Intraoperative Neurophysiological Monitoring in Neuro-oncology

Neurosurgery can be considered a radical method to treat some illnesses and can seriously damage the nervous system. To avoid deleterious effects, such injuries must be detected during their initial development by means of intraoperative neurophysiological techniques (including intraoperative neurophysiological monitoring (IONM) and functional mapping)

Inhomogeneous cortical synchronization and partial epileptic seizures

Objective: Interictal synchronization clusters have recently been described in several publications using diverse techniques, including neurophysiological recordings and fMRI, in patients suffering from epilepsy. However, little is known about the role of these hypersynchronous areas during seizures. In this work, we report an analysis of synchronization clusters jointly with several network measures during seizure activity; we then discuss our findings in the context of prior literature.Methods: Subdural activity was recorded by electrocorticography (with 60 electrodesplaced at temporal and parietal lobe locations) in a patient with temporal lobe epilepsywith partial seizures with and without secondary generalization (SG). Both interictal andictal activities (during four seizures) were investigated and characterized using local synchronization and complex network methodology. The modularity, density of links, average clustering coefficient, and average path lengthswere calculated to obtain information about the dynamics of the global network. Functional connectivity changes during the seizures were compared with the time evolution of highly synchronized areas.Results: Our findings reveal temporal changes in local synchronization areas during seizuresand a tight relationship between the cortical locations of these areas and the patterns oftheir evolution over time. Seizure evolution and SG appear to be driven by two differentunderlying mechanisms.Fil: Vega Zelaya, Lorena. Hospital Universitario la Princesa; EspañaFil: Pastor, Jesús Eduardo. Hospital Universitario la Princesa; EspañaFil: García de Sola, Rafael. Hospital Universitario la Princesa; EspañaFil: Ortega, Guillermo José. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes; Argentin

Utility of intraoperative cortico-cortical evoked potentials for the evaluation of language function during brain tumor resection

The cortico-cortical evoked potentials (CCEP) are a relatively recent intraoperative monitoring tool that has shown high reliability in detecting the functional language area and its connections. In this work we describe a patient with a tumor located in the language area who underwent tumor resection. A neurophysiological intraoperative mapping of the frontal and posterior language area with the anesthetized patient was carried out. Then the patient was awaked. To demonstrate the relationship between language function and CCEP, the Ojemann’s stimulation technique was used in the same electrodes were CCEPs were obtained. An alteration in the emission of language had been found on the electrodes where CCEP was obtained and in adjacent electrodes. During tumor resection we used a double check for language function: neurological evaluation and CCEPs. We obtained a biunivocal relationship between warning criteria in the CCEP and immediate language impairment on neurological examination. We always observed a significant decrease in the CCEP associated with language impairment. The CCEP are able to obtain information in real time with a good spatial resolution of the language function. Future studies should be carried out in order to analyse the robustness of this technique to perform it in anesthetized patientsThis work was financed by a grant from the Ministerio de Sanidad FIS PI17/02193 and was partially supported by FEDER (Fonds Europeen de Developpement Economique et Regional

The role of ultrasound-guided perineural injection of the tibial nerve with a sub-anesthetic dosage of lidocaine for the diagnosis of tarsal tunnel syndrome

BackgroundTarsal tunnel syndrome (TTS) involves entrapment of the tibial nerve at the medial ankle beneath the flexor retinaculum and its branches, the medial and lateral plantar nerves, as they course through the porta pedis formed by the deep fascia of the abductor hallucis muscle. TTS is likely underdiagnosed, because diagnosis is based on clinical evaluation and history of present illness. The ultrasound-guided lidocaine infiltration test (USLIT) is a simple approach that may aid in the diagnosis of TTS and predict the response to neurolysis of the tibial nerve and its branches. Traditional electrophysiological testing cannot confirm the diagnosis and only adds to other findings.MethodsWe performed a prospective study of 61 patients (23 men and 38 women) with a mean age of 51 (29–78) years who were diagnosed with idiopathic TTS using the ultrasound guided near-nerve needle sensory technique (USG-NNNS). Patients subsequently underwent USLIT of the tibial nerve to assess the effect on pain reduction and neurophysiological changes.ResultsUSLIT led to an improvement in symptoms and nerve conduction velocity. The objective improvement in nerve conduction velocity can be used to document the pre-operative functional capacity of the nerve. USLIT may also be used as a possible quantitative indicator of whether the nerve has the potential to improve in neurophysiological terms and ultimately inform prognosis after surgical decompression.ConclusionUSLIT is a simple technique with potential predictive value that can help the clinician to confirm the diagnosis of TTS before surgical decompression

Necessity of Quantitative EEG for Daily Clinical Practice

The two main problems in the daily clinical practice of EEG are i) its under-use dedicated mainly to epilepsy and ii) subjectivity in de visu analysis. However, both problems can be overcome by using numerical tools in clinical practice that broaden the scope and introduce real objectivity to bioelectrical measurements. We have developed a method for quantitative EEG (qEEG) for daily use based on the homeostatic foundation of EEG. This method is robust, easy, and not time consuming and is arranged in two branches: the analysis of the spectral composition in each channel and synchronization. Notably, channels are arranged in differential mode. Since 2016, we have used this method for more than 4100 EEGs from scalp recordings in outpatients, epilepsy evaluation, and evaluation and monitoring in the intensive care unit (ICU). We have been able to identify numerical properties that are not visually evident in several pathologies, including COVID-19 in patients suffering encephalopathy, and have performed diagnosis in ICU patients and differentiation between epileptic and non-epileptic spells or minimum cognitive states. The use of numerical variables across successive recordings in the same patient has proven to be of great utility. We propose that qEEG use should be expanded globally for daily clinical practice

Network Theoretical Approach to Describe Epileptic Processes

Epilepsy is characterized by recurrent unprovoked seizures. Recent studies suggest that seizure generation may be caused by the abnormal activity of the entire network. This new paradigm requires new tools and methods for its study. In this sense, synchronization by linear as well as nonlinear measures are used to determine network structure and functional connectivity of neurophysiological data. Electroencephalography (EEG) data can be analyzed using each electrode’s activity as a node of the underlying cortical network. The information provided by the synchronization matrix is the basic brick upon which several lines of analysis can be performed thereafter. Detection of community structures, identification of centrality nodes, transformation of the underlying network into a simpler one, and the identification of the basic network architecture are only some of the many lines of basic works that can be done in order to characterize the epilepsy as a network disease. This chapter describes new approaches in network epilepsy, provides mathematical concepts in order to understand the complex network analyses, and reviews the advances in network analyses and its application to epilepsy research

Potential EEG biomarkers of sedation doses in intensive care patients unveiled by using a machine learning approach

Objective. Sedation of neurocritically ill patients is one of the most challenging situation in ICUs. Quantitative knowledge on the sedation effect on brain activity in that complex scenario could help to uncover new markers for sedation assessment. Hence, we aim to evaluate the existence of changes of diverse EEG-derived measures in deeply-sedated (RASS-Richmond agitation-sedation scale -4 and -5) neurocritically ill patients, and also whether sedation doses are related with those eventual changes. Approach. We performed an observational prospective cohort study in the intensive care unit of the Hospital de la Princesa. Twenty-six adult patients suffered from traumatic brain injury and subarachnoid hemorrhage were included in the present study. Long-term continuous electroencephalographic (EEG) recordings (2141 h) and hourly annotated information were used to determine the relationship between intravenous sedation infusion doses and network and spectral EEG measures. To do that, two different strategies were followed: assessment of the statistical dependence between both variables using the Spearman correlation rank and by performing an automatic classification method based on a machine learning algorithm. Main results. More than 60% of patients presented a correlation greater than 0.5 in at least one of the calculated EEG measures with the sedation dose. The automatic classification method presented an accuracy of 84.3% in discriminating between different sedation doses. In both cases the nodes' degree was the most relevant measurement. Significance. The results presented here provide evidences of brain activity changes during deep sedation linked to sedation doses. Particularly, the capability of network EEG-derived measures in discriminating between different sedation doses could be the framework for the development of accurate methods for sedation levels assessment.Fil: Sanz García, Ancor. Universidad Autonoma de Madrid. Hospital Universitario de la Princesa; EspañaFil: Pérez Romero, Miriam. Universidad Autonoma de Madrid. Hospital Universitario de la Princesa; EspañaFil: Pastor, Jesús. Universidad Autonoma de Madrid. Hospital Universitario de la Princesa; EspañaFil: Sola, Rafael G.. Universidad Autonoma de Madrid. Hospital Universitario de la Princesa. Servicio de Neurocirugia. Grupo de Epilepsia; EspañaFil: Vega Zelaya, Lorena. Universidad Autonoma de Madrid. Hospital Universitario de la Princesa; EspañaFil: Vega, Gema. Universidad Autonoma de Madrid. Hospital Universitario de la Princesa; EspañaFil: Monasterio, Fernando. Universidad Autonoma de Madrid. Hospital Universitario de la Princesa; EspañaFil: Torrecilla, Carmen. Universidad Autonoma de Madrid. Hospital Universitario de la Princesa; EspañaFil: Pulido, Paloma. Universidad Autonoma de Madrid. Hospital Universitario de la Princesa. Servicio de Neurocirugia. Grupo de Epilepsia; EspañaFil: Ortega, Guillermo José. Universidad Autonoma de Madrid. Hospital Universitario de la Princesa; España. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Functional Heterogeneity of Mouse and Human Brain OPCs: Relevance for Preclinical Studies in Multiple Sclerosis.

Besides giving rise to oligodendrocytes (the only myelin-forming cell in the Central Nervous System (CNS) in physiological conditions), Oligodendrocyte Precursor Cells (OPCs) are responsible for spontaneous remyelination after a demyelinating lesion. They are present along the mouse and human CNS, both during development and in adulthood, yet how OPC physiological behavior is modified throughout life is not fully understood. The activity of adult human OPCs is still particularly unexplored. Significantly, most of the molecules involved in OPC-mediated remyelination are also involved in their development, a phenomenon that may be clinically relevant. In the present article, we have compared the intrinsic properties of OPCs isolated from the cerebral cortex of neonatal, postnatal and adult mice, as well as those recovered from neurosurgical adult human cerebral cortex tissue. By analyzing intact OPCs for the first time with 1H High Resolution Magic Angle Spinning Nuclear Magnetic Resonance (1H HR-MAS NMR) spectroscopy, we show that these cells behave distinctly and that they have different metabolic patterns in function for their stage of maturity. Moreover, their response to Fibroblast Growth Gactor-2 (FGF-2) and anosmin-1 (two molecules that have known effects on OPC biology during development and that are overexpressed in individuals with Multiple Sclerosis (MS)) differs in relation to their developmental stage and in the function of the species. Our data reveal that the behavior of adult human and mouse OPCs differs in a very dynamic way that should be very relevant when testing drugs and for the proper design of effective pharmacological and/or cell therapies for MS.post-print753 K

Características electrofisiológicas del núcleo centromediano talámico humano

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Medicina, Departamento de Anatomía, Histología y Neurociencia. Fecha de lectura: 15-09-2017Esta tesis tiene embargado el acceso al texto completo hasta el 15-03-2019El objetivo principal de esta tesis fue el análisis de las características electrofisiológicas (propiedades del potencial de acción –PA- y patrón de descarga), mediante el registro extracelular del núcleo talámico centromediano (Ce) en pacientes anestesiados. Se reconstruyó la trayectoria teórica de los electrodos sobre los diferentes núcleos talámicos, asignando un núcleo en cada profundidad de la trayectoria. El análisis de las propiedades de cada grupo neuronal que componen los núcleos talámicos más relevantes, se realizó a través de un proceso de sorting y agrupamiento. Los resultados muestran diferencias significativas entre los subdominios del núcleo Ce (magnocelular y parvocelular), tanto para las características morfológicas promedio de los PA, como para las propiedades de descarga. El análisis de las propiedades del resto de núcleos del tálamo también mostró diferencias significativas entre el Ce, núcleo ventral-intermedio (V.im.) y ventro-caudal (V.c.). Con el objetivo de definir los criterios de abordaje del Ce en relación con el núcleo V.c., se analizó durante el procedimiento la respuesta a la estimulación eléctrica del nervio mediano contralateral, registrada a través de los microelectrodos (potenciales evocados somato-sensoriales, PESS). Se encontraron 3 tipos de respuestas: i) potenciales de campo local (LFP), que son de morfología compleja y distribución más o menos localizada; ii) oscilaciones de alta frecuencia (HFO), con una distribución más extendida e inespecífica; iii) oscilaciones de baja frecuencia (LFO), respuesta que no había sido descrita en la literatura, son potenciales más localizados y están íntimamente relacionados con el V.c. Este trabajo demuestra que la utilización de las características electrofisiológicas de los PA registrados extracelularmente, así como las de los PESS, pueden mejorar la identificación de los diferentes núcleos talámicos,aumentando la precisión de la cirugía de ECP.The main goal of this thesis was the analysis of the electrophysiological features (properties of the action potential -AP- and pattern of discharge), by the extracellular recording of centromedian thalamic nucleus (Ce) in anesthetized patients. The theoretical trajectory of the electrodes on the different thalamic nuclei was reconstructed, assigning a nucleus to each depth of the trajectory. The analysis of the properties of each neuronal group that compose the most relevant thalamic nuclei was performed through a process of sorting and clustering. Results show significant differences between the subdomains of the Ce nucleus (magnocellular and parvocellular), both for the average morphological characteristics of the AP, and for the discharge properties. The analysis of the properties of the remaining nuclei of the thalamus also showed significant differences between Ce, ventral-intermediate nucleus (V.im.) and ventro-caudal nucleus (V.c.). In order to define the criteria for approaching Ce in relation to the V.c. nucleus, the response to electrical stimulation of the contralateral median nerve, recorded through microelectrodes (somatosensory evoked potentials, SSEP), was analyzed during the procedure. Three types of responses were found: (i) local field potentials (LFP), which are of complex morphology and a more or less localized distribution; (ii) high frequency oscillations (HFO), with a more widespread and nonspecific distribution; (iii) low-frequency oscillations (LFO), a response that has not been previously described in the literature, are more localized and are intimately related to V.c. This work demonstrates that the use of the electrophysiological characteristics of the extracellularly recorded APs, as well as those of the SSEPs, can improve the identification of the different thalamic nuclei, increasing the accuracy of Deep Brain Stimulation surger