Anatomical step-by-step dissection of common approaches to the third ventricle for trainees: surgical anatomy of the anterior transcortical and interhemispheric transcallosal approaches, surgical principles, and illustrative pediatric cases.

PURPOSE: To create a high-quality, cadaver-based, operatively oriented resource documenting the anterior transcortical and interhemispheric transcallosal approaches as corridors to the third ventricle targeted towards neurosurgical trainees at all levels. METHODS: Two formalin-fixed, latex-injected specimens were dissected under microscopic magnification and endoscopic-assisted visualization. Dissections of the transcortical and transcallosal craniotomies with transforaminal, transchoroidal, and interforniceal transventricular approaches were performed. The dissections were documented in a stepwise fashion using three-dimensional photographic image acquisition techniques and supplemented with representative cases to highlight pertinent surgical principles. RESULTS: The anterior transcortical and interhemispheric corridors afford excellent access to the anterior two-thirds of the third ventricle with varying risks associated with frontal lobe versus corpus callosum disruption, respectively. The transcortical approach offers a more direct, oblique view of the ipsilateral lateral ventricle, whereas the transcallosal approach readily establishes biventricular access through a paramedian corridor. Once inside the lateral ventricle, intraventricular angled endoscopy further enhances access to the extreme poles of the third ventricle from either open transcranial approach. Subsequent selection of either the transforaminal, transchoroidal, or interforniceal routes can be performed through either craniotomy and is ultimately dependent on individual deep venous anatomy, the epicenter of ventricular pathology, and the concomitant presence of hydrocephalus or embryologic cava. Key steps described include positioning and skin incision; scalp dissection; craniotomy flap elevation; durotomy; transcortical versus interhemispheric dissection with callosotomy; the aforementioned transventricular routes; and their relevant intraventricular landmarks. CONCLUSIONS: Approaches to the ventricular system for maximal safe resection of pediatric brain tumors are challenging to master yet represent foundational cranial surgical techniques. We present a comprehensive operatively oriented guide for neurosurgery residents that combines stepwise open and endoscopic cadaveric dissections with representative case studies to optimize familiarity with third ventricle approaches, mastery of relevant microsurgical anatomy, and preparation for operating room participation.

Endoscopic Anatomy of Transcallosal Hemispherotomy: Laboratory Study with Advanced Three-Dimensional Modeling.

BACKGROUND: Epilepsy surgery has an important role in the treatment of patients with medically intractable seizures. Various authors have proposed an endoscopic technique to perform disconnective procedures. A detailed description of intracerebral anatomy seen through an endoscopic transcallosal corridor has not been reported. The aim of this study was to present a cadaveric step-by-step anatomical demonstration of endoscopic transcallosal hemispherotomy using a dedicated three-dimensional model. METHODS: Anatomical dissections were performed on 6 cadaveric heads (12 hemispheres), and the disconnective procedure was performed using an endoscopic transcallosal approach. A dedicated three-dimensional model was used to better illustrate each step. A simulation of the disconnective procedure was performed by recreating the surgical steps on a subject from the Human Connectome Project dataset, and a calculation of the fiber tracts intersected was performed. RESULTS: Analyzing data extracted from the three-dimensional model and tractography simulation, 100% of the fibers (streamlines) of corpus callosum, corticopontine tracts, corticospinal tract, and inferior fronto-occipital fascicle were transected. Moreover, a satisfactory number of fibers (>95%) of the thalamocortical tracts, corticostriatal tracts, corona radiata, fornix, and uncinate fascicle were disconnected. CONCLUSIONS: This anatomical study described the relevant neurovascular structures to enable prediction of feasibility and control of the surgical procedure using the endoscopic transcallosal approach. The quantitative analysis permitted estimation of the theoretical efficacy of the procedure, confirming its relevant role in disconnective surgery.

Anatomía del cuerpo calloso en ratas sometidas a estrés prenatal crónico / Anatomy of corpus callosum in rats submitted to chronic prenatal stress

RESUMEN: El cuerpo calloso (CC), es la mayor comisura de sustancia blanca del encéfalo de los mamíferos placentados, constituida por numerosos haces de fibras transversales que conectan áreas corticales de ambos hemisferios cerebrales. Por otro lado, el estrés se define como una respuesta general del organismo ante demandas externas o internas, inicialmente amenazantes, que consiste en movilizar recursos fisiológicos y psicológicos para poderlas afrontar. Dada la importancia del cuerpo calloso en las conexiones cortico-corticales, el objetivo del presente estudio, fue evaluar el efecto en ratas, de un estrés prenatal crónico por inmovilización, sobre la anatomía macroscópica del CC. Se utilizaron seis ratas preñadas de la cepa Wistar de 250 g, de las cuales tres fueron sometidas, a partir del octavo día postconcepción, a una restricción de movimiento por diez días (2h/día). Posteriormente, las madres prosiguieron su gestación, parto y lactancia. Al nacimiento, las camadas fueron ajustadas a seis crías machos por madre (n=36), destetadas a los 21 días y sacrificadas a los 45-52 días de edad. Los encéfalos fueron seccionados a través de la cisura interhemisférica y ambos hemisferios fotografiados por su cara medial. Las imágenes fueron digitalizadas y analizadas mediante el programa Scion Image®, para la medición del área total, parciales (tercio anterior, medio, posterior y quinto posterior) y perímetro callosal. Es así como, el estrés prenatal por inmovilización, afectó significativamente (p<0,01), la morfología macroscópica del cuerpo calloso. Evidenciándose una disminución del área total, áreas parciales y perímetro callosal, en los animales sometidos a restricción prenatal. Estableciendo una relación directa entre número de axones y área callosal e inversa entre diámetro y densidad axonal; lo observado podría tener incidencia en la transferencia interhemisférica.

SUMMARY: The Corpus Callosum (CC) is the largest white matter commissure in the brain of placental mammals, consisting of numerous transverse fiber bundles that connect cortical areas of both cerebral hemispheres. On the other hand, stress is defined as a general response of the organism to external or internal demands, initially threatening, which consists of mobilizing physiological and psychological resources to be able to face them. Given the importance of CC in cortico-cortical connections, the aim of the present study, was to evaluate the effect of chronic pre-natal immobilization stress on the macroscopic anatomy of CC in rats. Six 250g pregnant rats of the Wistar strain were used, of which three were subjected, starting on the eighth post-conception day, to movement restriction for ten days (2h/day). Subsequently, the mothers continued their gestation, delivery and lactation. At birth, litters were adjusted to six male offspring per mother (n=36), which were weaned at 21 days and slaughtered at 45-52 days of age. The brains were fixed, and later sectioned through the interhemispheric fissure and both hemispheres photographed by their medial aspect. The images were digitized and analyzed using the Scion Image® program, for the measurement of the total area, partial area (ante- rior, middle and posterior thirds, as well as posterior fifth) and callosal perimeter. Thus, prenatal stress due to immobilization significantly affected (p<0.01), the macroscopic morphology of the CC. Evidence shows a decrease in the total area, partial areas and callosal perimeter in the animals subjected to prenatal restraint, as compared to normal animals. Establishing a direct relationship between number of axons and callosal area and an inverse relationship between diameter and axonal density, what was observed may have an impact on interhemispheric transfer.

Corpus Callosum and Its Connections: A Fiber Dissection Study.

OBJECTIVE: We performed a fine white fiber dissection to demonstrate the extensive connections of the corpus callosum. MATERIAL AND METHODS: Three formalin-fixed frozen cadaveric human brain specimens were dissected using Klingler's technique. On one half of each hemisphere, the superior connections of the corpus callosum were dissected and in the other half the inferior connections of the corpus callosum were dissected. RESULTS: The mean length of the corpus callosum from the rostrum to the splenium was 7.8 cm. The fibers of the corpus callosum were classified as superior/dorsal radiations, inferior/ventral radiations, anterior radiations, and posterior radiations. The entire transverse length of the dorsal callosal radiation from one hemisphere to the other was 8.1 cm. For anterior interhemispheric approaches, an incision in the anterior part of the body not extending beyond 3.5 cm from the genu was found to be safe with regards to crossing motor fibers. CONCLUSIONS: The corpus callosum was found to have intricate connections with all the lobes of the cerebral hemispheres, including the insular region and the limbic and paralimbic areas. Based on the course and traverse of the callosal fibers, a transverse incision in the corpus callosum should be preferred when performing a callosotomy to access intraventricular lesions as this splits the callosal fibers instead of transecting them. The analysis of the course of the callosal radiations enhances understanding of the growth pattern of primary corpus callosal gliomas and helps to design a safe surgical strategy.

Increased Callosal Connectivity in Reeler Mice Revealed by Brain-Wide Input Mapping of VIP Neurons in Barrel Cortex.

The neocortex is composed of layers. Whether layers constitute an essential framework for the formation of functional circuits is not well understood. We investigated the brain-wide input connectivity of vasoactive intestinal polypeptide (VIP) expressing neurons in the reeler mouse. This mutant is characterized by a migration deficit of cortical neurons so that no layers are formed. Still, neurons retain their properties and reeler mice show little cognitive impairment. We focused on VIP neurons because they are known to receive strong long-range inputs and have a typical laminar bias toward upper layers. In reeler, these neurons are more dispersed across the cortex. We mapped the brain-wide inputs of VIP neurons in barrel cortex of wild-type and reeler mice with rabies virus tracing. Innervation by subcortical inputs was not altered in reeler, in contrast to the cortical circuitry. Numbers of long-range ipsilateral cortical inputs were reduced in reeler, while contralateral inputs were strongly increased. Reeler mice had more callosal projection neurons. Hence, the corpus callosum was larger in reeler as shown by structural imaging. We argue that, in the absence of cortical layers, circuits with subcortical structures are maintained but cortical neurons establish a different network that largely preserves cognitive functions.

Evaluation of Ideal Extent of Corpus Callosotomy Based on the Location of Intracallosal Motor Fibers.

BACKGROUND: The corpus callosotomy (CCT) has been reported as an effective procedure to alleviate drop attacks. However, the extent of CCT remains debatable. Classical studies suggest that motor fibers traverse mainly through the anterior half of the corpus callosum (CC), although recent diffusion tensor imaging studies described that motor fibers crossed the CC in a more posterior location, emphasizing the posterior midbody and the isthmus. METHODS: Cortical and subcortical structures were examined in 30 hemispheres prepared for white matter fiber dissection. Dissections were carried out under surgical magnification to trace fibers originating from the primary motor cortex and their course through the CC. The distance of the most anterior and posterior motor fibers to the tip of the genu were measured, and the extent of CCT enabling disconnection of all motor fibers was calculated. RESULTS: Motor fibers coursed through the posterior half of the CC in the majority of hemispheres, mainly locating in posterior midbody and the isthmus. Callosal fibers should be interrupted to an average of 61% ± 0.07% point of the CC to reach the anterior limit of motor fibers and to an average of 69% ± 0.07% point to include posterior limit of motor fibers. Motor fibers were extending until the posterior one third of the CC in 22 specimens. CONCLUSIONS: Anterior-half CCT did not include all motor fibers in any specimen. Anterior two thirds CCT disrupted all motor fibers in one fourth of the cases. Our findings suggest that an ideal CCT should extend to the posterior midbody and isthmus of the CC.

Central neurocytoma originating in third ventricle with expansion into the cerebral aqueduct and fourth ventricle: Case report and review of literature.

BACKGROUND: Central Neurocytomas (CNs) are rare brain tumors, making up less than 1% of all primary tumors within the CNS. They are commonly located in the lateral ventricles, and often present with visual changes and symptoms of obstructive hydrocephalus. Histopathology shows characteristics similar to ependymomas and oligodendrogliomas, however tumor cells display neuronal differentiation, and immunohistochemical stains typically for synaptophysin. Gross total resection is the most important prognostic indicator of survival. CASE DESCRIPTION: We describe the case of a 48-year-old male with a CN originating in the third ventricle with expansion through the cerebral aqueduct into the fourth ventricle. He presented with bi-frontal headaches, imaging revealed an avidly enhancing tumor occupying the inferior third ventricle, cerebral aqueduct, with expansion into the fourth ventricle. An interhemispheric craniotomy with a transcallosal transchoroidal approach to the third ventricle was performed, this provided a trajectory that paralleled the long axis of the tumor. Postoperative imaging confirmed a near total resection with linear residual enhancement on the anterior wall of the fourth ventricle. Intensity modulated radiotherapy was performed, 7-month follow-up imaging was clean. CONCLUSION: CNs are rare brain tumors, most commonly located within the lateral ventricles. We describe a rare case of a CN spanning from the third ventricle into the cerebral aqueduct and fourth ventricle. To our knowledge, this is only the fourth reported case of such a tumor. Surgical approach must be carefully selected, as gross total resection is the most important prognostic indicator.

The splenium of the corpus callosum: embryology, anatomy, function and imaging with pathophysiological hypothesis.

BACKGROUND AND PURPOSE: The splenium of the corpus callosum is the most posterior part of the corpus callosum. Its embryological development, anatomy, vascularization, function, imaging of pathology, possible pathophysiological mechanisms by which pathology may develop and the clinical consequences are discussed. METHODS: A literature-based description is provided on development, anatomy and function. MR and CT images are used to demonstrate pathology. The majority of pathology, known to affect the splenium, and the clinical effects are described in three subsections: (A) limited to the splenium, with elaboration on pathophysiology of reversible splenial lesions, (B) pathology in the cerebral white matter extending into or deriving from the splenium, with special emphasis on tumors, and (C) splenial involvement in generalized conditions affecting the entire brain, with a hypothesis for pathophysiological mechanisms for the different diseases. RESULTS: The development of the splenium is preceded by the formation of the hippocampal commissure. It is bordered by the falx and the tentorium and is perfused by the anterior and posterior circulation. It contains different caliber axonal fibers and the most compact area of callosal glial cells. These findings may explain the affinity of specific forms of pathology for this region. The fibers interconnect the temporal and occipital regions of both hemispheres reciprocally and are important in language, visuospatial information transfer and behavior. Acquired pathology may lead to changes in consciousness. CONCLUSION: The development, location, fiber composition and vascularization of the splenium make it vulnerable to specific pathological processes. It appears to play an important role in consciousness.

Endoscopic Interhemispheric Disconnection for Intractable Multifocal Epilepsy: Surgical Technique and Functional Neuroanatomy.

BACKGROUND: Callosotomy represents a palliative procedure for intractable multifocal epilepsy. The extent of callosotomy and the benefits of adding anterior and posterior commissurotomy are debated. OBJECTIVE: To describe a new technique of a purely endoscopic procedure to disconnect the corpus callosum, the anterior, posterior, and habenular commissures through the use of a single burr hole via a transfrontal transventricular route. METHODS: Our surgical series was retrospectively reviewed in terms of seizure control (Engel's class) and complication rate. Five cadaveric specimens were used to demonstrate the surgical anatomy of commissural fibers and third ventricle. RESULTS: The procedure may be divided into 3 steps: (1) endoscopic transventricular transforaminal anterior commissure disconnection; (2) disconnection of posterior and habenular commissures; and (3) total callosotomy. Fifty-seven patients were included in the analysis. A favorable outcome in terms of epilepsy control (Engel class 1 to 3) was found in 71.4% of patients undergoing callosotomy coupled with anterior, posterior, and habenular commissure disconnection against 53% of patients with isolated callosotomy (P = .26). Patients with drop attacks had better epilepsy outcome independently from the surgical procedure used. CONCLUSION: The full endoscopic callosotomy coupled with disconnection of anterior, posterior and habenular commissures is a safe alternative to treat multifocal refractory epilepsy. A gain in seizure outcome might be present in this cohort of patients treated with total interhemispheric disconnection when compared with isolated callosotomy. Larger studies are required to confirm these findings.

Thalamus Cavernous Malformation Resection of via Contralateral Anterior Interhemispheric Transcallosal Approach: Two-Dimensional Operative Video.

Thalamic cavernous malformations (CM) are highly challenging surgically. In this illustrative video (Video 1), we present the case of a 36-year-old man with a CM at the left medial thalamus, which was successfully treated by a contralateral anterior interhemispheric transcallosal approach. Informed consent was obtained from the patient. Preoperative imaging demonstrated that the CM appeared to have reached the pial surface superiorly and medially, and diffusion tensor imaging showed the pyramidal tracts to be traveling laterally to the CM. Based on the "Two-point" principle and to avoid pyramidal tract impingement, an anterior interhemispheric transcallosal approach was chosen. Furthermore, to avoid excessive retraction on the ipsilateral hemisphere, we selected the contralateral trajectory over the ipsilateral trajectory. The head was positioned with the right side down; thus, the space between the right hemisphere and the falx could expand because of gravity autoretraction, which could minimize the need of retraction during the interhemispheric dissection. A small incision on the corpus callosum was performed under the guidance of neuronavigation, and the left ventricle was subsequently entered. After a thin layer of hemosiderin-stained pia was opened on the superior surface of the left thalamus, some sandlike old hemorrhagic component was removed for decompression, and the lesion was carefully dissected away from the normal parenchyma within the surrounding gliosis boundary. The CM was removed en bloc, and the deep venous anomaly was well protected. The patient did not experience any intraoperative changes shown by electrophysiologic monitoring, and he recovered well postoperatively.

Microsurgical anatomy of the sagittal stratum.

BACKGROUND: The sagittal stratum (SS) is a critical neural crossroad traversed by several white matter tracts that connect multiple areas of the ipsilateral hemisphere. Scant information about the anatomical organization of this structure is available in literature. The goal of this study was to provide a detailed anatomical description of the SS and to discuss the functional implications of the findings when a surgical approach through this structure is planned. METHODS: Five formalin-fixed human brains were dissected under the operating microscope by using the fiber dissection technique originally described by Ludwig and Klingler. RESULTS: The SS is a polygonal crossroad of associational fibers situated deep on the lateral surface of the hemisphere, medial to the arcuate/superior longitudinal fascicle complex, and laterally to the tapetal fibers of the atrium. It is organized in three layers: a superficial layer formed by the middle and inferior longitudinal fascicles, a middle layer corresponding to the inferior fronto-occipital fascicle, and a deep layer formed by the optic radiation, intermingled with fibers of the anterior commissure. It originates posteroinferiorly to the inferior limiting sulcus of the insula, contiguous with the fibers of the temporal stem, and ends into the posterior temporo-occipito-parietal cortex. CONCLUSION: The white matter fiber dissection reveals the tridimensional architecture of the SS and the relationship between its fibers. A detailed understanding of the anatomy of the SS is essential to decrease the operative risks when a surgical approach within this area is undertaken.

Corpus callosum and cerebellar vermis size in very preterm infants: Relationship to long-term neurodevelopmental outcome.

BACKGROUND: The neonatal changes of corpus callosum or cerebellar volume in preterm infants have been shown to link with abnormal mentality and motor disability in early childhood. This study aims to predict the long-term neurological outcomes by measuring these changes on neonatal brain ultrasound in preterm infants. METHODS: Our cohort consisted of infants aged below 32 weeks' gestation with very low birth body weights who completed neuro-assessments at 5 years of age. Corpus callosum or cerebellar vermis were measured at 28-30 weeks and at 37-40 weeks gestational age in premature infants with cerebral palsy (CP), mental retardation (MR) and normal control premature infants. RESULTS: There are 12 patients in MR group, 12 in CP group and 27 patients as controls for final analysis. There was no significant difference in other factors between study groups except lower gestational age (P = 0.043) in CP group. Respiratory distress syndrome was more common in MR group (P = 0.037) and cystic periventricular leukomalacia was more common in CP group (P < 0.001) than controls. After adjusting for sex and birth body weight, the MR group had smaller cerebellar vermis area at 37-40 gestational weeks (P = 0.002) than controls. They also reduced the growth of corpus callosum area (difference = -0.12 ± 0.16, P = 0.029) and cerebellar vermis area (difference = 1.10 ± 0.44, P = 0.020) from 28 to 30 gestational weeks to 37-40 gestational weeks compared with controls (difference = 0.03 ± 0.15, 1.92 ± 0.70, respectively). In contrast, the CP group had reduced the growth of corpus callosum body (difference = -0.02 ± 0.18, P = 0.034) compared with controls (difference = 0.03 ± 0.04). They subsequently had smaller body thickness of corpus callosum (0.10 ± 0.02, P = 0.015) at 37-40 gestational weeks than controls (0.14 ± 0.04). CONCLUSIONS: Serial monitoring corpus callosum and cerebellar vermis size in early life of very preterm babies may predict the motor or mentality neurological outcome at 5 years of age.

Sex Difference in the Morphology of Pineal Gland in Adults Based on Brain Magnetic Resonance Imaging.

PURPOSE: We aimed to figure out the anatomical features of pineal gland region on magnetic resonance imaging (MRI) and to explore the sex difference in pineal gland-related parameters with increasing age. METHODS: We measured the pineal gland on MRI images from 198 healthy adults (96 males and 102 females). Included subjects were divided into 4 age groups. After 3-dimensional reconstruction, the anatomic features of pineal gland and its distances to superior colliculus and splenium of corpus callosum were analyzed in each group. The prevalence of cystic pineal gland was calculated. Moreover, we calculated the volume of pineal gland (PGV) and explored the differences of PGV in males and females across different age groups. Linear regression analysis was performed to detect the relationship between age and pineal gland-related parameters. RESULTS: In 198 subjects, the mean length, width, and height of pineal gland were 7.58 ±â€Š0.45 mm, 4.92 ±â€Š0.40 mm, and 2.90 ±â€Š0.20 mm. The distances between pineal gland and superior colliculus as well as splenium of corpus callosum were 3.96 ±â€Š0.92 mm and 4.3 ±â€Š1.89 mm, respectively. The PGV was 54.1 ±â€Š7.02 mm. Significant sex differences were found in pineal gland length (P < 0.001), cranial cavity diameter (P < 0.001), pineal gland index (P < 0.001) and PGV values (P = 0.02). The prevalence of cystic pineal gland was 36.4% in total subjects, 41.7% in males and 32.4% in females. No linear relationship was found between age and pineal gland parameters. CONCLUSION: We measured the pineal gland morphology based on MRI images. Significant influences on pineal gland parameters were found in subjects with different sex, whereas no effect was observed from age.

The crossed frontal aslant tract: A possible pathway involved in the recovery of supplementary motor area syndrome.

Introduction: Supplementary motor area (SMA) syndrome is a constellation of temporary symptoms that may occur following tumors of the frontal lobe. Affected patients develop akinesia and mutism but often recover within weeks to months. With our own case examples and with correlations to fiber tracking validated by gross anatomical dissection as ground truth, we describe a white matter pathway through which recovery may occur. Methods: Diffusion spectrum imaging from the Human Connectome Project was used for tractography analysis. SMA outflow tracts were mapped in both hemispheres using a predefined seeding region. Postmortem dissections of 10 cadaveric brains were performed using a modified Klingler technique to verify the tractography results. Results: Two cases were identified in our clinical records in which patients sustained permanent SMA syndrome after complete disconnection of the SMA and corpus callosum (CC). After investigating the postoperative anatomy of these resections, we identified a pattern of nonhomologous connections through the CC connecting the premotor area to the contralateral premotor and SMAs. The transcallosal fibers have projections from the previously described frontal aslant tract (FAT) and thus, we have termed this path the "crossed FAT." Conclusions: We hypothesize that this newly described tract may facilitate recovery from SMA syndrome by maintaining interhemispheric connectivity through the supplementary motor and premotor areas.

Posterior Quadrant Disconnection: A Fiber Dissection Study.

BACKGROUND: Posterior quadrant disconnection can be highly effective in the surgical treatment of selected cases of refractory epilepsy. The technique aims to deafferent extensive areas of epileptogenic posterior cortex from the rest of the brain by isolating the temporoparietooccipital cortex. OBJECTIVE: To describe this procedure and relevant white matter tracts with a specific emphasis on the extent of callosotomy in an anatomic study. METHODS: Twenty hemispheres were dissected according to Klingler's fiber dissection technique illustrating the peri-insular (temporal stem, superior longitudinal fasciculus, corona radiata) and mesial disconnection (mesiotemporal cortex, cingulum, and corpus callosum). RESULTS: Extensive white matter tract disconnection is obtained after posterior quadrant disconnection. Callosal fibers connecting the anterior most part of the parietal cortex invariably ran through the isthmus of the corpus callosum and need to be disconnected, while frontal lobe connections including the corticospinal tract and the anterior two-thirds of the corpus callosum are spared during the procedure. CONCLUSION: Our findings suggest the involvement of both the splenium and the isthmus in interhemispheric propagation in posterior cortex epilepsies. Sectioning the total extent of the posterior one-third of the corpus callosum might therefore be necessary to achieve optimal outcomes in posterior quadrant epilepsy surgery.

Splenial Lesions of the Corpus Callosum: Disease Spectrum and MRI Findings.

The corpus callosum (CC) is the largest white matter structure in the brain, consisting of more than 200-250 million axons that provide a large connection mainly between homologous cerebral cortical areas in mirror image sites. The posterior end of the CC is the thickest part, which is called the splenium. Various diseases including congenital to acquired lesions including congenital anomalies, traumatic lesions, ischemic diseases, tumors, metabolic, toxic, degenerative, and demyelinating diseases, can involve the splenium of the CC and their clinical symptoms and signs are also variable. Therefore, knowledge of the disease entities and the imaging findings of lesions involving the splenium is valuable in clinical practice. MR imaging is useful for the detection and differential diagnosis of splenial lesions of the CC. In this study, we classify the disease entities and describe imaging findings of lesions involving the splenium of the CC based on our experiences and a review of the literature.

The Superior Frontal Transsulcal Approach to the Anterior Ventricular System: Exploring the Sulcal and Subcortical Anatomy Using Anatomic Dissections and Diffusion Tensor Imaging Tractography.

OBJECTIVE: To explore the superior frontal sulcus (SFS) morphology, trajectory of the applied surgical corridor, and white matter bundles that are traversed during the superior frontal transsulcal transventricular approach. METHODS: Twenty normal, adult, formalin-fixed cerebral hemispheres and 2 cadaveric heads were included in the study. The topography, morphology, and dimensions of the SFS were recorded in all specimens. Fourteen hemispheres were investigated through the fiber dissection technique whereas the remaining 6 were explored using coronal cuts. The cadaveric heads were used to perform the superior frontal transsulcal transventricular approach. In addition, 2 healthy volunteers underwent diffusion tensor imaging and tractography reconstruction studies. RESULTS: The SFS was interrupted in 40% of the specimens studied and was always parallel to the interhemispheric fissure. The proximal 5 cm of the SFS (starting from the SFS precentral sulcus meeting point) were found to overlie the anterior ventricular system in all hemispheres. Five discrete white matter layers were identified en route to the anterior ventricular system (i.e., the arcuate fibers, the frontal aslant tract, the external capsule, internal capsule, and the callosal radiations). Diffusion tensor imaging studies confirmed the fiber tract architecture. CONCLUSIONS: When feasible, the superior frontal transsulcal transventricular approach offers a safe and effective corridor to the anterior part of the lateral ventricle because it minimizes brain retraction and transgression and offers a wide and straightforward working corridor. Meticulous preoperative planning coupled with a sound microneurosurgical technique are prerequisites to perform the approach successfully.

Cortical and subcortical functional neuroanatomy for low-grade glioma surgery.

Knowledge of the encephalon anatomy is crucial for neurosurgical practice, especially the main cortical functional structures and their connections. General organisation of the encephalon is presented with frontal, parietal, occipital, temporal, limbic and insular lobes and their Brodmann correspondence. Secondly, subcortical anatomy will be presented with main white matter fasciculi in three separated categories: association, commissural and projection fibers. Main association fibers are inferior occipitofrontal fasciculus, superior longitudinal fasciculus, arcuate fasciculus, inferior longitudinal fasciculus, uncinate fasciculus, and cingulum. Commissural fibers include anterior commissure, corpus callosum and fornix. Projection fibers are internal capsule and optic radiations.

Callosotopy: leg motor connections illustrated by fiber dissection.

Precise anatomical knowledge of the structure of the corpus callosum is important in split-brain research and during neurosurgical procedures sectioning the callosum. According to the classic literature, commissural fibers connecting the motor cortex are situated in the anterior part of the corpus callosum. On the other hand, more recent imaging studies using diffusion tensor imaging indicate a more posterior topography of callosal fibers connecting motor areas. Topographical knowledge is especially critical when performing disconnective callosotomies in epilepsy patients who experience sudden loss of leg motor control, so-called epileptic drop attacks. In the current study, we aim to precisely delineate the topography of the leg motor connections of the corpus callosum. Of 20 hemispheres obtained at autopsy, 16 were dissected according to Klingler's fiber dissection technique to study the course and topography of callosal fibers connecting the most medial part of the precentral gyrus. Fibers originating from the anterior bank of the central sulcus were invariably found to be located in the isthmus of the corpus callosum, and no leg motor fibers were found in the anterior part of the callosum. The current results suggest that the disconnection of the pre-splenial fibers, located in the posterior one-third of the corpus callosum, is paramount in obtaining a good outcome after callosotomy.

Comparative Anatomical Study on Operability in Surgical Approaches to the Anterior Part of the Third Ventricle.

BACKGROUND: Surgery of the third ventricle still represents a challenge in modern neurosurgery. To optimize the surgical planning, some aspects, related to ventricular anatomy, have to be taken into consideration. An operability score could represent a preoperative tool to evaluate these variables to choose a tailored surgical approach. METHODS: We compared the transcallosal transforaminal approach and the combined interhemispheric subcommissural translamina terminalis approach (CISTA) to the anterior part of the third ventricle, applying the operability score. RESULTS: Compared with the transcallosal transforaminal approach, the CISTA provides a statistically significant improvement in terms of depth of surgical field, surgical angle of attack, and maneuverability arc considering as 4 approach-related critical structures: the optic chiasm (P value: <0.0001, <0.0001, <0.0001, respectively), the anterior commissure (P value: <0.0001, <0.0001, <0.0001 respectively), the tuber cinereum (P value: <0.0001, 0.0224, 0.0173), and the interthalamic adhesion (P value: 0.2917, <0.0001, <0.0001 respectively). CONCLUSIONS: Tumors originating from the anterosuperior part of the third ventricle can be easily approached through a transcallosal transforaminal route, whereas lesions arising from the anteroinferior portion of the third ventricle might be safely and effectively approached through the CISTA.