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Lesions in the ventral striatum region (above the anterior perforated substance) are a challenge for neurosurgeons due to their direct relationship with the lenticulostriate arteries, which difficult the surgical access. The standard approaches for this region include the following: 1) transfrontal approach, 2) transanterior perforating substance approach, 3) transcallosal transventricular approach, and 4) pterional transsylvian-transinsular route. In this study, we aimed to describe a novel anatomical approach through the anterior limiting sulcus of the insula in order to access the ventral striatum.We reviewed the literature and performed a detailed dissection of this region by using Klingler's technique with brain specimens injected with silicone, paying special attention to the white fibers and lenticulostriate arteries, and provided a description of an illustrative case of a cavernous malformation.Neuroanatomical dissections showed that the lenticulostriate arteries had an inverted C-shaped anterior concavity, leaving less significant vascular relationships in the depth of the anterior limiting sulcus of the insula. In the case we described, the cavernous malformation was completely resected and the patient was discharged without any neurological deficits.The transanterior limiting sulcus of the insula approach to the ventral striatum offers a safe access route for selected cases and can be performed on the basis of anatomical references. Three-dimensional understanding of the intrinsic brain architecture and its relationships with vascular structures in this specific area is important and can be acquired mainly through laboratory training.

Deep understanding of neuroanatomy is mandatory in planning and execution of surgery for intraventricular lesions. These operative procedures include both open and endoscopic approaches, and choosing the appropriate trajectory to the various parts of the ventricles can minimize the resulting morbidity of the approach, which may occur in addition to the potential risk to the surrounding structures during resection of the lesion itself. The use of the natural spaces provided by the cerebral fissures and sulci allows access to the ventricular cavities whenever possible, however, traversing neural tissue eventually is inevitable. The juxta-midline location of the frontal horns and body of the lateral ventricle and the third ventricle allows the use of interhemispheric approaches. On the other hand, transcortical/trans-sulcal approaches are necessary for lesions located within the atrium or temporal horns of the lateral ventricle. In planning these approaches not only exquisite knowledge of the functional anatomy of the cortex is required, but also understanding the subcortical architecture of the white matter fibres to choose the safest rather than just the shortest route. Furthermore, appreciating the potential morbidity from injuring the surrounding intra- and peri-ventricular structures and awareness of the blind spots related to the various trajectories cannot be underestimated. Surgery for fourth ventricular lesions is covered elsewhere.

Background Learning surgical anatomy of the petrous pyramid can be a challenge, especially in the beginning of the training process. Providing an easier, holistic approach can be of help to everyone with interest in learning and teaching skull base anatomy. We present the complex organization of petrous pyramid anatomy using a new compartmental approach that is simple to understand and remember. Methods The surfaces of the petrous pyramid of two temporal bones were examined; and the contents of the petrous pyramid of 8 temporal bones were exposed through progressive drilling of the superior surface. Results The petrous pyramid is made up of a bony container, and its contents were grouped into 4 compartments (mucosal, cutaneous, neural, and vascular). Two reference lines were identified (mucosal and external-internal auditory canal lines) intersecting at the level of the middle ear. The localization of contents relative to these reference lines was then described, and 2 methods of segmentation (the X method and the V method) were then proposed. This description was then used to describe middle ear relationships, facial nerve anatomy, and air cell distribution. Conclusions This new compartmental approach allows a comprehensive understanding of the distribution of petrous pyramid contents. Dividing it into anatomic compartments, and then navigating this mental map along specific reference points, lines, spaces, and segments, could create a useful tool to teach or learn its complex tridimensional anatomy.

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.

This book is the first to offer a comprehensive guide to understanding the brain's architecture from a topographical viewpoint. Authored by a leading expert in surgical neuroanatomy, this practical text provides tri-dimensional understanding of the cerebral hemispheres, and the relationships between cerebral surfaces and the skull's outer surfaces through detailed brain dissections and actual clinical cases with operative photographs and correlative neuroimaging. For neurosurgeons, neuroradiologists and neurologists at all levels, this book emphasises the anatomy of the sulci and gyri of the cerebral surface. It is an essential resource for the general neurosurgery practice, and more particularly for planning surgical access routes for intracranial tumors.

OBJECTIVEThe 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.METHODSThe 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.RESULTSThe 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.CONCLUSIONSAs 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.

Objective To study the ideal patient's head positioning for the anterior circulation aneurysms microsurgery. Method We divided the study in two parts. Firstly, 10 fresh cadaveric heads were positioned and dissected in order to ideally expose the anterior circulation aneurysm sites. Afterwards, 110 patients were submitted to anterior circulation aneurysms microsurgery. During the surgery, the patient's head was positioned accordingly to the aneurysm location and the results from the cadaveric study. The effectiveness of the position was noted. Results We could determine mainly two patterns for head positioning for the anterior circulation aneurysms. Conclusion The best surgical exposure is related to specific head positions. The proper angle of microscopic view may minimize neurovascular injury and brain retraction. Objetivo Estudar o posicionamento da cabeça para a cirurgia de aneurismas cerebrais da circulação anterior. Método Dividimos o estudo em duas partes. Inicialmente, dez cabeças de cadáveres frescos foram posicionadas e dissecadas de modo a expor, de maneira ideal, os principais sítios de aneurismas na circulação anterior do cérebro. Posteriormente, 110 pacientes foram submetidos a microcirurgia para clipagem de aneurismas cerebrais da circulação anterior. Durante as cirurgias, as cabeças foram posicionadas de acordo com a localização específica de cada aneurisma e o resultado obtido no estudo dos cadáveres. Cada paciente teve sua posição avaliada quanto a sua eficácia. Resultados Obtivemos basicamente dois padrões de posicionamento da cabeça para cirurgias de aneurismas cerebrais da circulação anterior. Conclusão A melhor exposição cirúrgica está relacionada à posição específica da cabeça para cada localização aneurismática. O ângulo de visão microscópica adequado minimiza lesões neurovasculares e a excessiva retração cerebral.

Rationale Lymphomatosis cerebri is a rare form of PCNSL, characterized by diffuse infiltration of lymphoma cells in cerebral parenchyma, without mass-formation and mild or no contrast enhancement on magnetic resonance (MR) imaging. There are less than 50 cases described in the literature under the term Lymphomatosis cerebri. Patient concerns A 74-year-old man presented to our service with progressive dementia for 12 months and accelerated cognitive decline within the last two months. Brain magnetic resonance imaging showed areas of hyperintensity involving predominantly the white matter of frontal lobes and knee of the corpus callosum, along with areas of blood-brain barrier disruption and areas of restricted diffusion. Stereotaxy brain surgery was indicated into contrasting areas and histologically there was heterogeneous foci of discreet infiltration of rare medium-large lymphoid cells intermingled with inflammatory cells and these atypical lymphoid cells were placed on breakdown neuropil and did not form tumor mass or sheets of cells, but occasionally displayed perivascular distribution. Immunohistochemically, these atypical lymphoid cells expressed CD20, Bcl2, Bcl6 and, heterogeneously, IRF4/MUM1. Diagnosis The diagnosis of a primary CNS diffuse large B-cell lymphoma manifested as lymphomatosis cerebri was performed. Interventions The treatment of choice was: temozolomide 100 mg/m (D1 to D5), methotrexate 3 g/m (D1, D10, and D20) and rituximab 375 mg/m. Outcomes The patient evolved with progressive neurological deterioration, regardless of the improvement on neuroimaging. Lessons We described the diagnostic dilemma we faced with an elderly man with rapid cognitive impairment and a myriad of differential diagnoses, diagnosed with primary CNS diffuse large B-cell lymphoma with a lymphomatosis cerebri-like pattern.

Object The surface of the developing fetal brain undergoes significant morphological changes during fetal growth. The purpose of this study was to evaluate the morphological development of the brain sulci from the fetal to the early postnatal period. Methods Two hundred fourteen brain hemispheres from 107 human brain specimens were examined to evaluate the timing of sulcal formation, from its appearance to its complete development. These brains were obtained from cadavers ranging in age from 12 weeks of gestation to 8 months of postnatal life. Results The order of appearance of the cerebral sulci, and the number and percentages of specimens found in this study were as follows: longitudinal cerebral fissure at 12 weeks (10/10, 100%); callosal sulcus at 12 weeks (10/10, 100%); hippocampal sulcus at 15 weeks (7/10, 70%); lateral sulcus at 17 weeks (20/22, 90.9%); circular insular sulcus at 17 weeks (18/22, 81.8%); olfactory sulcus at 17 weeks (18/22, 81.8%); calcarine sulcus at 17 weeks (14/22, 63.6%); parietooccipital sulcus at 17 weeks (11/22, 50%); cingulate sulcus at 19 weeks (16/20, 80%); central sulcus at 21 weeks (22/38, 57.9%); orbital sulcus at 22 weeks (9/16, 56.2%); lunate sulcus at 24 ± 2 weeks (12/16, 75%); collateral sulcus at 24 ± 2 weeks (8/16, 50%); superior frontal sulcus at 25 ± 2 weeks (5/6, 83.3%); rhinal sulcus at 25 ± 2 weeks (3/6, 50%); precentral sulcus at 26 ± 3 weeks (2/4, 50%); postcentral sulcus at 26 ± 3 weeks (2/4, 50%); superior temporal sulcus at 26 ± 3 weeks (2/4, 50%); central insular sulcus at 29 ± 2 weeks (4/4, 100%); intraparietal sulcus at 29 ± 2 weeks (2/4, 50%); paraolfactory sulcus at 29 ± 2 weeks (2/4, 50%); inferior frontal sulcus at 30 ± 3 weeks (2/4, 50%); transverse occipital sulcus at 30 ± 3 weeks (2/4, 50%); occipitotemporal sulcus at 30 ± 3 weeks (2/4, 50%); marginal branch of the cingulate sulcus at 30 ± 3 weeks (2/4, 50%); paracentral sulcus at 30 ± 3 weeks (2/4, 50%); subparietal sulcus at 30 ± 3 weeks (2/4, 50%); inferior temporal sulcus at 31 ± 3 weeks (3/6, 50%); transverse temporal sulcus at 33 ± 3 weeks (6/8, 75%); and secondary sulcus at 38 ± 3 weeks (2/4, 50%). Conclusions The brain is subjected to considerable morphological changes throughout gestation. During fetal brain development the cortex begins to fold in, thereby increasing the cortical surface. All primary sulci are formed during fetal life. The appearance of each sulcus follows a characteristic timing pattern, which may be used as one of the reliable guides pertinent to gestational age and normal fetal development.

This review intended to describe in a didactic and practical manner the frontotemporosphenoidal craniotomy, which is usually known as pterional craniotomy and constitute the cranial approach mostly utilized in the modern neurosurgery. This is, then, basically a descriptive text, divided according to the main stages involved in this procedure, and describes with details how the authors currently perform this craniotomy. A presente revisão visou descrever de forma didática e prática a realização da craniotomia frontotemporoesfenoidal, usualmente denominada pterional, que constitui a craniotomia mais utilizada na prática neurocirúrgica atual. Trata-se, portanto, de um texto fundamentalmente descritivo, dividido conforme as principais etapas envolvidas na realização desse procedimento, que mostra com detalhes a técnica utilizada atualmente pelo presente grupo de autores.

Background The fiber dissection technique provides unique 3-dimensional anatomic knowledge of the white matter. Objective To examine the optic radiation anatomy and its important relationship with the temporal stem and to discuss its findings in relation to the approaches to temporal lobe lesions. Methods We studied 40 cerebral hemispheres of 20 brains that had been fixed in formalin solution for 40 days. After removal of the arachnoid membrane, the hemispheres were frozen, and the Klingler technique was used for dissection under magnification. Stereoscopic 3-dimensional images of the dissection were obtained for illustration. Results The optic radiations are located deep within the superior and middle temporal gyri, always above the inferior temporal sulcus. The mean distance between the cortical surface and the lateral edge of the optic radiation was 21 mm. Its fibers are divided into 3 bundles after their origin. The mean distance between the anterior tip of the temporal horn and the Meyer loop was 4.5 mm, between the temporal pole and the anterior border of the Meyer loop was 28.4 mm, and between the limen insulae and the Meyer loop was 10.7 mm. The mean distance between the lateral geniculate body and the lateral margin of the central bundle of the optic radiation was 17.4 mm. Conclusion The white matter fiber dissection reveals the tridimensional intrinsic architecture of the brain, and its knowledge regarding the temporal lobe is particularly important for the neurosurgeon, mostly because of the complexity of the optic radiation and related fibers.

Object The anatomy of the occipital lobe convexity is so intricate and variable that its precise description is not found in the classic anatomy textbooks, and the occipital sulci and gyri are described with different nomenclatures according to different authors. The aim of this study was to investigate and describe the anatomy of the occipital lobe convexity and clarify its nomenclature. Methods The configurations of sulci and gyri on the lateral surface of the occipital lobe of 20 cerebral hemispheres were examined in order to identify the most characteristic and consistent patterns. Results The most characteristic and consistent occipital sulci identified in this study were the intraoccipital, transverse occipital, and lateral occipital sulci. The morphology of the transverse occipital sulcus and the intraoccipital sulcus connection was identified as the most important aspect to define the gyral pattern of the occipital lobe convexity. Conclusions Knowledge of the main features of the occipital sulci and gyri permits the recognition of a basic configuration of the occipital lobe and the identification of its sulcal and gyral variations.

Object The primary aim of this study was to establish standard sites for bur holes that maintain constant anatomical relationships with the skull base and neural structures and can serve as the basal aspect of supratentorial temporooccipital craniotomies. Methods To determine cranial–cerebral relationships, the authors created bur holes in 16 adult cadaveric skulls. Three bur holes were made on each side of the skulls (32 cerebral hemispheres). The authors then introduced plastic catheters through the bur holes to evaluate pertinent cranial and neural landmarks. The first bur hole, located anterior to the auricle of the ear, appeared to have a particular anatomical relationship with the anterior aspect of the petrous portion of the temporal bone and the most anterior aspect of the midbrain. The second bur hole, whose base was located 1 cm above the interface of the parietomastoid and squamous sutures, had a particular relationship with the posterior border of the petrous portion of the temporal bone and with the posterior aspect of the midbrain. The third bur hole, whose base was located 1 cm above the asterion, was mostly supratentorial and particularly related to the preoccipital notch. Conclusions The preauricular bur hole and the bur hole whose base was located 1 cm above the interface of the parietomastoid and squamous sutures delimit anteriorly and posteriorly the external projection of the petrous bone and the midbrain. The middle fossa floor is located anterior to the site of the preauricular bur hole, and the superior surface of the tentorium is posterior to the bur hole located above the parietomastoid–squamous suture interface. Together with the bur hole whose base is located above the asterion, these bur holes can be considered standards for temporooccipital craniotomies.

OBJECT Brainstem surgery remains a challenge for the neurosurgeon despite recent improvements in neuroimaging, microsurgical techniques, and electrophysiological monitoring. A detailed knowledge of the microsurgical anatomy of the brainstem surface and its internal architecture is mandatory to plan appropriate approaches to the brainstem, to choose the safest point of entry, and to avoid potential surgical complications. METHODS An extensive review of the literature was performed regarding the brainstem surgical approaches, and their correlations with the pertinent anatomy were studied and illustrated through dissection of human brainstems properly fixed with 10% formalin. The specimens were dissected using the fiber dissection technique, under ×6 to ×40 magnification. 3D stereoscopic photographs were obtained (anaglyphic 3D) for better illustration of this study. RESULTS The main surgical landmarks and their relationship with the cerebellum and vascular structures were identified on the surface of the brainstem. The arrangements of the white matter (ascending and descending pathways as well as the cerebellar peduncles) were demonstrated on each part of the brainstem (midbrain, pons, and medulla oblongata), with emphasis on their relationships with the surface. The gray matter, constituted mainly by nuclei of the cranial nerves, was also studied and illustrated. CONCLUSIONS The objective of this article is to review the microsurgical anatomy and the surgical approaches pertinent to the brainstem, providing a framework of its external and internal architecture to guide the neurosurgeon during its related surgical procedures.

Background Surgical access to the temporal horn is necessary to treat tumors and vascular lesions, but is used mainly in patients with mediobasal temporal epilepsy. The surgical approaches to this cavity fall into 3 primary categories: lateral, inferior, and transsylvian. The current neurosurgical literature has underestimated the interruption of involved fiber bundles and the correlated clinical manifestations. Objective To delineate the interruption of fiber bundles during the different approaches to the temporal horn. Methods We simulated the lateral (trans-middle temporal gyrus), inferior (transparahippocampal gyrus), and transsylvian approaches in 20 previously frozen, formalin-fixed human brains (40 hemispheres). Fiber dissection was then done along the lateral and inferior aspects under the operating microscope. Each stage of dissection and its respective fiber tract interruption were defined. Results The lateral (trans-middle temporal gyrus) approach interrupted "U" fibers, the superior longitudinal fasciculus (inferior arm), occipitofrontal fasciculus (ventral segment), uncinate fasciculus (dorsolateral segment), anterior commissure (posterior segment), temporopontine, inferior thalamic peduncle (posterior fibers), posterior thalamic peduncle (anterior portion), and tapetum fibers. The inferior (transparahippocampal gyrus) approach interrupted "U" fibers, the cingulum (inferior arm), and fimbria, and transected the hippocampal formation. The transsylvian approach interrupted "U" fibers (anterobasal region of the extreme capsule), the uncinate fasciculus (ventromedial segment), and anterior commissure (anterior segment), and transected the anterosuperior aspect of the amygdala. Conclusion White matter dissection improves our knowledge of the complex anatomy surrounding the temporal horn. Identifying the fiber bundles at risk during each surgical approach adds important information for choosing the appropriate surgical strategy.

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.

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 na constituição dos hemisférios cerebrais. Imagens estereoscópicas anaglíficas ilustram o texto para a melhor visualização da tridimensionalidade dessas estruturas nervosas.

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. O artigo termina mencionando a experiência da Disciplina de Topografia Estrutural Humana do Departamento de Cirurgia da FMUSP com o desenvolvimento de material didático estereoscópico, utilizando a técnica anaglífica para impressão e a técnica polarizada para projeção, ambas atualmente com tecnologia digital. Esquemas didáticos e imagens estereoscópicas anaglíficas ilustram o texto.

Os ventrículos laterais, compostos pelos seus respectivos corno 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 telencefálicas profundas. Imagens estereoscópicas anaglíficas ilustram o texto para a melhor visualização da tridimensionalidade dessas estruturas nervosa.

Transient evoked otoacoustic emissions are believed to be sensitive to the effects of the cochlear efferent system. The most well-known function of this system is inhibitory on cochlear response. It has been demonstrated that crossed medial efferent system section produces inhibitory control of the outer hair cells mechanisms responsible for non-linear transient evoked otoacoustic emissions generation. However, we suppose that the uncrossed medial efferent system plays a role in outer hair cell function too. We recorded the non-linear part of transient evoked otoacoustic emissions in 17 chinchillas before and after section of the vestibular nerve (crossed and uncrossed fibers). Responses at frequencies bands centered on 0.8, 1.6, 2.4, 3.2 and 4.0 kHz, as well as total emission responses, were analyzed. After vestibular nerve section, there were significant increases in the amplitudes of the 2.4- and 4.0 kHz responses and of the total response. These results indicate that the medial efferent system is important to maintain normal cochlear mechanics. Uncrossed medial efferent system and lateral efferent system seem to be not important in maintaining normal cochlear mechanics.

O implante auditivo de tronco cerebral é uma opção os pacientes surdos que não têm a integridade das vias auditivas preservada. A cirurgia, por sua complexidade anatômica e funcional, requer treinamento específico em laboratório de anatomia por parte do cirurgião. OBJETIVOS: Estudar a anatomia cirúrgica da cirurgia do implante auditivo de tronco cerebral. FORMA DE ESTUDO: Estudo anatômico. MATERIAL E MÉTODO: Neste estudo dissecamos cadáver fresco preparado com solução corante injetada nas artérias e veias intra-cranianas. O local de inserção do eletrodo do implante auditivo de tronco cerebral foi estudado através do acesso translabiríntico. RESULTADOS: A técnica cirúrgica utilizada para a implantação do eletrodo de tronco cerebral é semelhante à utilizada na remoção do shwannoma vestibular. O complexo de núcleo coclear, composto pelo núcleo coclear ventral e dorsal, é o local para a colocação do eletrodo. O núcleo coclear ventral é o principal núcleo de transmissão de impulsos neurais do VIII par e seus axônios formam a principal via ascendente do nervo coclear. Tanto o núcleo ventral como o dorsal não são visíveis durante a cirurgia e sua localização depende de identificação de estruturas anatômicas adjacentes. CONCLUSÃO: A região de implantação do eletrodo do implante auditivo de tronco cerebral apresenta referências anatômicas que permitem sua fácil identificação durante a cirurgia.Auditory brainstem implant (ABI) is an option for deaf patients who do not have the whole auditory pathways preserved. The surgery, because of its anatomical and functional complexity, requires specific training of the surgeon in an anatomy lab. AIM: To study the surgical anatomy of the auditory brainstem implant surgery. STUDY DESIGN: Anatomic study. MATERIAL AND METHOD: In the present study, we dissected a fresh cadaver prepared with a dye solution injected into the arteries and intracranial veins. The location of the insertion of the ABI electrode was studied through translabyrinthine access. RESULTS: The surgical technique used for implanting the brainstem electrode is similar to that used in the removal of vestibular schwannoma. The cochlear nucleus complex, comprising ventral and dorsal cochlear nuclei, is the optimal electrode site. The ventral cochlear nucleus is the principal nucleus for transmission of neural impulses from the 8th pair and form the main ascending route of the cochlear nerve. Neither the ventral nor the dorsal nuclei are visible during surgery and their location depends on the identification of adjacent anatomical structures. CONCLUSION: The region for the implantation of the electrode in the auditory brainstem implant presents anatomical landmarks that allow its easy identification during surgery.

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 ± 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.

Summary A uditory brainstem implant (ABI) is an option for deaf patients who do not have the whole auditory pathways preserved. The surgery, because of its anatomical and functional complexity, requires specific training of the surgeon in an anatomy lab. Aim : To study the surgical anatomy of the auditory brainstem implant surgery. Study design : Anatomic study. Material and Method : In the present study, we dissected a fresh cadaver prepared with a dye solution injected into the arteries and intracranial veins. The location of the insertion of the ABI electrode was studied through translabyrinthine access. Results : The surgical technique used for implanting the brainstem electrode is similar to that used in the removal of vestibular schwannoma. The cochlear nucleus complex, comprising ventral and dorsal cochlear nuclei, is the optimal electrode site. The ventral cochlear nucleus is the principal nucleus for transmission of neural impulses from the 8th pair and form the main ascending route of the cochlear nerve. Neither the ventral nor the dorsal nuclei are visible during surgery and their location depends on the identification of adjacent anatomical structures. Conclusion : The region for the implantation of the electrode in the auditory brainstem implant presents anatomical landmarks that allow its easy identification during surgery.

GBM may manifest rapidly de novo(primary GBM), or may develop slowly from grade II orgrade III astrocytomas (secondary GBM), suggesting thatthey are distinct disease entities that evolve throughdifferent genetic pathways.In recent genome-wide analyses, high rates of sponta-neous mutations in the gene encoding cytosolic NADP-dependent isocitrate dehydrogenase 1 (IDH1) have beenreported in diffuse gliomas including WHO grades II andIII astroglial and oligodendroglial lineages.

The educational value of stereoscopic imaging in neurosurgical training has increasingly been appreciated and its use increased during the last decade. We describe a technique that we developed to acquire and reproduce intra-operative stereoscopic images.

✓ The authors describe how to use the three-dimensional (3D) anaglyphic method to produce stereoscopic prints for anatomical and surgical teaching and reports preparation by using currently available nonprofessional photographic and computer methods. As with any other method of producing stereoscopic images, the anaglyphic procedure is based on the superimposition of two slightly different images of the object to be reproduced, one seen more from a left-sided point of view and the other seen more from a right-sided point of view. The pictures are obtained using a single camera, which following the first shot can be slid along a special bar for the second shot, or by using two cameras affixed to a surgical microscope. After the images have been distinguished from each other by applying different complementary color dyes, the images are scanned and superimposed on each other with the aid of nonprofessional imaging-manipulation software used on a standard personal computer (PC), and are printed using a standard printer. To be seen stereoscopically, glasses with colored lenses, normally one red and one blue, have to be used. Stereoscopic 3D anaglyphic prints can be produced using standard photographic and PC equipment; after some training, the prints can be easily reproduced without significant cost and are particularly helpful to disclose the 3D character of anatomical structures.

The surface of the developing fetal brain undergoes significant morphological changes during fetal growth. The purpose of this study was to evaluate the morphological development of the brain sulci from the fetal to the early postnatal period.Two hundred fourteen brain hemispheres from 107 human brain specimens were examined to evaluate the timing of sulcal formation, from its appearance to its complete development. These brains were obtained from cadavers ranging in age from 12 weeks of gestation to 8 months of postnatal life.The order of appearance of the cerebral sulci, and the number and percentages of specimens found in this study were as follows: longitudinal cerebral fissure at 12 weeks (10/10, 100%); callosal sulcus at 12 weeks (10/10, 100%); hippocampal sulcus at 15 weeks (7/10, 70%); lateral sulcus at 17 weeks (20/22, 90.9%); circular insular sulcus at 17 weeks (18/22, 81.8%); olfactory sulcus at 17 weeks (18/22, 81.8%); calcarine sulcus at 17 weeks (14/22, 63.6%); parietooccipital sulcus at 17 weeks (11/22, 50%); cingulate sulcus at 19 weeks (16/20, 80%); central sulcus at 21 weeks (22/38, 57.9%); orbital sulcus at 22 weeks (9/16, 56.2%); lunate sulcus at 24 ± 2 weeks (12/16, 75%); collateral sulcus at 24 ± 2 weeks (8/16, 50%); superior frontal sulcus at 25 ± 2 weeks (5/6, 83.3%); rhinal sulcus at 25 ± 2 weeks (3/6, 50%); precentral sulcus at 26 ± 3 weeks (2/4, 50%); postcentral sulcus at 26 ± 3 weeks (2/4, 50%); superior temporal sulcus at 26 ± 3 weeks (2/4, 50%); central insular sulcus at 29 ± 2 weeks (4/4, 100%); intraparietal sulcus at 29 ± 2 weeks (2/4, 50%); paraolfactory sulcus at 29 ± 2 weeks (2/4, 50%); inferior frontal sulcus at 30 ± 3 weeks (2/4, 50%); transverse occipital sulcus at 30 ± 3 weeks (2/4, 50%); occipitotemporal sulcus at 30 ± 3 weeks (2/4, 50%); marginal branch of the cingulate sulcus at 30 ± 3 weeks (2/4, 50%); paracentral sulcus at 30 ± 3 weeks (2/4, 50%); subparietal sulcus at 30 ± 3 weeks (2/4, 50%); inferior temporal sulcus at 31 ± 3 weeks (3/6, 50%); transverse temporal sulcus at 33 ± 3 weeks (6/8, 75%); and secondary sulcus at 38 ± 3 weeks (2/4, 50%).The brain is subjected to considerable morphological changes throughout gestation. During fetal brain development the cortex begins to fold in, thereby increasing the cortical surface. All primary sulci are formed during fetal life. The appearance of each sulcus follows a characteristic timing pattern, which may be used as one of the reliable guides pertinent to gestational age and normal fetal development.

Objective To describe the microsurgical anatomy, branches, and anatomic relationships of the posterior cerebral artery (PCA) represented in three-dimensional images. Methods Seventy hemispheres of 35 brain specimens were studied. They were previously injected with red silicone and fixed in 10% formalin for at least 40 days. Four of the studied specimens were frozen at −10° to −15°C for 14 days, and additional dissection was done with the Klingler's fiber dissection technique at ×6 to ×40 magnification. Each segment of the artery was measured and photographed to obtain three-dimensional stereoscopic images. Results The PCA origin was in the interpeduncular cistern at the pontomesencephalic junction level in 23 specimens (65.7%). The PCA was divided into four segments: P1 extends from the PCA origin to its junction with the posterior communicating artery with an average length of 7.7 mm; P2 was divided into an anterior and posterior segment. The P2A segment begins at the posterior communicating artery and ends at the most lateral aspect of the cerebral peduncle, with an average length of 23.6 mm, and the P2P segment extends from the most lateral aspect of the cerebral peduncle to the posterior edge of the lateral surface of the midbrain, with an average length of 16.4 mm; P3 extends from the posterior edge of the lateral surface of the midbrain and ends at the origin of the parieto-occipital sulcus along the calcarine fissure, with an average length of 19.8 mm; and the P4 segment corresponds to the parts of the PCA that run along or inside both the parieto-occipital sulcus and the distal part of the calcarine fissure. Conclusions To standardize the neurosurgical practice and knowledge, surgical anatomic classifications should be used uniformly and further modified according to the neurosurgical experience gathered. The PCA classification proposed intends to correlate its anatomic segments with their required microneurosurgical approaches.

Surgical approaches to the frontal basal region as those applied to the anterior communicating artery (AntCommA) aneurysms can lead to post-operative deficits such as memory impairment, executive function disturbances and personality changes1-4. Some of such disturbances may be caused by an aneurysm rupture itself followed by vasospasm or direct injury to the brain parenquima3,4. This is especially true when we consider that many AnCommA aneurysm surgery cases are performed with a variable coagulation degree followed by the gyrus rectus aspiration [...]