Conectividad funcional a partir de la perfusión cerebral en pacientes epilépticos y con enfermedad de Parkinson / Functional connectivity from cerebral perfusion in patients with epilepsy and Parkinson's disease

Introducción: La epilepsia y la enfermedad de Parkinson han sido descritos como trastornos de redes neurales. El estudio de la conectividad por modalidades moleculares puede ser más relevante fisiológicamente que los basados en señales hemodinámicas. Objetivo: Proponer una metodología para la descripción de patrones de conectividad funcional a partir de la perfusión cerebral por tomografía por emisión de fotón único. Métodos: La metodología incluye cuatro pasos principales: preprocesamiento espacial, corrección del volumen parcial, cálculo del índice de perfusión y obtención de la matriz de conectividad funcional mediante el coeficiente de correlación de Pearson. Se implementó en 25 pacientes con distintos trastornos neurológicos: 15 con epilepsia farmacorresistente y 10 con enfermedad de Parkinson. Resultados: Se encontraron diferencias significativas entre los índice de perfusión de varias regiones de los hemisferios ipsilateral y contralateral tanto en pacientes con epilepsia del lóbulo frontal como en pacientes con epilepsia del lóbulo temporal. Igual resultado se obtuvo en los pacientes con enfermedad de Parkinson con distintos estadios de la enfermedad. Para cada grupo se identificaron patrones de conectividad funcional que involucran a regiones relacionadas con la patología en estudio. Conclusiones: Con el desarrollo de esta metodología se ha demostrado que la tomografía por emisión de fotón único aporta información valiosa para estudiar la organización de las redes funcionales del cerebro. Futuras investigaciones con mayor número de pacientes contribuirían a hacer inferencias sobre los correlatos neurales de los distintos trastornos cerebrales(AU)

Introduction: Epilepsy and Parkinson's disease have been described as disorders of neural networks. The study of connectivity by molecular modalities may be more physiologically relevant than those based on hemodynamic signals. Aim: The aim of the present work is to propose a methodology for the description of functional connectivity patterns from brain perfusion by single photon emission tomography. Methods: The methodology includes four main steps: spatial preprocessing, partial volume correction, calculation of the perfusion index and obtaining the functional connectivity matrix using Pearson's correlation coefficient. It was implemented in 25 patients with different neurological disorders: 15 with drug-resistant epilepsy and 10 suffering Parkinson's disease. Results: Significant differences were found between the perfusion indexes of various regions of the ipsilateral and contralateral hemispheres in both patients with frontal lobe epilepsy and patients with temporal lobe epilepsy. The same result was obtained in Parkinson's disease patients with different stages of the disease. For each group, functional connectivity patterns involving regions related to the pathology under study were identified. Conclusions: With the development of this methodology, it has been demonstrated that single photon emission tomography provides valuable information to study the organization of functional brain networks. Future research with a larger number of patients would contribute to make inferences about the neural correlates of the different brain disorders(AU)

Herramienta basada en código abierto para el cálculo de blindaje en las instalaciones de Medicina Nuclear / Open Source Based Tool for Shielding Calculation in Nuclear Medicine Installations

Uno de los requerimientos indispensables en el diseño de las instalaciones donde se trabaja con radiación ionizante es la determinación del espesor adecuado de las paredes, pisos, techo y puertas de los locales, que garanticen dosis por debajo de las restricciones establecidas por la autoridad regulatoria. El objetivo del presente trabajo es desarrollar una herramienta interactiva, libre y de código abierto para calcular los blindajes requeridos en una instalación de Medicina Nuclear. En el código, desarrollado en Phyton utilizando el entorno interactivo Jupiter Notebook, se incluyó el análisis tanto para Tomografía por Emisión de Fotón Único como para Tomografía por Emisión de Positrones. La herramienta fue implementada para el cálculo de los blindajes de un departamento de Medicina Nuclear del Centro Internacional de Restauración Neurológica (CIREN). Esta herramienta libre y de código abierto facilita los cálculos de blindaje aumentando la velocidad, lo que contribuye a lograr una optimización de la protección radiológica, pero también puede usarse como herramienta pedagógica(AU)

One of the indispensable requirements in the design of the facilities where ionizing radiation is used is the determination of the adequate thickness of the walls, floors, ceiling and doors of the premises, which guarantee doses below the restrictions established by the regulatory authority. The goal of this work is to develop an interactive, free and open source tool to calculate the shields required in a Nuclear Medicine installation. Analysis for both Single Photon Emission Tomography and Positron Emission Tomography was included in the code, developed in Phyton using the interactive Jupiter Notebook environment. The tool was implemented to calculate the shields of a Nuclear Medicine department of the International Center for Neurological Restoration (CIREN). This free and open source tool facilitates shielding calculations by increasing speed, which contributes to the optimization of radiation protection, but can also be used as a pedagogical tool(AU)

A Novel Noninvasive Approach Based on SPECT and EEG for the Location of the Epileptogenic Zone in Pharmacoresistant Non-Lesional Epilepsy.

Background and objectives: The aim of this study is to propose a methodology that combines non-invasive functional modalities electroencephalography (EEG) and single photon emission computed tomography (SPECT) to estimate the location of the epileptogenic zone (EZ) for the presurgical evaluation of patients with drug-resistant non-lesional epilepsy. Materials and Methods: This methodology consists of: (i) Estimation of ictal EEG source imaging (ESI); (ii) application of the subtraction of ictal and interictal SPECT co-registered with MRI (SISCOM) methodology; and (iii) estimation of ESI but using the output of the SISCOM as a priori information for the estimation of the sources. The methodology was implemented in a case series as an example of the application of this novel approach for the presurgical evaluation. A gold standard and a coincidence analysis based on measures of sensitivity and specificity were used as a preliminary assessment of the proposed methodology to localize EZ. Results: In patients with good postoperative evolution, the estimated EZ presented a spatial coincidence with the resection site represented by high values of sensitivity and specificity. For the patient with poor postoperative evolution, the methodology showed a partial incoherence between the estimated EZ and the resection site. In cases of multifocal epilepsy, the method proposed spatially extensive epileptogenic zones. Conclusions: The results of the case series provide preliminary evidence of the methodology's potential to epileptogenic zone localization in non-lesion drug-resistant epilepsy. The novelty of the article consists in estimating the sources of ictal EEG using SISCOM result as a prior for the inverse solution. Future studies are necessary in order to validate the described methodology. The results constitute a starting point for further studies in order to support the clinical reliability of the proposed methodology and advocate for their implementation in the presurgical evaluation of patients with intractable non-lesional epilepsy.

Spontaneous Subdural Hematoma and Behavioral Changes Due to a Dural Arteriovenous Fistula. A Case Report and Literature Review.

Dural arteriovenous fistulas (DAVFs) represent 10-15% of intracranial arteriovenous malformations. Of these, only 12-29% cause intracranial hemorrhage. The presentation of DAVF as a subdural hematoma (SDH) and intraparenchymal hemorrhage (IPH) is infrequent; additionally, behavioral changes are not common among these patients. We report, for the first time in our country, the case of a 23-year-old man with no history of head injury, in which a brain computed tomography (CT) scan revealed SDH and IPH with behavioral disturbances. The angiotomography showed ecstatic venous vessels, indicating the presence of a DAVF, which was later confirmed by cerebral angiography. Endovascular therapy, which followed the clinical diagnosis, resulted in satisfactory evolution two years after treatment. A review of the literature concerning cases with DAVF and behavioral disturbances is presented. DAVF may lead to cognitive impairment, behavioral changes, and dementia as a result of diffuse white matter and thalamus modifications related to venous ischemia, and it should be considered as a reversible cause of vascular dementia.

Episodic memory in mild cognitive impairment inversely correlates with the global modularity of the cerebral blood flow network.

Cerebral blood flow (CBF) SPECT is an interesting methodology to study brain connectivity in mild cognitive impairment (MCI) since it is accessible worldwide and can be used as a biomarker of neuronal injury in MCI. In CBF SPECT, connectivity is grounded in group-based correlation networks. Therefore, topological metrics derived from the CBF correlation network cannot be used to support diagnosis and prognosis individually. However, methods to extract the individual patient contribution to topological metrics of group-based correlation networks were developed although not yet applied to MCI patients. Here, we investigate whether the episodic memory of 24 amnestic MCI patients correlates with individual patient contributions to topological metrics of the CBF correlation network. We first compared topological metrics of the MCI group network with the network corresponding to 26 controls. Metrics that showed significant differences were then used for the individual patient contribution analysis. We found that the global network modularity was increased while global efficiency decreased in the MCI network compared to the control. Most importantly, we found that episodic memory inversely correlates with the patient contribution to the global network modularity, which highlights the potential of this approach to develop a CBF connectivity-based biomarker at the individual level.

Subtle alterations in cerebrovascular reactivity in mild cognitive impairment detected by graph theoretical analysis and not by the standard approach.

There is growing support that cerebrovascular reactivity (CVR) in response to a vasodilatory challenge, also defined as the cerebrovascular reserve, is reduced in Alzheimer's disease dementia. However, this is less clear in patients with mild cognitive impairment (MCI). The current standard analysis may not reflect subtle abnormalities in CVR. In this study, we aimed to investigate vasodilatory-induced changes in the topology of the cerebral blood flow correlation (CBFcorr) network to study possible network-related CVR abnormalities in MCI. For this purpose, four CBFcorr networks were constructed: two using CBF SPECT data at baseline and under the vasodilatory challenge of acetazolamide (ACZ), obtained from a group of 26 MCI patients; and two equivalent networks from a group of 26 matched cognitively normal controls. The mean strength of association (SA) and clustering coefficient (C) were used to evaluate ACZ-induced changes on the topology of CBFcorr networks. We found that cognitively normal adults and MCI patients show different patterns of C and SA changes. The observed differences included the medial prefrontal cortices and inferior parietal lobe, which represent areas involved in MCI's cognitive dysfunction. In contrast, no substantial differences were detected by standard CVR analysis. These results suggest that graph theoretical analysis of ACZ-induced changes in the topology of the CBFcorr networks allows the identification of subtle network-related CVR alterations in MCI, which couldn't be detected by the standard approach.

Predictores de enfermedad de alzheimer en pacientes con deterioro cognitivo leve / Predictors for alzheimer's disease in patients with mild cognitive impairment

El objetivo de la investigación fue identificar marcadores clínicos predictores de Enfermedad de Alzheimer (EA) en pacientes con Deterioro Cognitivo Leve (DCL). Se realizó un estudio longitudinal que incluyó a pacientes de 50 ó más de edad, divididos en dos grupos (DCL = 40 y Controles = 26). Se recibieron en la consulta de Demencia del Hospital «Dr. Carlos J. Finlay,¼ entre noviembre del 2003 y julio del 2006. A todos se les aplicó el mini-examen-mental (MMSE) y tres subtest de la escala de memoria de Wechsler. El 20.5 por ciento de los pacientes con DCL presentaron conversión a EA. El tiempo promedio de conversión fue de 18.12 meses. El promedio de edad fue mayor en aquellos que convirtieron. La escolaridad fue significativamente menor en los pacientes con DCL que presentaron conversión a EA. Los antecedentes patológicos familiares estuvieron presentes en 75 por ciento de los pacientes que convirtieron. El MMSE se comportó similar entre los que convirtieron o no a EA. Las puntuaciones medias de los subtest de Wechsler practicados, fueron inferiores en los que convirtieron a EA; destacándose las obtenidas en Memoria lógica A, Aprendizaje asociativo difícil y puntaje total, como las de mayor valor predictivo de EA.

The goal of this research was to identify clinic markers as Alzheimer's disease (AD) predictors in patients with mild cognitive impairment (MCI). A longitudinal study was accomplished including patients ranging from 50 year's olds and older, which were divided in two groups (MCI=40 and Controls=26). These patients were recruited from memory clinic-based sample at «Dr. Carlos J. Finlay¼ Hospital in a period that lasted from November/2003 to July/2006. Mini Mental State Exam (MMSE) and three subtest of Wechsler memory scale were applied to all of them. A 20.5 percent of patients with MCI exhibited conversion to AD. The average time for conversion was 18.12 month. The average age was higher in those that made conversion. Educational level was significantly lower in patients with MCI that made conversion to Alzheimer. Family pathological records were found in 75 percent of converters patients. Results of MMSE were similar in patients that converted as those that not converted. Mean punctuation of Wechsler subtest was lower in converters patients. Logical memory A, Hard Associative Learning, and Total Score were distinguished as those with bigger predictive value.

Predictores de enfermedad de alzheimer en pacientes con deterioro cognitivo leve / Predictors for alzheimer's disease in patients with mild cognitive impairment

El objetivo de la investigación fue identificar marcadores clínicos predictores de Enfermedad de Alzheimer (EA) en pacientes con Deterioro Cognitivo Leve (DCL). Se realizó un estudio longitudinal que incluyó a pacientes de 50 ó más de edad, divididos en dos grupos (DCL igual a 40 y Controles igiual a 26). Se recibieron en la consulta de Demencia del Hospital Dr Carlos J Finlay, entre noviembre del 2003 y julio del 2006. A todos se les aplicó el mini-examen-mental (MMSE) y tres subtest de la escala de memoria de Wechsler. El 20.5 por ciento de los pacientes con DCL presentaron conversión a EA. El tiempo promedio de conversión fue de 18.12 meses. El promedio de edad fue mayor en aquellos que convirtieron. La escolaridad fue significativamente menor en los pacientes con DCL que presentaron conversión a EA. Los antecedentes patológicos familiares estuvieron presentes en 75 por ciento de los pacientes que convirtieron. El MMSE se comportó similar entre los que convirtieron o no a EA. Las puntuaciones medias de los subtest de Wechsler practicados, fueron inferiores en los que convirtieron a EA; destacándose las obtenidas en Memoria lógica A, Aprendizaje asociativo difícil y puntaje total, como las de mayor valor predictivo de EA(AU)

The goal of this research was to identify clinic markers as Alzheimer's disease (AD) predictors in patients with mild cognitive impairment (MCI). A longitudinal study was accomplished including patients ranging from 50 year's olds and older, which were divided in two groups (MCI equality 40 and Controls equality 26). These patients were recruited from memory clinic-based sample at Dr. Carlos J Finlay Hospital in a period that lasted from November/2003 to July/2006. Mini Mental State Exam (MMSE) and three subtest of Wechsler memory scale were applied to all of them. A 20.5 percent of patients with MCI exhibited conversion to AD. The average time for conversion was 18.12 month. The average age was higher in those that made conversion. Educational level was significantly lower in patients with MCI that made conversion to Alzheimer. Family pathological records were found in 75 percent of converters patients. Results of MMSE were similar in patients that converted as those that not converted. Mean punctuation of Wechsler subtest was lower in converters patients. Logical memory A, Hard Associative Learning, and Total Score were distinguished as those with bigger predictive value(AU)

Métodos para el mejoramiento de la cuantificación relativa del flujo sanguíneo cerebral mediante Spect / Methods for the improvement of the relative quantification of the cerebral sanguineous flow by means of Spect

En este trabajo se aborda la cuantificación relativa del flujo sanguíneo cerebral (FSC) mediante SPECT y cómo mejorar dicha cuantificación con la tecnología existente en nuestro país. Se demuestra que esta cuantificación se puede mejorar por dos vías: mejorando la resolución espacial tomográfica; y generalizando el método de cuantificación relativa que utiliza al cerebelo como región de referencia, considerada la mejor región para el proceso de normalización de las imágenes de SPECT. Con este fin, se desarrollaron y validaron dos métodos. El primer método permite mejorar la resolución espacial en un 18 por ciento, la cual es significativa para aquellos sistemas que no pueden ser modernizados con los más recientes avances tecnológicos. El segundo método consiste en un procedimiento de cuantificación relativa basado en un hecho fisiológico encontrado por los autores no reportado anteriormente. A partir de este hallazgo se define un nuevo valor de referencia, el "Pseudocerebelo", que permite generalizar al cerebelo como región de referencia, aplicable incluso a pacientes con hipoperfusión cerebelosa. Esta experiencia puede ser de utilidad en gran parte de América Latina, teniendo en cuenta que existen condiciones similares desde el punto de vista tecnológico.

Tomograf­a por emisi›n de fotones en la neurolog­a / Single Photon Emission Tomography in neurology

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