Biomarkers for dementia in Latin American countries: Gaps and opportunities.

Limited knowledge on dementia biomarkers in Latin American and Caribbean (LAC) countries remains a serious barrier. Here, we reported a survey to explore the ongoing work, needs, interests, potential barriers, and opportunities for future studies related to biomarkers. The results show that neuroimaging is the most used biomarker (73%), followed by genetic studies (40%), peripheral fluids biomarkers (31%), and cerebrospinal fluid biomarkers (29%). Regarding barriers in LAC, lack of funding appears to undermine the implementation of biomarkers in clinical or research settings, followed by insufficient infrastructure and training. The survey revealed that despite the above barriers, the region holds a great potential to advance dementia biomarkers research. Considering the unique contributions that LAC could make to this growing field, we highlight the urgent need to expand biomarker research. These insights allowed us to propose an action plan that addresses the recommendations for a biomarker framework recently proposed by regional experts.

Changes in brain activity of trainees during laparoscopic surgical virtual training assessed with electroencephalography.

OBJECTIVE: Evaluate changes in brain activity of trainees during laparoscopic surgical training from electroencephalographic (EEG) signals in an ecological scenario with few restrictions for the user. DESIGN: Longitudinal study with two follow-up measurements in the first and last session of a 4-week training with LapSim laparoscopic surgery simulator. Variables analyzed include EEG neuronal activations in theta and alpha bands, tasks performance measures, and subjective measures such as perception of mental workload. SETTING: Medical School, Universidad de Antioquia, Medellin, Colombia. PARTICIPANTS: First-year surgical residents (n = 16, age = 28.0 ± 2.6 years old, right-handed, 9 females) RESULTS: Significant improvements in tasks performance were found together with changes in neuronal activity over frontal and parietal cortex. These changes were also correlated with task performance through training sessions. CONCLUSIONS: The use of neurophysiological measures such as electroencephalography combined with source separation techniques allows evaluating neural changes associated with motor training. The experiment proposed in this work establishes less controlled recording conditions leading to a more realistic analysis scenario to cognitive assessment in residents training.

Impact of Social Support on Colorectal Cancer Screening among Adult Hispanics/Latinos: A Randomized Community-based Study in Central Pennsylvania.

In the United States, the five-year survival rate of colorectal cancer for Latinos is lower than it is for White, non-Latinos. Differences in survival are due, in part, to Latinos being diagnosed at a later stage. An ethnic gap in the use of colorectal cancer screening contributes to the difference in survival. We developed, implemented, and evaluated a targeted colorectal cancer screening intervention to increase colorectal cancer screening uptake by sex, ethnicity, and geography. We measured actual colorectal cancer screening uptake in both arms as a method to determine completion rates. We used a randomized, community-based, participatory design to test the impact of social support (intervention) on completion of a provider-recommended, take-home fecal immunochemical test (FIT) kit screening test among average-risk, urban, and rural Pennsylvania Latino adults age 50 and older not currently adherent to national colorectal cancer screening guidelines (n = 264). Participants in each arm attended a community-based educational program offered at eight sites. Among the 264 participants, 154 (58%) returned a completed usable FIT kit screening test. A higher return rate was observed among participants in the social support arm (66.0%) compared with the control (47.2%). Participants in the social support arm were statistically significant 2.67 times as likely to return a completed FIT kit. Of these, 27 (17.5%) had a positive FIT kit screening test result. The results of this study suggest that social support is an effective method to increase colorectal cancer screening rates among Latinos. Future studies should examine dissemination and implementation of community-based strategies among Latinos that include social support.

Precuneus Failures in Subjects of the PSEN1 E280A Family at Risk of Developing Alzheimer's Disease Detected Using Quantitative Electroencephalography.

BACKGROUND: Presenilin-1 (PSEN1) mutations are the most common cause of familial early onset Alzheimer's disease (AD). The PSEN1 E280A (E280A) mutation has an autosomal dominant inheritance and is involved in the production of amyloid-ß. The largest family group of carriers with E280A mutation is found in Antioquia, Colombia. The study of mutation carriers provides a unique opportunity to identify brain changes in stages previous to AD. Electroencephalography (EEG) is a low cost and minimally invasiveness technique that enables the following of brain changes in AD. OBJECTIVE: To examine how previous reported differences in EEG for Theta and Alpha-2 rhythms in E280A subjects are related to specific regions in cortex and could be tracked across different ages. METHODS: EEG signals were acquired during resting state from non-carriers and carriers, asymptomatic and symptomatic subjects from E280A kindred from Antioquia, Colombia. Independent component analysis (ICA) and inverse solution methods were used to locate brain regions related to differences in Theta and Alpha-2 bands. RESULTS: ICA identified two components, mainly related to the Precuneus, where the differences in Theta and Alpha-2 exist simultaneously at asymptomatic and symptomatic stages. When the ratio between Theta and Alpha-2 is used, significant correlations exist with age and a composite cognitive scale. CONCLUSION: Theta and Alpha-2 rhythms are altered in E280A subjects. The alterations are possible to track at Precuneus regions using EEG, ICA, and inverse solution methods.

Successful Object Encoding Induces Increased Directed Connectivity in Presymptomatic Early-Onset Alzheimer's Disease.

BACKGROUND: Recent studies report increases in neural activity in brain regions critical to episodic memory at preclinical stages of Alzheimer's disease (AD). Although electroencephalography (EEG) is widely used in AD studies, given its non-invasiveness and low cost, there is a need to translate the findings in other neuroimaging methods to EEG. OBJECTIVE: To examine how the previous findings using functional magnetic resonance imaging (fMRI) at preclinical stage in presenilin-1 E280A mutation carriers could be assessed and extended, using EEG and a connectivity approach. METHODS: EEG signals were acquired during resting and encoding in 30 normal cognitive young subjects, from an autosomal dominant early-onset AD kindred from Antioquia, Colombia. Regions of the brain previously reported as hyperactive were used for connectivity analysis. RESULTS: Mutation carriers exhibited increasing connectivity at analyzed regions. Among them, the right precuneus exhibited the highest changes in connectivity. CONCLUSION: Increased connectivity in hyperactive cerebral regions is seen in individuals, genetically-determined to develop AD, at preclinical stage. The use of a connectivity approach and a widely available neuroimaging technique opens the possibility to increase the use of EEG in early detection of preclinical AD.

Algorithm for simulation of craniotomies assisted by peripheral for 3D virtual navigation.

Neurosurgical procedures require high precision and an accurate localization of the structures. For that reason and due to the advances in 3D visualization, the software for planning and training neurosurgeries has become an important tool for neurosurgeons and students, but the manipulation of the 3D structures is not always easy for the staff that usually works with 2D images. This paper describes a system developed in open source software that allows performing a virtual craniotomy (a common procedure in neurosurgery that enables the access to intracranial lesions) in 3D slicer; the system includes a peripheral input in order to permit the manipulation of the 3D structures according to camera movements and to guide the movement of the craniotomy tool.

Emotional processing in Colombian ex-combatants and its relationship with empathy and executive functions.

In this work, the neural correlates of emotional processing in Colombian ex-combatants with different empathy profiles were compared to normal controls matched for age, gender and educational level. Forty ex-combatants and 20 non ex-combatants were recruited for this study. Empathy levels as well as executive functions were measured. Empathy level was used to create three groups. Group 1 (G1) included ex-combatants with normal empathy scores, and Group 2 included ex-combatants with low scores on at least one empathy sub-scales. In control group (Ctrl), participants with no antecedents of being combatants and with normal scores in empathy were included. Age, gender, educational and intelligence quotients level were controlled among groups. event-related potentials (ERPs) were recorded while individuals performed an affective picture processing task that included positive, neutral and negative emotional stimuli, which elicit an early modulation of emotion categorization (Early Posterior Negativity (EPN)) and late evaluative process (LPP). EPN differences were found among affective categories, but no group effects were observed at this component. LPP showed a main effect of category and group (higher amplitudes in ex-combatants). There was an inverse correlation between empathy and executive functions scores and ERPs. Results are discussed according to the impact of emotional processing on empathy profile.

Neurophysiological correlates in Mild Cognitive Impairment detected using group Independent Component Analysis.

Alzheimer's disease is the most prevalent cause of dementia. Mild Cognitive Impairment (MCI) is defined as a grey area between intact cognitive functioning and clinical dementia. Electroencephalography (EEG) has been used to identify biomarkers in dementia. Currently, there is a great interest in translating the study from raw signals to signal generators, trying to keep the relationship with neurophysiology. In the current study, EEG recordings during an encoding task were acquired in MCI subjects and healthy controls. Data was decomposed using group Independent Component Analysis (gICA) and the most neuronal components were analyzed using Phase Intertrial Coherence (PIC) and Phase shift Intertrial Coherence (PsIC). MCI subjects exhibited an increase of PIC in the theta band, while controls showed increase in PsIC in the alpha band. Correlation between PIC and PsIC and clinical scales were also found. Those findings indicate that the methodology proposed based in gICA can help to extract information from EEG recordings with neurophysiological meaning.

[Application of advanced neuroimaging in motor rehabilitation]. / Aplicación de técnicas avanzadas de neuroimágenes en rehabilitación motora.

INTRODUCTION: Functional magnetic resonance imaging is a noninvasive technique that allows mapping and visualizing of brain connectivity networks. The hemiparesis after a stroke is a good biological model to study changes in brain connectivity. This model can be expanded if information is obtained before and after neurorehabilitation therapy. OBJECTIVE: To present the functional neuroimaging findings in a patient with stroke before and after performing neurorehabilitation therapy. MATERIALS AND METHODS: As part of the neurorehabilitation protocol, resonance imaging was performed before and after treatment with an equipment operating at 1.5 T. Volumetric T1-weighted images, diffusion images for tractography, functional resonance images with the patient at rest and with the patient performing pincer movement with the right hand were obtained. RESULTS: Functional maps before and after therapy were obtained, which are presented together with structural connectivity images obtained by tractography. Clinical changes can be seen accompanied by changes in activation patterns obtained by functional magnetic resonance imaging. CONCLUSION: The versatility of magnetic resonance imaging allows further knowledge of the structural and functional state of the brain generating new possibilities for diagnosis and prognosis in patients undergoing neurorehabilitation therapy. Neurological rehabilitation processes can be quantified and they can reveal certain postlesional neuroplasticity dynamic processes that the central nervous system possesses.

Conectividad funcional en un paciente con alucinaciones complejas. Un caso de autoscopia / Functional connectivity in a patient with complex hallucinations. A case of autoscopy

La autoscopia, del griego autos (sí mismo) y skopeo (mirar), son alucinaciones complejas durante las cuales el paciente experimenta una duplicación visual de su cuerpo. El presente artículo discute algunos correlatos de conectividad cerebral obtenida por resonancia funcional en reposo, en una paciente con epilepsia refractaria y alucinaciones autoscópicas durante sus crisis. El objetivo es presentar los hallazgos por neuroimágenes funcionales de una paciente que presenta alucinaciones del tipo autoscópico. Como parte del protocolo de evaluación de pacientes con epilepsia refractaria se realiza examen de videomonitoreo electroencefalográfico, imágenes de tomografía por emisión de positrones e imágenes de resonancia magnética funcional en reposo a una paciente que sufre alucinaciones autoscópicas durante las crisis. La información obtenida por estos estudios se correlaciona con la información clínica. En la paciente, el estudio de tomografía por emisión de positrones y el videomonitoreo electroencefalográfico indican alteraciones en el lóbulo occipital derecho, hallazgos que coinciden con reportes en la literatura sobre autoscopia. La sincronización neuronal, medida por resonancia funcional, es anormal en la misma región alterada en la tomografía por emisión de positrones, permitiendo relacionar el fenómeno autoscópico con cambios de la conectividad cerebral. La paciente cuenta con características clínicas de alucinación autoscópica. La resonancia magnética indica zonas con alteraciones de la dinámica cerebral que, en el caso de la paciente, coinciden con regiones reportadas en la literatura. El presente estudio aporta evidencias sobre el papel de los mecanismos de sincronización neuronal y la percepción de alucinaciones.

Autoscopy, from Greek autos (self) and skopeo (looking at), are complex hallucinations wherein the patient feels a visual duplication of his body. The current paper presents some brain connectivity correlates, obtained from resting state functional magnetic resonance, in a patient with refractory epilepsy who suffers autoscopic hallucinations during her seizures. Introduce the functional neuroimaging findings in a patient with autoscopic hallucinations. As part of the evaluation protocol for patients with refractory epilepsy, electroencephalographic video monitoring, positron emission tomography and resting state functional magnetic resonance imaging, were done to a patient that suffers autoscopic hallucinations during her crisis. The information obtained from those studies are correlated with clinical information. In the patient, the positron emision tomography and the electroencephalographic video monitoring study indicate an injury in the right occipital lobe, findings that coincide with previous literature report about autoscopy. The neuronal synchronization, measured by functional resonance, is abnormal in the same region where is altered the positron emision tomography imaging, enabling to relate the autoscopy phenomena with brain connectivity alterations. The patient has clinical features of autoscopic hallucination. MRI indicates areas with altered brain dynamics in the case of the patient coincide with regions reported in the literature. This study provides evidence on the role of neuronal synchronization mechanisms and the perception of hallucinations.

Aplicación de técnicas avanzadas de neuroimágenes en rehabilitación motora / Application of advanced neuroimaging in motor rehabilitation

Introducción. La resonancia magnética funcional es una técnica no invasiva que permite el mapeo cerebral y la visualización de redes de conectividad. La hemiparesia posterior a un accidente cerebrovascular constituye un buen modelo biológico para estudiar los cambios en la conectividad cerebral. El uso de este modelo se puede expandir si se obtiene información antes y después de la rehabilitación neurológica. Objetivo. Presentar los hallazgos por neuroimágenes funcionales de un paciente con accidente cerebrovascular antes y después del tratamiento de rehabilitación neurológica. Materiales y métodos. Como parte del protocolo de rehabilitación neurológica se tomaron imágenes de resonancia antes y después del tratamiento con un equipo que operaba a 1,5 T. Se obtuvieron imágenes volumétricas potenciadas en T1, imágenes de difusión para tractografía, imágenes de resonancia funcional con el paciente en reposo y haciendo movimientos de pinza con la mano derecha. Resultados. Se obtuvieron mapas funcionales antes y después de la terapia, los cuales se presentan conjuntamente con las imágenes de conectividad estructural obtenidas mediante tractografía. Se observó que los cambios clínicos estaban acompañados de cambios en los patrones de activación obtenidos por resonancia magnética funcional. Conclusión. La versatilidad que ofrece la resonancia magnética permite conocer el estado funcional y estructural del cerebro, generando así nuevas posibilidades de diagnóstico y pronóstico en pacientes que reciben rehabilitación neurológica, con lo que se pueden cuantificar y develar ciertos procesos dinámicos de plasticidad neuronal posteriores a una lesión, que son propios del sistema nervioso central.

Introduction: Functional magnetic resonance imaging is a noninvasive technique that allows mapping and visualizing of brain connectivity networks. The hemiparesis after a stroke is a good biological model to study changes in brain connectivity. This model can be expanded if information is obtained before and after neurorehabilitation therapy. Objective: To present the functional neuroimaging findings in a patient with stroke before and after performing neurorehabilitation therapy. Materials and methods: As part of the neurorehabilitation protocol, resonance imaging was performed before and after treatment with an equipment operating at 1.5 T. Volumetric T1-weighted images, diffusion images for tractography, functional resonance images with the patient at rest and with the patient performing pincer movement with the right hand were obtained. Results: Functional maps before and after therapy were obtained, which are presented together with structural connectivity images obtained by tractography. Clinical changes can be seen accompanied by changes in activation patterns obtained by functional magnetic resonance imaging. Conclusion: The versatility of magnetic resonance imaging allows further knowledge of the structural and functional state of the brain generating new possibilities for diagnosis and prognosis in patients undergoing neurorehabilitation therapy. Neurological rehabilitation processes can be quantified and they can reveal certain postlesional neuroplasticity dynamic processes that the central nervous system possesses.

Creación de plantillas personalizadas para la implementación de morfometría basada en vóxeles / Custom Template Construction to Implement Voxel-Based Morphometry

Introducción: La morfometría basada en vóxeles es una técnica desarrollada para caracterizar diferencias cerebrales in vivo, usando imágenes estructurales por resonancia magnética de manera automática, sin necesidad de definir regiones de interés. Dentro del procesamiento de las imágenes se encuentran tareas que requieren el uso de plantillas de referencia. Sin embargo, el uso de plantillas que difieran demográficamente de la población de estudio puede llevar a interpretaciones erróneas de los resultados. Objetivo: Describir la construcción de plantillas que capturen la variabilidad y las características propias de la población en estudio, adaptando el uso de la morfometría basada en vóxeles. Metodología: De una población de 50 sujetos voluntarios sanos se construyeron plantillas de sustancia gris, sustancia blanca y líquido cefalorraquídeo, que luego fueron comparadas con la plantilla del Instituto Neurológico de Montreal, y posteriormente utilizadas como datos de referencias en los procesamientos de morfometría basada en vóxeles bajo una prueba de género. Los resultados fueron comparados con los obtenidos al utilizar las plantillas del instituto y validados según estudios similares presentados en la literatura. Resultados: El uso del conjunto de algoritmos DARTEL en la metodología propuesta permitió generar plantillas con mejor detalle morfológico, y la implementación de estas en morfometría basada en vóxeles aumentó la sensibilidad de la técnica. Conclusiones: Las plantillas generadas representan mejor la variabilidad local de la población y posibilitan la personalización de técnicas como la morfometría basada en vóxeles, al mejorar los resultados de la segmentación y otras tareas de procesamiento.

Introduction: Voxel-based morphometry (VBM) has been developed to characterize in vivo brain anatomic and functional differences using magnetic resonance imaging (MRI) automatically, without having to define regions of interest. Compared to other techniques, VBM does not require manual delineation of regions of interest. Image processing includes tasks which require the use of reference templates. However, the use of templates that differ demographically from the studied population could lead to incorrect interpretations of the results. Objective: To scribe the construction of templates which describe the variability and the specific morphological characteristics of the studied population. Methodology: Gray matter, white matter and cerebrospinal fluid templates were built from a population of 50 willing healthy persons. These templates were then compared with the template of the Montreal Neurological Institute and were subsequently used as reference data in the processing of voxel-based morphometry in a gender test. The results were compared with those obtained by using templates of the Montreal Neurological Institute and validated by similar studies reported in the literature. Results: We found that the use of DARTEL algorithms in the suggested methodology can generate better morphological detail templates, and the implementation of their algorithms in voxelbased morphometry increases the sensitivity of the technique. Conclusions: Our templates improve local variability of the population and enable personalization of techniques such as voxel-based morphometry, by improving segmentation results and other processing tasks.

Construcción de una escala de violencia intrafamiliar, Cuenca - Ecuador 2013 / Construction of intra-family violence scale. Cuenca- Ecuador. 2013

Objetivo: Construir una escala para la medición del tipo y severidad de violencia intra-familiar en las usuarias que acuden a las Unidades de Violencia en la ciudad de Cuenca, Junio-Noviembre de 2013.Método: Estudio cuantitativo de construcción de prueba diagnóstica. Población referencial 2.555 mujeres, usuarias de las Comisarías de la Mujer, Cuenca 2013. La muestra se obtuvo con un nivel de confianza del 95%, prevalen-cia esperada del 60%, peor aceptable del 65% n= 324 mujeres más 10% de posibles pérdidas, muestra total 356 participantes. Se utilizó un formulario tipo Likert estructurado ad hoc de-nominado VIFJ4 para medir tipo y severidad de la violencia intrafamiliar. La consistencia in-terna de la prueba diagnóstica determinada por Alfa de Cronbach. Resultados: La escala VIFJ4 mantiene su consistencia interna a través del tiempo, con un Alfa de Cronbach inicial de 0,938, y un Alfa de Cronbach Retest de 0,944. Conclusiones: La escala VIFJ4 es un instrumen-to útil para el diagnóstico del tipo y severidad de la violencia intrafamiliar.

Objective: To build up a scale in order to mea-sure the type and severity of domestic violence upon women attended at the Violence Units located in Cuenca, June - November 2013.Methods: Quantitative, Buildup of a diagnos-tic test. Reference was made to a universe of 2555 women who reported domestic violence at the "Comisarías de la Mujer" in Cuenca du-ring the year 2011. The sample was obtained with a confidence level of 95%, an expected prevalence of 60%, a worst acceptable of 65%, n= 324 women, also calculating a possible 10% lost cases thereby obtaining a sample of 356 participants. A form type Likert structured for this purpose named VIFJ4 was used to deter-mine the type and severity of domestic violen-ce. Internal validity of this diagnostic test was determined with Cronbach ́s Alpha. Results: This test maintains its internal consisten-cy throughout time; it has an initial Cronbach ́s Alpha of 0,938, and a retest Cronbach ́s Alpha of 0,944. Conclusions: The test VIFJ4 maintains its inter-nal consistency being useful to evaluate the type and severity of domestic violence.

Volumen y función hipocampal en epilepsia del lóbulo temporal medial / Volume and hippocampal function in medial temporal lobe epilepsy

Introducción: La resonancia magnética funcional (fMRI ) es fundamental en la evaluación de lenguaje y memoria en pacientes con epilepsia del lóbulo temporal. También ha permitido observar cómo las estructuras de la corteza medial temporal tienen lateralidad funcional de acuerdo con la dominancia del lenguaje, con un hemisferio especializado tanto en los aspectos expresivos y receptivos del lenguaje como en la memorización de material verbal. Objetivo: Relacionar la integridad del hipocampo izquierdo con el grado de asimetría de la dominancia del lenguaje vista por fMRI. Materiales y métodos: Mediante resonador de 1,5 T se obtienen imágenes con información en T1 volumétricas y EPI con información en T2 durante la ejecución de paradigmas de codificación de escenas complejas, generación de palabras y decisión semántica en un conjunto de 12 individuos sanos y en diferentes pacientes candidatos a cirugía de epilepsia. Resultados: La volumetría automatizada de los hipocampos del grupo control no muestra asimetría significativa. En los diferentes pacientes con esclerosis hipocampal se obtienen índices numéricos que corroboran la implicación de la integridad del hipocampo izquierdo con los índices de asimetría en las pruebas de lenguaje. Conclusiones: En los resultados de la implementación del protocolo de memoria y lenguaje por fMRI para pacientes con epilepsia del lóbulo temporal se destacan las evidencias obtenidas acerca de la implicación del hipocampo en la red del lenguaje y el efecto que tiene la afectación del hipocampo izquierdo en los patrones de migración del lenguaje hacia el hemisferio contralateral.

Introduction: The functional Magnetic Resonance (fMRI) is important in the evaluation of language and memory of patients with temporal lobe epilepsy. The fMRI has also enabled to observe how the structures in the medial temporal cortex have functional laterality according to the dominance of language, with a hemisphere which is specialized in the expressive and receptive aspects of language and the encoding of verbal material. Objective: To relate the left hippocampus integrity with the degree of asymmetry of the language dominance seen by fMRI. Materials and methods: Images with T1 volumetric information and EPI with T2 information are obtained using a 1.5T magnetic resonator, during the execution of complex scenes encoding paradigms, as well as during the generation of words and a semantic decision in a set of 12 control subjects and different patients who are potential candidates for epilepsy surgery. Results: The automatized volumetric properties of the control group hippocampus do not show significant asymmetry. Indifferent patients with hippocampal sclerosis, numerical indexes are obtained, which are in accordance with the implication of the integrity of the left hippocampus with the asymmetry indexes in the language paradigms. Conclusions: Among the results of the implementation of the memory and language protocol, using fMRI for patients with temporal lobe epilepsy, one can emphasize the evidences obtained using fMRI regarding the implications of the left hippocampus in the language network and the effects of its dysfunction in the migration patterns of language towards the contralateral hemisphere.

Implementación de un método para la visualización de electrodos subdurales en cirugía de epilepsia / Implementation of a method to visualize subdural electrodes in epilepsy surgery

Introducción: Los electrodos subdurales son muy importantes en el estudio de un alto porcentaje de pacientes evaluados para cirugía de epilepsia. La actividad eléctrica fuera del rango de la electroencefalografía de superficie puede ser capturada a nivel subdural. Los procedimientos de lectura y estimulación para localizar la zona epileptógena usando electrodos subdurales están bien establecidos y las complicaciones son bajas, aunque tienden a aumentar con el tiempo de permanencia del paciente con los electrodos. Objetivo: Proponer un método para la visualización de electrodos subdurales que permita agilizar la toma de decisiones. Materiales y métodos: Imágenes volumétricas de resonancia magnética potenciadas en T1 con equipo que opera a 1,5 Tesla y de tomografía multidetector de 6 canales se toman luego del proceso de implantación de los electrodos subdurales. Mediante operaciones de procesamiento de imágenes se obtienen representaciones 3D de los electrodos y la corteza cerebral. Estas representaciones son utilizadas durante el proceso de búsqueda del foco epileptógeno. Resultados: La técnica ha sido utilizada de manera rutinaria por el grupo de cirugía de epilepsia aportando información relevante sobre la ubicación de los electrodos luego de su proceso de implantación. Conclusiones: La técnica presentada es reproducible y ha mostrado ser útil en el grupo de cirugía de epilepsia al facilitar la discusión y validación de hipótesis acerca de la ubicación del foco epileptógeno.

Introduction: Subdural electrodes play an important role in the study of a high percentage of patients evaluated for epilepsy surgery. The electrical activity outside the surface electroencephalography range can be captured at the subdural level. The reading and stimulation procedures used to locate the epileptogenic zone using subdural electrodes are well established and complications are low. However, these complications tend to increase with the time of permanence of the electrodes in the patient. Objective: To suggest a method for the visualization of subdural electrodes for faster decision-making. Materials and Methods: Volumetric MRI images, potentiated in T1-using equipment operating at 1.5T and with multi detector 6-channel CT-are acquired after the implementation of subdural electrodes. A 3D visualization is acquired through image processing of the electrodes and the cortex. This visualization is used while searching the epileptogenic focus. Results: This technique has been routinely used by the epilepsy surgery group, which in turn supplies relevant information about the location of the subdural electrodes. Conclusions: This technique can be reproduced. It has been useful in the epilepsy surgery group, as it has eased the discussion and validation of hypotheses regarding the location of the seizure focus.

Evaluación de la conectividad cerebral mediante teoría de grafos / Cerebral Connectivity Analysis Using Graph Theory

Introducción: Las últimas técnicas de análisis de RM funcional permiten medir el cambio espontáneo de la señal BOLD en reposo. Los métodos de análisis derivados de estos estudios se dividen en: mapas de conectividad funcional y conectividad cerebral por grafos. Un grafo permite representar cualquier sistema compuesto de elementos interconectados. Este enfoque es, en teoría, aplicable a cualquier escala, modalidad o cantidad de información neurocientífica. Objetivo: Presentar los resultados de la implementación de un algoritmo para analizar la conectividad funcional por teoría de grafos. Materiales: Resonador de 1,5 T para obtener imágenes con información en T1 volumétricas, para capturar la información estructural, y EPI con información en T2, para capturar la señal BOLD en reposo, de 19 individuos sanos y 1 paciente con epilepsia con diagnóstico imaginológico de displasia cortical. Se les solicitó permanecer despiertos, con los ojos cerrados, evitando pensar en algo particular. Los estudios fueron preprocesados y luego analizados mediante un grafo construido a partir de 8196 vóxeles de la corteza cerebral. Resultados: El enfoque permite obtener imágenes que codifican el patrón de correlación que tiene la señal BOLD en un vóxel con todos los otros vóxeles en la corteza cerebral. Este enfoque es replicable. Conclusiones: Se ha presentado un enfoque para analizar la conectividad funcional por teoría de grafos que permite cuantificar el grado de correlación de la señal BOLD en una muestra de vóxeles de la corteza cerebral y se ha presentado cómo cambia el patrón de correlación en un caso de epilepsia del lóbulo frontal.

Introduction: The latest analysis techniques of functional magnetic resonance enable to measure the spontaneous change of the BOLD signal during rest periods. The analysis and presentation methods which derive from the information obtained from these studies are divided in two approaches: functional connectivity at rest and functional connectivity using graph theory. A graph enables the representation of any system composed of interconnected elements. This approach is applicable to any scale, modality or quantity of neuroscientific data. Objective: To present the results of the implementation of one algorithm for the analysis of functional connectivity using graph theory. Materials and methods: The use of a 1.5 T magnetic resonator to obtain T1 volumetric images, in order to capture the structural information and the use of EPI with information in T2 in order to capture the BOLD signal at rest, in 19 healthy patients and 1 patient with epilepsy with a imaging diagnosis of cortical dysplasia. The patients were awake during the acquisition. Their eyes were closed, and they avoided specific thoughts. The studies are preprocessed using the approach reported in the literature and are analyzed with graphs using 8196 points of the cerebral cortex. Results: The presented approach enables to obtain images which encode the correlation pattern in the BOLD signal in a single. Meanwhile,the other voxels are in the cerebral cortex. This approach is replicable with other patients. Conclusions: An approach has been presented in order to analyze functional connectivity using graph theory. This enables to quantify the degree of correlation of a BOLD signal, in a voxel sample from the cerebral cortex. This approach also indicates how the correlation pattern changes in case of frontal lobe epilepsy.

Imagen en demencia / Imaging in dementia

La demencia en un síndrome que incluye alteraciones cognitivas y neuropsiquiátricas que afectan al menos dos dominios, como la memoria, el lenguaje, las habilidades visuoespaciales, las funciones ejecutivas, la personalidad y el comportamiento. Para hablar de demencia, estas alteraciones han de representar una disminución de los niveles funcionales previos e interferir con las funciones sociales y las actividades de la vida diaria. Los estudios de neuroimagen y especialmente la resonancia magnética (RM) hacen parte del estudio inicial de un paciente con un síndrome demencial, debido a que sirve para identificar causas potencialmente reversibles de la demencia, reconocer lesiones vasculares o atrofias focales y, según los hallazgos, poder diferenciar entre los diferentes tipos de demencia. Los avances en el campo de la neuroimagen y el uso de técnicas de neuroimagen funcional y metabólica han permitido encontrar sustratos anatómicos y funcionales, tanto en el envejecimiento normal como en el síndrome demencial avanzado, lo cual ha aportado al desarrollo de nuevas opciones terapéuticas

Dementia is a syndrome which includes cognitive and neuropsychiatric alterations which affect at least two domains, such as memory, language, visual-spatial abilities, executive functions, personality and behavior. Regarding dementia, all these alterations represent a decrease in the prior functional level of the patient, which interferes with social tasks and daily activities. Neuroimaging techniques, especially MRI, are part of the initial study of a patient with dementia, because it serves to identify potentially reversible causes of dementia, as well as recognize vascular lesions or focal atrophy. It can also differentiate among the different types of dementia, according to the findings. Advances in the field of neuroimaging, and the use of functional neuroimaging techniques and nuclear medicine have enabled to find anatomical and functional substrates, both in the normal aging process and in advanced dementia, which has contributed to the development of new therapeutic options.