Applying a unified model of fiber dissection, tractography, microscopic anatomy and plastination techniques for basic neuroanatomy education: Hacettepe University experience / Aplicación de un modelo unificado de disección de fibras, tractografía, anatomía microscópica y técnicas de plastinación para la educación básica en neuroanatomía: experiencia de la Universidad Hacettepe

SUMMARY: Anatomy education has gathered together a great many of many new modalities and was modified from classical lecture-based and laboratory practice system to the blended modules. In the scope of the present study, we develop a new, practical, cost- effective and efficient three dimensional (3D) educational model, which aimed to be helpful for the detection and better understanding of basic neuroanatomy education. Tractographic imaging, fiber dissection, microscopic anatomy and plastination techniques were applied to the white matter regions of the two brains. After the photographs that were taken were converted to 3D images, the specimens were plastinated. By way of establishing an educational model as a whole, we applied it to 202 second-year medical students. The students were separated into two groups when they attended to the theoretical lecture. Group 1 took the classical laboratory education; on the other hand, Group 2 received the newly designed educational model. Pre and post-tests were introduced to each group before and after laboratory sessions, respectively. The success scores were put to comparison. The average achievement scores of each group showed increase significantly (p<0.05) after the laboratory sessions, besides the increase in the post-test results of Group 2 was more statistically significant (p<0.05). Consequently, this new educational model enriched by newly designed unified methods could be regarded as useful for grasping and improving the basic neuroanatomy knowledge.

La educación en anatomía ha reunido una gran cantidad de nuevas modalidades, modificándose el sistema clásico de la práctica del laboratorio y de las clases basadas en conferencias, hacia los módulos combinados. En el ámbito del presente estudio, desarrollamos un modelo educativo tridimensional (3D) nuevo, práctico, rentable y eficiente, que pretendía ser útil para la detección y una mejor comprensión de la educación básica en neuroanatomía. Se tomaron imágenes tractográficas, disección de fibras, anatomía microscópica y técnicas de plastinación en los cerebros. Después de convertir las fotografías que se tomaron en imágenes 3D, se plastinaron los especímenes. A modo de establecer un modelo educativo en su conjunto, lo aplicamos a 202 estudiantes de segundo año de medicina. Los estudiantes fueron separados en dos grupos cuando asistieron a la clase teórica. El Grupo 1 tomó la educación clásica de laboratorio; por su parte, el Grupo 2 recibió el nuevo modelo educativo diseñado para el estudio. Se introdujeron pruebas previas y posteriores a cada grupo, antes y después de las sesiones de laboratorio. Se compararon las puntuaciones. Los puntajes promedio de rendimiento de cada grupo mostraron un aumento significativo (p<0,05) después de las sesiones de laboratorio. Además, se obtuvo un aumento en los resultados positivos, posteriores a la prueba del Grupo 2, siendo estadísticamente significativo (p<0,05). En consecuencia, este modelo educativo, enriquecido por métodos unificados de nuevo diseño, podría considerarse útil para captar y mejorar los conocimientos básicos de neuroanatomía.

El papel de la tractografía en la localización del núcleo ventralis intermedius del tálamo y el haz dentatorrubrotalámico en el tratamiento del temblor / The role of tractography in the localization of the Vim nucleus of the thalamus and the dentato-rubro-thalamic tract for the treatment of tremor

Introducción: La diana habitual empleada para el tratamiento quirúrgico del temblor es el núcleo ventralis intermedius (Vim) del tálamo. Su localización es compleja, ya que no se puede visualizar con métodos de imagen convencionales, por lo que para el procedimiento quirúrgico se toman clásicamente medidas indirectas y se correlacionan con la clínica y neurofisiología intraoperatorias. Sin embargo, procedimientos ablativos actuales como la talamotomía por gamma-knife o por ultrasonidos (MRgFUS) hacen que sea preciso buscar otras alternativas para su localización. El objetivo del presente trabajo es comparar la localización indirecta del Vim mediante técnica esterotáctica con la realizada directamente por tractografía para el tratamiento del temblor.DiscusiónLa definición citoarquitectónica más empleada del Vim es la del atlas de Schaltenbrand-Wahren. Existe un límite claro entre el tálamo motor y el sensitivo; las neuronas del Vim responden a movimientos pasivos articulares y su actividad es sincrónica con el temblor periférico. Las coordenadas estereotácticas del Vim más frecuentemente utilizadas se basan en mediciones indirectas respecto a la línea intercomisural y el III ventrículo, las cuales dependen de variaciones interindividuales. Estudios recientes han propuesto el haz dentatorrubrotalámico como una diana óptima para el control del temblor, postulando que se asocia a una mejoría clínica; sin embargo, esto no ha sido corroborado por otros autores.ConclusionesLa visualización de la vía cerebelorrubrotalámica por tractografía puede ayudar a definir la localización del Vim. Esta técnica tiene limitaciones inherentes y sería necesaria una estandarización del método para lograr resultados más precisos. La posible mayor utilidad de la diana por tractografía, directa, sobre la indirecta queda por demostrar a largo plazo en pacientes con temblor. (AU)

Introduction: The ventralis intermedius (Vim) nucleus of the thalamus is the usual surgical target for tremor. However, locating the structure may be difficult as it is not visible with conventional imaging methods; therefore, surgical procedures typically use indirect calculations correlated with clinical and intraoperative neurophysiological findings. Current ablative surgical procedures such as Gamma-Knife thalamotomy and magnetic resonance-guided focused ultrasound require new alternatives for locating the Vim nucleus. In this review, we compare Vim nucleus location for the treatment of tremor using stereotactic procedures versus direct location by means of tractography.DiscussionThe most widely used cytoarchitectonic definition of the Vim nucleus is that established by Schaltenbrand and Wahren. There is a well-defined limit between the motor and the sensory thalamus; Vim neurons respond to passive joint movements and are synchronous with peripheral tremor. The most frequently used stereotactic coordinates for the Vim nucleus are based on indirect calculations referencing the mid-commissural line and third ventricle, which vary between patients. Recent studies suggest that the dentato-rubro-thalamic tract is an optimal target for controlling tremor, citing a clinical improvement; however, this has not yet been corroborated.ConclusionsVisualisation of the cerebello-rubro-thalamic pathway by tractography may help in locating the Vim nucleus. The technique has several limitations, and the method requires standardisation to obtain more precise results. The utility of direct targeting by tractography over indirect targeting for patients with tremor remains to be demonstrated in the long-term. (AU)

Estimulación cerebral profunda en la enfermedad de Parkinson: análisis de la anisotropía fraccional cerebral en pacientes intervenidos mediante estimulación cerebral profunda / Deep brain stimulation in Parkinson’s disease: analysis of brain fractional anisotropy differences in operated patients

Introducción: La estimulación cerebral profunda (ECP) del núcleo subtalámico actualmente es una opción terapéutica basada en la evidencia para los síntomas motores en pacientes con enfermedad de Parkinson (EP), aunque otros síntomas no motores pueden verse afectados por la estimulación. Objetivo: Nuestro objetivo es evaluar los cambios globales en la conectividad de la red estructural a gran escala en pacientes con EP que han obtenido un beneficio de la ECP subtalámica. Sujetos y métodos: Estudio retrospectivo de 31 sujetos: siete pacientes con EP con ECP subtalámica (grupo A), 12 pacientes con EP no operados de la misma edad y sexo (B) y 12 controles sanos (C). Todos los sujetos se habían sometido a una resonancia magnética cerebral de 1,5 T con imagen del tensor de la difusión. Las imágenes DICOM se procesaron con el software FSL5.0 y la herramienta estadística espacial basada en el tracto. Resultados: El grupo de estudio estuvo compuesto por 23 hombres y ocho mujeres. No se encontraron diferencias estadísticamente significativas en edad, sexo, puntuación en la escala de Hoehn y Yahr y seguimiento medio entre el grupo A y B, y en edad y sexo entre los grupos A y C. El análisis estadístico reveló diferencias en la anisotropía fraccional de los diferentes grupos en ciertas áreas: tracto corticoespinal bilateral, radiaciones talámicas anteriores, fascículo frontooccipital bilateral, ambos fascículos longitudinales superiores y fascículo longitudinal inferior izquierdo. Conclusiones: En nuestra serie, los pacientes con EP tratados con ECP subtalámica bilateral mostraron una anisotropía fraccional significativamente mayor en áreas extensas de la sustancia blanca cerebral, lo que sugiere que la neuromodulación produce cambios de conectividad en diferentes redes neuronales.(AU)

Introduction: Deep brain stimulation (DBS) of the subthalamic nucleus is currently an evidence-based therapeutic option for motor symptoms in patients with Parkinson’s disease (PD), although other non-motor symptoms can be affected by stimulation. Aim: Our objective is to evaluate the global changes in the connectivity of the large-scale structural network in PD patients that have obtained a benefit from subthalamic DBS. Subjects and methods: Retrospective study of 31 subjects: 7 PD patients with subthalamic DBS (group A), 12 age and gender-matched non-operated PD (B) and 12 healthy controls (C). All subjects had undergone a 1.5 T brain MRI with DTI. DICOM images were processed with the FSL5.0 software and TBSS tool. Results: The study group comprised 23 men and 8 women. No statistically significant differences in age, gender, scores on the H&Y scale and mean follow-up between group A and B were found, and in age and gender between groups A and C. Statistical analysis revealed differences in the fractional anisotropy of the different groups in certain areas: bilateral corticospinal tract, anterior thalamic radiations, bilateral fronto-occipital fascicle, both superior longitudinal fascicles, and left inferior longitudinal fascicle. Conclusions: In our series, PD patients treated with bilateral subthalamic DBS showed a significantly higher fractional anisotropy in widespread areas of the cerebral white matter; suggesting that neuromodulation produces connectivity changes in different neural networks.(AU)

The role of tractography in the localization of the Vim nucleus of the thalamus and the dentato-rubro-thalamic tract for the treatment of tremor. / El papel de la tractografía en la localización del núcleo ventralis intermedius del tálamo y el haz dentatorrubrotalámico en el tratamiento del temblor.

INTRODUCTION: The ventralis intermedius (Vim) nucleus of the thalamus is the usual surgical target for tremor. However, locating the structure may be difficult as it is not visible with conventional imaging methods; therefore, surgical procedures typically use indirect calculations correlated with clinical and intraoperative neurophysiological findings. Current ablative surgical procedures such as Gamma-Knife thalamotomy and magnetic resonance-guided focused ultrasound require new alternatives for locating the Vim nucleus. In this review, we compare Vim nucleus location for the treatment of tremor using stereotactic procedures versus direct location by means of tractography. DISCUSSION: The most widely used cytoarchitectonic definition of the Vim nucleus is that established by Schaltenbrand and Wahren. There is a well-defined limit between the motor and the sensory thalamus; Vim neurons respond to passive joint movements and are synchronous with peripheral tremor. The most frequently used stereotactic coordinates for the Vim nucleus are based on indirect calculations referencing the mid-commissural line and third ventricle, which vary between patients. Recent studies suggest that the dentato-rubro-thalamic tract is an optimal target for controlling tremor, citing a clinical improvement; however, this has not yet been corroborated. CONCLUSIONS: Visualisation of the cerebello-rubro-thalamic pathway by tractography may help in locating the Vim nucleus. The technique has several limitations, and the method requires standardisation to obtain more precise results. The utility of direct targeting by tractography over indirect targeting for patients with tremor remains to be demonstrated in the long-term.

The role of tractography in the localisation of the Vim nucleus of the thalamus and the dentatorubrothalamic tract for the treatment of tremor.

INTRODUCTION: The ventralis intermedius (VIM) nucleus of the thalamus is the usual surgical target for tremor. However, locating the structure may be difficult as it is not visible with conventional imaging methods; therefore, surgical procedures typically use indirect calculations correlated with clinical and intraoperative neurophysiological findings. Current ablative surgical procedures such as Gamma-Knife thalamotomy and magnetic resonance-guided focused ultrasound require new alternatives for locating the VIM nucleus. In this review, we compare VIM nucleus location for the treatment of tremor using stereotactic procedures versus direct location by means of tractography. DISCUSSION: The most widely used cytoarchitectonic definition of the VIM nucleus is that established by Schaltenbrand and Wahren. There is a well-defined limit between the motor and the sensory thalamus; VIM neurons respond to passive joint movements and are synchronous with peripheral tremor. The most frequently used stereotactic coordinates for the VIM nucleus are based on indirect calculations referencing the mid-commissural line and third ventricle, which vary between patients. Recent studies suggest that the dentato-rubro-thalamic tract is an optimal target for controlling tremor, citing a clinical improvement; however, this has not yet been corroborated. CONCLUSIONS: Visualisation of the cerebello-rubro-thalamic pathway by tractography may help in locating the VIM nucleus. The technique has several limitations, and the method requires standardisation to obtain more precise results. The utility of direct targeting by tractography over indirect targeting for patients with tremor remains to be demonstrated in the long-term.

Cavernoma Paraventricular / Paraventricular Cavernoma

Introducción: Los cavernomas representan el 5 al 13% de las malformaciones cerebrales y suelen tener una localización supratentorial. Clínicamente pueden permanecer asintomáticos o presentar síntomas neurológicos progresivos. Para estos últimos, así como los que presentan hemorragia recurrente, la resección quirúrgica es el tratamiento de elección. Sin embargo, para aquellos que presentan una localización profunda es menester estudiar la relación que existe entre la lesión y las estructuras cerebrales adyacentes. La tractografía (DTI) y las técnicas de navegación intraoperatoria son herramientas fundamentales para planificar y guiar el abordaje a la lesión y realizar un mapeo de las vías de proyección, asociación y comisurales, permitiendo un acceso seguro mediante corticotomías pequeñas y mínima retracción del parénquima cerebral. Objetivo: Describir la técnica quirúrgica guiada por neuronavegación para la resección de un cavernoma frontal derecho profundo yuxtaventricular a través de una pequeña corticotomía. Caso: Paciente de sexo masculino de 20 años de edad, deportista profesional, con parestesias miembro superior izquierdo y cefalea severa. Resonancia magnética evidencia lesión heterogénea en T1 y T2 y presencia de un halo de hemosiderina, compatible con cavernoma a nivel del techo del cuerpo en el ventrículo lateral derecho. Mide 28 mm x 31 mm x 28 mm en sus diámetros transversal, dorso-ventral y rostro-caudal. Tractografía evidencia lesión en íntima relación con el tracto corticoespinal en su recorrido por la corona radiada. Resultados: Exéresis completa de la lesión. El paciente evolucionó sin déficit neurológico y fue dado de alta a las 72 horas del postoperatorio. Conclusión: El uso de la tractografía y de la navegación intraoperatorio, permite abordar lesiones profundas, en contacto con áreas elocuentes, mediante corticotomías pequeñas con mínima retracción cerebral

Introduction: Cavernous malformation represents among 5 to 13% of brain vascular malformations, most of them have a supratentorial location. Clinically they can remain asymptomatic or present with neurological symptoms. In cavernomas with recurrent hemorrhage, located in safe areas, surgical resection is the treatment of choice. However, for those which have a deep yuxta-ventricular localization it is necessary to know the relationship between the lesion and eloquent cerebral structures. Fiber tractography and intraoperative navigation systems are essentials tools to plan and guide the surgical approach and make a mapping of the projection, association and commissural fibers in order to have a safe access to the lesion. Objective: To describe the surgical technique using neuronavigation for the resection of a right frontal yuxta-ventricular cavernous malformation through a minimal approach. Case: A 20-year-old man, professional athlete with left arm paresthesia and severe headache. Magnetic resonance shows a heterogeneous lesion in T1 and T2 with a hemosiderin in the roof of the right lateral ventricle, compatible with a cavernous malformation. Its size was 28 mm x 31mm x 28 mm in the transversal, dorsoventral and rostrocaudal diameter. The fiber tractography shows an intimate relationship with the corticospinal tract on its path through the corona radiata. Results: Complete resection of the lesion. The patient evolved without a neurological deficit and was discharged 72 hours later. Conclusion: The fiber tractography and the intraoperative navigation system allow the deep lesions approach, especially for those who have an intimal relationship with eloquent ́s areas, using minimally corticotomy with less parenchymal retraction.

Volumetría de fascículos cerebrales en población sana / Brain fascicles volumetry in healthy population

Objetivo Desde la aparición de la tractografía, al tratarse de una técnica no invasiva y que usa la ampliamente conocida resonancia magnética (RM), el estudio de la sustancia blanca se ha facilitado. A partir de eso, se han logrado grandes descubrimientos en cuanto a fascículos cerebrales involucrados en funciones cognitivas. Sin embargo, su evaluación sigue siendo subjetiva y depende de la experiencia y entrenamiento del evaluador, razón por la cual se ha limitado su aplicabilidad en la práctica clínica. En ese sentido, es conveniente parametrizar volúmenes cerebrales de sustancia blanca en población sana a través de una herramienta electrónica que se pueda reproducir y así poderlo aplicar en enfermos. Materiales y métodos Se reportan 10 sujetos sanos desde el punto de vista neurológico. Para cada sujeto, se adquirieron imágenes ponderadas por difusión y los resultados se visualizaron mediante FiberNavigator (http://scilus.github.io/fibernavigator). Finalmente, esa misma herramienta fue utilizada para purificar los fascículos objeto de estudio y realizar el conteo de las fibras. Resultados Se obtuvieron valores de volumetría del fascículo longitudinal superior (FLS), fascículo longitudinal inferior (FLI), fascículo frontoccipital inferior (FFI), fascículo uncinado (FU) y fascículo del cíngulo (FC), identificando que no existen diferencias estadísticamente significativas entre el número de fibras que componen los fascículos cerebrales. Discusión Los resultados alcanzados de la anatomía y la direccionalidad de fibras de los fascículos cerebrales de este estudio coinciden con el resto de la evidencia publicada hasta el momento, sin encontrar diferencias en cuanto a su organización y recorrido. Conclusión Aunque esos resultados no sirven como valores de referencia para ser aplicados en pacientes con patología neurológica, brindamos información inexistente hasta el momento, con ese equipo en específico y la reproducción entre los distintos usuarios y el software.

Objective Since the appearance of tractography, as it is a non-invasive technique and uses the widely known magnetic resonance (MR), the study of white matter has been facilitated. After this, great discoveries have been made regarding the brain fascicles involved in cognitive functions. However, its evaluation continues to be subjective and depends on the evaluator's experience and training. That the reason why its applicability has been limited in clinical practice. Because of this, it is convenient to parametrize cerebral volumes of white matter in healthy population through an electronic, reproducible tool that could be applied in patients. Materials and Methods Ten neurologically healthy subjects are reported, for each subject we acquired images weighted by diffusion and the results were visualized by means of FiberNavigator (http://scilus.github.io/fibernavigator). Finally, this same tool was used to purify the fascicles under study and perform the fiber count. Results Volumetric values of the upper longitudinal fasciculus, inferior longitudinal fasciculus, inferior frontoccipital fasciculus, uncinated fasciculus and cingulate fasciculus were obtained, identifying that there are not statistically significant differences in the number of fibers that make up the cerebral fascicles. Discussion The results achieved of the anatomical and fiber directionality of the cerebral fascicles of this study, coincide with the rest of the evidence published up to now, without finding differences regarding its organization and route. Conclusion Although these results do not serve as reference values to be applied in patients with neurological pathology, do we provide nonexistent information so far, with this specific equipment and the reproducibility between the different users and the software.

Nuevos conceptos en neuromodulación cerebral: rol de DTI y estimulación de tractos / New concepts in brain neuromodulation: role of DTI and tract stimulation

Introducción: La estimulación cerebral profunda es una técnica difundida y validada para eltratamiento de múltiples dolencias neurológicas y psiquiátricas, entre ellas el temblor esencial. Objetivo: Evaluar si existe un correlato clínico-anatómico, para un paciente con TE, entre la mejor estimulación lograda y los tractos involucrados. Para esto se realiza una descripción de la técnica utilizada, incluyendo el procesamiento de imágenes necesario. Material y métodos: Se presenta el caso de un paciente de 53 años de edad, con una historia de 23 años de temblor esencial progresivo e incapacitante. Se realizó un implante de DBS bilateral en Vim. Se realizó un post procesamiento de imágenes con un método desarrollado por nuestro equipo a través del cual se permitió evaluar gráficamente el área de estimulación cerebral y sus relaciones con los tractos implicados en la patología (dento-rubro-talámico, haz piramidal y haz lemniscal). Resultados: El paciente presentó una mejoría del 55% medido por escala de temblor de Tolosa. Se obtuvo una correlación anatómica y funcional de lo esperado según imágenes y la respuesta clínica del paciente. Se constataron efectos adversos cuando la estimulación implicaba fibras del haz piramidal y lemniscal, presentando los mejores efectos clínicos cuando el haz dento-rubro-talámico era influenciado por el área de acción del campo eléctrico. Conclusiones: En este reporte mostramos la aplicabilidad de DTI y tractografía para explicar los efectos de la programación de los pacientes con estimulación cerebral profunda.

Introduction: Deep brain stimulation is a widespread and validated technique for the treatment of multiple neurological and psychiatric disorders, including essential tremor. Objective: To evaluate if there is a clinical-anatomical correlate, for a patient with essential tremor, between the best stimulation achieved and the tracts involved. For this, a description of the technique used is made, including the necessary image processing. Methods: We present the case of a 53-year-old patient with a 23-year history of progressive and disabling essential tremor. A bilateral DBS implant was performed on Vim. We performed a post-processing of images with a method developed by our team through which we were able to graphically evaluate the area of brain stimulation and its relationships with the tracts involved in the pathology (dento-rubro-thalamic tract, pyramidal tract and lemniscal tract). Conclusions: In this report we showed the applicability of DTI and tractography to explain the clinical effects of the programming features in patients with deep brain stimulation.

3D microsurgical anatomy of the cortico-spinal tract and lemniscal pathway based on fiber microdissection and demonstration with tractography. / Anatomía microquirúrgica en 3D del tracto corticoespinal y de la vía del lemnisco basada en microdisección de fibras y demostración a través de tractografía.

OBJECTIVE: To demonstrate tridimensionally the anatomy of the cortico-spinal tract and the medial lemniscus, based on fiber microdissection and diffusion tensor tractography (DTT). MATERIAL AND METHODS: Ten brain hemispheres and brain-stem human specimens were dissected and studied under the operating microscope with microsurgical instruments by applying the fiber microdissection technique. Brain magnetic resonance imaging was obtained from 15 healthy subjects using diffusion-weighted images, in order to reproduce the cortico-spinal tract and the lemniscal pathway on DTT images. RESULTS: The main bundles of the cortico-spinal tract and medial lemniscus were demonstrated and delineated throughout most of their trajectories, noticing their gross anatomical relation to one another and with other white matter tracts and gray matter nuclei the surround them, specially in the brain-stem; together with their corresponding representation on DTT images. CONCLUSIONS: Using the fiber microdissection technique we were able to distinguish the disposition, architecture and general topography of the cortico-spinal tract and medial lemniscus. This knowledge has provided a unique and profound anatomical perspective, supporting the correct representation and interpretation of DTT images. This information should be incorporated in the clinical scenario in order to assist surgeons in the detailed and critic analysis of lesions located inside the brain-stem, and therefore, improve the surgical indications and planning, including the preoperative selection of optimal surgical strategies and possible corridors to enter the brainstem, to achieve safer and more precise microsurgical technique.

Neuroradiologic correlation with aphasias. Cortico-subcortical map of language. / Correlación neurorradiológica de las afasias. Mapa cortico-subcortical del lenguaje.

Aphasia is an acquired language disorder due to a cerebral lesion; it is characterized by errors in production, denomination, or comprehension of language. Although most aphasias are mixed, from a practical point of view they are classified into different types according to their main clinical features: Broca's aphasia, Wernicke's aphasia, conduction aphasia, transcortical aphasia, and alexia with or without agraphia. We present the clinical findings for the main subtypes of aphasia, illustrating them with imaging cases, and we provide an up-to-date review of the language network with images from functional magnetic resonance imaging and tractography.

Current concepts on the pathophysiology of idiopathic chronic adult hydrocephalus: Are we facing another neurodegenerative disease? / Actualización en la fisiopatología de la hidrocefalia crónica del adulto idiopática: ¿nos enfrentamos a otra enfermedad neurodegenerativa?

INTRODUCTION: Since its description five decades ago, the pathophysiology of idiopathic chronic adult hydrocephalus (iCAH) has been traditionally related to the effect that ventricular dilatation exerts on the structures surrounding the ventricular system. However, altered cerebral blood flow, especially a reduction in the CSF turnover rate, are starting to be considered the main pathophysiological elements of this disease. DEVELOPMENT: Compression of the pyramidal tract, the frontostriatal and frontoreticular circuits, and the paraventricular fibres of the superior longitudinal fasciculus have all been reported in iCAH. At the level of the corpus callosum, gliosis replaces a number of commissural tracts. Cerebral blood flow is also altered, showing a periventricular watershed region limited by the subependymal arteries and the perforating branches of the major arteries of the anterior cerebral circulation. The CSF turnover rate is decreased by 75%, leading to the reduced clearance of neurotoxins and the interruption of neuroendocrine and paracrine signalling in the CSF. CONCLUSIONS: iCAH presents as a complex nosological entity, in which the effects of subcortical microangiopathy and reduced CSF turnover play a key role. According to its pathophysiology, it is simpler to think of iCAH more as a neurodegenerative disease, such as Alzheimer disease or Binswanger disease than as the classical concept of hydrocephalus.

[3D anatomy of cerebellar peduncles based on fibre microdissection and a demonstration with tractography]. / Anatomía de los pedúnculos cerebelosos en 3D basada en microdisección de fibras y demostración a través de tractografía.

OBJECTIVE: To perform an anatomical and radiological study, using fibre microdissection and diffusion tensor tractography (DTT), to demonstrate the three-dimensionality of the superior, middle and inferior cerebellar peduncles. MATERIAL AND METHODS: A total of 15 brain-stem, 15 cerebellar hemispheres, and 5 brain hemispheres were dissected in the laboratory under the operating microscope with microsurgical instruments between July 2014 and July 2015. Brain magnetic resonance imaging was obtained from 15 healthy subjects between July and December of 2015, using diffusion-weighted images, in order to reproduce the cerebellar peduncles on DTT. RESULTS: The main bundles of the cerebellar peduncles were demonstrated and delineated along most of their trajectory in the cerebellum and brain-stem, noticing their overall anatomical relationship to one another and with other white matter tracts and the grey matter nuclei the surround them, with their corresponding representations on DTT. CONCLUSIONS: The arrangement, architecture, and general topography of the cerebellar peduncles were able to be distinguished using the fibre microdissection technique. This knowledge has given a unique and profound anatomical perspective, supporting the correct representation and interpretation of DTT images. This information should be incorporated in the clinical scenario in order to assist surgeons in the detailed and critical analysis of lesions that may be located near these main bundles in the cerebellum and/or brain-stem, and therefore, improve the surgical planning and achieve a safer and more precise microsurgical technique.

Síndrome de Melas: correlación clínica con hallazgos imagenológicos en espectroscopia y tractografía, reporte de caso / Melas syndrome: clinical correlation with imaging findings in spectroscopy and tractography, case report

El síndrome de Melas es una enfermedad de herencia mitocondrial caracterizada por encefalopatía mitocondrial, acidosis láctica y eventos similares a ataque cerebrovascular, secundaria a una mutación en los genes que codifican las proteínas transportadoras de electrones, limitando la producción energética y generando disfunción multiorgánica, que afecta principalmente el sistema músculo esquelético y el sistema nervioso, lo que está en correlación con las características clínicas que presentan los pacientes. El diagnostico se basa en la sospecha clínica, los hallazgos paraclínicos e imagenológicos y la confirmación de la mutación a través del estudio genético. No existe tratamiento específico, se basa únicamente en el manejo sintomático y requiere apoyo multidisciplinario. Presentamos el caso de un paciente con antecedente de Melas, que ingresó por evento cerebrovascular isquémico bioccipital y correlación con hallazgos en neuroimágenes (espectroscopia y tractografía).

Melas syndrome is a disease characterized by mitochondrial inheritance of mitochondrial encephalopathy, lactic acidosis and events like stroke secondary to a mutation in the gene encoding the electron transport proteins limiting energy production and generating multiorgan dysfunction being affected mainly musculoskeletal system and the nervous system which correlates with the clinical characteristics presented by patients. The diagnosis is based on clinical suspicion, laboratory, and imaging findings and confirmation of the mutation through genetic study. No specific treatment is Is available, but symptomatic treatment is needed and requires multidisciplinary support. We report a patient with a history of Melas who who had bioccipital cerebral ischemic event and correlation with findings in neuroimaging (spectroscopy and tractography).

Neuropatía óptica postraumática, presentación de un caso / Post-traumatic optic neuropathy: case presentation

Introducción: la neuropatía óptica postraumática (NOP) es una entidad en la cual se presenta una lesión del nervio óptico secundaria a un traumatismo directo o indirecto. Puede ser muy fácil de diagnosticar cuando existe la sospecha clínica y se encuentran alteraciones funcionales pupilares. Existen varios estudios que pueden resultar útiles como auxiliares diagnósticos. El objetivo de presentar este caso clínico es el analizar un paciente con diagnóstico de NOP con afección bilateral, con estudio de tractografía positivo para lesión del nervio óptico, con el fin de enfatizar la necesidad de evaluar siempre funcionalmente los ojos en un paciente con traumatismo craneal y conocer la utilidad o no del tratamiento con corticoides en altas dosis. Caso clínico: hombre de 28 años de edad con antecedente de ingesta de licor, es asaltado y sufre traumatismo craneoencefálico con pérdida de la conciencia. A las 16 horas del evento únicamente percibía luz. Se inició tratamiento con corticoides intravenosos ante la sospecha de una neuropatía óptica postraumática. La tractografía de nervios ópticos demostró la presencia de lesión. Conclusiones: el análisis de este caso indica la necesidad de identificar la neuropatía óptica traumática, incluso en ausencia de signos anatómicos. Se debe implementar tempranamente tratamiento a base de corticoesteroides.

Introduction: post traumatic Optic Neuropathy (PON) is an entity in which a lesion of the optic nerve occurs after a direct or indirect trauma. It can be very easy to diagnose when there is clinical suspicion and functional pupillary abnormalities are present. There are several studies available that may be useful as diagnostic aids. The purpose of presenting this case report is to analyze a patient diagnosed with PON with bilateral involvement, with positive tractography study of the optic nerve, in order to emphasize the need to assess functionally the eyes of a patient with head trauma and to establish how useful or not a treatment with high-doses of corticosteroids can be. Clinical case: a 28 year old male with a history of intake of liquor, is assaulted and presented head trauma with loss of consciousness. At 16 hours after the accident there only was light perception. Treatment was initiated with intravenous corticosteroids suspicion of posttraumatic optic neuropathy. Tractography of the optic nerve showed the presence of injury. Conclusions: the analysis of this case indicates the need to identify Postraumatic Optic Neuropathy even in the absence of ocular abnormalities. Early treatment with corticosteroids must be implemented.

Correlación entre el defecto del campo visual y tractografía postoperatoria en casos de cirugía de epilepsia por esclerosis temporomesial. Estudio anátomo-imagenológico del fascículo de Meyer / Correlation between visual field defect and postoperative tractography in cases of epilepsy surgery due to temporomandibular sclerosis. Anatomic-imaging study of Meyer's fascicle

Objetivo: describir la anatomía del fascículo de Meyer (FM) y los resultados del campo visual computarizado (CVC) y tractografía, por tensor de difusión (TTD) en la identificación del compromiso de este fascículo en pacientes tratados quirúrgicamente por epilepsia refractaria. Introducción: Hasta un 80% de los pacientes con epilepsia temporo-mesial asociada a esclerosis hipocampal son refractarios a la medicación. Para estos pacientes la cirugía es un tratamiento bien establecido y efectivo. No obstante son frecuentes los defectos del campo visual por lesión del FM luego de este tipo de procedimientos. Materiales y métodos: Se realizó disección de fibras blancas de tres cerebros humanos, fijados en formaldehído, mediante la técnica de Klingler, con el fin de reconocer los fascículos que conforman la vía visual en la profundidad del lóbulo temporal. A su vez, se estudiaron 8 pacientes sometidos a lobectomía temporal anterior y amigdalohipocampectomía por esclerosis temporomesial, realizándose TTD y CVC, al menos 3 meses después de la cirugía. Los individuos se clasificaron en cuatro grupos según el defecto campimétrico y se realizaron distintas mediciones en tractografía y resonancia magnética. Finalmente se correlacionaron los resultados de las distintas variables y se realizó una extensa revisión bibliográfica...

Objective: to describe the anatomy of the Meyer´s loop (ML) and the results of computerized visual field (CVF) and diffusion tensor tractography (DTT) to identify the damage of this fascicle in patients surgically treated for refractory epilepsy secondary to mesial-temporal sclerosis. Introduction: Up to 80% of patients with temporo-mesial epilepsy associated with hippocampal sclerosis are refractory to medication. For these patients, surgery is a well established and effective treatment. However visual field defects are frequent by optic radiation´s injury after these procedures. Materials and methods: We performed the dissection of white fibers on three human brains, previously fixed in formaldehyde, by Klingler´s technique, to recognize the fascicles that make up the visual pathway in the depth of the temporal lobe. Then, eight patients submitted to anterior temporal lobectomy and amygdalohippocampectomy were studied performing CVF and TTD at least 3 months after surgery. Individuals were classified into four groups according to visual field defects and other measurements in magnetic resonance imaging and tractography. Finally the results of the different variables were correlated and an extensive review of literature was performed...

[Insular-opercular associative tracts: Review of their anatomy and relevance for the trans-opercular approach to the insula]. / Fascículos asociativos ínsulo-operculares: revisión de su anatomía y de las implicaciones para el abordaje transopercular a la ínsula.

INTRODUCTION: The insula is a highly connected area, as an intricate network of afferent and efferent projections connect it with adjacent and distant cortical regions. OBJECTIVE: To perform an extensive review of recent literature to analyse the anatomy of the associative tracts related to the insula. RESULTS: The frontal aslant tract, arcuate fasciculus, horizontal portion of the superior longitudinal fasciculus and the middle longitudinal fasciculus are associative tracts connected to the opercula. The inferior fronto-occipital fasciculus (IFOF) and uncinate fasciculus run under the anterior and inferior portion of the insula. CONCLUSIONS: the pars triangularis and orbicularis of the inferior frontal gyrus, as well as the middle and anterior part of the superior temporal gyrus, have few connections with the perisylvian associative network. Consequently, in the trans-opercular approach to the insula, these 2 regions represent anatomical corridors that give access to the insula. The IFOF and the uncinate fasciculus represent the deep functional margin of resection.

[Tourette syndrome and reading disorder in a boy with left parietofrontal tract disruption]. / Trastorno de Tourette y de la lectura en un niño con disrupción del tracto parietofrontal izquierdo.

We present the case of a nine-year-old boy with Tourette syndrome and reading disorder with a history of a severe infectious process in the late neonatal period. Brain MRI showed a left parietal malacotic cavity and diffusion tensor imaging and tractography showed a striking disruption of the white matter bundle that joins the left parietal region with the ipsilateral frontal region with involvement of the left superior longitudinal fasciculus and of the left arcuate fasciculus. Although Tourette syndrome and reading disorder are fundamentally hereditary neuropsychiatric disorders, they can also occur secondary to cerebral alterations like those existing in this boy. The introduction of modern neuroimaging techniques in patients with neuropsychiatric disorders (or the risk of developing them) can be very useful in the diagnosis and prognosis in the future.

[Tractography of the uncinate fasciculus and the posterior cingulate fasciculus in patients with mild cognitive impairment and Alzheimer disease]. / Tractografía del fascículo uncinado y el fascículo uncinado posterior en pacientes con deterioro cognitivo leve y enfermedad de Alzheimer.

INTRODUCTION: Brain tractography is a non-invasive medical imaging technique which enables in vivo visualisation and various types of quantitative studies of white matter fibre tracts connecting different parts of the brain. We completed a quantitative study using brain tractography with diffusion tensor imaging in patients with mild cognitive impairment, patients with Alzheimer disease, and normal controls, in order to analyse the reproducibility and validity of the results. SUBJECTS AND METHODS: Fractional anisotropy (FA) and mean diffusivity (MD) were measured across the uncinate fasciculus and the posterior cingulate fasciculus in images, obtained from a database and a research centre, representing 52 subjects distributed among the 3 study groups. Two observers took the measurements twice in order to evaluate intra- and inter-observer reproducibility. RESULTS: Measurements of FA and MD of the uncinate fasciculus delivered an intraclass correlation coefficient above 0.9; ICC was above 0.68 for the posterior cingulate fasciculus. Patients with Alzheimer disease showed lower values of FA and higher MD values in the right uncinate fasciculus in images from the research centre. A comparison of the measurements from the 2 centres revealed significant differences. CONCLUSION: We established a reproducible methodology for performing tractography of the tracts in question. FA and MD indexes may serve as early indicators of Alzheimer disease. The type of equipment and the method used to acquire images must be considered because they may alter results as shown by comparing the 2 data sets in this study.

Helical structure of the cardiac ventricular anatomy assessed by diffusion tensor magnetic resonance imaging with multiresolution tractography.

INTRODUCTION AND OBJECTIVES: Deeper understanding of the myocardial structure linking the morphology and function of the heart would unravel crucial knowledge for medical and surgical clinical procedures and studies. Several conceptual models of myocardial fiber organization have been proposed but the lack of an automatic and objective methodology prevented an agreement. We sought to deepen this knowledge through advanced computer graphical representations of the myocardial fiber architecture by diffusion tensor magnetic resonance imaging. METHODS: We performed automatic tractography reconstruction of unsegmented diffusion tensor magnetic resonance imaging datasets of canine heart from the public database of the Johns Hopkins University. Full-scale tractographies have been built with 200 seeds and are composed by streamlines computed on the vector field of primary eigenvectors at the diffusion tensor volumes. We also introduced a novel multiscale visualization technique in order to obtain a simplified tractography. This methodology retains the main geometric features of the fiber tracts, making it easier to decipher the main properties of the architectural organization of the heart. RESULTS: Output analysis of our tractographic representations showed exact correlation with low-level details of myocardial architecture, but also with the more abstract conceptualization of a continuous helical ventricular myocardial fiber array. CONCLUSIONS: Objective analysis of myocardial architecture by an automated method, including the entire myocardium and using several 3-dimensional levels of complexity, reveals a continuous helical myocardial fiber arrangement of both right and left ventricles, supporting the anatomical model of the helical ventricular myocardial band described by F. Torrent-Guasp.

Cortical and subcortical mapping of language areas: correlation of functional MRI and tractography in a 3T scanner with intraoperative cortical and subcortical stimulation in patients with brain tumors located in eloquent areas.

OBJECTIVE: To describe the detection of cortical areas and subcortical pathways involved in language observed in MRI activation studies and tractography in a 3T MRI scanner and to correlate the findings of these functional studies with direct intraoperative cortical and subcortical stimulation. MATERIAL AND METHODS: We present a series of 14 patients with focal brain tumors adjacent to eloquent brain areas. All patients underwent neuropsychological evaluation before and after surgery. All patients underwent MRI examination including structural sequences, perfusion imaging, spectroscopy, functional imaging to determine activation of motor and language areas, and 3D tractography. All patients underwent cortical mapping through cortical and subcortical stimulation during the operation to resect the tumor. Postoperative follow-up studies were done 24 hours after surgery. RESULTS: The correlation of motor function and of the corticospinal tract determined by functional MRI and tractography with intraoperative mapping of cortical and subcortical motor areas was complete. The eloquent brain areas of language expression and reception were strongly correlated with intraoperative cortical mapping in all but two cases (a high grade infiltrating glioma and a low grade glioma located in the frontal lobe). 3D tractography identified the arcuate fasciculus, the lateral part of the superior longitudinal fasciculus, the subcallosal fasciculus, the inferior fronto-occipital fasciculus, and the optic radiations, which made it possible to mark the limits of the resection. The correlation with the subcortical mapping of the anatomic arrangement of the fasciculi with respect to the lesions was complete. CONCLUSION: The best treatment for brain tumors is maximum resection without associated deficits, so high quality functional studies are necessary for preoperative planning.