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.

The Paramedian Supracerebellar Approach: A Less Disruptive and More Flexible Operative Corridor to the Pineal and Posterior Upper Brainstem Regions.

The paramedian supracerebellar craniotomy is an underrecognized route to the midline and paramedian regions of the upper posterior brainstem. As compared with its midline supracerebellar counterpart, this less disruptive approach preserves the majority of the midline bridging veins, requires less cerebellar retraction, and is significantly more efficient. In this offering, I will emphasize the realities of this flexible route and its remarkable advantages in reaching deep-seated lesions.

Expanded endoscopic endonasal approach for extending suprasellar and third ventricular lesions.

BACKGROUND: Expanded endonasal approaches can provide direct access to the midline skull base from the anterior cranial fossa to the ventral foramen magnum. Surgical strategies of bone drilling, dural opening, and intradural dissection can determine the area of surgical exposure and instrument handling, affecting the safety of devascularizing/debulking suprasellar tumors. METHODS: We describe an expanded endoscopic endonasal approach for suprasellar lesions, with stepwise image-guided dissections highlighting surgical pearls and pitfalls to enhance surgical safety. This article presents transnasal intra-third-ventricular anatomy from trans-tuber cinereum, and trans-lamina terminalis approaches, comparing subchiasmatic and suprachiasmatic trajectories. CONCLUSION: The rostral extension via endoscopic endonasal transsellar-transtubercular-transplanum approaches can provide a safe and feasible route for suprasellar lesions, in subchiasmatic, suprachiasmatic, and intraventricular regions.

An Alternative Route to the Posterior Half of the Third Ventricle: The Transoccipital Horn Approach. Technical Note.

BACKGROUND: Lesions arising or abutting in the posterior half of the third ventricle are approached through established routes to avoid damage of essential brain structures. Occasionally, the features of the lesion require rethinking these traditional routes and tailoring the surgical approach to cause fewer debilitating sequelae to the patient. We introduce a modification of previously described transcortical approaches to lesions of the posterior third ventricle. The technique and possible indications are discussed. METHODS: Two cases of posterior third ventricle tumors are presented. In both patients, a small posterior fossa and large tentorial veins located along the surgical route, as well as the position of the lesion underneath the internal cerebral veins, encouraged the concept of a novel transoccipital horn approach that was developed to access the tumor with less postoperative deficits. RESULTS: Both lesions were removed with transitory postoperative visual deficits. CONCLUSIONS: The transoccipital horn approach is a feasible alternative to other surgical routes to the posterior part of the third ventricle in cases of particularly challenging anatomy and tumor characteristics. It allows reaching the lesion along its major axis, fully exploiting the natural space created by the tumor in its growth and avoiding the internal cerebral veins.

An anatomical study of the foramen of Monro: implications in management of pineal tumors presenting with hydrocephalus.

BACKGROUND: For pineal tumors presenting with hydrocephalus, simultaneous endoscopic third ventriculostomy (ETV) and tumor biopsy is commonly used as the initial step in management. To analyze the restriction which the foramen of Monro poses to this procedure, one must start with a detailed description of the microsurgical anatomy of the foramen in living subjects. However, the orientation and shape of the foramen of Monro make this description difficult with conventional imaging techniques. METHOD: Virtual reality technology was applied on MRIs on living subject without hydrocephalus, as well as patients with hydrocephalus, to generate precise anatomical models with sub-millimeter accuracy. The morphometry of the foramen of Monro was studied in each group. In addition, displacement of the margins of the foramen was studied in detail for simultaneous ETV and pineal tumor biopsy through a single burr hole. RESULTS: In 30 normal subjects, the foramen of Monro had oval-shaped openings averaging 5.23 mm2. The foramen was larger in people above age 55 (p = 0.007) and on the left side compared to the right (p = 0.002). For patients with clinical presentation of hydrocephalus, the average opening was 32.6 mm2. Simulated single burr hole simultaneous ETV and pineal tumor biopsy was performed in 10 specimens. Average displacement of the posterior and anterior margins of the foramen was 5.71 mm and 5.76 mm, respectively. However, maximum displacement reached 9.3 mm posteriorly and 10 mm anteriorly. CONCLUSIONS: The foramen of Monro is an oval-shaped cylinder that changes in size and orientation in the hydrocephalic patient. If universally applied to all patients regardless of foramen and tumor size, ETV/biopsy can displace structures around the Foramen of Monro up to 1 cm, which can potentially lead to neurological damage. Careful pre-operative assessment is critical to determine if a single burr hole approach is safe.

Schwalbe's Triangular Fossa: Normal and Pathologic Anatomy on Frozen Cadavers. Anatomo-Magnetic Resonance Imaging Comparison and Surgical Implications in Colloid Cyst Surgery.

BACKGROUND: The fornix is a region of greatest neurosurgical interest in regards to its complex anatomy and surgical approaches to this area. The objective of this study was to evaluate the morphology of the triangular recess (TR) and its role in the growth pattern of the colloid cysts (CC) within the third ventricle and in the choice of the surgical approach for their removal. Furthermore, to compare the results of the dissections with measurements performed on a magnetic resonance imaging scan. METHODS: In the anatomic study, 20 cadaveric specimens were dissected and analyzed. In the radiologic study, a magnetic resonance imaging scan was performed in 20 healthy volunteers. In the clinical study, a retrospective analysis of all the patients affected with CCs microsurgically removed at our institute between 2010 and 2018 was conducted. RESULTS: In the anatomic study, the width, height, and the area of the TR were respectively 0.31 cm, 0.33cm, and 0.051 cm2. In the radiologic study, 3 different typologies of TR were identified: open recess in ventriculomegaly (7 patients); open recess in physiologic ventricular system (3 patients); closed or blind recess (10 patients). Three different growth patterns of CCs were identified: type 1) CCs localized at the foramen of Monro growing behind the fornix and below the third ventricular roof; type 2) CCs growing rostrally between the column of fornix; and type 3) CCs growing above the plane of the third ventricular roof. CONCLUSIONS: The anatomy of the TR influences the growth pattern of CC within the ventricular cavity and determines the surgical strategy for their removal.

The Clival Line as an Important Arachnoid Landmark During Endoscopic Third Ventriculostomy: An Anatomic Study.

OBJECTIVE: Endoscopic third ventriculostomy (ETV) is a well-accepted treatment option instead of ventriculoperitoneal shunt placement in cases of obstructive hydrocephalus. A sufficient flow from the ventricles to the basal cisterns requires perforation of the arachnoid membranes in the retroclival region. This point is critical to achieve an optimal outcome. The complex arachnoid relations were investigated in the retroclival region from the viewpoint of ETV, and anatomic landmarks were defined for subarachnoid dissections. METHODS: Sixty fresh human cadaveric specimens were dissected under macroscopic, microscopic, and endoscopic control. The recordings of 100 operated cases of ETVs were analyzed to ascertain the clinical-anatomic relevance. RESULTS: The Liliequist membrane complex and the anterior pontine membranes are located just above and parallel to both sides of the basilar artery. The basal attachment of these membranes forms an inverted U-shaped, white-grey thickening on the outer arachnoid. We refer to this structure as the clival line. During ETV, if arachnoid dissections were performed ventrally to the clival line, the outer arachnoid was opened; this resulted in a limited flow to the subarachnoid spaces (ventriculo-subdural). If the perforation on the arachnoid membranes was dorsal to the clival line, the prepontine cistern could be directly reached through the Liliequist membrane complex. CONCLUSIONS: Sufficient arachnoid dissection is essential for a successful ETV. The clival line is an important landmark that helps to perform the subarachnoid dissections correctly and achieve an undisrupted cerebral spinal fluid flow between the ventricles and the basal cisterns.

Quantitative Anatomic Analysis of the Transcallosal-Transchoroidal Approach and the Transcallosal-Subchoroidal Approach to the Floor of the Third Ventricle: An Anatomic Study.

OBJECTIVE: To compare transcallosal-transchoroidal and transcallosal-subchoroidal approaches to the ipsilateral and contralateral edges of the floor of the third ventricle using quantitative analyses. METHODS: Five formalin-fixed cadaveric human heads (10 sides) were examined under the operating microscope. Quantitative measurements (area of surgical freedom and angle of attack) were obtained using 3-T magnetic resonance imaging and a StealthStation image guidance system. The limits of the surgical approaches were shown by touching a probe to 6 designated points on the floor of the third ventricle. RESULTS: The transchoroidal approach provided greater surgical freedom than the subchoroidal approach to access ipsilateral and contralateral middle landmarks at the edges of the floor of the third ventricle in both longitudinal and horizontal planes (P ≤ 0.03). No significant difference between the 2 approaches was found in accessing the anterior and posterior landmarks of the third ventricle in each plane. The surgical freedom to the contralateral anterior, middle, and posterior landmarks was greater than to the ipsilateral landmarks in both the transchoroidal and subchoroidal approaches. CONCLUSIONS: The transcallosal-transchoroidal approach, compared with the transcallosal-subchoroidal approach, may provide better exposure and require less retraction for removal of ipsilateral or contralateral lesions located in the midbrain or hypothalamus and situated near the floor of the third ventricle. The contralateral transcallosal approach with either the transchoroidal or subchoroidal approach may provide good surgical freedom for removal of lesions located near the floor of the third ventricle, such as lesions in the midbrain.

The third ventricle roof: an anatomical study using constructive interference in steady-state magnetic resonance imaging.

PURPOSE: The third ventricle roof in vivo has been infrequently explored. The aim of the present study was to delineate the neurovascular structures relevant to the third ventricle roof using magnetic resonance (MR) imaging. METHODS: A total of 78 patients were enrolled in the study. Following initial examinations with conventional MR sequences, the constructive interference in steady-state (CISS) sequence was performed in coronal sections on 67 patients and in sagittal sections on 11 patients. RESULTS: In the coronal sections, the fornices and internal cerebral veins were delineated in all 67 patients. The cross-sectional appearance and size of the fornices were variable, and the relationship between fornices presented as five different types. In 82% of patients, dominance of one relationship type was not found. The diameter of the internal cerebral veins (ICVs) was also variable, and the relationship between ICVs presented as four different types. In 70% of patients, dominance of one relationship type was not found. In 52% of patients, the lower layer of the third ventricle roof was identified as an inhomogeneous membranous structure. In the sagittal sections, the lower layer of the third ventricle roof was delineated as an inhomogeneous linear structure with variable slopes. CONCLUSIONS: The third ventricle roof appears highly variable in morphology. Visualization of the third ventricle roof using the CISS sequence may be useful for planning safe and effective surgical maneuvers around the region.

Three-Dimensional Imaging Anatomic Study and Clinical Application of the Third Ventricle Transcallosal-Transforniceal Approach.

The third ventricle is a narrow, funnel-shaped, unilocular, midline cavity located between the 2 thalami, under the body of the lateral ventricle, in the center of the head. Damaging of brain tissue in the third ventricle when conducting operation under the microscope will lead to serious consequence. The study aimed to precisely detect the relative location of specific structures on the approach to the third ventricle. The authors rebuilt a 3-dimensional reconstruction of the brain and selected specific sections and then measured several crucial distance, angle to precisely assure the approaching pathway and localize the hypothalamic sulcus, interthalamic adhesion, anterior commissure, optic chiasm, and pineal body. In the study, canthomeatal line was used as base line to measure angle. Parameters were obtained from 58 samples (22 males and 36 females) between 21 and 76 years old. Means and standard deviation were calculated as well as the 95% confidence interval for the mean value of the measured data. The data were analyzed by SPSS, statistical software with the comparison between sexes and sides. The results could be reference for clinical and anatomic utilities.

The suprapineal recess of the third ventricle: an anatomic study with magnetic resonance imaging.

PURPOSE: The suprapineal recess (SPR) is a small, backward extension of the third ventricle. Few radiological studies have investigated the morphology of the SPR. Here, we explore the SPR with magnetic resonance (MR) imaging. METHODS: A total of 124 patients underwent thin-slice MR imaging examinations with T2-weighted imaging and the constructive interference steady-state (CISS) sequence. Imaging data were transferred to a workstation for analysis. RESULTS: The pineal gland (P) was delineated in 99% of the patients on T2-weighted imaging and 100% of the patients on the CISS sequence. In contrast, the SPR was identified in 27% of the patients on T2-weighted imaging and 82% of the patients on the CISS sequence. The location of the P relative to the lowest point of the splenium was roughly classified into two types. Of them, the anterior P location was the more frequent type and observed in 73% of the patients. The angle formed by the roof and floor of the SPR showed remarkable interindividual diversity. A membranous posterior extension with variable length, spanning between the posterosuperior margin of the P and Galenic complex was found in 55% of the identified SPRs on T2-weighted imaging and 45% on the CISS sequence. CONCLUSIONS: The SPR is a distinct structure with diversity in appearance among individuals but commonly extends posterior to the P. High-resolution MR imaging is useful for delineating the SPR in vivo.

Comparative anatomical analysis of the transcallosal-transchoroidal and transcallosal-transforniceal-transchoroidal approaches to the third ventricle.

OBJECTIVE Access to the third ventricle is a veritable challenge to neurosurgeons. In this context, anatomical and morphometric studies are useful for establishing the limitations and advantages of a particular surgical approach. The transchoroidal approach is versatile and provides adequate exposure of the middle and posterior regions of the third ventricle. However, the fornix column limits the exposure of the anterior region of the third ventricle. There is evidence that the unilateral section of the fornix column has little effect on cognitive function. This study compared the anatomical exposure afforded by the transforniceal-transchoroidal approach with that of the transchoroidal approach. In addition, a morphometric evaluation of structures that are relevant to and common in the 2 approaches was performed. METHODS The anatomical exposure provided by the transcallosal-transchoroidal and transcallosal-transforniceal-transchoroidal approaches was compared in 8 fresh cadavers, using a neuronavigation system. The working area, microsurgical exposure area, and angular exposure on the longitudinal and transversal planes of 2 anatomical targets (tuber cinereum and cerebral aqueduct) were compared. Additionally, the thickness of the right frontal lobe parenchyma, thickness of the corpus callosum trunk, and longitudinal diameter of the interventricular foramen were measured. The values obtained were submitted to statistical analysis using the Wilcoxon test. RESULTS In the quantitative evaluation, compared with the transchoroidal approach, the transforniceal-transchoroidal approach provided a greater mean working area (transforniceal-transchoroidal 150 ± 11 mm2; transchoroidal 121 ± 8 mm2; p < 0.05), larger mean microsurgical exposure area (transforniceal-transchoroidal 101 ± 9 mm2; transchoroidal 80 ± 5 mm2; p < 0.05), larger mean angular exposure area on the longitudinal plane for the tuber cinereum (transforniceal-transchoroidal 71° ± 7°; transchoroidal 64° ± 6°; p < 0.05), and larger mean angular exposure area on the longitudinal plane for the cerebral aqueduct (transforniceal-transchoroidal 62° ± 6°; transchoroidal 55° ± 5°; p < 0.05). No differences were observed in angular exposure along the transverse axis for either anatomical target (tuber cinereum and cerebral aqueduct; p > 0.05). The mean thickness of the right frontal lobe parenchyma was 35 ± 3 mm, the mean thickness of the corpus callosum trunk was 10 ± 1 mm, and the mean longitudinal diameter of the interventricular foramen was 4.6 ± 0.4 mm. In the qualitative assessment, it was noted that the transforniceal-transchoroidal approach led to greater exposure of the third ventricle anterior region structures. There was no difference between approaches in the exposure of the structures of the middle and posterior region. CONCLUSIONS The transforniceal-transchoroidal approach provides greater surgical exposure of the third ventricle anterior region than that offered by the transchoroidal approach. In the population studied, morphometric analysis established mean values for anatomical structures common to both approaches.

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.

Cilia-based flow network in the brain ventricles.

Cerebrospinal fluid conveys many physiologically important signaling factors through the ventricular cavities of the brain. We investigated the transport of cerebrospinal fluid in the third ventricle of the mouse brain and discovered a highly organized pattern of cilia modules, which collectively give rise to a network of fluid flows that allows for precise transport within this ventricle. We also discovered a cilia-based switch that reliably and periodically alters the flow pattern so as to create a dynamic subdivision that may control substance distribution in the third ventricle. Complex flow patterns were also present in the third ventricles of rats and pigs. Our work suggests that ciliated epithelia can generate and maintain complex, spatiotemporally regulated flow networks.

3D shape analysis of the brain's third ventricle using a midplane encoded symmetric template model.

BACKGROUND: Structural changes of the brain's third ventricle have been acknowledged as an indicative measure of the brain atrophy progression in neurodegenerative and endocrinal diseases. To investigate the ventricular enlargement in relation to the atrophy of the surrounding structures, shape analysis is a promising approach. However, there are hurdles in modeling the third ventricle shape. First, it has topological variations across individuals due to the inter-thalamic adhesion. In addition, as an interhemispheric structure, it needs to be aligned to the midsagittal plane to assess its asymmetric and regional deformation. METHOD: To address these issues, we propose a model-based shape assessment. Our template model of the third ventricle consists of a midplane and a symmetric mesh of generic shape. By mapping the template's midplane to the individuals' brain midsagittal plane, we align the symmetric mesh on the midline of the brain before quantifying the third ventricle shape. To build the vertex-wise correspondence between the individual third ventricle and the template mesh, we employ a minimal-distortion surface deformation framework. In addition, to account for topological variations, we implement geometric constraints guiding the template mesh to have zero width where the inter-thalamic adhesion passes through, preventing vertices crossing between left and right walls of the third ventricle. The individual shapes are compared using a vertex-wise deformity from the symmetric template. RESULTS: Experiments on imaging and demographic data from a study of aging showed that our model was sensitive in assessing morphological differences between individuals in relation to brain volume (i.e. proxy for general brain atrophy), gender and the fluid intelligence at age 72. It also revealed that the proposed method can detect the regional and asymmetrical deformation unlike the conventional measures: volume (median 1.95ml, IQR 0.96ml) and width of the third ventricle. Similarity measures between binary masks and the shape model showed that the latter reconstructed shape details with high accuracy (Dice coefficient ≥0.9, mean distance 0.5mm and Hausdorff distance 2.7mm). CONCLUSIONS: We have demonstrated that our approach is suitable to morphometrical analyses of the third ventricle, providing high accuracy and inter-subject consistency in the shape quantification. This shape modeling method with geometric constraints based on anatomical landmarks could be extended to other brain structures which require a consistent measurement basis in the morphometry.

The chiasmatic recess of the third ventricle: delineation with magnetic resonance imaging.

PURPOSE: The chiasmatic recess (CR) is a small, downward extension in the most rostral third ventricle. Few studies have highlighted its morphology. Accordingly, we explored the CR using magnetic resonance imaging. METHODS: A total of 104 patients were enrolled in this study. Magnetic resonance imaging examinations were performed in axial and sagittal sections. Imaging data were obtained as thin-sliced, seamless sections. RESULTS: The CR was clearly identified in 98 % of axial and 96 % of sagittal sections. The lamina terminalis was delineated as a membranous structure with homogenous thickness. The CR was consistently delineated as a smoothly tapering, cerebrospinal fluid-filled space. The number of axial images required to encompass the entire CR was 1 slice for 1.9 % of samples, 2 for 32.7 %, 3 for 49 %, 4 for 12.5 %, 5 for 1 %, and 6 for 1 %. On axial view, the CR generally presented as a long horizontal ellipse. On sagittal view, the CR showed variable shape and length. The optic chiasm-lamina terminalis angle, formed by the upper surface of the optic chiasm and inner surface of the lamina terminalis and measured on midsagittal sections, showed considerable variability. CONCLUSIONS: The CR is a hollow structure with various contours. Recognition of the morphological characteristics of the CR and lamina terminalis may be helpful for safe perforation of the lamina terminalis. Magnetic resonance imaging is useful for exploring the CR.

The Anterior Subcallosal Approach to Third Ventricular and Suprasellar Lesions: Anatomical Description and Technical Note.

BACKGROUND: Surgical access to the third ventricle is challenging, given the depth of the operative field and close proximity of vital neural structures that must be traversed. For anterior third ventricular lesions, approach options include anterior transcallosal or transcortical, subfrontal, frontotemporal, or endonasal. The subcallosal approach, a translamina terminalis approach, is unique in that the surgical corridor is just below the corpus callosum, minimizes retraction and preserves corpus callosum integrity. Case examples are provided, and an anatomical study delineating the dimensions of the surgical corridor is performed. METHODS: Two latex-injected cadaver heads were used to describe the subcallosal corridor. A magnetic resonance imaging scan was obtained and registered with neuronavigation for correlative anatomical illustration. Depth, dimensions, and cross-sectional area were measured for the subcommunicating and supracommunicating corridors. RESULTS: The surgical depth for anterior transcallosal, subcallosal, and subfrontal approaches was 7.5 cm, 7.7 cm, and 7.6 cm respectively. The average corridor dimensions for the subcallosal approach were 14.75 × 6.63 mm compared with 8.88 × 5.38 mm for the subcommunicating corridor. Cross-sectional area of the subcommunicating corridor was 30.62 mm(2) compared with 80.42 mm(2) for supracommunicating. This was easily enlarged to 156.62 mm(2) with gentle retraction. CONCLUSIONS: The anterior subcallosal approach is a safe approach for lesions of the third ventricle that avoids splitting the corpus callosum and resecting unnecessary brain and minimizes brain retraction. This corridor is superior to the traditional subfrontal approach in terms of working space and compares favorably to the anterior transcallosal approach without disrupting the corpus callosum.

Stereotactic Localization of the Monro Foramen and the Safest Stereotactic Interforniceal Approach to the Third Ventricle: A Neuroanatomical Study.

BACKGROUND AND OBJECTIVE: To localize the human foramen of Monro stereotactically, to define the anatomical parameters of the safest stereotactic transcallosal transseptal interforniceal approach to the third ventricle, and to show how neurosurgeons could use them in preoperative planning. MATERIAL AND METHODS: Our material consisted of 44 formalin-fixated human cerebral hemispheres. We found the location of the anterior (AC) and posterior commissure at the internal hemispheric surface. The posterosuperior border of the AC (point A) was our stereotactic reference point with coordinates (X, Y, Z) = (0, 0, 0). We found the Monro foramen location and measured the stereotactic coordinates of its anterior inferior border (point B). The safest trajectory to the third ventricle has to pass as far as possible from points A and B so as not to traumatize the choroid plexus of the Monro foramina or the AC. The midpoint of the AB distance (point M) is the stereotactic point that provides this safest trajectory. We also measured AB length and point M stereotactic coordinates. RESULTS: Mean stereotactic coordinates of the (midline projection of the) point B were (X, Y, Z) = (0, -0.6, 2.4). Point B was located averagely 3.2 mm far from point A. Mean stereotactic coordinates of the point M, a necessary component of the trajectory of the safest stereotactic interforniceal approach to the third ventricle, were (X, Y, Z) = (0, -0.3, 1.2). Point M was located 1.6 mm far from point A. CONCLUSIONS: The present study shows how neurosurgeons can localize and use crucial anatomical landmarks, namely the AC and foramen of Monro, to approach the third ventricle safely via a stereotactic interforniceal technique. This can be achieved during preoperative planning with simple identification of stereotactic points A, B, and M on preoperative median sagittal magnetic resonance images.

Stereoscopic neuroanatomy lectures using a three-dimensional virtual reality environment.

INTRODUCTION: Three-dimensional (3D) computer graphics are increasingly used to supplement the teaching of anatomy. While most systems consist of a program which produces 3D renderings on a workstation with a standard screen, the Dextrobeam virtual reality VR environment allows the presentation of spatial neuroanatomical models to larger groups of students through a stereoscopic projection system. MATERIALS AND METHODS: Second-year medical students (n=169) were randomly allocated to receive a standardised pre-recorded audio lecture detailing the anatomy of the third ventricle accompanied by either a two-dimensional (2D) PowerPoint presentation (n=80) or a 3D animated tour of the third ventricle with the DextroBeam. Students completed a 10-question multiple-choice exam based on the content learned and a subjective evaluation of the teaching method immediately after the lecture. RESULTS: Students in the 2D group achieved a mean score of 5.19 (±2.12) compared to 5.45 (±2.16) in the 3D group, with the results in the 3D group statistically non-inferior to those of the 2D group (p<0.0001). The students rated the 3D method superior to 2D teaching in four domains (spatial understanding, application in future anatomy classes, effectiveness, enjoyableness) (p<0.01). CONCLUSION: Stereoscopically enhanced 3D lectures are valid methods of imparting neuroanatomical knowledge and are well received by students. More research is required to define and develop the role of large-group VR systems in modern neuroanatomy curricula.

Measures of ventricles and evans' index: from neonate to adolescent.

Ventricle sizes are important for the early diagnosis of hydrocephalus or for follow-up after ventriculostomy. Diameters of ventricles may change, especially in childhood. This study aims to provide normative data about ventricle diameters. Among 14,854 cranial MRI performed between 2011 and 2013, 2,755 images of Turkish children aged 0-18 years were obtained. After exclusions, 517 images were left. Four radiologists were trained by a pediatric radiologist. Twenty images were assessed by all radiologists for a pilot study to see that there was no interobserver variation. There were 10-22 children in each age group. The maximum width of the third ventricle was 5.54 ± 1.29 mm in males in age group 1 and 4.98 ± 1.08 mm in females in age group 2. The Evans' index was <0.3 and consistent with the literature. The third ventricle/basilar artery width ratio was found to be >1 and <2 in all age groups and both gender groups. Our study showed the ventricle size data of children in various age groups from newborn to adolescent. The ventricle volume/cerebral parenchyma ratio seems to decrease with age. We think that these data can be applied in clinical practice, especially for the early diagnosis of hydrocephalus.