Invasive Electrodes Research Articles

Urinary urge seizure semiology localization by intracranial monitoring

ABSTRACTSeizures may present with many different symptom complexes. Seizure semiologies have localization value when contemplating surgical therapies. Epilepsy presenting as a desire to micturate is exceedingly rare, with only a handful of published cases. We present a patient who had initially unexplained childhood urinary urge that progressed into lapses of memory and confusion that was eventually diagnosed as epilepsy in adulthood. Due to refractoriness to medical management, our patient's epileptic focus was localized through both noninvasive and invasive subdural electrode arrays to the nondominant medial temporal lobe and successfully treated with an amygdalohippocampectomy. Only one other case of ictal urinary urgency seizures has been recorded with intracranial electroencephalogram monitoring in the literature.

ECG Electrode Configuration to Extract Real Time FECG Signals

Monitoring fetal health early in pregnancy helps to avert possible fetal damage and even fetal death. Among various fetal monitoring techniques the invasive fetal scalp electrode method is the most accurate method at labor. However this method may cause risk to the baby if used for antepartum monitoring. The Non-invasive fetal ECG (NIFECG) is a simple and the next best method to extract fetal heart rate (FHR) before full term. NIFECG can extract the fetal morphology from the FECG signal which can aid in diagnosing fetal health ahead of delivery. This paper aims to locate the most optimum points to place the ECG electrodes on the maternal abdomen so as to get the best FECG signals. After reviewing few previous techniques, we proposed three schemes using a standard 12 lead ECG recorder. It was observed that the scheme 2 successfully displayed the average FHR as compared to the ultrasound report of a single subject. A further researching and experimental procedures are required in this abdominal ECG (aECG) placement electrode positioning schemes before a standardized electrode configuration which can be introduced in clinical practice.

Adipose tissue: a new target for electroporation-enhanced DNA vaccines

DNA vaccines delivered using electroporation (EP) have had clinical success, but these EP methods generally utilize invasive needle electrodes. Here, we demonstrate the delivery and immunogenicity of a DNA vaccine into subcutaneous adipose tissue cells using noninvasive EP. Using finite element analysis, we predicted that plate electrodes, when oriented properly, could effectively concentrate the electric field within adipose tissue. In practice, these electrodes generated widespread gene expression persisting for at least 60 days in vivo within interscapular subcutaneous fat pads of guinea pigs. We then applied this adipose-EP protocol to deliver a DNA vaccine coding for an influenza antigen into guinea pigs. The resulting host immune responses elicited were of a similar magnitude to those achieved by skin delivery with EP. The onset of the humoral immune response was more rapid when the DNA dose was spread over multiple injection sites, and increasing the voltage of the EP device increased the magnitude of the immune response. This study supports further development of EP protocols delivering gene-based therapies to subcutaneous fat.

An evaluation of irreversible electroporation thresholds in human prostate cancer and potential correlations to physiological measurements.

Irreversible electroporation (IRE) is an emerging cancer treatment that utilizes non-thermal electric pulses for tumor ablation. The pulses are delivered through minimally invasive needle electrodes inserted into the target tissue and lead to cell death through the creation of nanoscale membrane defects. IRE has been shown to be safe and effective when performed on tumors in the brain, liver, kidneys, pancreas, and prostate that are located near critical blood vessels and nerves. Accurate treatment planning and prediction of the ablation volume require a priori knowledge of the tissue-specific electric field threshold for cell death. This study addresses the challenge of defining an electric field threshold for human prostate cancer tissue. Three-dimensional reconstructions of the ablation volumes were created from one week post-treatment magnetic resonance imaging (MRIs) of ten patients who completed a clinical trial. The ablation volumes were incorporated into a finite element modeling software that was used to simulate patient-specific treatments, and the electric field threshold was calculated by matching the ablation volume to the field contour encompassing the equivalent volume. Solutions were obtained for static tissue electrical properties and dynamic properties that accounted for electroporation. According to the dynamic model, the electric field threshold was 506 ± 66 V/cm. Additionally, a potentially strong correlation (r = −0.624) was discovered between the electric field threshold and pre-treatment prostate-specific antigen levels, which needs to be validated in higher enrollment studies. Taken together, these findings can be used to guide the development of future IRE protocols.

Epidermal Electrode Technology for Detecting Ultrasonic Perturbation of Sensory Brain Activity.

We aim to demonstrate the in vivo capability of a wearable sensor technology to detect localized perturbations of sensory-evoked brain activity. Cortical somatosensory evoked potentials (SSEPs) were recorded in mice via wearable, flexible epidermal electrode arrays. We then utilized the sensors to explore the effects of transcranial focused ultrasound, which noninvasively induced neural perturbation. SSEPs recorded with flexible epidermal sensors were quantified and benchmarked against those recorded with invasive epidural electrodes. We found that cortical SSEPs recorded by flexible epidermal sensors were stimulus frequency dependent. Immediately following controlled, focal ultrasound perturbation, the sensors detected significant SSEP modulation, which consisted of dynamic amplitude decreases and altered stimulus-frequency dependence. These modifications were also dependent on the ultrasound perturbation dosage. The effects were consistent with those recorded with invasive electrodes, albeit with roughly one order of magnitude lower signal-to-noise ratio. We found that flexible epidermal sensors reported multiple SSEP parameters that were sensitive to focused ultrasound. This work therefore 1) establishes that epidermal electrodes are appropriate for monitoring the integrity of major CNS functionalities through SSEP; and 2) leveraged this technology to explore ultrasound-induced neuromodulation. The sensor technology is well suited for this application because the sensor electrical properties are uninfluenced by direct exposure to ultrasound irradiation. The sensors and experimental paradigm we present involve standard, safe clinical neurological assessment methods and are thus applicable to a wide range of future translational studies in humans with any manner of health condition.

P385 Analysis of EEG correlates during n-back working memory test in epilepsy patients investigated with surface and invasive electrodes

Introduction The brain process of short term storage of multimodal information is called generally as working memory. This is thought to be located in the frontal and parietal lobes, however recent evidences show that the temporal lobe has important function in maintaining short-term and spatial information. Among multiple neuropsychological tests used for short term memory, the N-back test (NBT) has the advantage, that higher values of memory load can be set by increasing the recall distance (value n ). Methods We involved therapy resistant epilepsy patients undergoing video-EEG with scalp and invasive intracranial electrodes for visual and verbal NBT. The stimuli were presented gradually from 0 to 2 backs. The EEG graphs were filtered and averaged, and time-frequency analysis was performed (EEGLAB). Results Verbal NBT showed significant left-sided increase in gamma power, while during visual NBT right-sided gamma power increase was observed. The power correlated with the elevation of memory load. Intracranial data showed less increase in frontal regions compared to temporal. Conclusions Increase of gamma power seemed to be a good psychoneural correlate of memory processes during verbal and visual NBT. It showed appropriate lateralization and correlation with memory load. Based on our preliminary data the role of temporal lobe in short term memory can be hypothesized. We plan to include more patients.

Detection of Norepinephrine in Whole Blood via Fast Scan Cyclic Voltammetry.

Bioelectronic Medicines is an emerging field that capitalizes on minimally-invasive technology to stimulate the autonomic nervous system in order to evoke therapeutic biomolecular changes at the end-organ. The goal of Bioelectronic Medicines is to realize both 'precision and personalized' medicine. 'Precise' stimulation of neural circuitry creates biomolecular changes targeted exactly where needed to maximize therapeutic effects while minimizing off-target changes associated with side-effects. The therapy is then 'personalized' by utilizing implanted sensors to measure the biomolecular concentrations at, or near, the end-organ of interest and continually adjusting therapy to account for patient-specific biological changes throughout the day. To realize the promise of Bioelectronic Medicines, there is a need for minimally invasive, real-time measurement of biomarkers associated with the effects of autonomic nerve stimulation to be used for continuous titration of therapy. In this study we examine the feasibility of using fast scan cyclic voltammetry (FSCV) to measure norepinephrine levels, a neurochemical relevant to end-organ function, directly from blood. FSCV is a well-understood method for measuring electroactive neurochemicals in the central nervous system with high temporal and high spatial resolution that has yet to be adapted to the study of the autonomic nervous system. The results demonstrate that while detecting the electroactive neurochemical norepinephrine in blood is more challenging than obtaining the same FSCV measurements in a buffer solution due to biofouling of the electrode, it is feasible to utilize a minimally invasive FSCV electrode to obtain neurochemical measurements in blood.

MP26-12 MOTOR UNIT NUMBER ESTIMATION OF THE PUBORECTALIS MUSCLE

You have accessJournal of UrologyUrodynamics/Lower Urinary Tract Dysfunction/Female Pelvic Medicine: Basic Research & Pathophysiology I1 Apr 2017MP26-12 MOTOR UNIT NUMBER ESTIMATION OF THE PUBORECTALIS MUSCLE Nicholas Dias, Yun Peng, Jinbao He, Charles Popeney, and Yingchun Zhang Nicholas DiasNicholas Dias More articles by this author , Yun PengYun Peng More articles by this author , Jinbao HeJinbao He More articles by this author , Charles PopeneyCharles Popeney More articles by this author , and Yingchun ZhangYingchun Zhang More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2017.02.783AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Motor unit number estimation (MUNE) techniques estimate the number of functioning motor units (MUs) in a muscle, and serve as a biomarker for neuromuscular and muscular atrophy. Application of current MUNE techniques to the pelvic floor is impractical because of the need for either multiple stimulations or invasive needle electrodes. The objective is to propose a novel MUNE technique applicable to pelvic floor muscles, by combining a high-density surface EMG (HD-sEMG) decomposition approach with pudendal nerve stimulation, negating the need for invasive needles or multiple stimulations. METHODS All procedures were approved by UH IRB. The pudendal nerve was stimulated transrectally with a St. Mark′s electrode mounted on the operator′s glove. HD-sEMG recordings were acquired from the puborectalis muscle with a vaginal EMG probe (Figure 1b) during supramaximal stimulation and three maximal voluntary contractions of pelvic floor muscles. Firstly, single motor unit action potentials (SMUPs) were decomposed from EMG recordings during muscle contraction using our recently developed K-Means Clustering Convolution Kernel Compensation (KmCKC) Algorithm. All SMUPs were grouped into left or right side by visually checking their innervation zone locations following an established procedure. Next, mean SMUPs were derived for both sides by averaging all HD-sEMG profiles of grouped SMUPs. Last, MUNE was calculated as the weighted average of compound muscle action potential (CMAP) size to mean SMUP size ratios for both sides. RESULTS Left and right branches of the pudendal nerve were simulated. Four SMUPs were decomposed from HD-sEMG signals (left: 3 and right: 1). MUNE for the left and right sides were 22.8 and 27.0, respectively. CONCLUSIONS This pilot study proves the feasibility of a novel MUNE technique for muscles in the pelvic floor region. The KmCKC algorithm enables a non-invasive collection of SMUPs, negating the need for repeated electrical stimulation or invasive needle electrodes. Results from more subjects will be available from our ongoing subject recruitment. © 2017FiguresReferencesRelatedDetails Volume 197Issue 4SApril 2017Page: e324 Advertisement Copyright & Permissions© 2017MetricsAuthor Information Nicholas Dias More articles by this author Yun Peng More articles by this author Jinbao He More articles by this author Charles Popeney More articles by this author Yingchun Zhang More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Minimally Invasive Microneedle Array Electrodes Employing Direct Electron Transfer Type Glucose Dehydrogenase for the Development of Continuous Glucose Monitoring Sensors

Closed loop systems hinge on the accuracy and precision of the continuous glucose monitoring sensors. Most of the commercially available continuous glucose monitoring sensors is implanted subcutaneously for a period of 7-14 days. The subsequent biofouling effects have implications on the performance of the sensors over time especially at low glucose concentrations. In addition, the commercially available sensors are sensitive to the presence of interfering species such as acetaminophen in the skin compartment. We report here on the marriage of minimally invasive, continuous glucose sensors and a direct electron transfer type glucose dehydrogenase enzymatic system. Whilst the microneedles here are designed to sit in the dermal interstitial fluid over a 24-48 hour period to minimize the biofouling effect, the direct electron transfer enzyme allows operation of the electrochemical sensor at lower potentials to minimize the effect of interference. The microneedle structure design also enables the use of compensation electrodes for background subtraction to further nullify the effects of interference.

Role of magnetoencephalography and stereo-electroencephalography in the presurgical evaluation in patients with drug-resistant epilepsy.

In selected patients with drug-resistant focal epilepsies (DRFE), who otherwise are likely to be excluded from epilepsy surgery (ES) because of the absence of a magnetic resonance imaging (MRI)-demonstrable lesion or discordant anatomo-electro-clinical (AEC) data, magnetoencephalography (MEG) may help to generate an AEC hypothesis and stereo-electroencephalography (SEEG) may help to verify the hypothesis and proceed with ES. The sensitivity of MEG is much better in localizing the spiking zone in relation to lateral temporal and extratemporal cortical regions compared to the mesial temporal structures. MEG has a dominant role in the presurgical evaluation of patients with MRI-negative DRFEs, insular epilepsies, and recurrent seizures after failed epilepsy surgeries, and in guiding placement of invasive electrodes. Moreover, postoperative seizure freedom is better if MEG spike source localized cortical region is included in the resection. When compared to subdural grid electrode recording, SEEG is less invasive and safer. Those who are otherwise destined to suffer from uncontrolled seizures and their consequences, SEEG guided ES is a worthwhile and a cost-effective option. Depending on the substrate pathology, there is > 80-90% chance of undergoing ES and 60-80% chance of becoming seizure-free following SEEG. Recent noninvasive techniques aimed at better structural imaging, delineating brain connectivity and recording specific intracerebral EEG patterns such as high frequency oscillations might decrease the need for SEEG; but more importantly, make SEEG exploration more goal-directed and hypothesis-driven.

Lateralization of cortical negative motor areas.

The lateral and mesial aspects of the central and frontal cortex were studied by direct electrical stimulation of the cortex in epilepsy surgery candidates in order to determine the localization of unilateral and bilateral negative motor responses. Results of electrical cortical stimulation were examined in epilepsy surgery candidates in whom invasive electrodes were implanted. The exact localization of subdural electrodes was defined by fusion of 3-dimensional reconstructed MRI and CT images in 13 patients and by analysis of plane skull X-rays and intraoperative visual localization of the electrodes in another 7 patients. Results of electrical stimulation of the cortex were evaluated in a total of 128 patients in whom invasive electrodes were implanted for planning resective epilepsy surgery. Twenty patients, in whom negative motor responses were obtained, were included in the study. Bilateral upper limb negative motor responses were more often elicited from stimulation of the mesial frontal cortex whereas stimulation of the lateral central cortex leads to contralateral upper limb negative motor responses (p<0.0001). Bilateral negative motor responses were exclusively found in the superior frontal gyrus whereas contralateral negative motor responses localized predominantly in the anterior part of the precentral gyrus (p<0.0001). Exact localization using 3-D fusion methods revealed that negative motor areas are widely distributed throughout the precentral gyrus and the mesial fronto-central cortex showing functional differences with regard to unilateral and bilateral upper limb representation. The lateral fronto-central negative motor area serves predominantly contralateral upper limb motor control whereas the mesial frontal negative motor area represents bilateral upper limb movement control.

Evaluation of the fetal QT interval using non-invasive fetal ECG technology

Non-invasive fetal electrocardiography (NI-FECG) is a promising alternative continuous fetal monitoring method that has the potential to allow morphological analysis of the FECG. However, there are a number of challenges associated with the evaluation of morphological parameters from the NI-FECG, including low signal to noise ratio of the NI-FECG and methodological challenges for getting reference annotations and evaluating the accuracy of segmentation algorithms. This work aims to validate the measurement of the fetal QT interval in term laboring women using a NI-FECG electrocardiogram monitor. Fetal electrocardiogram data were recorded from 22 laboring women at term using the NI-FECG and an invasive fetal scalp electrode simultaneously. A total of 105 one-minute epochs were selected for analysis. Three pediatric electrophysiologists independently annotated individual waveforms and averaged waveforms from each epoch. The intervals measured on the averaged cycles taken from the NI-FECG and the fetal scalp electrode showed a close agreement; the root mean square error between all corresponding averaged NI-FECG and fetal scalp electrode beats was 13.6 ms, which is lower than the lowest adult root mean square error of 16.1 ms observed in related adult QT studies. These results provide evidence that NI-FECG technology enables accurate extraction of the fetal QT interval.

Improved electrode material for deep brain stimulation.

Deep brain stimulation (DBS) devices have been implanted for treatment of basic tremor, Parkinson's disease and dystonia. These devices use electrodes in contact with tissue to deliver electrical pulses to targeted cells, to elicit specific therapeutic responses. In general, the neuromodulation industry has been evolving towards smaller, less invasive electrodes. However, current electrode materials do not support small sizes without severely restricting the stimulus output. Hence, an improved electrode material will benefit present and future DBS systems. In this study, five DBS leads were modified using a cost-effective and materials-efficient process for applying an ultra-low impedance platinum-iridium alloy coating. One DBS lead was used for insertion test and four DBS leads were chronically pulsed for 12 weeks. The platinum-iridium alloy significantly improved the electrical properties of the DBS electrodes and was robust to insertion into brain and to 12 weeks of chronic pulsing.

Decoding force from deep brain electrodes in Parkinsonian patients.

Limitations of many Brain Machine Interface (BMI) systems using invasive electrodes include reliance on single neurons and decoding limited to kinematics only. This study investigates whether force-related information is present in the local field potential (LFP) recorded with deep brain electrodes using data from 14 patients with Parkinson's disease. A classifier based on logistic regression (LR) is developed to classify various force stages, using 10-fold cross validation. Least Absolute and Shrinkage Operator (Lasso) is then employed in order to identify the features with the most predictivity. The results show that force-related information is present in the LFP, and it is possible to distinguish between various force stages using certain frequency-domain (delta, beta, gamma) and time-domain (mobility) features in real-time.

Comparison of Subdermal Needle and Surface Adhesive Stimulating Electrodes for Somatosensory Evoked Potential Monitoring during Anterior Cervical Discectomy and Fusion

ABSTRACTIntroduction: Needle stick injuries remain a physical and psychological burden to healthcare workers. Noninvasive surface adhesive stimulating electrodes used to generate somatosensory evoked potentials can help decrease this risk.Methods: We performed a retrospective observational study of patients who underwent anterior cervical discectomy and fusion (ACDF) surgery to determine the utility and variability of using surface adhesive stimulating electrodes. Our analysis for utility compared alarm (significant changes) frequency, defined by established alarm criteria, between subdermal needle (Group I) and surface adhesive electrodes (Group II). We compared the variability by comparing the frequency of alarms based on establishing baselines during various stages of the procedure.Results: Between Group I and Group II, no significant differences were found in demographic, age, number of levels decompressed and fused, and length of surgery variability. However, stimulation intensity was significantly higher in Group II. Significant differences in the mean frequency of alarm of cortical, subcortical, and Erb’s somatosensory evoked potential (SSEP) responses for the upper extremities between the two groups were only observed for the upper left Erb’s point amplitude (p = 0.03) at retraction and upper right cortical amplitude at incision (p = 0.02).The frequency of alarms of the amplitude of left ulnar cortical responses from SSEPs using surface adhesives when baselines were established at the beginning of the procedure, at the time of incision, and at placement of retractors were 13.83 % (±14.08%), 7.50 % (±7.56%) and 3.42 % (±3.48%), respectively. Comparatively, the frequencies of alarms of the amplitude of left ulnar cortical responses from SSEPs using needle electrodes were 18.07 % (±22.85%), 12.13 % (±17.30%) and 7.37 % (±11.82%), respectively. Similar results were observed from frequency for alarms from the right ulnar SSEPs.Conclusion: This study found little significant difference between the frequencies of alarm in patients who had SSEP responses obtained using surface adhesive electrodes when compared to needle electrodes. This lack of significant difference was observed even when alarms were established at various stages of the surgery before any major manipulation. For short procedures monitoring the upper extremities only, surface adhesive electrodes may provide a reliable alternative to invasive needle electrodes.

A Preclinical Study of Laryngeal Motor-Evoked Potentials as a Marker Vagus Nerve Activation.

Vagus nerve stimulation (VNS) is a treatment for refractory epilepsy and depression. Previous studies using invasive recording electrodes showed that VNS induces laryngeal motor-evoked potentials (LMEPs) through the co-activation of the recurrent laryngeal nerve and subsequent contractions of the laryngeal muscles. The present study investigates the feasibility of recording LMEPs in chronically VNS-implanted rats, using a minimally-invasive technique, to assess effective current delivery to the nerve and to determine optimal VNS output currents for vagal fiber activation. Three weeks after VNS electrode implantation, signals were recorded using an electromyography (EMG) electrode in the proximity of the laryngeal muscles and a reference electrode on the skull. The VNS output current was gradually ramped up from 0.1 to 1.0 mA in 0.1 mA steps. In 13/27 rats, typical LMEPs were recorded at low VNS output currents (median 0.3 mA, IQR 0.2-0.3 mA). In 11/27 rats, significantly higher output currents were required to evoke electrophysiological responses (median 0.7 mA, IQR 0.5-0.7 mA, p < 0.001). The latencies of these responses deviated significantly from LMEPs (p < 0.05). In 3/27 rats, no electrophysiological responses to simulation were recorded. Minimally invasive LMEP recordings are feasible to assess effective current delivery to the vagus nerve. Furthermore, our results suggest that low output currents are sufficient to activate vagal fibers.

Electromagnetic Initiation and Propagation of Bipolar Radiofrequency Tissue Reactions via Invasive Non-Insulated Microneedle Electrodes.

Radiofrequency (RF) energy can be emitted into the skin, either non- or invasively, via a monopolar mode that utilizes an active electrode and a grounded electrode or via a bipolar mode that employs two active electrodes. In this experimental study of RF tissue reactions, bipolar RF energy was emitted in vivo to micropig skin at varying microneedle penetration depths, signal amplitudes, and conduction times. Immediately after RF treatment, skin samples exhibited RF-induced coagulation columns of thermal injury, separately generated around each microneedle in the dermis. In ex vivo bovine liver tissue, the thermal coagulation columns were found to be concentrated maximally around the pointed tips of each electrode. After a RF conduction time of 2 seconds, the individual areas of thermal coagulation began to converge with neighboring RF-induced coagulation columns; the convergence of coagulation columns was found to start from the tips of neighboring electrodes.

Slow Spatial Recruitment of Neocortex during Secondarily Generalized Seizures and Its Relation to Surgical Outcome.

Understanding the spatiotemporal dynamics of brain activity is crucial for inferring the underlying synaptic and nonsynaptic mechanisms of brain dysfunction. Focal seizures with secondary generalization are traditionally considered to begin in a limited spatial region and spread to connected areas, which can include both pathological and normal brain tissue. The mechanisms underlying this spread are important to our understanding of seizures and to improve therapies for surgical intervention. Here we study the properties of seizure recruitment-how electrical brain activity transitions to large voltage fluctuations characteristic of spike-and-wave seizures. We do so using invasive subdural electrode arrays from a population of 16 patients with pharmacoresistant epilepsy. We find an average delay of ∼30 s for a broad area of cortex (8 × 8 cm) to be recruited into the seizure, at an estimated speed of ∼4 mm/s. The spatiotemporal characteristics of recruitment reveal two categories of patients: one in which seizure recruitment of neighboring cortical regions follows a spatially organized pattern consistent from seizure to seizure, and a second group without consistent spatial organization of activity during recruitment. The consistent, organized recruitment correlates with a more regular, compared with small-world, connectivity pattern in simulation and successful surgical treatment of epilepsy. We propose that an improved understanding of how the seizure recruits brain regions into large amplitude voltage fluctuations provides novel information to improve surgical treatment of epilepsy and highlights the slow spread of massive local activity across a vast extent of cortex during seizure.

Elektrokochleografie mit Trommelfell-, Gehörgangs- und transtympanaler Elektrode bei V.a. Morbus Menière

Aim of this study was to explore the clinical value of non-invasive recordings of electrocochleography in comparison to the use of invasive electrodes for the diagnosis of endolymphatic hydrops in patients with suspicious Morbus Menière. 15 patients with clinical suspicion of Morbus Menière underwent electrocochleography with transtympanic needle-electrode as well as tympanic membrane electrode. 10 patients received electrocochleography with transtympanic needle-electrode and ear canal electrode. A control group of 12 healthy adults was evaluated using tympanic membrane electrode. The negative electrode was placed on the ipsilateral mastoid, the ground electrode in the middle of the forehead. For stimulation broadband click stimulus as well as long tone bursts of 1, 2 and 4 kHz were applied. In addition the impedance of the electrode was registered. While transtympanic electrocochleography gave reliable results in 100% of these cases, extratympanic recordings often manifested poor wave morphology. The electrocochleographic measures following stimulation with 1 and 2 kHz long tone bursts were the best measures to identify endolymphatic hydrops. This was the case with transtympanic as well as with tympanic membrane electrodes. There was no correlation between impedance and wave morphology. For the evaluation of Morbus Menière non-invasive electrocochleography showed good results using a tympanic canal electrode with 1 and 2 kHz tone bursts. Yet in unclear cases transtympanic electrocochleography should be preferred.

The start and development of epilepsy surgery in Europe: a historical review.

Epilepsy has not always been considered a brain disease, but was believed to be a demonic possession in the past. Therefore, trepanation was done not only for medical but also for religious or spiritual reasons, originating in the Neolithic period (3000 BC). The earliest documentation of trepanation for epilepsy is found in the writings of the Hippocratic Corpus and consisted mainly of just skull surgery. The transition from skull surgery to brain surgery took place in the middle of the nineteenth century when the insight of epilepsy as a cortical disorder of the brain emerged. This led to the start of modern epilepsy surgery. The pioneer countries in which epilepsy surgery was performed in Europe were the UK, Germany, and The Netherlands. Neurosurgical forerunners like Sir Victor Horsley, William Macewen, Fedor Krause, and Otfrid Foerster started with “modern” epilepsy surgery. Initially, epilepsy surgery was mainly done with the purpose to resect traumatic lesions or large surface tumours. In the course of the twentieth century, this changed to highly specialized microscopic navigation-guided surgery to resect lesional and non-lesional epileptogenic cortex. The development of epilepsy surgery in Southern Europe, which has not been described until now, will be elaborated in this manuscript. To summarize, in this paper, we provide (1) a detailed description of the evolution of European epilepsy surgery with special emphasis on the pioneer countries; (2) novel, never published information about the development of epilepsy surgery in Southern Europe; and (3) we review the historical dichotomy of invasive electrode implantation strategy (Anglo-Saxon surface electrodes versus French-Italian stereoencephalography (SEEG) model).