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.

An anatomical and volumetric study on brain ventricles in sheep using different techniques.

This study investigated the morphological features of the ventricular system of the brain in Akkaraman sheep in a measured and structural manner. In the study, 24 adults male Akkaraman sheep, which is a common and hornless breed were used. Anatomical features of the ventricular system were determined by latex injection and dissection, acrylic injection and corrosion cast and magnetic resonance imaging. In the measurements, a precise digital calliper, Archimedes' principle, Cavalieri's principle and ITK-SNAP imaging were used by comparing them with each other. The average weight of fresh sheep brains was 102 g (0.226 lb), the volume 115.8 mL and the length, height and width were 130.78, 40.58 and 70.08 mm, respectively. The olfactoric bulb contained a cavity associated with the lateral ventricle, large enough to be called a ventricle. The cavity of septum pellucidum has a large cavity was observed. However, there was no cerebrospinal fluid in this cavity. The interventricular foramen of the dissected brain was also an opening measuring 1.4 mm × 3.9 mm × 5.5 mm. The total volume of the ventricles of the brain of Akkaraman sheep was found to be 7107.71 ± 479, 7115 ± 737 and 7080 ± 647 mm3 and 6200 mm3 using the Planimetry, Point Counting method, ITK-SNAP program, and Archimedes' principle, respectively. In the study, species and breed-specific brain indices values and many detailed morphometric data were obtained.

Interactions of brain, blood, and CSF: a novel mathematical model of cerebral edema.

BACKGROUND: Previous models of intracranial pressure (ICP) dynamics have not included flow of cerebral interstitial fluid (ISF) and changes in resistance to its flow when brain swelling occurs. We sought to develop a mathematical model that incorporates resistance to the bulk flow of cerebral ISF to better simulate the physiological changes that occur in pathologies in which brain swelling predominates and to assess the model's ability to depict changes in cerebral physiology associated with cerebral edema. METHODS: We developed a lumped parameter model which includes a representation of cerebral ISF flow within brain tissue and its interactions with CSF flow and cerebral blood flow (CBF). The model is based on an electrical analog circuit with four intracranial compartments: the (1) subarachnoid space, (2) brain, (3) ventricles, (4) cerebral vasculature and the extracranial spinal thecal sac. We determined changes in pressure and volume within cerebral compartments at steady-state and simulated physiological perturbations including rapid injection of fluid into the intracranial space, hyperventilation, and hypoventilation. We simulated changes in resistance to flow or absorption of CSF and cerebral ISF to model hydrocephalus, cerebral edema, and to simulate disruption of the blood-brain barrier (BBB). RESULTS: The model accurately replicates well-accepted features of intracranial physiology including the exponential-like pressure-volume curve with rapid fluid injection, increased ICP pulse pressure with rising ICP, hydrocephalus resulting from increased resistance to CSF outflow, and changes associated with hyperventilation and hypoventilation. Importantly, modeling cerebral edema with increased resistance to cerebral ISF flow mimics key features of brain swelling including elevated ICP, increased brain volume, markedly reduced ventricular volume, and a contracted subarachnoid space. Similarly, a decreased resistance to flow of fluid across the BBB leads to an exponential-like rise in ICP and ventricular collapse. CONCLUSIONS: The model accurately depicts the complex interactions that occur between pressure, volume, and resistances to flow in the different intracranial compartments under specific pathophysiological conditions. In modelling resistance to bulk flow of cerebral ISF, it may serve as a platform for improved modelling of cerebral edema and blood-brain barrier disruption that occur following brain injury.

Longitudinal Reference Values for Cerebral Ventricular Size in Preterm Infants Born at 23-27 Weeks of Gestation.

OBJECTIVE: To establish longitudinal reference values for cerebral ventricular size in the most vulnerable patients at risk for intraventricular hemorrhage (IVH) and posthemorrhagic ventricular dilatation (PHVD). STUDY DESIGN: This retrospective study included neurologically healthy preterm neonates born at 230/7-266/7 weeks of gestational age between September 2011 and April 2019. Patients were treated at 2 Austrian tertiary centers, Medical University of Vienna and Medical University of Innsbruck. All available cerebral ultrasound scans until 30 weeks corrected age were analyzed. Ventricular measurements included ventricular index, anterior horn width (AHW), and thalamo-occipital distance (TOD) and longitudinal percentiles were created. RESULTS: The study cohort consisted of 244 preterm neonates, with a median gestational age of 253/7 weeks (IQR, 244/7-260/7 weeks) and a median birth weight of 735 g (IQR, 644-849 g). A total of 993 ultrasound scans were available for analysis, resulting in >1800 measurements of ventricular index, AHW, and TOD. Special attention was given to the 97th percentile as well as 2 mm and 4 mm above the 97th percentile, which are used internationally as cutoffs for intervention in the presence of PHVD. CONCLUSIONS: We present percentile charts based on a cohort of extremely premature infants including neonates born at the border of viability suited to follow-up the most vulnerable patients at risk for IVH and PHVD. Furthermore, we provide an extensive literature research and comparison of all available reference values, focusing on ventricular index, AHW, and TOD.

Freehand stereotactic ventricular catheter insertion for ventriculoperitoneal shunts based on individualized radio-anatomical landmarks.

INTRODUCTION: The accurate placement of the ventricular catheter (VC) is critical in reducing the incidence of proximal failure of ventriculoperitoneal shunts (VPSs). The standard freehand technique is based on validated external anatomical landmarks but remains associated with a relatively high rate of VC malposition. Already proposed alternative methods have all their specific limitations. Herein, we evaluate the accuracy of our adapted freehand technique based on an individualized radio-anatomical approach. Reproducing the preoperative imaging on the patient's head using common anatomical landmarks allows to define stereotactic VC coordinates to be followed at surgery. MATERIAL AND METHODS: Fifty-five consecutive patients treated with 56 VPS between 11/2005 and 02/2020 fulfilled the inclusion criteria of this retrospective study. Burr hole coordinates, VC trajectory, and length were determined in all cases on preoperative computed tomography (CT) scan and were accurately reported on patients' head. The primary endpoint was to evaluate VC placement accuracy. The secondary endpoint was to evaluate the rate and nature of postoperative VC-related complications. RESULTS: Our new technique was applicable in all patients and no VC-related complications were observed. Postoperative imaging showed VC optimally placed in 85.7% and sub-optimally placed in 14.3% of cases. In all procedures, all the holes on the VC tip were found in the ventricular system. CONCLUSIONS: This simple individualized technique improves the freehand VC placement in VPS surgery, making its accuracy comparable to that of more sophisticated and expensive techniques. Further randomized controlled studies are required to compare our results with those of the other available techniques.

ViceCT and whiceCT for simultaneous high-resolution visualization of craniofacial, brain and ventricular anatomy from micro-computed tomography.

Up to 40% of congenital diseases present disturbances of brain and craniofacial development resulting in simultaneous alterations of both systems. Currently, the best available method to preclinically visualize the brain and the bones simultaneously is to co-register micro-magnetic resonance (µMR) and micro-computed tomography (µCT) scans of the same specimen. However, this requires expertise and access to both imaging techniques, dedicated software and post-processing knowhow. To provide a more affordable, reliable and accessible alternative, recent research has focused on optimizing a contrast-enhanced µCT protocol using iodine as contrast agent that delivers brain and bone images from a single scan. However, the available methods still cannot provide the complete visualization of both the brain and whole craniofacial complex. In this study, we have established an optimized protocol to diffuse the contrast into the brain that allows visualizing the brain parenchyma and the complete craniofacial structure in a single ex vivo µCT scan (whiceCT). In addition, we have developed a new technique that allows visualizing the brain ventricles using a bilateral stereotactic injection of iodine-based contrast (viceCT). Finally, we have tested both techniques in a mouse model of Down syndrome, as it is a neurodevelopmental disorder with craniofacial, brain and ventricle defects. The combined use of viceCT and whiceCT provides a complete visualization of the brain and bones with intact craniofacial structure of an adult mouse ex vivo using a single imaging modality.

Handedness related differences in the intracranial fluid spaces in healthy adults.

Purpose: Our study aimed to determine the possible differences in linear measurements and linear indices values of intracranial fluid spaces (IFS) between right- and left-handed adults.Methods: This work has been carried out on 148 subjects (72 men and 76 women). In the study, 88 right-handers and 60 left-handers were included. Forty of the right-handers were male, 48 were female, and 32 of the left-handers were male, and 28 were female. The ages were between 20 and 50 years. Linear measurements were obtained based on magnetic resonance imaging (MRI) studies. A 1.5-T MRI scanner was used to obtain axial images. The ten parameters were estimated from MRI scans.Results: There was no correlation between parameters and age. In our study, interestingly, as can be seen from the tables, most of the parameters with statistically significant differences were higher in favour of left-handed subjects. In most of the linear measurement results, IFS values of the right hemisphere in right-handers, and the left hemisphere in left-handers were higher. Similar results were found in favour of the left-handed in most of the linear ventricular indices.Conclusion: Linear measurements and linear indices values of IFS were mostly higher in left-handers than in right-handed individuals.

The Caudate Nucleus: Its Connections, Surgical Implications, and Related Complications.

BACKGROUND: The caudate nucleus is a C-shaped structure that is located in the center of the brain and is divided into 3 parts: the head, body, and tail. METHODS: We detail the anatomic connections, relationships with other basal ganglia structures, and clinical implications of injury to the caudate nucleus. RESULTS: Anatomically, the most inferior transcapsular gray matter is the lentiform peduncle, which is the connection between the lentiform nucleus and caudate nucleus as well as the amygdala. The border between the tail and body of the caudate nucleus is the posterior insular point. The tail of the caudate nucleus is extraependymal in some parts and intraependymal in some parts of the roof of the temporal horn of the lateral ventricle. The tail of the caudate nucleus crosses the inferior limiting sulcus (temporal stem), and section of the tail during approaches to lesions involving the temporal stem may cause motor apraxia. The mean distance from the temporal limen point, which is the junction of the limen insula and inferior limiting sulcus, to the tail of the caudate nucleus in the temporal stem is 15.87 ± 3.10 mm. CONCLUSIONS: Understanding of the functional anatomy and connections of the distinct parts of the caudate nucleus is essential for deciding the extent of resection of lesions involving the caudate nucleus and the types of deficits that may be found postoperatively.

Association between scripture memorization and brain atrophy using magnetic resonance imaging.

We investigated the association between scripture memorization and brain tissue using magnetic resonance imaging techniques. Participants comprised 63 healthy adults between the ages of 35 and 80 years old with no neurological or psychological disorders. Of these, 19 had completely memorized the Quran, 28 had partially memorized parts of Quran while 16, the control group, had not committed the Quran into their memory. White matter, grey matter and cerebrospinal fluid volumes were calculated. The brain tissue volumes of those who memorized the entire Quran and those who memorized only a small portion were compared with the control group using one­way ANOVA implemented in SPSS. There was no significant effect of age between the three groups (p>0.50). The group who completely memorized the Quran had larger grey matter and white matter volumes than the control group. Our results showed that those who memorized scripture had more brain tissues preserved compared with those who had not memorized scripture. These findings suggest that engaging our brains by memorizing scripture may increase brain health.

From the wax cast of brain ventricles (1508-9) by Leonardo da Vinci to air cast ventriculography (1918) by Walter E. Dandy.

The mold of the human cerebral ventricles produced in 1918 by Walter E. Dandy had an experimental precedent, a wax cast of ox ventricles made four hundred years earlier (1508-9) by Leonardo da Vinci (1452-1519). This paper is an homage to the epitome of Renaissance and polymath Leonard da Vinci, as well as to Walter Edward Dandy (1886-1946) who developed the ventriculography (1918) and pneumoencephalography (1919) techniques. Pneumoencephalography was applied broadly up to the late 1970s, when it was replaced by less invasive and more accurate neuroimaging techniques.

A critical appraisal of Monro's erroneous description of the cerebral interventricular foramina: Age-related magnetic resonance imaging spatial morphometry and a proposed new terminology.

Anatomic connections between the cerebral lateral and third ventricles have been mischaracterized since Monro's original erroneous description of his eponymous foramina (FoMs) as being only one T-shaped passage. Accurate knowledge of the in vivo three-dimensional (3D) configuration of FoM has important clinical neuroendoscopic, neurosurgical, and neuroimaging implications. We retrospectively analyzed volumetric high-resolution brain magnetic resonance imaging of 100 normal individuals to characterize the normal spatial anatomy and morphometry for each FoM. We measured the true anatomical 3D angulations of FoMs relative to standard neuroimaging orthogonal planes, and their minimum width, depth, and distance between the medial borders of bilateral FoMs. The right and left FoMs were separate, distinct, and in a V-shaped configuration. Each FoM was a round, oval, or crescent-shaped canal-like passage with well-defined borders formed by the semicircular concavity of the ipsilateral forniceal column. The plane of FoM was angled on average 56.8° ± 9.1° superiorly from the axial plane, 22.5° ± 10.7° laterally, and 37.0° ± 6.9° anteriorly from the midsagittal plane; all these angles changing significantly with increasing age. The mean narrowest diameter of FoM was 2.8 ± 1.2 mm, and its depth was 2.5 ± 0.2 mm. Thus, the true size and orientation of FoM differs from that depicted on standard neuroimaging. Notably, in young subjects, FoM has a diameter smaller than its depth, a configuration akin to a short, small canal. We propose that the eponym "Monro" no longer be associated with this structure, and the term "foramen" be abandoned. Instead, FoM should be more appropriately renamed as the "interventricular canaliculus," or IVC, for short.

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.

Review of Temporal Bone Microanatomy : Aqueducts, Canals, Clefts and Nerves.

Temporal bone microanatomy is a common source of consternation for radiologists. Serpentine foramina, branching cranial nerves, and bony canals containing often clinically relevant but often miniscule arterial branches may all cause confusion, even among radiologists familiar with temporal bone imaging. In some cases, the tiniest structures may be occult or poorly visualized, even on thin-slice computed tomography (CT) images. Consequently, such structures are often either ignored or mistaken for pathologic entities. Yet even the smallest temporal bone structures have significant anatomic and pathologic importance. This paper reviews the anatomy and function of the temporal bone aqueducts, canals, clefts, and nerves, as well as the relevant developmental, inflammatory, and neoplastic processes that affect each structure.

The hippocampal-to-ventricle ratio (HVR): Presentation of a manual segmentation protocol and preliminary evidence.

Disentangling age-related changes from developmental variations in hippocampal volume has proven challenging. This article presents a manual segmentation protocol for the hippocampal-to-ventricle ratio (HVR), a measure combining the assessment of hippocampal volume with surrounding ventricular volume. By providing in a single measure both a standard volumetric assessment of the hippocampus and an approximation of volume loss, based on ventricular enlargement, we believe the HVR provides a superior cross-sectional estimation of hippocampal structural integrity. In a first attempt to validate this measure, we contrasted the HVR and standard hippocampal volume in their associations with age and memory performance in two independent cohorts of healthy aging individuals. The first cohort consisted in 50 cognitively normal subjects (mean age: 66.8 years, SD: 4.96, range: 60-75 years), while the second cohort included 88 cognitively normal subjects (mean age: 65.06 years, SD: 6.42, range: 55-80 years). We showed that the manual segmentation protocol for the HVR can be implemented with high reliability. In both cohorts, the HVR showed stronger negative associations with age than standard hippocampal volume. Correlations with memory performance were also numerically superior with the HVR than standard hippocampal volume, across the two cohorts. These findings support an added benefit of using the HVR over standard hippocampal volume when examining relationships with age or memory function in aging individuals. Although further validation is required, we propose that the computation of the HVR is a promising method to improve the evaluation of hippocampal integrity from cross-sectional MR images.

Morphometric MRI study of the brain ventricles in healthy Turkish subjects / Estudio morfométrico de resonancia magnética de los ventrículos cerebrales en sujetos turcos sanos

The aim of this study was to determine the normal values of brain ventricles and indices in healthy subjects in our population using magnetic resonance imaging (MRI) and to reveal sex and age related differences. The MRI of two hundred-sixty-five healthy individuals aged between eighteen and eighty-seven years were examined and the midsagittal and axial images were used for measurements. The measurements were performed from MRI on a Workstation. The following mean values of brain ventricles and indices were observed; frontal horn width (FHW) (33.14 mm); third (3rd) ventricle width (TVW) (3.37 mm); fourth ventricle anteroposterior width (FVWAP) (9.93 mm); fourth ventricle transverse width (FVWT) (12.40 mm); and the maximum transverse inner diameter of the skull (TIDS) (128.75 mm) in females. The same dimensions were 34.85 mm, 3.91 mm, 10.26 mm, 12.81 mm, and 134.68 mm in males, respectively. There were statistically significantly differences in the frontal horn width, third (3rd) ventricle width, and the maximum transverse inner diameter of the skull values in between sexes. The mean values of Evans' index which obtanied with maximum width between the frontal horns of the lateral ventricles divided by the maximum transverse inner diameter of the skull were found as 0.280 ±0.172 in females; whereas the same dimensions were calculated 0.276±0.161 in males. These values were lower in healthy male subjects than females, however; there were no found significantly difference between groups. Present findings obtained from MRI are necessary anatomical baseline data for interpreting pathological changes, planning surgery, and determining presence and progress of some neurological diseases.

El objetivo de este estudio fue determinar los valores normales de los ventrículos e índices cerebrales en sujetos sanos en nuestra población mediante el uso de imágenes de resonancia magnética (RM) y revelar las diferencias relacionadas con el sexo y la edad. Se examinó la resonancia magnética de 265 individuos sanos de entre 18 y 87 años, y se utilizaron las imágenes en sentido medio y sagital para las mediciones. Las mediciones se realizaron a partir de IRM en una estación de trabajo. Se observaron los siguientes valores medios de ventrículos e índices cerebrales: longitud del asta frontal (FHW) (33,14 mm); longitud del tercer ventrículo (TVW) (3,37 mm); longitud anteroposterior del cuarto ventrículo (FVWAP) (9,93 mm); longitud transversal del cuarto ventrículo (FVWT) (12,40 mm); y el diámetro transversal máximo del cráneo (SID) (128,75 mm) en las hembras. Las mismas dimensiones fueron 34,85 mm, 3,91 mm, 10,26 mm, 12,81 mm y 134,68 mm en machos, respectivamente. Hubo diferencias estadísticamente significativas en el ancho del asta frontal, el ancho del tercer ventrículo y el diámetro interno transversal máximo de los valores del cráneo entre los sexos. Los valores medios del índice de Evans que obtuvieron el ancho máximo entre los cuernos frontales de los ventrículos laterales dividido por el diámetro interno transversal máximo del cráneo se encontraron en 0,280 ± 0,172 en las mujeres; mientras que las mismas dimensiones se calcularon en hombres (0,276 ± 0,161). Sin embargo, estos valores fueron más bajos en hombres sanos que en mujeres; no se encontraron diferencias significativas entre los grupos. Los hallazgos actuales obtenidos de IRM son datos anatómicos de referencia necesarios para interpretar los cambios patológicos, planificar la cirugía y determinar la presencia y el progreso de algunas enfermedades neurológicas.

The effect of ventricular volume increase in the amplitude of intracranial pressure.

We study the impact of vascular pulse in the cerebrospinal fluid (CSF) pressure measured on the lateral cerebral ventricles, as well as its sensitivity with respect to ventricular volume change. Recent studies have addressed the importance of the compliance capacity in the brain and its relation to arterial pulse abortion in communicating hydrocephalus. Nevertheless, this mechanism is not fully understood. We propose a fluid-structure interaction (FSI) model on a 3 D idealized geometry based on realistic physiological and morphological parameters. The computational model describes the pulsatile deformation of the third ventricle due to arterial pulse and the resulting CSF dynamics inside brain pathways. The results show that when the volume of lateral ventricles increases up to 3.5 times, the amplitudes of both average and maximum pressure values, computed on the lateral ventricles surface, substantially decrease. This indicates that the lateral ventricles expansion leads to a dumping effect on the pressure exerted on the walls of the ventricles. These results strengthen the possibility that communicant hydrocephalus may, in fact, be a natural response to reduce abnormal high intracranial pressure (ICP) amplitude. This conclusion is in accordance with recent hypotheses suggesting that communicant hydrocephalus is related to a disequilibrium in brain compliance capacity.

Three-Dimensional Printed Models in Anatomy Education of the Ventricular System: A Randomized Controlled Study.

BACKGROUND: The ventricular system is a set of brain cavities without solid tissues and the basis of surgical brain anatomy. To the best of our knowledge, the effect of using 3-dimensional (3D) printed models (3DPMs) on anatomy education of the ventricular system has not been reported. METHODS: We established 3DPMs for the ventricular system and performed a randomized controlled study to evaluate the educational effect of 3DPMs, 3D images (3DIs), and 2-dimensional images (2DIs). We randomly divided 60 second-year medical students into 3 groups, with 3DPMs, 3DIs, and 2DIs used as teaching aids, 1 for each group. Before and after the anatomy class on the features of ventricular system, all students completed the same test. RESULTS: No statistical significant differences were detected between the mean values of the pretest scores of the 3 groups (P > 0.05). For the post-test scores, the students in the 3DPM and 3DI groups performed significantly better than those in the 2DI group in terms of the practice test score (3DPM group vs. 2DI group, P < 0.001; 3DPM group vs. 2DI group, P = 0.009) and total score (3DPM group vs. 2DI group, P = 0.001; 3DI group vs. 2DI group, P = 0.025). From the students' evaluation results, the 3DPM group performed better than the 3DI group for "enjoyment" and "attitude" (P = 0.039 and P = 0.025, respectively). CONCLUSIONS: Compared with 2DIs, use of 3DPMs and 3DIs could improve the effectiveness of teaching the anatomy of the complex ventricular system. In addition, 3DPMs could markedly increase the interest and enthusiasm of students.

Generation of the squamous epithelial roof of the 4th ventricle.

We use the transparency of zebrafish embryos to reveal the de novo generation of a simple squamous epithelium and identify the cellular architecture in the epithelial transition zone that ties this squamous epithelium to the columnar neuroepithelium within the embryo's brain. The simple squamous epithelium of the rhombencephalic roof plate is pioneered by distinct mesenchymal cells at the dorsal midline of the neural tube. Subsequently, a progenitor zone is established at the interface between columnar epithelium of the rhombic lip and the expanding squamous epithelium of the roof plate. Surprisingly, this interface consists of a single progenitor cell type that we have named the veil cell. Veil cells express gdf6a and constitute a lineage restricted stem zone that generates the squamous roof plate by direct transformation and asymmetrically fated divisions. Experimental restriction of roof plate expansion leads to extrusion of veil cell daughters and squamous cells, suggesting veil cell fate is regulated by the space available for roof plate growth.