Three-Dimensional Modeling and Augmented Reality and Virtual Reality Simulation of Fiber Dissection of the Cerebellum and Brainstem

Surgeons must understand the complex anatomy of the cerebellum and brainstem and their 3-dimensional (3D) relationships with each other for surgery to be successful. To the best of our knowledge, there have been no fiber dissection studies combined with 3D models, augmented reality (AR), and virtual reality (VR) of the structure of the cerebellum and brainstem. In this study, we created freely accessible AR and VR simulations and 3D models of the cerebellum and brainstem.

OBJECTIVE: To create 3D models and AR and VR simulations of cadaveric dissections of the human cerebellum and brainstem and to examine the 3D relationships of these structures.

METHODS: Ten cadaveric cerebellum and brainstem specimens were prepared in accordance with the Klingler’s method. The cerebellum and brainstem were dissected under the operating microscope, and 2-dimensional and 3D images were captured at every stage. With a photogrammetry tool (Qlone, EyeCue Vision Technologies, Ltd.), AR and VR simulations and 3D models were created by combining several 2-dimensional pictures.

RESULTS: For the first time reported in the literature, high-resolution, easily accessible, free 3D models and AR and VR simulations of cerebellum and brainstem dissections were created.

CONCLUSION: Fiber dissection of the cerebellum-brainstem complex and 3D models with AR and VR simulations are a useful addition to the goal of training neurosurgeons worldwide.

Internal Carotid Artery Classification Systems: An Illustrative Review

World Neurosurg. (2022) 163:41-49

The internal carotid artery (ICA) course has been discussed extensively. Several classification systems have attempted to delineate an accurate and helpful trajectory for microsurgical and endoscopic guidance, thus allowing a better neurosurgical performance while avoiding intraoperative complications. Also, the practicality of the classification systems has been emphasized for scholarly communication among disciplines. Nevertheless, the nomenclature of the ICA remains heterogeneous and confusing for health care professionals, trainees, and students.

We present an illustrative review of 8 notable ICA classification systems using lateral and anterior views as a rapid tool for neuroanatomic consultation. The appraisal of the vessel anatomy from different perspectives while recognizing their usefulness and limitations might provide a comprehensive understanding of the ICA, optimize the intraoperative performance, and facilitate communication

The membrane of Liliequist—a safe haven in the middle of the brain.

Acta Neurochirurgica (2020) 162:2235–2244

The membrane of Liliequist is one of the best-known inner arachnoid membranes and an essential intraoperative landmark when approaching the interpeduncular cistern but also an obstacle in the growth of lesions in the sellar and parasellar regions. The limits and exact anatomical description of this membrane are still unclear, as it blends into surrounding structures and joins other arachnoid membranes.

Methods We performed a systematic narrative review by searching for articles describing the anatomy and the relationship of the membrane of Liliequist with surrounding structures in MEDLINE, Embase and Google Scholar. Included articles were crosschecked for missing references. Both preclinical and clinical studies were included, if they detailed the clinical relevance of the membrane of Liliequist.

Results Despite a common definition of the localisation of the membrane of Liliequist, important differences exist with respect to its anatomical borders. The membrane appears to be continuous with the pontomesencephalic and pontomedullary membranes, leading to an arachnoid membrane complex around the brainstem. Furthermore, Liliequist’s membrane most likely continues along the oculomotor nerve sheath in the cavernous sinus, blending into and giving rise to the carotid-oculomotor membrane.

Conclusion Further standardized anatomical studies are needed to clarify the relation of the membrane of Liliequist with surrounding structures but also the anatomy of the arachnoid membranes in general. Our study supports this endeavour by identifying the knowledge hiatuses and reviewing the current knowledge base.

The temporoinsular projection system: an anatomical study

J Neurosurg 132:615–623, 2020

Connections between the insular cortex and the amygdaloid complex have been demonstrated using various techniques. Although functionally well connected, the precise anatomical substrate through which the amygdaloid complex and the insula are wired remains unknown. In 1960, Klingler briefly described the “fasciculus amygdaloinsularis,” a white matter tract connecting the posterior insula with the amygdala. The existence of such a fasciculus seems likely but has not been firmly established, and the reported literature does not include a thorough description and documentation of its anatomy. In this fiber dissection study the authors sought to elucidate the pathway connecting the insular cortex and the mesial temporal lobe.

METHODS Fourteen brain specimens obtained at routine autopsy were dissected according to Klingler’s fiber dissection technique. After fixation and freezing, anatomical dissections were performed in a stepwise progressive fashion.

RESULTS The insula is connected with the opercula of the frontal, parietal, and temporal lobes through the extreme capsule, which represents a network of short association fibers. At the limen insulae, white matter fibers from the extreme capsule converge and loop around the uncinate fasciculus toward the temporal pole and the mesial temporal lobe, including the amygdaloid complex.

CONCLUSIONS The insula and the mesial temporal lobe are directly connected through white matter fibers in the extreme capsule, resulting in the appearance of a single amygdaloinsular fasciculus. This apparent fasciculus is part of the broader network of short association fibers of the extreme capsule, which connects the entire insular cortex with the temporal pole and the amygdaloid complex. The authors propose the term “temporoinsular projection system” (TIPS) for this complex.

Microsurgical anatomy of the central core of the brain

J Neurosurg 129:752–769, 2018

The purpose of this study was to describe in detail the cortical and subcortical anatomy of the central core of the brain, defining its limits, with particular attention to the topography and relationships of the thalamus, basal ganglia, and related white matter pathways and vessels.

METHODS The authors studied 19 cerebral hemispheres. The vascular systems of all of the specimens were injected with colored silicone, and the specimens were then frozen for at least 1 month to facilitate identification of individual fiber tracts. The dissections were performed in a stepwise manner, locating each gray matter nucleus and white matter pathway at different depths inside the central core. The course of fiber pathways was also noted in relation to the insular limiting sulci.

RESULTS The insular surface is the most superficial aspect of the central core and is divided by a central sulcus into an anterior portion, usually containing 3 short gyri, and a posterior portion, with 2 long gyri. It is bounded by the anterior limiting sulcus, the superior limiting sulcus, and the inferior limiting sulcus. The extreme capsule is directly underneath the insular surface and is composed of short association fibers that extend toward all the opercula. The claustrum lies deep to the extreme capsule, and the external capsule is found medial to it. Three fiber pathways contribute to form both the extreme and external capsules, and they lie in a sequential anteroposterior disposition: the uncinate fascicle, the inferior fronto-occipital fascicle, and claustrocortical fibers. The putamen and the globus pallidus are between the external capsule, laterally, and the internal capsule, medially. The internal capsule is present medial to almost all insular limiting sulci and most of the insular surface, but not to their most anteroinferior portions. This anteroinferior portion of the central core has a more complex anatomy and is distinguished in this paper as the “anterior perforated substance region.” The caudate nucleus and thalamus lie medial to the internal capsule, as the most medial structures of the central core. While the anterior half of the central core is related to the head of the caudate nucleus, the posterior half is related to the thalamus, and hence to each associated portion of the internal capsule between these structures and the insular surface. The central core stands on top of the brainstem. The brainstem and central core are connected by several white matter pathways and are not separated from each other by any natural division. The authors propose a subdivision of the central core into quadrants and describe each in detail. The functional importance of each structure is highlighted, and surgical approaches are suggested for each quadrant of the central core.

CONCLUSIONS As a general rule, the internal capsule and its vascularization should be seen as a parasagittal barrier with great functional importance. This is of particular importance in choosing surgical approaches within this region.

Surgical Approaches to the Temporal Horn: An Anatomic Analysis of White Matter Tract Interruption

Operative Neurosurgery 13:258–270, 2017

Surgical access to the temporal horn is necessary to treat tumors and vascular lesions, but is used mainly in patients with mediobasal temporal epilepsy. The surgical approaches to this cavity fall into 3 primary categories: lateral, inferior, and transsylvian. The current neurosurgical literature has underestimated the interruption of involved fiber bundles and the correlated clinical manifestations.

OBJECTIVE: To delineate the interruption of fiber bundles during the different approaches to the temporal horn.

METHODS:We simulated the lateral (trans-middle temporal gyrus), inferior (transparahippocampal gyrus), and transsylvian approaches in 20 previously frozen, formalin-fixed human brains (40 hemispheres). Fiber dissection was then done along the lateral and inferior aspects under the operating microscope. Each stage of dissection and its respective fiber tract interruption were defined.

RESULTS: The lateral (trans-middle temporal gyrus) approach interrupted “U” fibers, the superior longitudinal fasciculus (inferior arm), occipitofrontal fasciculus (ventral segment), uncinate fasciculus (dorsolateral segment), anterior commissure (posterior segment), temporopontine, inferior thalamic peduncle (posterior fibers), posterior thalamic peduncle (anterior portion), and tapetum fibers. The inferior (transparahippocampal gyrus) approach interrupted “U” fibers, the cingulum (inferior arm), and fimbria, and transected the hippocampal formation. The transsylvian approach interrupted “U”fibers (anterobasal region of the extreme capsule), the uncinate fasciculus (ventromedial segment), and anterior commissure (anterior segment), and transected the anterosuperior aspect of the amygdala.

CONCLUSION: White matter dissection improves our knowledge of the complex anatomy surrounding the temporal horn. Identifying the fiber bundles at risk during each surgical approach adds important information for choosing the appropriate surgical strategy.


Virtual and stereoscopic anatomy: when virtual reality meets medical education


J Neurosurg 125:1105–1111, 2016

The authors sought to construct, implement, and evaluate an interactive and stereoscopic resource for teaching neuroanatomy, accessible from personal computers.

Methods Forty fresh brains (80 hemispheres) were dissected. Images of areas of interest were captured using a manual turntable and processed and stored in a 5337-image database. Pedagogic evaluation was performed in 84 graduate medical students, divided into 3 groups: 1 (conventional method), 2 (interactive nonstereoscopic), and 3 (interactive and stereoscopic). The method was evaluated through a written theory test and a lab practicum.

Results Groups 2 and 3 showed the highest mean scores in pedagogic evaluations and differed significantly from Group 1 (p < 0.05). Group 2 did not differ statistically from Group 3 (p > 0.05). Size effects, measured as differences in scores before and after lectures, indicate the effectiveness of the method. ANOVA results showed significant difference (p < 0.05) between groups, and the Tukey test showed statistical differences between Group 1 and the other 2 groups (p < 0.05). No statistical differences between Groups 2 and 3 were found in the practicum. However, there were significant differences when Groups 2 and 3 were compared with Group 1 (p < 0.05).

Conclusions The authors conclude that this method promoted further improvement in knowledge for students and fostered significantly higher learning when compared with traditional teaching resources.

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