a laboratory with regular technical expertise. The constructed amplifier provides an inexpensive yet practical tool for research and teaching purposes while the experience obtained during construction and setting up of the patch-clamp amplifier provides the basic and advanced understanding required for operating an advanced cell potential recording apparatus.

Implementation of a miniature sized, battery powered electrophysiological signal-generator for testing multi-channel recording equipments

Testing electrophysiological recording equipments is an important task in multi-channel extracellular in vivo electrophysiology. In this paper, a miniature, battery powered multi-channel electrophysiological signal-generator (ESG) is described that was designed for this purpose. The device is based on a Xilinx CPLD (Complex Programmable Logic Device) and it is powered by a 3V lithium coin battery. It is a useful tool for calibration and testing the performance, quality and parameters of the recording equipments used for acquiring EEG, field potentials, ECG, EMG, and multiple unit activity. The device is ideally suited to identify instances when errors interfere with the proper recording, and repair of wiring or service of the equipment is needed. Two versions of the device are described; one is for 16 (ESG16), and another is for 32 channels (ESG32). Both versions provide amplitude and time calibration, as well as cross-talk and CMRR (common mode rejection ratio) testing for the recording equipment.

Using intraoperative electrophysiologic monitoring as a diagnostic tool for determining levels to decompress in the cervical spine: a case report

OBJECTIVE

This report describes the clinical usefulness of using intraoperative electrophysiologic monitoring as a diagnostic tool for determining levels to decompress in the cervical spine.

METHODS

A 59-year-old man was experiencing intractable neck and left upper extremity pain after sustaining a second spinal injury. (The patient had previously undergone an anterior cervical discectomy and fusion at C5-C6 with plating to treat injuries from a motor vehicle accident.) On examination, he had no motor changes but did have pain in his left upper extremity and numbness of the left thumb and index finger. A myelogram and postmyelogram computed tomography scan revealed a disc herniation at C4-C5 with severe neural foraminal disease on the left side of C4-C5 and residual posterior osteophytes with questionable neuroforaminal stenosis on the left side of C5-C6. Routine electrophysiologic studies showed mild irritation of the left biceps (left C5-C6 nerve root), indicating radiculopathy. The patient was admitted with plans to undergo plate removal, exploration of the fusion at C5-C6, and an anterior cervical discectomy with foraminotomies and fusion at C4-C5. Continuous free-running electromyography was recorded during the surgical procedures.

RESULTS

The surgery was performed as planned; however, the irritation observed at C5-C6 did not subside. Relying on this information, as an extension of the patient's history and physical examination, a decision was made to remove the previous fusion at C5-C6 and to explore the left C6 root. A very tight neural foramen was found at this level. After decompression and foraminotomy, no electrophysiologic activity above baseline was recorded at C5-C6. The patient was then fused and plated from C4 to C6, and awoke with no left upper extremity pain. Neurologic examination was normal immediately after surgery and at 3 months follow-up.

CONCLUSIONS

Intraoperative, continuous free-running electromyography proved clinically effective in determining the course of surgery.

On the meaning and interpretation of global descriptors of brain electrical activity. Including a reply to X. Pei et al

Global descriptors of the brain's electrical activity, Sigma, Phi, and Omega, provide a comprehensive characterisation of brain functional states. Recently, Pei et al. [Pei, X., Zheng, C., Zhang, A., Duan, F., Bin, G., 2005. Discussion on "Towards a quantitative characterisation of functional states of the brain: from the nonlinear methodology to the global linear description" by J. Wackermann. Int. J. Psychophysiol. 56, 201-207] discussed the effects of signal power on the global measure of spatial complexity, Omega, and suggested a modification consisting in epoch-wise and channel-wise normalisation of input data to unit power. In the present paper, the basic principles of the global approach are reviewed, and the issues of Pei et al.'s approach are assessed. The original and the modified measures of spatial complexity are compared in two case studies. Numerical simulation shows that both methods veridically estimate small numbers of signal sources, but systematically underestimate as the number increases; the modified method yields a minor relative improvement. A study on real EEG data shows that the two measures sensibly differ only where artefactual inhomogeneities in channel variances affect the data; a combined procedure, consisting in record-wise equalisation of channel variances before Omega calculations, is suggested as the optimal strategy. Differences between the original objectives of the global methodology and the proposed modifications are pointed out and critically discussed.

ISCEV standard for clinical pattern electroretinography--2007 update

The pattern electroretinogram (PERG) is a retinal response evoked by viewing a temporally alternating pattern, usually a black and white checkerboard or grating. The PERG is important in clinical and research applications because it provides information both about retinal ganglion cell function and, because the stimulus is customarily viewed with central fixation, the function of the macula. The PERG can therefore facilitate interpretation of an abnormal pattern VEP by revealing the retinal responses to a similar stimulus to that used for the VEP. However, practitioners may have difficulty choosing between the different techniques for recording the PERG that have been described in the literature. The International Society for Clinical Electrophysiology of Vision published a standard for clinical PERG recording in 2000 to assist practitioners in obtaining good quality reliable responses and to facilitate inter-laboratory communication and comparison. This document is the scheduled revision of that standard.

[Progress of standardizations for clinical visual electrophysiology]

To meet the needs for standardizations of clinical visual electrophysiology, the International Society for Clinical Electrophysiology of Vision (ISCEV) has issued serial proposals of standards since the last decade of the 20th century. The present state of standardization in the laboratories of our country has been improved, but it needs more efforts to meet the latest requirements. This article reviewed the main contents of these standards.

Pediatric clinical visual electrophysiology: a survey of actual practice

PURPOSE

Survey the actual clinical practice of pediatric visual electrophysiology. The electrophysiologists surveyed were members of the International Society for Clinical Electrophysiology of Vision (ISCEV).

METHODS

A self-administered questionnaire with 55 items about visual evoked potential (VEP) and electroretinogram (ERG) testing of pediatric patients was sent to ISCEV members. The survey queried personnel, facilities, referral patterns and conduct of tests.

RESULTS

Nearly all respondents (94%) had advanced scientific or clinical degrees or both, and most (96%) worked in academic or medical facilities. Of the 71 respondents, 68 tested patients 12 years or younger, and nearly all of those performed both VEPs and ERGs. However, fewer than a third did high volume (>10/month) testing of infants and young children (< or =6 years). Eye care professionals and neurologists made the majority (57%) of the referrals, with the most common reason for referral being suspected visual impairment. Conduct of a pediatric test session often required more than one practitioner. For both VEP and ERG, more than 70% of respondents required at least 30 min for each test. The majority indicated that they followed the ISCEV standards for stimuli and data acquisition. Almost all (94%) reported using the ISCEV recommended VEP electrode configuration. For ERG, most (88%) used ocular contact electrodes (including contact lens, thread, foil and HK loop), but 12% used skin electrodes exclusively and some (17%) used skin electrodes at times.

CONCLUSIONS

Pediatric ERG and VEP testing is a labor intensive endeavor of highly trained professionals. ISCEV technical standards are typically met or exceeded, indicating that high quality testing of infants and children is feasible. Revision of the ISCEV ERG standard is necessary to bring actual practice into accord with evidence-based recommendations for infant testing.

Pilot measurements of ELF contact currents in some electric utility occupations

Contact currents from touching objects with different voltages can produce electric fields within the body that produce neurological and other biological effects. To begin measuring these exposures among electric utility workers, a new contact current meter (CCM) was tested in a pilot study at Southern California Edison. The CCM was worn for 82 full-shift measurements by 76 volunteers from eight occupations who did not work directly with energized electrical equipment. The volunteers were exposed to an average of 285.8 contact current events above the meter's 1-microA threshold, but most of these were electrostatic spark discharges. Fourteen employees experienced an average of 135.1 contact currents events whose primary frequency was 60 Hz. Using a circuit model of the human body, the average contact currents going from arm to arm was 9.8 microA (maximum = 178.0 microA), and the average going down the torso was 25.5 microA (maximum = 662.0). The maximum exposures were experienced by a technical support employee working in a substation. All measurements in this pilot study were below the 3000 microA maximum permissible exposure for contact currents set by the Institute of Electrical and Electronic Engineers (IEEE). Combining these current measurements with the results of high-resolution dosimetry, the internal electric fields averaged an estimated 1.7 mV/m in the heart (maximum = 21.0 mV/m), and 1.9 mV/m in the hematopoietic bone marrow in the torso (maximum = 56.5 mV/m). These internal electric fields from contact currents are below the basic restriction of 943 mV/m in the IEEE exposure standards but are above 1 mV/m, a level where biological effects have been often reported in laboratory studies. Safety concerns limited the measurements to de-energized equipment, so we did not obtain data on work in energized high-voltage environments, the most likely sources of high contact currents. This pilot study identified other improvements to the contact current meter that would make it better able to measure exposures in future health studies.

Development of a new rapid measurement technique for fish embryo membrane permeability studies using impedance spectroscopy

Information on fish embryo membrane permeability is vital in their cryopreservation. Whilst conventional volumetric measurement based assessment methods have been widely used in fish embryo membrane permeability studies, they are lengthy and reduce the capacity for multi-embryo measurement during an experimental run. A new rapid ‘real-time’ measurement technique is required to determine membrane permeability during cryoprotectant treatment. In this study, zebrafish (Danio rerio) embryo membrane permeability to cryoprotectants was investigated using impedance spectroscopy. An embryo holding cell, capable of holding up to 10 zebrafish embryos was built incorporating the original system electrods for measuring the impedance spectra. The holding cell was tested with deionised water and a series of KCl solutions with known conductance values to confirm the performance of the modified system. Untreated intact embryos were then tested to optimise the loading capacity and sensitivity of the system. To study the impedance changes of zebrafish embryos during cryoprotectant exposure, three, six or nine embryos at 50% epiboly stage were loaded into the holding cell in egg water, which was then removed and replaced by 0.5, 1.0, 2.0 or 3 M methanol or dimethyl sulfoxide (DMSO). The impedance changes of the loaded embryos in different cryoprotectant solutions were monitored over 30 min at 22 °C, immediately following embryo exposure to cryoprotectants, at the frequency range of 10–10⁶ Hz. The impedance changes of the embryos in egg water were used as controls. Results from this study showed that the optimum embryo loading level was six embryos per cell for each experimental run. The optimum frequency was identified at 10^3.14 or 1380 Hz which provided good sensitivity and reproducibility. Significant impedance changes were detected after embryos were exposed to different concentrations of cryoprotectants. The results agreed well with those obtained from conventional volumetric based studies.

Noradrenaline overflow in mouse dentate gyrus following locus coeruleus and natural stimulation: real-time monitoring by in vivo voltammetry

The pattern of catecholaminergic innervation of the dentate gyrus (DG) of the hippocampus, particularly the relatively dense and selective noradrenergic input, creates favourable conditions for real-time monitoring of noradrenaline (NA) release following stimulation of the locus coeruleus (LC) by in vivo voltammetry. Two electrochemically active species with different temporal characteristics were registered in the DG following electrical stimulation of the LC. Several approaches, including testing of anatomical and pharmacological specificity, coating of microelectrodes with Nafion and use of fast cyclic voltammetry, were used to verify the characteristics of electrochemical responses. The first sharp peak that appeared immediately during stimulation was definitely associated with NA overflow. The second late peak was possibly attributable to ascorbic acid. We examined the characteristics of alpha-2 adrenoceptor regulation of NA release in the DG, and showed for the first time that noradrenergic terminals resemble dopaminergic terminals in their mechanisms of increasing the refilling rate of the readily releasable pool following stimulation repeated at short intervals. Amperometric registration of NA in the DG was complicated by interference with electrical activity of hippocampus. This interference could be used, after appropriate filtration, for simultaneous recording from the same microelectrode of NA release and electrical activity of the hippocampus.

Reference values of fractionated neurography of the ulnar nerve at the wrist in healthy subjects

OBJECTIVE

This study is designed to derive a normative database for nerve conduction values of the ulnar nerve in the wrist.

METHODS

Ulnar nerve study at the wrist (UNSW) was performed in 204 hands of 102 control subjects. The UNSW was composed of motor and sensory tests. Motor UNSW was done with first dorsal interosseous muscle recording. Sensory UNSW was performed antidromically with fifth finger recording. The 3 stimulation points were 2 cm proximal to the pisiform, just lateral to pisiform, and 3 cm distal to the pisiform.

RESULTS

Mean latency differences in the proximal and distal segments were 0.4 +/- 0.1 and 0.5 +/- 0.1 ms in motor UNSW and 0.4 +/ -0.1 and 0.5 +/- 0.1 ms in sensory UNSW. The 95th percentile values for motor and sensory UNSW were 0.5 ms in the proximal segment and 0.7 ms in the distal segment.

CONCLUSIONS

When the 95-percentile value was considered as the normal upper limit, the criteria of abnormality for motor and sensory UNSW were greater than 0. 5 ms in the proximal segment and greater than 0.7 ms in the distal segment.

SIGNIFICANCE

The normative values of UNSW may be useful in screening for ulnar neuropathy at the wrist.

Optimizing the use of electrophysiology in the diagnosis of chronic inflammatory demyelinating polyneuropathy: a study of 20 cases

Current electrophysiologic criteria for chronic inflammatory demyelinating polyneuropathy (CIDP) are highly specific but poorly sensitive. The required extensiveness and best practical way of performing nerve conduction studies to achieve optimal sensitivity remain unknown. We here initially retrospectively analyzed the motor nerve conduction study results of 20 consecutive patients with a clinical diagnosis of CIDP (four performed prior to, and 16 after, treatment initiation) to assess the sensitivity of six published sets of criteria (Nicolas et al., 2002; Thaisetthawatkul et al., 2002; Ad Hoc Subcommittee of the American Academy of Neurology AIDS Taskforce, 1991; Magda et al., 2003; Hughes et al., 2001; Saperstein et al., 2001), as well as four combinations (Nicolas et al., 2002; Ad Hoc Subcommittee of the American Academy of Neurology AIDS Taskforce, 1991; Hughes et al., 2001; Saperstein et al., 2001, each individually combined with Thaisetthawatkul et al., 2002). Sensitivity was highest for the combination of Nicolas et al. (2002) and Thaisetthawatkul et al. (2002) (100%). We then determined the sensitivity of this combined criteria, using five different, hypothetical, nerve conduction study protocols, applied retrospectively to the neurophysiologic data of our 20 patients (exclusive upper limb studies with proximal stimulations; exclusive lower limb studies; full forearm and foreleg studies without proximal stimulations; right-sided studies with proximal stimulations; and left-sided studies with proximal stimulations). The findings showed that exhaustive upper limb or, alternatively, four-limb forearm and foreleg testing would have proved considerably more sensitive than unilateral or lower limb studies to achieve an electrophysiologic diagnosis of CIDP.

Pathophysiology inferred from electrodiagnostic nerve tests and classification of polyneuropathies. Suggested guidelines

OBJECTIVE

To present criteria for pathophysiological interpretation of motor and sensory nerve conduction studies and for pathophysiological classification of polyneuropathies suggested by a group of European neurophysiologists.

METHODS

Since 1992 seven neurophysiologists from six European countries have collected random samples of their electrodiagnostic examinations for peer review medical audit in the ESTEEM (European Standardized Telematic tool to Evaluate Electrodiagnostic Methods) project. Based on existing criteria in the literature, the experience with a patient material of 572 peer reviewed electrodiagnostic examinations, and productive discussions between the physicians at workshops, the collaboration has produced a set of criteria now routinely used at the centres involved in the project.

RESULTS

The first part of the paper considers pathophysiology of individual nerve segments. For interpretation of motor and sensory nerve conduction studies, figures showing change in amplitude versus change in conduction velocity/distal latency and change in F-wave frequency versus change in F-wave latency are presented. The suggested boundaries delimit areas corresponding to normal, axonal, demyelinated, or neuropathic nerve segments. Criteria for motor conduction block in upper and lower extremities are schematically depicted using the parameters CMAP amplitude and CMAP duration. The second part of the paper suggests criteria for classification of polyneuropathies into axonal, demyelinating, or mixed using the above-mentioned criteria.

CONCLUSIONS

The suggested criteria are developed during many years of collaboration of different centres and may be useful for standardization in clinical neurophysiology.

SIGNIFICANCE

Consistent interpretation of nerve conduction studies is an important step in optimising diagnosis and treatment of nerve disorders.

Current perception thresholds in the lower urinary tract: Sine- and square-wave currents studied in young healthy volunteers

AIMS

To establish normative current perception threshold (CPT) values with neuroselective sine-wave current in the lower urinary tract and to compare these values with square-wave current CPTs.

MATERIALS AND METHODS

10 female and 8 male healthy volunteers were used for this study. A filling cystometry was performed and CPTs were determined with square-wave current at a frequency of 2.5 Hz and with neuroselective sine-wave current at 5 (C-fiber), 250 (Adelta-fiber), and 2000 Hz (Abeta-fiber) in the bladder, the posterior, and the distal urethra.

RESULTS

Bladder CPTs were significantly higher compared with CPTs in the posterior urethra (P < 0.028) and in the distal urethra (P < 0.002) with all three sine-wave frequencies. No significant difference was found with any sine-wave frequency between the posterior and distal urethra (P > 0.30). Using square-wave pulses at 2.5 Hz, CPTs decreased towards the distal urethra, with a significant difference between the three stimulation sites (P < 0.0001). At all sites tested, the CPT's determined with sine-wave current at 2000 Hz were significantly higher than those at 250 Hz (P < 0.002) and 5 Hz (P < 0.001). No significant difference was found between 5 Hz and 250 Hz at any site in the LUT (P > 0.50). At all sites, CPTs determined with square-wave pulses at 2.5 Hz were significantly higher than those determined with sine-wave current at all frequencies (P < 0.001). CPTs determined with all sine-wave currents were not correlated with CPTs using square-wave pulses. There was no correlation between the volumes at which sensation of filling occurred and the CPTs.

CONCLUSIONS

We described normative values in young healthy volunteers at three sites in the LUT using sine-wave current. Although this type of current is said to be neuroselctive, this needs to be confirmed. Stimulation with sine-wave current is different and might be more physiologic compared to square-wave stimulation. Our data show that sine-wave current stimulation at 5 Hz, 250 Hz, and 2000 Hz can probably not be used as a semi-objective measurement of the sensation of bladder filling because no correlation was found between CPTs and the cystometeric sensation of filling.

Tremor analysis in two normal cohorts

OBJECTIVE

Quantitative tremor analyses using almost identical methods were compared between two independent large normal cohorts, to separate robust measures that may readily be used diagnostically from more critical ones needing lab-specific normalization.

METHODS

Hand accelerometry and surface EMG from forearm flexors and extensors were recorded with (500 and 1000 g) and without weight loading under postural conditions in 117 and 67 normal volunteers in two different specialty centers for movement disorders in Germany.

RESULTS

Tremor amplitude (total power) and frequency fell within a similar range but differed significantly. A significant reduction of tremor frequency under 1000 g weight load (>1 Hz), and a lack of rhythmic EMG activity at the tremor frequency in around 85-90% of the recordings were robust findings in both centers.

CONCLUSIONS

The differences in frequency and total power indicate that these measures critically depend on the details of the recording conditions being slightly different between the two centers. Thus each lab needs to establish its own normative data. We estimate that at least 25 normal subjects have to be recorded to obtain normal values. The reduction of tremor frequency under load and lacking tremor-related EMG activity were well reproducible allowing a differentiation of physiological from low amplitude pathological tremor.

SIGNIFICANCE

This study provides a framework for more standardized tremor analyses in clinical neurophysiology.

Transcranial electrical stimulation as predictor of elicitation of intraoperative muscle-evoked potentials

STUDY DESIGN

Preoperative electrophysiological and neurologic findings from patients with cervical myelopathy were evaluated statistically to determine their predictive value relative to the success of eliciting intraoperative motor-evoked potentials.

OBJECTIVES

To determine which preoperative variables accurately predicted the success of eliciting an intraoperative muscle-evoked potential.

SUMMARY OF BACKGROUND DATA

Motor-evoked potential recorded from the muscles after transcranial electrical stimulation is one of the most widely used methods for intraoperative spinal cord monitoring. However, motor-evoked potentials recorded from lower limb muscles are not detectable in patients with severe cervical myelopathy. Therefore, it is helpful to know the probability of the intraoperative transcranial electrical stimulation-motor evoked potential elicitation before the operation.

METHODS

There were 38 patients with cervical myelopathy. Before the operation, motor-evoked potentials following transcranial magnetic stimulation were recorded from the flexor hallucis brevis, and central motor conduction times were measured. Neurologic function was evaluated using the Japanese Orthopedic Association score. During the operation, transcranial electrical stimulation-motor evoked potential from the flexor hallucis brevis was recorded. The Japanese Orthopedic Association score, threshold intensity of magnetic stimulation, and central motor conduction times were statistically evaluated for their potential of being predictors.

RESULTS

The intraoperative transcranial electrical stimulation-motor evoked potential was detectable in all cases in which the preoperative transcranial magnetic stimulation-motor evoked potential was elicited by a lower intensity than 50% of the maximum output of the stimulator. Therefore, simultaneous use of other methods of monitoring should be considered in such cases that need higher output. However, the Japanese Orthopedic Association score or central motor conduction times were not useful criteria. CONCLUSIONS.: The threshold intensity of the preoperative transcranial magnetic stimulation-motor evoked potential was helpful in predicting elicitation of the intraoperative transcranial electrical stimulation-motor evoked potential.

Ultrastructure at carbon fiber microelectrode implantation sites after acute voltammetric measurements in the striatum of anesthetized rats

This work seeks to establish the feasibility of characterizing the ultrastructure of brain tissue disruption associated with the implantation of carbon fiber voltammetric microelectrodes. In vivo recording was performed by fast scan cyclic voltammetry in conjunction with carbon fiber microelectrodes (3.5 microm radius) in the striatum of rats anesthetized with chloral hydrate. After 4 h of in vivo recording, the microelectrodes were removed from the brain and the animals underwent intracardial perfusion. Brain tissue was collected and sectioned in the horizontal plane perpendicular to the axis of the microelectrodes. With microelectrodes of a conventional single barreled design, the tissue tracks were often too small to be followed by light microscopy to the point of deepest penetration, which would correspond to the implantation site of the carbon fiber itself. The enlarged tissue tracks formed by the implantation of double barreled electrodes, however, could be followed to their termination by light microscopy. Anatomical mapping was used to identify the fields laying 100 microm deeper than the deepest trace of such tracks. Electron microscopy of these fields revealed a spot of tissue damage presumed to be associated with the implantation site of the carbon fiber microelectrode. The spot of maximal tissue damage had a radius of 2.5 microm and was surrounded by an annular region with a width of 4 microm that contained a mix of healthy and damaged elements. Beyond this annular region, i.e. beyond 6.5 microm from the center of the spot of maximal damage, signs of microelectrode-associated damage were rare and consisted primarily of neurons with darkened cytoplasm.

Posterior antebrachial cutaneous nerve conduction studies in normal subjects

OBJECTIVE

The posterior antebrachial cutaneous (PABC) nerve is a sensory nerve that branches out from the radial nerve at the level of the spiral groove. Thus it can be affected in a radial nerve lesion at or proximal to its origin in the spiral groove. However, there has been limited knowledge about the normal values of PABC nerve conduction studies. This study was done to determine these normal values.

METHODS

Sixty-three healthy adults (23 males) with a mean age of 41.5+/-10.6 (range, 20-90) years were recruited with informed consent. A total of 126 nerves were studied. The nerve conduction studies were performed using a Dantec Counterpoint EMG machine (Dantec, Skovlunde, Denmark).

RESULTS

The mean+/-standard deviation values for the onset as well as peak latency, conduction velocity, amplitude and side-to-side amplitude ratio were 2.07+/-0.16 (range, 1.80-2.60) ms, 2.35+/-0.15 (range, 2.05-2.90) ms, 58.21+/-4.29 (range, 46.15-66.67) m/s, 6.10+/-2.11 (range, 2.90-13.00) microV and 0.83+/-0.12 (range, 0.60-0.99), respectively. There was a significant correlation between the subject age and the PABC onset and peak latencies as well as the amplitudes.

CONCLUSIONS

The PABC nerve is assessable for nerve conduction studies and these normal values may be useful in evaluation of patients with suspected radial nerve lesions.

Neurophysiological tests and neuroimaging procedures in non-acute headache: guidelines and recommendations

The use of instrumental examinations in headache patients varies widely. In order to evaluate their usefulness, the most common instrumental procedures were evaluated, on the basis of evidence from the literature, by an EFNS Task Force (TF) on neurophysiological tests and imaging procedures in non-acute headache patients. The conclusions of the TF regarding each technique are expressed in the following guidelines for clinical use. 1 Interictal electroencephalography (EEG) is not routinely indicated in the diagnostic evaluation of headache patients. Interictal EEG is, however, indicated if the clinical history suggests a possible diagnosis of epilepsy (differential diagnosis). Ictal EEG could be useful in certain patients suffering from hemiplegic and basilar migraine. 2 Recording of evoked potentials is not recommended for the diagnosis of headache disorders. 3 There is no evidence to justify the recommendation of autonomic tests for the routine clinical examination of headache patients. 4 Manual palpation of pericranial muscles, with standardized palpation pressure, can be recommended for subdividing patient groups but not for diagnosis. Pressure algometry and electromyography (EMG) cannot be recommended as clinical diagnostic tests. 5 In adult and paediatric patients with migraine, with no recent change in attack pattern, no history of seizures, and no other focal neurological signs or symptoms, the routine use of neuroimaging is not warranted. In patients with atypical headache patterns, a history of seizures and/or focal neurological signs or symptoms, magnetic resonance imaging (MRI) may be indicated. 6 If attacks can be fully accounted for by the standard headache classification [International Headache Society (IHS)], a positron emission tomography (PET) or single-photon emission computerized tomography (SPECT) and scan will generally be of no further diagnostic value. 7 Nuclear medicine examinations of the cerebral circulation and metabolism can be carried out in subgroups of headache patients for diagnosis and evaluation of complications, when patients experience unusually severe attacks, or when the quality or severity of attacks has changed. 8 Transcranial Doppler examination is not helpful in headache diagnosis. Although many of the examinations described are of little or no value in the clinical setting, most of the tools have a vast potential for further exploring the pathophysiology of headaches and the effects of pharmacological treatment.

Reliability of quantitative motor unit action potential parameters

We evaluated the test-retest reliability (reproducibility) of motor unit action potential (MUAP) parameters in multi-MUAP analysis over time. Reproducibility studies are not available for needle quantitative electromyography (QEMG) performed by the same examiner. Fourteen consecutive individuals (10 men and 4 women) had repeat QEMG at 3 hours after the first examination, and seven (5 men and 2 women) had a repeat QEMG after 4-10 days. The intraclass correlation coefficient (ICC) was 87-97% with same-day testing and 52-81% with different-day testing. Size index and firing rate were the most reproducible, suggesting use in follow-up multi-MUAP studies.

Measurement and reproducibility of strength and voluntary activation of lower-limb muscles

Accurate measurement of muscle strength and voluntary muscle activation is important in the assessment of disorders that affect the motor pathways or muscle. We designed a multipurpose system to assess the variability and reproducibility of isometric torque measurements obtained during maximal voluntary efforts of the knee flexor, knee extensor, ankle dorsiflexor, and ankle plantarflexor muscles on each side. It used two isometric myographs mounted on an adjustable frame. Measurements of maximal voluntary torque (range, 25-188 Nm) displayed low variability within a testing session and over five testing sessions (coefficient of variation range, 5-11%). We used the same equipment to measure voluntary activation of the triceps surae muscles. Voluntary activation, measured with a sensitive twitch interpolation method, increased with increasing voluntary contraction torque (P < 0.001) and was very high during maximal efforts (mean, 97.8 +/- 2.1%; median, 98.5%). Furthermore, measurements of voluntary activation during maximal efforts were reproducible across testing sessions with very little variability (coefficient of variation, <2%). The myograph system and the testing procedures should allow accurate measurement of strength and voluntary drive in longitudinal patient studies.

Development of a mechanical testing and loading system for trabecular bone studies for long term culture

A highly accurate (+/-3%) mechanical loading and measurement system combined with a trabecular bone diffusion culture-loading chamber has been developed, which provides the ability to study trabecular bone (and possibly) cartilage under controlled culture and loading conditions over long periods of time. The loading device has been designed to work in two main modes, either to apply a specific compressive strain to a trabecular bone cylinder or to apply a specific force and measure the resulting deformation. Presently, precisely machined bone cylinders can be loaded at frequencies between 0.1 Hz to 50 Hz and amplitudes over 7,000 microepsilon. The system allows accurate measurement of many mechanical properties of the tissue in real time, including visco-elastic properties. This paper describes the technical components, reproducibility, precision, and the calibration procedures of the loading system. Data on long term culture and mechanical responses to different loading patterns will be published separately.

Factors affecting the stability of the spike-triggered averaged force in the human first dorsal interosseus muscle

The reproducibility of motor unit twitches obtained using spike-triggered averaging (STA) was examined in the human first dorsal interosseus. For each motor unit (30 total) a series of STA twitches was derived using a 30 s averaging window. Within each averaging window, eight independent measures characterizing motor unit discharge and whole muscle force properties were recorded. These included the mean and standard deviation (S.D.) of the interspike interval (ISI), the mean and S.D. of pre and post-trigger ISIs used in averaging, and mean and S.D. of whole muscle force. To determine the relative importance of the independent variables on twitch reproducibility, the variables were used in a multiple regression analysis performed on STA twitch peak force (PF), time to peak force (TTP) and time of half-force decay (HFD). It was found that PF was significantly correlated to the mean and S.D. of whole muscle force, and mean post-trigger ISI. TTP was significantly correlated to the S.D. of the post-trigger ISI and mean whole muscle force while HFD was related to the mean and S.D. of the pre-trigger ISI and the mean post-trigger ISI. It was concluded that by minimizing whole muscle force variability and the mean and S.D. of acceptable ISIs used in the STA process, the reproducibility of the STA twitch is improved.