Prognostic significance of telomerase reverse transcriptase promoter gen mutations in high grade meningiomas / Importancia pronóstica de las mutaciones del gen promotor de la transcriptasa inversa de la telomerasa en los meningiomas de alto grado

Introduction: Mutations in the promoter region of telomerase reverse transcriptase occur frequently in meningiomas. Objective: To estimate the prognostic importance of telomerase reverse transcriptase mutations in Colombian patients with grades II and III meningioma. Materials and methods: This was a multicenter retrospective cohort study of patients diagnosed with refractory or recurrent WHO grades II and III meningiomas, recruited between 2011 and 2018, and treated with systemic therapy (sunitinib, everolimus ± octreotide, and bevacizumab). Mutation status of the telomerase reverse transcriptase promoter was established by PCR. Results: Forty patients were included, of which telomerase reverse transcriptase mutations were found in 21 (52.5%), being C228T and C250T the most frequent variants with 87.5 % and 14.3 %, respectively. These were more frequent among patients with anaplastic meningiomas (p=0.18), with more than 2 recurrences (p=0.04); and in patients with parasagittal region and anterior fossa lesions (p=0.05). Subjects characterized as having punctual mutations were more frequently administered with everolimus, sunitinib and bevacizumab drug series (p=0.06). Overall survival was 23.7 months (CI95% 13.1-34.2) and 43.4 months (CI95% 37.5-49.3; p=0.0001) between subjects with and without mutations, respectively. Multivariate analysis showed that the number of recurrences and the presence of telomerase reverse transcriptase mutations were tthe only variables that negatively affected overall survival. Conclusions: Mutations in telomerase reverse transcriptase allows the identification of high-risk patients and could be useful in the selection of the best medical treatment.

Introducción. En los meningiomas, ocurren con frecuencia mutaciones en la región promotora de la transcriptasa inversa de la telomerasa. Objetivo. Estimar la importancia pronóstica de las mutaciones de la transcriptasa inversa de la telomerasa en pacientes colombianos con meningiomas de grados II y III. Materiales y métodos. Es un estudio de cohorte, retrospectivo y multicéntrico, que incluyó pacientes con diagnóstico de meningioma persistente o recidivante, de grados II y III, según la clasificación de la OMS, reclutados entre el 2011 y el 2018, con tratamiento sistémico (sunitinib, everolimus con octreótido o sin él, y bevacizumab). El estado de la mutación del promotor de la transcriptasa inversa de la telomerasa se determinó por medio de la PCR. Resultados. Se incluyeron 40 pacientes, en 21 (52,5 %) de los cuales se encontraron mutaciones en la transcriptasa inversa de la telomerasa, siendo las variantes más frecuentes la C228T (87,5 %) y la C250T (14,3 %). Estas fueron más frecuentes entre los pacientes con meningiomas anaplásicos (p=0,18), en aquellos con más de dos recurrencias (p=0,04), y en los que presentaron lesiones en la región parasagital y la fosa anterior (p=0,05). Los sujetos caracterizados por tener alteraciones puntuales fueron tratados con mayor frecuencia con la serie de medicamentos everolimus, sunitinib y bevacizumab (p=0,06). Tras el inicio del tratamiento médico, la supervivencia global fue de 23,7 meses (IC95% 13,1-34,2) en los pacientes con mutaciones y, de 43,4 meses (IC95% 37,5-49,3), entre aquellos sin mutaciones (p=0,0001). Los resultados del análisis multivariado demostraron que, únicamente, el número de recurrencias y la presencia de mutaciones en el gen de la transcriptasa inversa de la telomerasa, fueron factores que afectaron negativamente la supervivencia global. Conclusiones. Las mutaciones en el gen promotor de la transcriptasa inversa de la telomerasa permiten identificar los pacientes con alto riesgo, cuya detección podría ser de utilidad para seleccionar el mejor esquema terapéutico.

Congenital meningocele associated with corpus callosum agenesis and midline superior labial cleft due to Tessier 0-14 facial fissure: A case report.

A case of a 31-day-old infant patient with a Tessier 0-14 deformity related to multiple midline deformities is presented. Although Transnasal endoscopic surgery is the mainstay for the treatment of anterior and middle skull base meningoceles, there are complex cases in which a combined and multidisciplinary approach is necessary. The surgical decisions and techniques are described. To date, this is the first patient reported with Tessier 0-14 deformity treated with a combined endoscopic and external surgical approach.

Estimating interdependences in networks of weakly coupled deterministic systems.

The extraction of information from measured data about the interactions taking place in a network of systems is a key topic in modern applied sciences. This topic has been traditionally addressed by considering bivariate time series, providing methods which are sometimes difficult to extend to multivariate data, the limiting factor being the computational complexity. Here, we present a computationally viable method based on black-box modeling which, while theoretically applicable only when a deterministic hypothesis about the processes behind the recordings is plausible, proves to work also when this assumption is severely affected. Conceptually, the method is very simple and is composed of three independent steps: in the first step a state-space reconstruction is performed separately on each measured signal; in the second step, a local model, i.e., a nonlinear dynamical system, is fitted separately on each (reconstructed) measured signal; afterward, a linear model of the dynamical interactions is obtained by cross-relating the (reconstructed) measured variables to the dynamics unexplained by the local models. The method is successfully validated on numerically generated data. An assessment of its sensitivity to data length and modeling and measurement noise intensity, and of its applicability to large-scale systems, is also provided.

Importancia pronóstica de las mutaciones del gen promotor de la transcriptasa inversa de la telomerasa en los meningiomas de alto grado / Prognostic significance of telomerase reverse transcriptase promoter gen mutations in high grade meningiomas

Introducción. En los meningiomas, ocurren con frecuencia mutaciones en la región promotora de la transcriptasa inversa de la telomerasa. Objetivo. Estimar la importancia pronóstica de las mutaciones de la transcriptasa inversa de la telomerasa en pacientes colombianos con meningiomas de grados II y III. Materiales y métodos. Es un estudio de cohorte, retrospectivo y multicéntrico, que incluyó pacientes con diagnóstico de meningioma persistente o recidivante, de grados II y III, según la clasificación de la OMS, reclutados entre el 2011 y el 2018, con tratamiento sistémico (sunitinib, everolimus con octreótido o sin él, y bevacizumab). El estado de la mutación del promotor de la transcriptasa inversa de la telomerasa se determinó por medio de la PCR. Resultados. Se incluyeron 40 pacientes, en 21 (52,5 %) de los cuales se encontraron mutaciones en la transcriptasa inversa de la telomerasa, siendo las variantes más frecuentes la C228T (87,5 %) y la C250T (14,3 %). Estas fueron más frecuentes entre los pacientes con meningiomas anaplásicos (p=0,18), en aquellos con más de dos recurrencias (p=0,04), y en los que presentaron lesiones en la región parasagital y la fosa anterior (p=0,05). Los sujetos caracterizados por tener alteraciones puntuales fueron tratados con mayor frecuencia con la serie de medicamentos everolimus, sunitinib y bevacizumab (p=0,06). Tras el inicio del tratamiento médico, la supervivencia global fue de 23,7 meses (IC95% 13,1-34,2) en los pacientes con mutaciones y, de 43,4 meses (IC95% 37,5-49,3), entre aquellos sin mutaciones (p=0,0001). Los resultados del análisis multivariado demostraron que, únicamente, el número de recurrencias y la presencia de mutaciones en el gen de la transcriptasa inversa de la telomerasa, fueron factores que afectaron negativamente la supervivencia global. Conclusiones. Las mutaciones en el gen promotor de la transcriptasa inversa de la telomerasa permiten identificar los pacientes con alto riesgo, cuya detección podría ser de utilidad para seleccionar el mejor esquema terapéutico.

Introduction: Mutations in the promoter region of telomerase reverse transcriptase occur frequently in meningiomas. Objective: To estimate the prognostic importance of telomerase reverse transcriptase mutations in Colombian patients with grades II and III meningioma. Materials and methods: This was a multicenter retrospective cohort study of patients diagnosed with refractory or recurrent WHO grades II and III meningiomas, recruited between 2011 and 2018, and treated with systemic therapy (sunitinib, everolimus ± octreotide, and bevacizumab). Mutation status of the telomerase reverse transcriptase promoter was established by PCR. Results: Forty patients were included, of which telomerase reverse transcriptase mutations were found in 21 (52.5%), being C228T and C250T the most frequent variants with 87.5 % and 14.3 %, respectively. These were more frequent among patients with anaplastic meningiomas (p=0.18), with more than 2 recurrences (p=0.04); and in patients with parasagittal region and anterior fossa lesions (p=0.05). Subjects characterized as having punctual mutations were more frequently administered with everolimus, sunitinib and bevacizumab drug series (p=0.06). Overall survival was 23.7 months (CI95% 13.1-34.2) and 43.4 months (CI95% 37.5-49.3; p=0.0001) between subjects with and without mutations, respectively. Multivariate analysis showed that the number of recurrences and the presence of telomerase reverse transcriptase mutations were the only variables that negatively affected overall survival. Conclusions: Mutations in telomerase reverse transcriptase allows the identification of high-risk patients and could be useful in the selection of the best medical treatment.

¿Es la atención primaria de salud integral parte de la respuesta a la pandemia de Covid-19 en Latinoamérica? / Is comprehensive primary health care part of the response to the COVID-19 pandemic in Latin America? / A atenção primária à saúde integral é parte da resposta à pandemia de Covid-19 na América Latina?

Resumen América Latina se ha convertido en uno de los epicentros de la pandemia de Covid-19, con una crisis sanitaria y humanitaria. El objetivo del artículo es analizar las medidas para enfrentar la pandemia en países de la Región y el rol de la Atención Primaria de Salud, discutiendo obstáculos y potencialidades. Son analizados los casos de Bolivia, Brasil, Chile, Colombia, Cuba, Uruguay y Venezuela. Los siete países adoptaran medidas de aislamiento social de diferentes alcances, con grados distintos de sostenibilidad. El énfasis de las respuestas estuvo más en la atención hospitalaria que en la vigilancia de la salud, identificación de casos y contactos y disposición de condiciones adecuadas para el confinamiento. En casi todos los países, se subestimó la capacidad de los servicios de atención primária en el territorio. No obstante, iniciativas de enfoque territorial y comunitario buscaron integrar la vigilancia de la salud con actividades de promoción, prevención y cuidado, aunque con alcance parcial. En este contexto la Atención Primaria Integral e integrada toma nuevo sentido y reclama desarrollos que contribuyan a recobrar el equilibrio entre sociedad y medio ambiente. Es necesario repensar los sistemas de salud y la importancia de la atención primaria de salud integrada e integral.

Abstract Latin America has become one of the epicenters of the COVID-19 pandemic, with a health and humanitarian crisis. The objective of the article is to analyze the strategies implemented by countries in the Region to face the pandemic and the role of Primary Health Care, considering obstacles and potential. The cases of Bolivia, Brazil, Chile, Colombia, Cuba, Uruguay and Venezuela were analyzed. The seven countries have adopted diverse social distancing strategies with varying degrees of sustainability. The responses emphasized hospital care more than surveillance, case identification, contact tracking, and enabling adequate conditions for isolation. In almost all cases studied, the capacity of primary care services in the territory was underestimated. Even so, primary care initiatives with a territorial and community focus sought to integrate health surveillance with promotion, prevention and care, despite partial implementation. In this context, comprehensive and integrated primary care takes on new meaning and requires new developments in order to contribute to the recovery of the balance between society and the environment. The pandemic showed the need to rethink health care systems and the importance of primary care for comprehensive and integrated health.

Resumo A América Latina tornou-se um dos epicentros da pandemia de Covid-19, com uma crise sanitária e humanitária. O objetivo do artigo é analisar as estratégias implementadas por países da Região para enfrentar a pandemia e o papel da Atenção Primária à Saúde, ponderando obstáculos e potencialidades. Foram analisados os casos de Bolívia, Brasil, Chile, Colômbia, Cuba, Uruguai e Venezuela. Os sete países adotaram estratégias de distanciamento social diversas com diferentes graus de sustentabilidade. As respostas enfatizaram mais a assistência hospitalar do que a vigilância, a identificação de casos, o rastreamento dos contatos e a viabilização de condições adequadas para isolamento. Em quase todos os casos estudados, foi subestimada a capacidade dos serviços de atenção primária no território. Ainda assim, iniciativas de atenção primária com enfoque territorial e comunitário buscaram integrar a vigilância à saúde com a promoção, prevenção e cuidado, apesar de implantação parcial. Nesse contexto, uma atenção primária integral e integrada adquire novo significado e requisita novos desenvolvimentos de forma a contribuir para a recuperação do equilíbrio entre a sociedade e o meio ambiente. A pandemia mostrou a necessidade de repensar os sistemas de atenção à saúde e a importância da atenção primária à saúde integral e integrada.

A method for determining neural connectivity and inferring the underlying network dynamics using extracellular spike recordings.

In the present paper we propose a novel method for the identification and modeling of neural networks using extracellular spike recordings. We create a deterministic model of the effective network, whose dynamic behavior fits experimental data. The network obtained by our method includes explicit mathematical models of each of the spiking neurons and a description of the effective connectivity between them. Such a model allows us to study the properties of the neuron ensemble independently from the original data. It also permits to infer properties of the ensemble that cannot be directly obtained from the observed spike trains. The performance of the method is tested with spike trains artificially generated by a number of different neural networks.

Clinical value of whole-genome sequencing of Mycobacterium tuberculosis.

Whole-genome sequencing (WGS) is now common as a result of new technologies that can rapidly sequence a complete bacterial genome for US$500 or less. Many studies have addressed questions about tuberculosis with WGS, and knowing the sequence of the entire genome, rather than only a few fragments, has greatly increased the precision of molecular epidemiology and contact tracing. Additionally, topics such as the mutation rate, drug resistance, the target of new drugs, and the phylogeny and evolution of the Mycobacterium tuberculosis complex bacteria have been elucidated by WGS. Nonetheless, WGS has not explained differences in transmissibility between strains, or why some strains are more virulent than others or more prone to development of multidrug resistance. With advances in technology, WGS of clinical specimens could become routine in high-income countries; however, its relevance will probably depend on easy to use software to efficiently process the sequences produced and accessible genomic databases that can be mined in future studies.

The Effect of a Global, Subject, and Device-Specific Model on a Noninvasive Glucose Monitoring Multisensor System.

BACKGROUND: We study here the influence of different patients and the influence of different devices with the same patients on the signals and modeling of data from measurements from a noninvasive Multisensor glucose monitoring system in patients with type 1 diabetes. The Multisensor includes several sensors for biophysical monitoring of skin and underlying tissue integrated on a single substrate. METHOD: Two Multisensors were worn simultaneously, 1 on the upper left and 1 on the upper right arm by 4 patients during 16 study visits. Glucose was administered orally to induce 2 consecutive hyperglycemic excursions. For the analysis, global (valid for a population of patients), personal (tailored to a specific patient), and device-specific multiple linear regression models were derived. RESULTS: We find that adjustments of the model to the patients improves the performance of the glucose estimation with an MARD of 17.8% for personalized model versus a MARD of 21.1% for the global model. At the same time the effect of the measurement side is negligible. The device can equally well measure on the left or right arm. We also see that devices are equal in the linear modeling. Thus hardware calibration of the sensors is seen to be sufficient to eliminate interdevice differences in the measured signals. CONCLUSIONS: We demonstrate that the hardware of the 2 devices worn on the left and right arms are consistent yielding similar measured signals and thus glucose estimation results with a global model. The 2 devices also return similar values of glucose errors. These errors are mainly due to nonstationarities in the measured signals that are not solved by the linear model, thus suggesting for more sophisticated modeling approaches.

Lista de chequeo preoperatorio para la cirugía endoscópica de hipófisis / Preoperative checklist for endoscopic pituitary surgery

Introducción: las listas de chequeo son herramientas que buscan evitar errores y complicaciones al momento de realizar un procedimiento. El adenoma hipofisiario es la primera causa de cirugía endoscópica transnasal de la región selar, y se estima que ocurren hasta un 20 % de complicaciones derivadas de esta cirugía. Objetivo: desarrollar una lista de chequeo preoperatoria que sirva como una guía para la evaluación prequirúrgica de los pacientes a quienes se les realicen cirugías de la región selar. Metodología: se realizó una revisión de la literatura para desarrollar una lista de chequeo preliminar y una serie de declaraciones que resumían los puntos importantes de la lista. Se construyó un comité de expertos en cirugía endoscópica de la base de cráneo conformado por neurocirujanos y otorrinolaringólogos de hospitales de Bogotá. Utilizando la metodología Delphi modificada, se llegó a un consenso para la realización de la lista de chequeo final. Resultados: se describieron 15 declaraciones; de estas, hubo una discrepancia en 6 declaraciones. Por esta razón, se realizaron modificaciones en 5 declaraciones, y se llegó a un consenso entre los expertos participantes. La lista de chequeo final aprobada está compuesta por 4 ítems. Discusión/conclusiones: la cirugía para el manejo de la patología de la región selar es compleja y requiere de un equipo quirúrgico entrenado y disciplinado para lograr los mejores desenlaces posibles. Consideramos que nuestra lista de chequeo es una herramienta que permitirá a los equipos que realizan estas cirugías en Colombia tener una visión más completa del paciente y, eventualmente, ayudar a evitar errores y posibles complicaciones.

Introduction: checklists that seek to avoid errors are very useful tools for any surgical practice. Pituitary adenomas are the leading indication to perform a transnasal endoscopic surgery in the sellar region and up to 20 % complications have been reported related to this procedure. Objetive: develop a preoperative checklist, based on an expert consensus, to serve as a guide for the skull base teams to consistently evaluate preoperatively all patients with pathologies in the sellar region. Methods: a literature review was conducted to develop a preliminary checklist and a series of statements summarizing the most important items on the list. A committee of experts in endoscopic skull base surgery was summoned, made up of neurosurgeons and otolaryngologists from hospitals in Bogotá. Using the modified Delphi methodology, a consensus was reached for the completion of the final checklist. Results: fifteen statements were developed. A discrepancy was seen in six statements. Modifications were made for five statements, thus reaching a consensus among the participating experts. The final approved checklist is made up of 4 items. Conclusion: surgery for treating different pathologies in the sellar region is complex and requires a welltrained and disciplined surgical team to achieve the best possible outcomes. We consider that our preoperative checklist is a valuable resource for skull base surgical teams performing transnasal endoscopic surgery of the sellar region. This tool will allow skull base surgical teams in Colombia to have a more comprehensive view of the patient and eventually help to avoid errors and possible complications.

An alternative to the neoliberal model in health: the case of Venezuela.

The authors present a synthesis of the proposals put forth by the health sector of Venezuela during the framing of the new Venezuelan Constitution. They summarize the background to the National Constituent Assembly and the legal framework typical of the health sector at that time, identify the methodological aspects that substantiated the health topics included in the new Constitution, and analyze the articles that shape the current constitutional health framework in Venezuela, summarizing their most important features and comparing them with neoliberal health proposals.

Data processing for noninvasive continuous glucose monitoring with a multisensor device.

BACKGROUND: Impedance spectroscopy has been shown to be a candidate for noninvasive continuous glucose monitoring in humans. However, in addition to glucose, other factors also have effects on impedance characteristics of the skin and underlying tissue. METHOD: Impedance spectra were summarized through a principal component analysis and relevant variables were identified with Akaike's information criterion. In order to model blood glucose, a linear least-squares model was used. A Monte Carlo simulation was applied to examine the effects of personalizing models. RESULTS: The principal component analysis was able to identify two major effects in the impedance spectra: a blood glucose-related process and an equilibration process related to moisturization of the skin and underlying tissue. With a global linear least-squares model, a coefficient of determination (R²) of 0.60 was achieved, whereas the personalized model reached an R² of 0.71. The Monte Carlo simulation proved a significant advantage of personalized models over global models. CONCLUSION: A principal component analysis is useful for extracting glucose-related effects in the impedance spectra of human skin. A linear global model based on Solianis Multisensor data yields a good predictive power for blood glucose estimation. However, a personalized linear model still has greater predictive power.

Craniocervical junction diseases treatment with a minimally invasive approach / Abordagem minimamente invasiva para tratamento de lesões da união craniocervical / Abordaje minimamente invasivo para tratamiento de lesiones de la union craneocervical

Objective: To introduce a new minimally invasive surgical approach to anterior and lateral craniocervical junction diseases, preserving the midline posterior cervical spine stabilizing elements and reducing the inherent morbidity risk associated with traditional approaches. Methods: We describe a novel surgical technique in four cases of extra-medullary anterolateral compressive lesions located in the occipito-cervical junction, including infections and intra- and/or extradural tumor lesions. We used a paramedian trasmuscular approach through an anatomical muscle corridor using a micro MaXcess® surgical expandable retractor, with the purpose of reducing morbidity and preserving the posterior muscle and ligamentous tension band. Results: This type of surgical approach provides adequate visualization and microsurgical resection of lesions and reduces muscle manipulation and devascularisation, preserving the tension of the ligament complex. There was minimal blood loss and a decrease in postoperative pain, with rapid start of rehabilitation and shorter hospitalization times. There were no intraoperative complications, and all patients recovered from their pre-operative symptoms. Conclusions: This novel surgical technique is feasible and adequate for the occipito-atlanto-axial complex, with better results than traditional procedures.

Objetivo: Realizamos esforços para desenvolver novas técnicas cirúrgicas para reduzir a morbidade e a mortalidade. Métodos: Descrevemos uma técnica cirúrgica nova em quatro casos de lesões extramedulares compressivas anterolaterais da junção occipitocervical, que incluem infecções e lesões tumorais intra e extradurais. As lesões foram excisadas por uma nova técnica cirúrgica minimamente invasiva, por meio de um corredor anatômico muscular, utilizando-se o afastador expansível MaXcess® (Nuvasive Inc., San Diego, CA, EUA) visando reduzir a morbidade e preservar a banda de tensão músculo-ligamentar. Resultados: Esse tipo de abordagem proporcionou visualização e excisão microcirúrgica adequada das lesões, com redução da manipulação muscular, preservando a tensão do complexo ligamentar nucal. Houve perda de sangue mínima, além da redução da dor pós-operatória, início rápido da reabilitação e pequena estadia hospitalar. Não foram observadas complicações intraoperatórias e os pacientes não tiveram mais os sintomas apresentados no pré-operatório. Conclusões: Essa nova técnica cirúrgica é uma opção de tratamento na região do complexo occipito-atlanto-axial anterolateral, com resultados superiores aos dos procedimentos tradicionais.

Objetivo: Se han realizado esfuerzos por desarrollar nuevas técnicas quirúrgicas que reduzcan morbimortalidad. Métodos: Describimos una novedosa técnica quirúrgica de tratamiento en cuatro casos de lesiones extramedulares compresivas anterolaterales de la unión occipitocervical que incluyen infecciones y lesiones tumorales intra y extradurales. Las lesiones fueron extirpadas por una nueva técnica quirúrgica mínimamente invasiva a través de un corredor anatómico muscular, utilizándose el retractor expansible MaXcess® (Nuvasive Inc., San Diego, CA, EEUU) con el objetivo de reducir la morbilidad y preservar la banda de tensión músculo-ligamentaria. Resultados: Este tipo de abordaje aportó adecuada visualización y resección microquirúrgica de las lesiones, con reducción de la manipulación muscular, preservando la tensión del complejo ligamentario nucal. Hubo mínima pérdida sanguínea además de disminución de dolor post-operatorio, rápido inicio de rehabilitación y corta estancia hospitalaria. No se presentaron complicaciones intraoperatorias y los pacientes se recuperaron de la sintomatología preoperatoria. Conclusiones: Esta nueva técnica quirúrgica se perfila como una opción de tratamiento a nivel del complejo occipito-atlanto-axial anterolateral con resultados superiores a los procedimientos tradicionales.

Procedimientos neuroquirúrgicoscerebrales guiados por estereotaxiarealizados en el Hospital Universitario de San Ignacio (HUSI): evolución a corto y mediano plazo / Neurosurgical Brain Estereotactic- Guided Procedures Performed at Hospital Universitario San Ignacio (HUSI): Development in the Short and Medium Term

Objetivo: Describir los resultados postoperatorios de los pacientes a los que se lesrealizaron procedimientos neuroquirúrgicos cerebrales guiados por estereotaxia enel Hospital Universitario de San Ignacio durante el periodo julio del 2009-julio del2011. Materiales y métodos: Se revisaron las historias clínicas de 78 pacientes,sus características clínicas, la localización de las lesiones en las neuroimágenes,el tipo de procedimiento, los resultados funcionales y los desenlaces a corto ymediano plazo. Resultados: 78 pacientes tuvieron procedimientos neuroquirúrgicosguiados por estereotaxia entre julio del 2009 y julio del 2011. El 64,1 % (n = 50)eran hombres. La localización de las lesiones fue en orden de frecuencia: gangliossubtalámicos, lóbulo frontal, lóbulo temporal, tálamo, unión córtico-subcortical, tallocerebral, ubicación frontotemporal, lóbulo occipital, ubicación parieto-occipital ybase del cráneo. Discusión: La implementación de procedimientos neuroquirúrgicosguiados por estereotaxia sigue siendo una de las mejores opciones en el abordaje depatologías cerebrales profundas o de difícil acceso. Tanto en Colombia como en elresto del mundo son procedimientos con una baja tasa de morbilidad y mortalidad.Conclusiones: Independientemente del tipo de procedimiento guiado por estereotaxiala tasa de complicaciones no excede el 5 %, tasas similares a las obtenidas en laliteratura mundial...

Objective: Retrospective description of postoperativeoutcomes of patients who underwentneurosurgical brain stereotactic guided proceduresat the Hospital Universitario San Ignacioduring the period July 2009-July 2011. Materialsand Methods: A review of medical recordsof 78 patients who were taken to neurosurgicalstereotactic guided procedures at the HospitalUniversitario San Ignaci. We reviewed the clinicalcharacteristics of patients, the location of thelesions on neuroimaging, management, type ofprocedure of each patient, functional results andoutcomes in the short and medium term. Results:78 patients who underwent neurosurgical brainstereotactic guided procedures between July2009 to July 2011 at the Hospital UniversitarioSan Ignacio. The 64.1 % (n = 50) were men. Thelocation of the lesions were in order of frequencysub-thalamic ganglia, frontal lobe, temporallobe, thalamus, cortico-subcortical junction, brainstem,fronto-temporal location, occipital lobe,parieto-occipital location, and at the skull’s base.Discussion: Implementing guided stereotacticneurosurgical procedures remains one of the bestoptions in dealing with deep brain pathologies ordifficult access. In both Colombia and the rest ofthe world, these are procedures with low morbidityand mortality. It must, however, developmulticenter studies that allow us to observe thedevelopment of stereotactic neurosurgery in ourcountry, also develop studies with a larger continuityto assess the long-term outcomes. Conclusions:Whatever type of stereotactic guidedprocedure the rate of complications does not exceed5 %, similar rates to those obtained from theglobal literature...

On the complexity of periodic and nonperiodic behaviors of a hysteresis-based electronic oscillator.

We investigate the families of periodic and nonperiodic behaviors admitted by a hysteresis-based circuit oscillator. The analysis is carried out by combining brute-force simulations with continuation methods. As a result of the analysis, it is shown that the existence of many different periodic solutions and of the chaotic behaviors associated with them is organized by few codimension-2 bifurcation points. This implies the possibility of switching between different periodic solutions by controlling only two bifurcation parameters, which makes the oscillator a possible generator of nontrivial periodic solutions suitable, for instance for actual radiofrequency identification systems applications.

A novel interhemispheric interaction: modulation of neuronal cooperativity in the visual areas.

BACKGROUND: The cortical representation of the visual field is split along the vertical midline, with the left and the right hemi-fields projecting to separate hemispheres. Connections between the visual areas of the two hemispheres are abundant near the representation of the visual midline. It was suggested that they re-establish the functional continuity of the visual field by controlling the dynamics of the responses in the two hemispheres. METHODS/PRINCIPAL FINDINGS: To understand if and how the interactions between the two hemispheres participate in processing visual stimuli, the synchronization of responses to identical or different moving gratings in the two hemi-fields were studied in anesthetized ferrets. The responses were recorded by multiple electrodes in the primary visual areas and the synchronization of local field potentials across the electrodes were analyzed with a recent method derived from dynamical system theory. Inactivating the visual areas of one hemisphere modulated the synchronization of the stimulus-driven activity in the other hemisphere. The modulation was stimulus-specific and was consistent with the fine morphology of callosal axons in particular with the spatio-temporal pattern of activity that axonal geometry can generate. CONCLUSIONS/SIGNIFICANCE: These findings describe a new kind of interaction between the cerebral hemispheres and highlight the role of axonal geometry in modulating aspects of cortical dynamics responsible for stimulus detection and/or categorization.

Dysconnection topography in schizophrenia revealed with state-space analysis of EEG.

BACKGROUND: The dysconnection hypothesis has been proposed to account for pathophysiological mechanisms underlying schizophrenia. Widespread structural changes suggesting abnormal connectivity in schizophrenia have been imaged. A functional counterpart of the structural maps would be the EEG synchronization maps. However, due to the limits of currently used bivariate methods, functional correlates of dysconnection are limited to the isolated measurements of synchronization between preselected pairs of EEG signals. METHODS/RESULTS: To reveal a whole-head synchronization topography in schizophrenia, we applied a new method of multivariate synchronization analysis called S-estimator to the resting dense-array (128 channels) EEG obtained from 14 patients and 14 controls. This method determines synchronization from the embedding dimension in a state-space domain based on the theoretical consequence of the cooperative behavior of simultaneous time series-the shrinking of the state-space embedding dimension. The S-estimator imaging revealed a specific synchronization landscape in schizophrenia patients. Its main features included bilaterally increased synchronization over temporal brain regions and decreased synchronization over the postcentral/parietal region neighboring the midline. The synchronization topography was stable over the course of several months and correlated with the severity of schizophrenia symptoms. In particular, direct correlations linked positive, negative, and general psychopathological symptoms to the hyper-synchronized temporal clusters over both hemispheres. Along with these correlations, general psychopathological symptoms inversely correlated within the hypo-synchronized postcentral midline region. While being similar to the structural maps of cortical changes in schizophrenia, the S-maps go beyond the topography limits, demonstrating a novel aspect of the abnormalities of functional cooperation: namely, regionally reduced or enhanced connectivity. CONCLUSION/SIGNIFICANCE: The new method of multivariate synchronization significantly boosts the potential of EEG as an imaging technique compatible with other imaging modalities. Its application to schizophrenia research shows that schizophrenia can be explained within the concept of neural dysconnection across and within large-scale brain networks.

Abordaje transepto-esfenoidal con septectomía posterosuperior para resección de craneofaringiomas: reporte de caso / Postero-superior septectomy and transphenoidal approach for craniopharyngiomas resection: case report

Craniopharyngiomas are rare benign tumors originated from epithelial remnants of Rathke’s pouch. Its localization may cause endocrine and visual disturbances. We present a case of a 49 year old male patient referred to our Institution for management of a large supraselar Craniopharyngioma. Surgical management was performed by the Skull Base team of the San Ignacio University Hospital (Neurosurgery and Otolaryngology) using a totally Endoscopic four hands technique through a Trans Selar approach.

Los craneofaringiomas son tumores benignos poco frecuentes, originados de restos epiteliales de la bolsa de Rathke, que por su localización puede producir alteraciones visuales y endocrinas. Presentamos el caso de un paciente masculino de 49 años de edad que nos fue referido a nuestra institución para manejar un gran craneofaringioma supraselar. El manejo quirúrgico se llevó a cabo por el Grupo de Cirugía Endoscópica de Base de Cráneo del Hospital Universitario San Ignacio (Neurocirugía - Otorrinolaringología), utilizando una técnica totalmente endoscópica a cuatro manos, a través de un abordaje Trans Selar. Se presenta este caso clínico para demostrar la técnica endoscópica transnasal que actualmente utilizamos para el manejo de los tumores de hipófisis, haciendo énfasis en las ventajas que ofrece estatécnica.

Assessment of EEG synchronization based on state-space analysis.

Cortical computation involves the formation of cooperative neuronal assemblies characterized by synchronous oscillatory activity. A traditional method for the identification of synchronous neuronal assemblies has been the coherence analysis of EEG signals. Here, we suggest a new method called S estimator, whereby cortical synchrony is defined from the embedding dimension in a state-space. We first validated the method on clusters of chaotic coupled oscillators and compared its performance to that of other methods for assessing synchronization. Then nine adult subjects were studied with high-density EEG recordings, while they viewed in the two hemifields (hence with separate hemispheres) identical sinusoidal gratings either arranged collinearly and moving together, or orthogonally oriented and moving at 90 degrees . The estimated synchronization increased with the collinear gratings over a cluster of occipital electrodes spanning both hemispheres, whereas over temporo-parietal regions of both hemispheres, it decreased with the same stimulus and it increased with the orthogonal gratings. Separate calculations for different EEG frequencies showed that the occipital clusters involved synchronization in the beta band and the temporal clusters in the alpha band. The gamma band appeared to be insensitive to stimulus diversity. Different stimulus configurations, therefore, appear to cause a complex rearrangement of synchronous neuronal assemblies distributed over the cortex, in particular over the visual cortex.

Self-emergence of chaos in the identification of irregular periodic behavior.

Various forms of chaotic synchronization have been proposed as ways of realizing associative memories and/or pattern recognizers. To exploit this kind of synchronization phenomena in temporal pattern recognition, a chaotic dynamical system representing the class of signals that are to be recognized must be established. This system can be determined by means of identification techniques. The fulfillment of the chaotic condition could be imposed as a constraint. However, it is shown here that, even for a very simple identification algorithm, chaos emerges by itself, allowing us to model the diversity of nearly periodic signals.