Anatomic evaluation of the posterior temporal approach via the Heschl's gyrus to the thalamus, internal capsule, and atrium.

OBJECTIVE: Posterior temporal craniotomy allows for the exposure of the superior surface of the planum temporale. Heschl's gyrus is the most prominent structure of the planum temporale and can be an anatomical landmark to approach deep brain structures such as the internal capsule, lateral thalamus, and ventricular atrium. METHODS: Ten human cadavers' heads underwent a posterior bilateral temporal craniotomy and the microsurgical dissection of Heschl's gyrus was performed and variables were measured with a neuronavigation system and statistically analyzed. RESULTS: The mean distance between the keyhole and Heschl's gyrus was 61.7 ± 7.3 mm, the mean distance between the stephanion to Heschl's gyrus was 40.8 ± 6.0 mm, and the mean distance between the temporal lobe and Heschl's gyrus was 54.9 ± 6.9 mm. The length of Heschl's gyrus was 24 ± 7.5 mm, and the inclination angle in the axial plane was 20.0 ± 3.7° having the vertex as its deepest point as the base on the surface of the temporal plane. From Heschl's gyrus, the distance from the surface to the internal capsule was 29.1 ± 5.6 mm, the distance to the lateral thalamus was 34.8 ± 7.3 mm, and the distance to the ventricular atrium was 39.6 ± 7.2 mm. No statistical difference was found between the right and left sides. CONCLUSIONS: Through a posterior temporal craniotomy, the temporal planum is exposed by opening the Sylvian fissure, where Heschl's gyrus can be identified and used as a natural corridor to approach the internal capsule, the ventricular atrium, and the lateral thalamus.

Stroke Due to Orthognathic Surgery: Case Report of a Rare Complication.

Le Fort I osteotomy is a frequent surgical procedure used in orthognathic surgeries to treat severe malocclusions and is associated with relatively rare surgical complications. Here, the authors report a case of thrombotic ischemic stroke as a result of this procedure, a complication still not described in the literature. A 19-year-old man with class II malocclusion and retrognathia underwent orthognathic surgery for aesthetic purposes. The surgery included a Le Fort I maxillary osteotomy with vertical impaction, bilateral sagittal split ramus osteotomy for mandibular advancement, and genioplasty. Postoperatively, the patient developed left eye blindness, headache, somnolence, aphasia, and right hemiplegia. Medical imaging showed the Le Fort I line of fracture extending from the maxillary osteotomy to the left optic canal and to the left carotid canal, with osseous fragments impinging the petrous segment of the internal carotid artery, left carotid artery occlusion and associated to an ischemic stroke at the left middle cerebral artery territory. Treatment required decompressive craniectomy and later focused on clinical stabilization, infection management, orthognathic care, neurorehabilitation, and cranioplasty. The hemiplegia and aphasia partially recovered during 12 months, and final dental occlusion was appropriate. Our report demonstrates that an unfavorable Le Fort I fracture trajectory can lead to ischemic stroke and severe neurological deficits.

Microsurgical approaches to the pulvinar: A comparative analysis.

OBJECTIVE: To compare the area of exposure to the cisternal thalamus associated with four surgical techniques: supracerebellar-infratentorial (SCIT), occipital interhemispheric (OI), transchoroidal (TC) and subtemporal before and after parahippocampal resection (ST and STh, respectively). METHODS: All approaches were performed on both sides of three heads. Qualitative anatomical analyses were performed to understand anatomical limits, advantages, and flaws of each technique. Quantitative analyses for multiple repeated dependent variables assessed significant differences between areas of exposure. RESULTS: Exposure area was significantly more extensive using TC and STh approaches compared to ST, OI, and SCIT. STh achieved a significantly wider exposure compared to ST. Regarding dissection angle, surrounding structures and limitations, ST approaches do not provide adequate exposure, nor alignment with the thalamic axis. The OI and STh may provide a better field of exposure, but without adequate alignment and challenging deeper dissections. TC provides better exposure of the cisternal pulvinar with access to lateral pulvinar at the atrium's anterior wall but is a transcortical route that disrupts non-pathological tissue. SCIT provides an adequate area of exposure with the possibility of alignment with the thalamus axis, thus allowing an easier dissection of deeper lesions. CONCLUSIONS: For lesions at the pulvinar surface, OI and STh are adequate. For lesions restricted to medial pulvinar and deep along the thalamus axis, SCIT approaches are recommended. Lesions extending to the lateral pulvinar and ventricular atrium are best removed through TC approaches. The ST approach was not suitable to the cisternal pulvinar due to its limited angular exposure.

Tractography of the ansa lenticularis in the human brain.

The aim of this study was to make a thorough investigation of the trajectory of the ansa lenticularis (AL) and its subcomponents using high-resolution fiber-tracking tractography. The subcomponents of the AL were reconstructed from one region of interest (ROI) in the area of the globus pallidus combined with another ROI in the red nucleus, substantia nigra, subthalamic nucleus, or thalamus. This fiber-tracking protocol was tested in an HCP-1065 template, 35 healthy subjects from Massachusetts General Hospital (MGH), and 20 healthy subjects from the human connectome project (HCP) using generalized q-sampling imaging (GQI)-based tractography. Quantitative anisotropy and fractional anisotropy were also computed for the AL subcomponents. The subcomponents of the AL could be reconstructed in the HCP-1065 template, 35 MGH healthy subjects, and 20 HCP healthy subjects. The AL descends from the globus pallidus and joins the ansa peduncularis for a short distance, subdividing later into fibers that continue separately to the red nucleus, substantia nigra, subthalamic nucleus, and thalamus. The study demonstrated the trajectory of the ansa lenticularis and its subcomponents using GQI-based tractography, improving our understanding of the anatomical connectivity between the globus pallidus and the thalamo-subthalamic region in the human brain. One Sentence Summary The investigation of the ansa lenticularis and its subcomponents using high-resolution diffusion images based tractography.

Composition and organization of the sagittal stratum in the human brain: a fiber dissection study.

OBJECTIVE: The sagittal stratum is divided into two layers. In classic descriptions, the stratum sagittale internum corresponds to optic radiations (RADs), whereas the stratum sagittale externum corresponds to fibers of the inferior longitudinal fasciculus. Although advanced for the time it was proposed, this schematic organization seems simplistic considering the recent progress on the understanding of cerebral connectivity and needs to be updated. Therefore, the authors sought to investigate the composition of the sagittal stratum and to detail the anatomical relationships among the macroscopic fasciculi. METHODS: The authors performed a layer-by-layer fiber dissection from the superolateral aspect to the ventricular cavity in 20 cadaveric human hemispheres. RESULTS: Diverse bundles of white matter were observed to contribute to the sagittal stratum and their spatial arrangement was highly consistent from one individual to another. This was the case of the middle longitudinal fasciculus, the inferior fronto-occipital fasciculus, the RADs, and other posterior thalamic radiations directed to nonvisual areas of the cerebral cortex. In addition, small contributions to the sagittal stratum came from the anterior commissure anteriorly and the inferior longitudinal fasciculus inferiorly. CONCLUSIONS: A general model of sagittal stratum organization in layers is possible, but the composition of the external layer is much more complex than is mentioned in classic descriptions. A small contribution of the inferior longitudinal fasciculus is the main difference between the present results and the classic descriptions in which this bundle was considered to entirely correspond to the stratum sagittale externum. This subject has important implications both for fundamental research and neurosurgery, as well as for the development of surgical approaches for the cerebral parenchyma and ventricular system.

The ansa peduncularis in the human brain: A tractography and fiber dissection study.

INTRODUCTION: The ansa peduncularis is a composite of white matter fiber bundles closely packed together that sweeps around the cerebral peduncle. The exact components of the ansa peduncularis and their anatomical trajectories are still not established firmly in the literature. OBJECTIVE: The aim of this study was to examine the topographical anatomy of the ansa peduncularis and its subcomponents using the fiber dissection and tractography techniques. METHODS: Ten formalin-fixed brains were prepared according to Klingler's method and dissected by the fiber dissection technique from the lateral, medial and inferior surfaces. The ansa peduncularis was also traced using high definition fiber tracking (HDFT) from the MRI data of twenty healthy adults and a 1021-subject template from the Human Connectome Project. RESULTS: The ventral amygdalofugal pathway system includes white matter fiber bundles with a topographically close relation as they sweep around the cerebral peduncle and contribute to form the ansa peduncularis: amygdaloseptal fibers connect the amygdala and anterior temporal cortex to the septal region and amygdalohypothalamic fibers project from the amygdala to the hypothalamus. Additionally, from the amygdala and anterior temporal cortex, amygdalothalamic fibers project to the medial thalamic region. The ansa lenticularis, which connects the globus pallidus to the thalamus, was not shown in our study. CONCLUSION: The study demonstrated the trajectory of the ansa peduncularis and its subcomponents, based on fiber dissection and tractography, improving our understanding of human brain anatomical connectivity.

Microsurgical anatomy of the central core of the brain.

OBJECTIVE The purpose of this study was to describe in detail the cortical and subcortical anatomy of the central core of the brain, defining its limits, with particular attention to the topography and relationships of the thalamus, basal ganglia, and related white matter pathways and vessels. METHODS The authors studied 19 cerebral hemispheres. The vascular systems of all of the specimens were injected with colored silicone, and the specimens were then frozen for at least 1 month to facilitate identification of individual fiber tracts. The dissections were performed in a stepwise manner, locating each gray matter nucleus and white matter pathway at different depths inside the central core. The course of fiber pathways was also noted in relation to the insular limiting sulci. RESULTS The insular surface is the most superficial aspect of the central core and is divided by a central sulcus into an anterior portion, usually containing 3 short gyri, and a posterior portion, with 2 long gyri. It is bounded by the anterior limiting sulcus, the superior limiting sulcus, and the inferior limiting sulcus. The extreme capsule is directly underneath the insular surface and is composed of short association fibers that extend toward all the opercula. The claustrum lies deep to the extreme capsule, and the external capsule is found medial to it. Three fiber pathways contribute to form both the extreme and external capsules, and they lie in a sequential anteroposterior disposition: the uncinate fascicle, the inferior fronto-occipital fascicle, and claustrocortical fibers. The putamen and the globus pallidus are between the external capsule, laterally, and the internal capsule, medially. The internal capsule is present medial to almost all insular limiting sulci and most of the insular surface, but not to their most anteroinferior portions. This anteroinferior portion of the central core has a more complex anatomy and is distinguished in this paper as the "anterior perforated substance region." The caudate nucleus and thalamus lie medial to the internal capsule, as the most medial structures of the central core. While the anterior half of the central core is related to the head of the caudate nucleus, the posterior half is related to the thalamus, and hence to each associated portion of the internal capsule between these structures and the insular surface. The central core stands on top of the brainstem. The brainstem and central core are connected by several white matter pathways and are not separated from each other by any natural division. The authors propose a subdivision of the central core into quadrants and describe each in detail. The functional importance of each structure is highlighted, and surgical approaches are suggested for each quadrant of the central core. CONCLUSIONS As a general rule, the internal capsule and its vascularization should be seen as a parasagittal barrier with great functional importance. This is of particular importance in choosing surgical approaches within this region.

Survival score scales of patients operated with spinal metastases: retrospective application in a Brazilian population / Escalas de prognóstico em pacientes operados com metástases vertebrais: aplicação retrospectiva em população brasileira

ABSTRACT Spinal cord epidural metastasis (SEM) is a common complication of systemic cancer. Predicting these patient’s survival is a key factor to select the proper treatment modality, but the three most used score scales to predict their survival (Tokuhashi revised score, Tomita score and Bauer modified score) were designed in single institutions and their reliability to predict correctly the patient’s survival were first tested only in those specific populations. This prognostication issue is addressed in this article, evaluating retrospectively the survival of 17 patients with SEM from a Brazilian general hospital with these score scales. Our results show that the actual survival of those patients were worse than the predicted of all three score scales, suggesting that differences between the different populations might have affected their reliability and alert that their usage as a major factor to select the most appropriate treatment have to be done with caution.

RESUMO Metástases vertebrais são uma complicação comum em pacientes com câncer sistêmico. Avaliar o prognóstico e a sobrevida desses pacientes é um fator de grande importância para escolher o tratamento mais adequado, porém as três escalas mais usadas atualmente para prever a sobrevida deles (Tokuhashi revisada, Tomita e Bauer modificada) foram desenhadas em instituições isoladas, e sua habilidade em estimar corretamente a sobrevida desses pacientes foram testadas primeiramente apenas nessas populações específicas. Essa questão de estimar o prognóstico é abordada nesse artigo, analisando retrospectivamente a sobrevida de 17 pacientes com metástase vertebral provenientes de um hospital geral no Brasil com essas escalas. Nossos resultados apontam que a sobrevida real desses pacientes foi menor que a prevista pelas três escalas, sugerindo que as diferenças entres as diferentes populações podem ter afetado a aplicabilidade delas. Assim, alertamos que o uso dessas escalas em populações diferentes das estudadas originalmente deve ser feito com cuidado.

Survival score scales of patients operated with spinal metastases: retrospective application in a Brazilian population.

Spinal cord epidural metastasis (SEM) is a common complication of systemic cancer. Predicting these patient's survival is a key factor to select the proper treatment modality, but the three most used score scales to predict their survival (Tokuhashi revised score, Tomita score and Bauer modified score) were designed in single institutions and their reliability to predict correctly the patient's survival were first tested only in those specific populations. This prognostication issue is addressed in this article, evaluating retrospectively the survival of 17 patients with SEM from a Brazilian general hospital with these score scales. Our results show that the actual survival of those patients were worse than the predicted of all three score scales, suggesting that differences between the different populations might have affected their reliability and alert that their usage as a major factor to select the most appropriate treatment have to be done with caution.

Three-dimensional digital projection in neurosurgical education: technical note.

Three-dimensional images have become an important tool in teaching surgical anatomy, and its didactic power is enhanced when combined with 3D surgical images and videos. This paper describes the method used by the last author (G.C.R.) since 2002 to project 3D anatomical and surgical images using a computer source. Projecting 3D images requires the superposition of 2 similar but slightly different images of the same object. The set of images, one mimicking the view of the left eye and the other mimicking the view of the right eye, constitute the stereoscopic pair and can be processed using anaglyphic or horizontal-vertical polarization of light for individual use or presentation to larger audiences. Classically, 3D projection could be obtained by using a double set of slides, projected through 2 slide projectors, each of them equipped with complementary filters, shooting over a medium that keeps light polarized (a silver screen) and having the audience wear appropriate glasses. More recently, a digital method of 3D projection has been perfected. In this method, a personal computer is used as the source of the images, which are arranged in a Microsoft PowerPoint presentation. A beam splitter device is used to connect the computer source to 2 digital, portable projectors. Filters, a silver screen, and glasses are used, similar to the classic method. Among other advantages, this method brings flexibility to 3D presentations by allowing the combination of 3D anatomical and surgical still images and videos. It eliminates the need for using film and film developing, lowering the costs of the process. In using small, powerful digital projectors, this method substitutes for the previous technology, without incurring a loss of quality, and enhances portability.

Microsurgical anatomy of the inferior limiting insular sulcus and the temporal stem.

OBJECT: The purpose of this study was to describe the location of each white matter pathway in the area between the inferior limiting insular sulcus (ILS) and temporal horn that may be crossed in approaches through the temporal stem to the medial temporal lobe. METHODS: The fiber tracts in 14 adult cadaveric cerebral hemispheres were examined using the Klingler technique. The fiber dissections were completed in a stepwise manner, identifying each white matter pathway in different planes and describing its position in relation to the anterior end of the ILS. RESULTS: The short-association fibers from the extreme capsule, which continue toward the operculae, are the most superficial subcortical layer deep to the ILS. The external capsule fibers are found deeper at an intermediate layer and are formed by the uncinate fasciculus, inferior frontooccipital fasciculus, and claustrocortical fibers in a sequential anteroposterior disposition. The anterior commissure forms the next deeper layer, and the optic radiations in the sublenticular part of the internal capsule represent the deepest layer. The uncinate fasciculus is found deep to the anterior third of the ILS, whereas the inferior frontooccipital fasciculus and optic radiations are found superficial and deep, respectively, at the posterior two-thirds of this length. CONCLUSIONS: The authors' findings suggest that in the transsylvian approach, a 6-mm incision beginning just posterior to the limen insula through the ILS will cross the uncinate fasciculus but not the inferior frontooccipital fasciculus or optic radiations, but that longer incisions carry a risk to language and visual functions.

O cérebro, a visão tridimensional, e as técnicas de obtenção de imagens estereoscópicas / The brain, tridimensional vision, and the techniques to obtain stereoscopic images

Em forma de artigo de revisão, os autores tratam aqui inicialmente do desenvolvimento filogenético e dos mecanismos oculares e neurais envolvidos com a visão tridimensional estereoscópica, e a seguir descrevem mais detalhadamente as diferentes técnicas disponíveis para a obtenção, impressão, projeção e visualização em monitores de imagens estereoscópicas...

In this review article the authors discuss initially the evolutionary development and the ocular and neural mechanisms involved with the stereoscopic tridimensional vision, and them describe with more details the different current techniques available to obtain, to print, to project and to see in computer monitors stereoscopic images...

Demonstração estereoscópica dos sulcos e giros cerebrais / Stereoscopic demonstration of the cerebral sulci and gyri

Os sulcos cerebrais constituem as delimitações anatômicas dos giros cerebrais e os principais corredores de acessos transparenquimatosos da moderna microneurocirurgia, e precisam ser compreendidos em conjunto com os giros quanto às suas configurações básicas...

The brain sulci constitute the fundamental anatomical delimiting landmarks of the cerebral gyri and the main surgical corridors of modern microneurosurgery, and should be understood together with the gyri particularly regarding their basics...

Demonstração estereoscópica dos ventrículos laterais do cérebro / Stereoscopic demonstration of the cerebral lateral ventricles

Os ventrículos laterais, compostos pelos seus respectivos como frontal, corpo, átrio e cornos temporal e occipital, são aqui apresentados em função das estruturas neurais que formam os seus assoalhos, tetos e paredes anteriores, mediais e laterais, visando em particular a melhor compreensão da tridimensionalidade das estruturas...

The lateral ventricles, constituted by their respective frontal horn, body, atrium, and temporal occipital horns, are here represented according to the neural structures that form their floors, roofs and their anterior, medial lateral walls, in order to optimize tyhe understanding of deep telencephalic structures...

The anterior sylvian point and the suprasylvian operculum.

OBJECT: The sylvian fissure or lateral sulcus is the most identifiable feature of the superolateral brain surface and constitutes the main microneurosurgical corridor, given the high frequency of approachable intracranial lesions through this route. The anterior sylvian point (ASyP) divides this fissure in its main anterior and posterior rami and was evaluated in this study for its morphology, exact location, and sulcal and neural relationships to assess its suitability as an initial, visually identifiable landmark for further neuroimaging and intraoperative estimation of its adjoining suprasylvian structures. METHODS: This study is based on 32 formalin-fixed cerebral hemispheres. The brains were removed from the skulls of 16 cadavers after the introduction of plastic catheters through properly positioned burr holes; the number of specimens for some of the analyzed data differed because of incorrect positioning of catheters or damage to the studied structures caused by the initial steps of the study. The ASyP had a cisternal aspect in 94% of the specimens and was always located inferior to the triangular part of the inferior frontal gyrus, 2.3 6 0.5 cm in front of the inferior rolandic point. The ASyP was located underneath the 1.5-cm-diameter cranial area of the anterior aspect of the squamous suture. Its adjoining structures that compose the suprasylvian operculum have constant basic morphological configurations. CONCLUSIONS: The ASyP underlies the anterior aspect of squamous suture just behind the pterion, can be easily recognized, and constitutes a reliable initial sulcal landmark for further estimation of the suprasylvian sulcal and gyral structures. The suprasylvian operculum can be understood as a series of convolutions roughly arranged as a V-shaped convolution, with its vertex constituted by the ASyP, followed by three U-shaped convolutions and one C-shaped convolution.