Last Updated: July 1, 2018
Cerebrovascular Operative Anatomy: An Immersive 3D and Virtual Reality Demonstration
Benjamin K. Hendricks, MD1,3; Jerome Hartman1; and Aaron A. Cohen-Gadol, MD, MSc, MBA1,2
- The Neurosurgical Atlas, Indianapolis, IN
- Goodman Campbell Brain and Spine & Indiana University Department of Neurosurgery, Indianapolis, IN
- Barrow Neurological Institute, Phoenix AZ
BACKGROUND: The innate detail of the cerebrovasculature is a demonstration of the structural complexity exhibited within the nervous system and highlights the challenges intrinsic to surgically influencing this system.
OBJECTIVE: The authors ventured to create virtually anatomically accurate cerebrovascular models with superior detail and visual appeal.
INTRODUCTION: The cerebrovascular tree holds an immense innate intricacy which is difficult to accurately represent in 2-dminensional (2D) resources. Bridging the knowledge gap between the 2D learning environment and the 3-dimensional (3D) clinical setting is a challenge requiring experience. Computer graphic technology provides an opportunity for the learner to step into a new era of learning via the use of interactive 3D models.
METHODS: High-resolution angiographic radiologic studies were utilized to create virtual 3D models which were edited for anatomical accuracy and artistic post-processing.
RESULTS: The authors have created anatomically realistic and detailed 3D virtual models of the cebebrovascular structures including the arterial and venous systems. The relevant surgical anatomy of the bony and brain structures was also included. In addition, these models were used to illustrate the pathoanatomy of a deep vascular malformation to demonstrate the potential of this technology.These models allow user interactivity in the 3D environment for improved understanding of anatomical relationships.
CONCLUSIONS: Advances in computer graphics have invited a new era of education and experiential learning. The authors have created an immersive virtual 3D model of the cerebrovasculature to augment education, research, and clinical applications.
Neuroanatomy poses an immense educational challenge. Surgical trainees require an intricate knowledge of neuroanatomy from an early stage in training to meet academic and clinical demands. Prior attempts for neuro-anatomic education have a gold standard of cadaveric dissection which can be cost prohibitive and time consuming. Alternative resources include two-dimensional (2D) representations of anatomical dissections and illustrations to provide a more rapid review. The surgeon must be able to recall anatomical detail in the 3D space to provide a meaningful reference intraoperatively. To augment the 3D learning modality to meet the needs of an increasingly technology-based trainee, a need exists for anatomically accurate computer-based 3D representations of the intricate operative anatomy.
The models developed by the authors attempt to provide an immersive 3D educational and virtual reality referential environment to augment the other available learning resources.
These methods were first described in the article titled Operative Anatomy of the Human Skull: A Virtual Reality Expedition, currently pending publication. Computed tomography and 2D as well as 3D reconstruction catheter-based angiograms were used for construction of the models.
The cerebrovascular anatomy has an endocranial and exocranial component that can be further divided into the anterior and posterior circulation based on the contribution of blood flow through the internal carotid arteries and vertebral arteries, respectively. These structures are illustrated in the following models.
Anterior (Carotid) Arterial Circulation
The anterior arterial circulation is the distal distribution of blood flow through the carotid system. This relevant cerebrovascular anatomy includes segmental divisions of the internal carotid arteries (ICAs), middle cerebral arteries (MCAs), and anterior cerebral arteries (ACAs), and subsequent branching arteries with corresponding perfusion zones.1 Multiple perforator arteries emanating from the terminal ICAs, MCAs, and ACAs have a large perfusion zone along the basal nuclei and basal forebrain.2
The segmental division of the major anterior circulation vessels provides important insight into the associated branches and pathologies that arise along these distributions. The ACAs and MCAs have been divided into segments (A1 to A5 and M1 to M4, respectively). These annotations are demonstrated on Model 3. The ICAs has been divided into seven segments (C1-7) from proximal to distal within the most recent classification system, see Model 3.1
The segmental divisions of the ICAs are visualized from an endoscopic perspective within Model 4. The divisions include parapharyngeal, petrous, paraclival, parasellar, paraclinoid, and intradural segments.3 This segmentation schematic provides an endoscopically relevant division of the ICA.
Posterior (Vertebrobasilar) Arterial Circulation
The posterior arterial circulation is the distal distribution of blood flow through the vertebrobasilar system and demonstrates intricate relationship between the vascular and neural structures within the posterior fossa and deep brainstem nuclei. The posterior fossa contains three sets of neurovascular complexes: upper, middle, and inferior.4
These complexes correspond to the superior cerebellar artery (SCA), anterior inferior cerebellar artery (AICA), and posterior inferior cerebellar artery (PICA).4 Similarly these complexes encompass a corresponding perfusion zone along the midbrain, cerebellar peduncle, and cerebellum.1 The SCA, AICA, and PICA are divided into segments (s1 to s4, a1 to a4, and p1 to p5, respectively). This anatomy is illustrated within Model 6. This segmental division of the individual arteries permits detailed anatomical descriptions of vascular lesions arising along these arteries.
The supratentorial extent of the posterior circulation includes anastomoses with the anterior circulation via the posterior communicating arteries (PCoAs) bilaterally, to varying degrees dependent on dominance and/or atresia of these vessels.1 The posterior cerebral arteries (PCAs) project posteriorly, segmented into P1 to P4 running proximal to distal, and provide watershed perfusion along the ACA and MCA distributions.1
Cerebral venous anatomy can be divided into the cerebral and posterior fossa anatomical compartments, both illustrated in Model 9. The cerebral venous configuration can be subdivided into a deep (subependymal) and superficial group. The superficial division, as Rhoton5 described, is a series of draining veins that can be grouped into four groups of bridging veins: a superior sagittal group, sphenoidal group, tentorial group, and falcine group. The high variation in location and dominance of the veins within these anatomical regions demonstrates the need for a region-based division.
The deep veins include those that drain the walls of the ventricles, choroid plexi, and basal cisterns. These structures include the basal venous system, internal cerebral venous system, and the vein of Galen.5 These structures can be visualized with associated venous anatomy in Model 9.
The deep and superficial cerebral venous groups then converge on the major draining sinuses, which include the superior sagittal sinus, inferior sagittal sinus, straight sinus, transverse sinuses, tentorial sinuses, cavernous sinuses, superior petrosal sinuses, sphenoparietal sinuses, sphenobasal sinuses, and sphenopetrosal sinuses.1,5,6 The majority of the drainage from the major draining sinuses converges on the internal jugular veins, which serve as the major outflow from the cranial vault.
The posterior fossa venous structures can be divided into four divisions: superficial, deep, brainstem, and bridging veins.7 Rhoton further subdivided the superficial draining veins into tentorial, suboccipital, and petrosal draining surfaces.7 The three superficial surfaces, deep posterior fossa veins along the cerebellar fissures, and plexi along the brainstem drain into one of the three groups of bridging veins: galenic, petrosal, or tentorial. The galenic group drains to the vein of Galen. The petrosal group drains into the inferior or superior petrosal sinuses. The tentorial group drains into the tentorial sinuses that ultimately drain onto the superior petrosal, straight, or transverse sinuses.7
Cerebrovascular pathologies involve some of the most demanding operative interventions and an intricate understanding of the relevant neurovascular anatomy is critical to the success of the procedure. An example of an arteriovenous malformation (AVM) is presented in Model 12.
The cerebrovasculature anatomy possesses an unparalleled complexity. We have attempted to represent the anatomy in an understandable manner using 3D virtual models for the purposes of furthering education, research, and clinical applications.
- A.G., O.,Diagnostic Cerebral Angiography. 1999: Lippincott Williams & Wilkins. 462.
- Rosner, S.S., et al., Microsurgical anatomy of the anterior perforating arteries. J Neurosurg, 1984.61(3): p. 468-85.
- Labib, M.A., et al., A road map to the internal carotid artery in expanded endoscopic endonasal approaches to the ventral cranial base. Neurosurgery, 2014.10 Suppl 3: p. 448-71; discussion 471.
- Rhoton, A.L., Jr., The cerebellar arteries. Neurosurgery, 2000.47(3 Suppl): p. S29-68.
- Rhoton, A.L., Jr., The cerebral veins. Neurosurgery, 2002.51(4 Suppl): p. S159-205.
- Rhoton, A.L., Jr., The cavernous sinus, the cavernous venous plexus, and the carotid collar. Neurosurgery, 2002.51 (4 Suppl): p. S375-410.
- Rhoton, A.L., Jr., The posterior fossa veins. Neurosurgery, 2000.47(3 Suppl): p. S69-92.
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