Dopaminergic denervation and associated MRI microstructural changes in the nigrostriatal projection in early Parkinson's disease patients.

Loss of dopaminergic neurons in the substantia nigra pars compacta (SNc) and a profound reduction of striatal dopamine are two hallmarks of Parkinson's disease (PD). However, it's unclear whether degeneration starts at the neuronal soma or the striatal presynaptic terminals, and how microstructural degeneration is linked to dopaminergic loss is also uncertain. In this study, thirty de novo PD patients and twenty healthy subjects (HS) underwent 6-[18F]-fluoro-L-dopa (FDOPA) PET and MRI studies no later than 12 months from clinical diagnosis. FDOPA uptake rate (Ki), fractional volume of free-water (FW), and iron-sensitive R2* relaxometry were quantified within nigrostriatal regions. Inter-group differences (PD vs HS) were studied using non-parametric statistics and complemented with Cohen's d effect sizes and Bayesian statistics. Correlation analyses were performed exploring biomarker dependencies and their association with bradykinesia scores. PD patients exhibited a significant decline in nigrostriatal dopaminergic activity, being post-commissural putamen (-67%) and posterolateral SNc (-11.7%) the most affected subregions within striatum and SNc respectively. Microstructural alterations (FW) were restricted to the hemisphere corresponding to the most affected side and followed similar spatial gradients as FDOPA Ki (+20% in posterior putamen and +11% in posterolateral SNc). R2* revealed no relevant significant changes. FDOPA and FW were correlated within the posterolateral SNc, and clinical severity was associated with FDOPA Ki loss. The asymmetry between striatal and SNc changes for both dopaminergic depletion and microstructural degeneration biomarkers is consistent with a neurodegenerative process that begins in the striatal terminals before progressing toward the cell bodies in the SNc.

Spatio-temporal correlations from fMRI time series based on the NN-ARx model.

For the purpose of statistical characterization of the spatio-temporal correlation structure of brain functioning from high-dimensional fMRI time series, we introduce an innovation approach. This is based on whitening the data by the Nearest-Neighbors AutoRegressive model with external inputs (NN-ARx). Correlations between the resulting innovations are an extension of the usual correlations, in which mean-correction is carried out by the dynamic NN-ARx model instead of the static, standard linear model for fMRI time series. Measures of dependencies between regions are defined by summarizing correlations among innovations at several time lags over pairs of voxels. Such summarization does not involve averaging the data over each region, which prevents loss of information in case of non-homogeneous regions. Statistical tests based on these measures are elaborated, which allow for assessing the correlation structure in search of connectivity. Results of application of the NN-ARx approach to fMRI data recorded in visual stimuli experiments are shown. Finally, a number of issues related with its potential and limitations are commented.

Brain magnetic resonance imaging findings in acute relapses of neuromyelitis optica spectrum disorders.

We studied cranial magnetic resonance imaging (MRI) lesions in three women with acute attacks of recurrent longitudinally extensive transverse myelitis (r-LETM), recurrent-optic neuritis (r-ON) and r-LETM-CNS. Neuromyelitis Optica -immunoglobulin (IgG) antibody was positive in all cases. Brain MRI (1.5 Tesla) was performed according to protocol from consortium MS centre. We described the cranial lesions in brain MRI of acute relapses. These lesions were different from MS, most had an asymptomatic course which disappeared with time, protocol from consortium of MS centre criteria for brain MRI and seropositivity of NMO-IgG are useful tools for differentiate acute lesions of NMO/MS.

[Computerized atlas for image-guided stereotactic functional neurosurgery]. / Atlas computarizado para la planificación de neurocirugías estereotácticas funcionales guiadas por imágenes.

OBJECTIVE: A computerized version of the Schaltenbrand and Wahren's stereotactic brain atlas for image-guided functional neurosurgery planning has been developed and integrated into our PC-based planning system. METHODS: The SW atlas plates were digitized, contoured and labeled for both hemispheres. The computerized atlas may be interactively registered with patient's data using linear and non-linear transformation. The implemented computational tools and applications are presented. RESULTS: Our computer system permits navigation through original or reconstructed slices, multiple-views synchronization and zoom to improve the localization of the commisures and the surgical targets, likewise the optimum path selection. Atlas position in the target's region can be interactively actualized and lesion's position and volume may be simulated. CONCLUSIONS: Its benefits of this approach include increased accuracy of target definition, decreased the number of electrode tracts and for instance the time of the surgery, and reduced surgical complications.

Atlas computarizado para la planificación de neurocirugías estereotácticas funcionales guiadas por imágenes / Computerized atlas for image-guided stereotactic functional neurosurgery

Objetivo. Desarrollar un atlas estereotáctico computarizado de Schaltenbrand y Wahren para la planificación de neurocirugías funcionales guiadas por imágenes. Este atlas está integrado al sistema de planificación STASSIS, desarrollado para computadoras personales. Métodos. Los cortes originales del atlas fueron digitalizados y se trazaron los contornos para ambos hemisferios. El corregistro del atlas con las imágenes del paciente se realiza mediante transformaciones rígidas y no rígidas. Se presentan las herramientas computacionales implementadas y sus aplicaciones durante el procedimiento quirúrgico. Resultados. El sistema permite la navegación continua tanto a través de los cortes originales como de las reconstrucciones, la sincronización de múltiples vistas y el uso de ampliaciones, lo que permite incrementar la exactitud en la localización de las comisuras y los blancos quirúrgicos, así como la selección óptima de las trayectorias. Los contornos del atlas se pueden ajustar a la anatomía del paciente. La posición del atlas en la región el blanco se puede actualizar de forma interactiva y simular la posición y volumen de las lesiones. Conclusiones. Los beneficios de esta metodología incluyen la mejora en la exactitud de la localización del primer blanco quirúrgico, disminución del número de trayectos con los electrodos y, por tanto, del tiempo de la cirugía, y la reducción de las posibles complicaciones quirúrgicas

Objective. A computerized version of the Schaltenbrand and Wahren's stereotactic brain atlas for image-guided functional neurosurgery planning has been developed and integrated into our PC-based planning system. Methods. The SW atlas plates were digitized, contoured and labeled for both hemispheres. The computerized atlas may be interactively registered with patient's data using linear and non-linear transformation. The implemented computational tools and applications are presented. Results. Our computer system permits navigation through original or reconstructed slices, multiple-views synchronization and zoom to improve the localization of the commissures and the surgical targets, likewise the optimum path selection. Atlas position in the target’s region can be interactively actualized and lesion’s position and volume may be simulated. Conclusions. Its benefits of this approach include increased accuracy of target definition, decreased the number of electrode tracts and for instance the time of the surgery, and reduced surgical complications

Atlas computarizado para la planificación de neurocirugías estereotácticas funcionales guiadas por imágenes / Computerized atlas for image-guided stereotactic functional

Objetivo. Desarrollar un atlas estereotáctico computarizadode Schaltenbrand y Wahren para la planificación de neurocirugías funcionales guiadas por imágenes.Este atlas está integrado al sistema de planificación STASSIS, desarrollado para computadoras personales.Métodos. Los cortes originales del atlas fueron digitalizados y se trazaron los contornos para ambos hemisferios. El corregistro del atlas con las imágenes del paciente se realiza mediante transformaciones rígidas y no rígidas. Se presentan las herramientas computacionales implementadas y sus aplicaciones durante el procedimiento quirúrgico.Resultados. El sistema permite la navegación continuatanto a través de los cortes originales como de las reconstrucciones, la sincronización de múltiples vistasy el uso de ampliaciones, lo que permite incrementar la exactitud en la localización de las comisuras y los blancos quirúrgicos, así como la selección óptima de las trayectorias.Los contornos del atlas se pueden ajustar a la anatomía del paciente. La posición del atlas en la regióndel blanco se puede actualizar de forma interactiva y simular la posición y volumen de las lesiones.Conclusiones. Los beneficios de esta metodología incluyen la mejora en la exactitud de la localización del primerblanco quirúrgico, disminución del número de trayectos con los electrodos y, por tanto, del tiempo de la cirugía, y lareducción de las posibles complicaciones quirúrgicas(AU)

OBJECTIVE. A computerized version of the Schaltenbrand and Wahren's stereotactic brain atlas for image-guided functional neurosurgery planning has been developed and integrated into our PC-based planning system. METHODS. The SW atlas plates were digitized, contoured and labeled for both hemispheres. The computerized atlas may be interactively registered with patient's data using linear and non-linear transformation. The implemented computational tools and applications are presented. RESULTS. Our computer system permits navigation through original or reconstructed slices, multiple-views synchronization and zoom to improve the localization of the commisures and the surgical targets, likewise the optimum path selection. Atlas position in the target's region can be interactively actualized and lesion's position and volume may be simulated. CONCLUSIONS. Its benefits of this approach include increased accuracy of target definition, decreased the number of electrode tracts and for instance the time of the surgery, and reduced surgical complications(AU)

[Subthalamic nucleus targeting and spatial variability]. / Localización bilateral y simetría del núcleo subtalámico.

AIM: The effectiveness of anatomic localization of the subthalamic nucleus (EAL) was assessed and the mapping method is described here. The symmetry of contralateral nuclei (SCN) was analyzed on 11 parkinsonian patients submitted to bilateral subthalamotomy with ablative lesioning. PATIENTS AND METHODS: To assess EAL the percentage so much of first trajectory (p1) as the total of trajectories (pt) that hit the target and the rest of subthalamic nucleus average distance (d) was calculated. The anatomic localization error (epsilon) is determined as a difference between first trajectory coordinates with those of medial determined nucleus point, through electrophysiological data as to the statistical significance of this error. SCN is analyzed by contrasting equality hypothesis at the nucleus maximum height alongside a trajectory, average electrophysiological position center and spatial distribution of all intranuclear recordings found in each hemisphere in all patients. RESULTS: The pi, pt and d obtained values were 86.36%, 86.13% and 1.41 +/- 1.01 mm respectively. The epsilon value was greater in anteroposterior direction of 1.11 +/- 0.83 mm without statistical significance. The average number of recorded trajectories for the first procedure was 6.45 and 6 for the second. The asymmetry of contralateral nucleus was not significant. CONCLUSIONS: An indirect method with CT brain images and a new electrophysiological mapping method with a multiunitary recording for first and second nucleus is safe enough and it yields a high effectiveness in anatomofunctional nucleus localization. The nucleus of a same patient are symmetrical. There is little space variability among patient non related to the differences in the intercommissural distance.

Corrección de la radiación dispersa en spect cerebral utilizando dos ventanas de energía / Scatter correction in brain spect using two

La dispersión de los rayos gamma dentro del tejido humano afecta la cuantificación en SPECT cerebral y degrada la calidad de la imagen. En esta investigación implementamos cuatro métodos de corrección de la dispersión, basados en un análisis espectral de energías. Se utilizaron adquisiciones tomográficas en fantomas que simulan lesiones frías y calientes en un medio dispersor, para calcular el contraste tomográfico y comprobar la linealidad de las correcciones con Tc-99m. En las mismas se realizó la cuantificación relativa de actividad,utilizando adquisiciones en aire como referencia. Las correcciones de la dispersión muestran una alta linealidad con la actividad. Con el método DEW se obtiene la mejor exactitud cuantitativa y recuperación de contraste. Este método muestra el mejor compromiso entre exactitud cuantitativa, recuperación de contraste y facilidad de implementación. Estos resultados demuestranque los métodos de corrección de la radiación dispersa utilizando dos ventanas de energía pueden mejorar significativamente la cuantificación en SPECT cerebral(AU)

Localización bilateral y simetría del núcleo subtalámico / subthalamic nucleus targeting and spatial variability

Objetivos. Se evalúa la efectividad de localización anatómica (ELAN) bilateral del núcleo subtalámico (NST), se describe el método de cartografiado electrofisiológico y se analiza la simetría de los núcleos contralaterales (SC) en 11 pacientes con enfermedad de Parkinson, sometidos a subtalamotomía bilateral. Pacientes y métodos. Para evaluar la ELAN se calcula el porcentaje tanto de los primeros trayectos (p1) como del total de trayectos (pt) que hicieron blanco, así como la distancia promedio (d) del resto al NST. Se define el error de localización anatómica ( Epsilon ) como la diferencia entre las coordenadas del primer trayecto y las del punto medio del núcleo, determinado por la información electrofisiológica, así como la significación estadística de este error. La SC se analiza con el contraste de la hipótesis de igualdad en la máxima altura del núcleo a lo largo de un trayecto, la posición promedio del centro electrofisiológico y la distribución espacial de todos los registros intranucleares en todos los pacientes encontrado en cada hemisferio. Resultados. Los valores de p1, pt y d obtenidos fueron 86,36 por ciento, 86,13 por ciento y 1,41 ñ 1,01 mm, respectivamente. El valor de fue mayor en la dirección anteroposterior (1,11 ñ 0,83 mm), aunque sin significación estadística (test ANOVA de Kruskal Wallis para la mediana y test de Wilcoxon para muestras apareadas; p = 0,05). El número promedio de trayectos de registros para el primer proceder fue 6,45, y para el segundo, 6. La asimetría de los núcleos contralaterales no fue significativa (test ANOVA de Kruskal Wallis para la mediana y test de Wilcoxon para muestras apareadas; p = 0,05). Conclusiones. Un método indirecto con imágenes de TAC y un novedoso método de cartografiado electrofisiológico con registro multiunitario, para el primer y el segundo núcleo, son seguros y brindan una alta efectividad en la localización anatomofuncional del núcleo. Los núcleos de un mismo paciente son simétricos. Se observó poca variabilidad espacial entre pacientes, no relacionada con las diferencias en la distancia intercomisural (AU)

Aim. The effectiveness of anatomic localization of the subthalamic nucleus (EAL) was assessed and the mapping method is described here. The symmetry of contralateral nuclei (SCN) was analyzed on 11 parkinsonian patients submitted to bilateral subthalamotomy with ablative lesioning. Patients and methods. To assess EAL the percentage so much of first trajectory (p1) as the total of trajectories (pt) that hit the target and the rest of subthalamic nucleus average distance (d) was calculated. The anatomic localization error (ε) is determined as a difference between first trajectory coordinates with those of medial determined nucleus point, through electrophysiological data as to the statistical significance of this error. SCN is analyzed by contrasting equality hypothesis at the nucleus maximum height alongside a trajectory, average electrophysiological position center and spatial distribution of all intranuclear recordings found in each hemisphere in all patients. Results. The pi, pt and d obtained values were 86.36%, 86.13% and 1.41±1.01 mm respectively. The ε value was greater in anteroposterior direction of 1.11±0.83mm without statistical significance. The average number of recorded trajectories for the first procedure was 6.45 and 6 for the second. The asymmetry of contralateral nucleus was not significant. Conclusions. An indirect method with CT brain images and a new electrophysiological mapping method with a multiunitary recording for first and second nucleus is safe enough and it yields a high effectiveness in anatomofunctional nucleus localization. The nucleus of a same patient are symmetrical. There is little space variability among patient non related to the differences in the intercomisural distance (AU)

A way to reduce the radius of rotation in brain SPET with a single-head system.

To optimize spatial resolution in single photon emission tomography (SPET), it is essential to minimize the radius of rotation. In brain studies, different methods have been used to avoid shoulder interference when the radius of rotation is minimized: rectangular fields of view, modifications to the shielding around circular detectors and fan or cone beam collimators. However, few single-head systems can adopt these developments, particularly older cameras. A non-standard image acquisition method to reduce the radius of rotation in brain SPET with a single-head gamma camera is presented. The method applies a defined transformation to the original acquired images, maintaining the whole of the brain inside the field of view without shoulder interference and meeting the condition: pixel size < or = FWHM/3. With this method, it is possible to reduce the radius of rotation to 16 cm and to obtain a transaxial spatial resolution of 15.98 mm, which is 3.5 mm less than with the standard method used in our laboratory. This procedure was implemented for a Siemens Gammasonics ZLC 3700 gamma camera and has been validated in single-slice brain phantom studies. The method has the advantage of not requiring any complex or costly hardware.

A way to reduce the radius of rotation in brain SPET with a single-head system

To optimize spatial resolution in single photon emission tomography (SPECT), it is essential to minimize the radius of rotation. In brain studies, different methods have been used to avoid shoulder interference when the radius of rotation is minimized: rectangular fields of view, modifications to the shielding around circular detectors and fan or cone beam collimators. However, few single-head systems can adopt these developments, particularly older cameras. A non-standard image acquisition method to reduce the radius of rotation in brain SPET with a single-head gamma camera is presented. The method applies a defined transformation to the original acquired images, maintaining the whole of the brain inside the field of view without shoulder interference and meeting the condition: pixel size <= FWHM/3. With this method, it is possible to reduce the radius of rotation to 16 cm and to obtain a transaxial spatial resolution of 15.98 mm less than with the standard method used in our laboratory. This procedure was implemented for a Siemens Gammasonics ZLC 3700 gamma camera and has been validated in single-slice brain phantom studies. The methods has the advantage of not requiring and complex or costly hardware (AU)

[Incidence of fetal macrosomia: maternal and fetal morbidity]. / Incidencia de macrosomía fetal. Morbilidad materna y fetal.

The macrosomia is an obstetric eventuality associated to high maternal-fetal morbidity-mortality. This assay was planned in order to know the incidence of macrosomia in our institution, the relation between vaginal and abdominal deliveries and the fetal-maternal morbidity we reviewed 3590 records and we found 5.6% incidence of macrosomia in the global obstetric population. There was 58% of vaginal deliveries, 68% of the newborn were male. The main complications were in the C. sections, 2 laceration of the hysterectomy, and 2 peroperative atonias. In the vaginal deliveries, the lacerations of III and IV grade were 9 of each grade. The main fetal complications were 5 slight to severe asphyxia and 4 shoulder dystocias. This assay concludes that the macrosomia in our service is similar to the already published ones, a 42% were C. section and the maternal-fetal morbidity was low.

[Agrarian movements, development alternatives and food security in Central America: scenarios of transition]. / Mouvements paysans, alternatives de developpement et securite alimentaire en Amerique Centrale: les scenarios d'une transition.

PIP: This article, based on personal experiences with a network of organizations of small and medium agricultural producers in Central America, aims to present the views of peasant organizations concerning agrarian problems in the region. The 3 major sections of work define the place of peasant agriculture in the traditional agrarian structure and the new problems resulting from the structural adjustment programs of the 1980s; separately describe the new peasant movements emerging in Honduras, El Salvador, Nicaragua, Costa Rica, and Panama, identifying common themes an efforts at international collaboration; and explore the positions of the peasant organizations on the optimal strategies for agricultural development and agrarian change. Agriculture remains the backbone of the Central American economies. But because the economic model in the region is 1 of accumulation characterized by dependency, concentration of capital, and social marginalization, the agrarian structure is at the basis of social tensions. Efforts to develop peasant agriculture and to give small producers access to marketing and credit services have been weak and sporadic. The new peasant movements are less inclined than those of the past to employ tactics of confrontation in their efforts to secure access to land and better working conditions. The new movement is the expression of small market producers sometimes grouped into associations who are oriented to production of basic foodstuffs for the internal market. A new concern with adaptation and negotiation is evident. The new organizations have in common a belief in their ability to propose new solutions to regional problems. Their views are founded on a positive assessment of the ability of peasant agriculture to produce food and add dynamism to the regional economy after barriers to credit, technological progress, and modernization in general are removed. Signs of increased cooperation are evident between peasant organizations and other groups representing the masses, and with other countries in the region. The positions of the peasant organizations call for access to lands for small proprietors as well as landless agricultural laborers, and for new forms of organizing production that will respect the conservation and development of natural resources.^ieng