Transorbital Route to Intracranial Space.

The endoscopic superior eyelid transorbital approach has emerged as a notable and increasingly utilized surgical technique in recent years. This chapter presents an overview of the approach, tracing its historical development and highlighting its growing acceptance within the skull base community.Beginning with an introduction and historical perspective, the chapter outlines the evolution of the transorbital approach, shedding light on its origins and the factors driving its adoption. Subsequently, a comprehensive exploration of the anatomic bone pillars and intracranial spaces accessible via this approach is provided. Hence, five bone pillars of the transorbital approach were identified, namely the lesser sphenoid wing, the anterior clinoid, the sagittal crest, the middle cranial fossa, and the petrous apex. A detailed correlation of those bone targets with respective intracranial areas has been reported.Furthermore, the chapter delves into the practical application of the technique through a case example, offering insights into its clinical utility, indications, and limitations.

Endoscopic transorbital approach bone pillars: a comprehensive stepwise anatomical appraisal.

OBJECTIVE: The endoscopic superior eyelid transorbital approach has garnered significant consideration and gained popularity in recent years. Detailed anatomical knowledge along with clinical experience has allowed refinement of the technique as well as expansion of its indications. Using bone as a consistent reference, the authors identified five main bone pillars that offer access to the different intracranial targeted areas for different pathologies of the skull base, with the aim of enhancing the understanding of the intracranial areas accessible through this corridor. METHODS: The authors present a bone-oriented review of the anatomy of the transorbital approach in which they conducted a 3D analysis using Brainlab software and performed dry skull and subsequent cadaveric dissections. RESULTS: Five bone pillars of the transorbital approach were identified: the lesser sphenoid wing, the sagittal crest (medial aspect of the greater sphenoid wing), the anterior clinoid, the middle cranial fossa, and the petrous apex. The associations of these bone targets with their respective intracranial areas are reported in detail. CONCLUSIONS: Identification of consistent bone references after the skin incision has been made and the working space is determined allows a comprehensive understanding of the anatomy of the approach in order to safely and effectively perform transorbital endoscopic surgery in the skull base.

The feasibility of three port endonasal, transorbital, and sublabial approach to the petroclival region: neurosurgical audit and multiportal anatomic quantitative investigation.

PURPOSE: The petroclival region represents the "Achille's heel" for the neurosurgeons. Many ventral endoscopic routes to this region, mainly performed as isolated, have been described. The aim of the present study is to verify the feasibility of a modular, combined, multiportal approach to the petroclival region to overcome the limits of a single approach, in terms of exposure and working areas, brain retraction and manipulation of neurovascular structures. METHODS: Four cadaver heads (8 sides) underwent endoscopic endonasal transclival, transorbital superior eyelid and contralateral sublabial transmaxillary-Caldwell-Luc approaches, to the petroclival region. CT scans were obtained before and after each approach to rigorously separate the contribution of each osteotomy and subsequentially to build a comprehensive 3D model of the progressively enlarged working area after each step. RESULTS: The addition of the contralateral transmaxillary and transorbital corridors to the extended endoscopic endonasal transclival in a combined multiportal approach provides complementary paramedian trajectories to overcome the natural barrier represented by the parasellar and paraclival segments of the internal carotid artery, resulting in significantly greater area of exposure than a pure endonasal midline route (8,77 cm2 and 11,14 cm2 vs 4,68 cm2 and 5,83cm2, extradural and intradural, respectively). CONCLUSION: The use of different endoscopic "head-on" trajectories can be combined in a wider multiportal extended approach to improve the ventral route to the most inaccessible petroclival regions. Finally, by combining these approaches and reiterating the importance of multiportal strategy, we quantitatively demonstrate the possibility to reach "far away" paramedian petroclival targets while preserving the neurovascular structures.

Extradural anterior clinoidectomy through endoscopic transorbital approach: laboratory investigation for surgical perspective.

BACKGROUND: The endoscopic transorbital approach (eTOA) is a new mini-invasive procedure used to explore different areas of the skull base. Authors propose an extradural anterior clinoidectomy (AC) through this corridor, defining the anatomical landmarks of the anterior clinoid process (ACP) projection onto the posterior orbit wall and the technical feasibility of this approach. We describe the exposure of the opticocarotid region and the surgical freedom and the angles of attack obtained with this novel approach. METHODS: Five cadaver heads underwent an eTOA at the Laboratory of Surgical Neuroanatomy of the University of Barcelona. A step-by-step description of the extradural endoscopic transorbital clinoidectomy was provided. A volumetric analysis of the morphometrics characteristics of the sphenoid wings was evaluated before and after dissection using CT scans. Pterional approach was performed to ascertain ACP removal. RESULTS: In all the specimens, it was possible to resect the ACP endo-orbitally aiming an optimal optic canal (OC) unroofing. The surface of the triangle corresponding to the ACP projection onto the posterior orbit wall was 0.42 ± 0.20 cm2. The drilled area to perform the extradural clinoidectomy via eTOA was 3.11 ± 2.27 cm2, and the volume of bone removal corresponding to the greater sphenoid wing (GSW) and lesser sphenoid wing (LSW) was 2.55 ± 1.41 and 0.26 ± 0.18 cm3 respectively. The area of surgical freedom provided by the eTOA was (3.11 ± 2.27cm2), and the angles of attack were 21.39 ± 9.13° in the horizontal axel and 30.63 ± 18.51° in the vertical. CONCLUSIONS: The described extradural anterior clinoidectomy by eTOA uses specific landmarks to localize the ACP on the posterior orbit wall. Resection of the ACP is a technically feasible approach, achieving the main goals of any clinoidectomy.

Case series of fluoroscopic findings and 3D reconstruction of human spinal MRIs of the space of Okada.

OBJECTIVE: To better understand the unexpected spread of contrast medium observed by conventional fluoroscopic X-ray images during standard neuraxial techniques used in the treatment of pain. The support of 3D reconstruction of MRI images of structures within the lumbar spine was used to better understand the space of Okada. METHODS: Lumbar facet joint and epidural corticosteroid injections in five patients under fluoroscopic guidance with loss of resistance to air or saline to identify the facet joints or epidural space. Next, in a retrospective study, the authors examined the retrodural space of Okada and the neighboring tissues with 3D reconstruction of spinal MRIs of seven patients without any demonstrable spinal pathology to better understand the characteristics of the space of Okada. RESULTS: Contrast medium spread to the ipsilateral and contralateral sides was observed in five patients. The contralateral spread was thought to be through the retrodural space of Okada, which is a potential space between the anterior surface of the vertebral lamina and the posterior surface of the ligamentum flavum. It facilitates communication between the contralateral articular facet joints of the spine. CONCLUSIONS: This study provides new evidence for the existence of the space of Okada where an unexpected contralateral spread occurred following facet joint and attempted epidural injection. The 3D reconstructions of MRIs may help us better understand the nature of the retrodural space of Okada and its clinical implications.

Structural characterization of the Extended Frontal Aslant Tract trajectory: A ML-validated laterality study in 3T and 7T.

The Extended Frontal Aslant Tract (exFAT) is a recently described tractography-based extension of the Frontal Aslant Tract connecting Broca's territory to both supplementary and pre-supplementary motor areas, and more anterior prefrontal regions. In this study, we aim to characterize the microstructural properties of the exFAT trajectories as a means to perform a laterality analysis to detect interhemispheric structural differences along the tracts using the Human Connectome Project (HCP) dataset. To that end, the bilateral exFAT was reconstructed for 3T and 7T HCP acquisitions in 120 randomly selected subjects. As a complementary exploration of the exFAT anatomy, we performed a white matter dissection of the exFAT trajectory of two ex-vivo left hemispheres that provide a qualitative assessment of the tract profiles. We assessed the lateralization structural differences in the exFAT by performing: (i) a laterality comparison between the mean microstructural diffusion-derived parameters for the exFAT trajectories, (ii) a laterality comparison between the tract profiles obtained by applying the Automated Fiber Quantification (AFQ) algorithm, and (iii) a cross-validated Machine Learning (ML) classifier analysis using single and combined tract profiles parameters for single-subject classification. The mean microstructural diffusion-derived parameter comparison showed statistically significant differences in mean FA values between left and right exFATs in the 3T sample. The diffusion parameters studied with the AFQ technique suggest that the inferiormost half of the exFAT trajectory has a hemispheric-dependent fingerprint of microstructural properties, with an increased measure of tissue hindrance in the orthogonal plane and a decreased measure of orientational dispersion along the main tract direction in the left exFAT compared to the right exFAT. The classification accuracy of the ML models showed a high agreement with the magnitude of those differences.

Review of the main surgical and angiographic-oriented classifications of the course of the internal carotid artery through a novel interactive 3D model.

The course of the internal carotid artery (ICA) and its segment classifications were reviewed by means of a new and freely available 3D interactive model of the artery and the skull base, based on human neuroimages, that can be freely downloaded at the Public Repository of the University of Barcelona (http://diposit.ub.edu/dspace/handle/2445/112442) and runs under Acrobat Reader in Mac and Windows computers and Windows 10 tablets. The 3D-PDF allows zoom, rotation, selective visualization of structures, and a predefined sequence view. Illustrative images of the different classifications were obtained. Fischer (Zentralbl Neurochir 3:300-313, 1938) described five segments in the opposite direction to the blood flow. Gibo-Rothon (J Neurosurg 55:560-574, 1981) follow the blood flow, incorporated the cervical and petrous portions, and divided the subarachnoid course-supraclinoid-in ophthalmic, communicating, and choroidal segments, enhancing transcranial microscopic approaches. Bouthillier (Neurosurgery 38:425-433, 1996) divided the petrous portion describing the lacerum segment (exposed in transfacial procedures and exploration of Meckel's cave) and added the clinoid segment between the proximal and distal dural rings, of interest in cavernous sinus surgery. The Kassam's group (2014), with an endoscopic endonasal perspective, introduces the "paraclival segment," including the "lacerum segment" and part of the intracavernous ICA, and details surgical landmarks to minimize the risk of injury. Other classifications are also analyzed. This review through an interactive 3D tool provides virtual views of the ICA and becomes an innovative perspective to the segment classifications and neuroanatomy of the ICA and surrounding structures.

Endoscopic endonasal and transorbital routes to the petrous apex: anatomic comparative study of two pathways.

BACKGROUND AND OBJECTIVE: Surgical approaches to the petrous apex region are extremely challenging; while subtemporal approaches and variations represent the milestone of the surgical modules to reach such deep anatomical target, in a constant effort to develop minimally invasive neurosurgical routes, the endoscopic endonasal approach (EEA) has been tested to get a viable corridor to the petroclival junction. Lately, another ventral endoscopic minimally invasive route, i.e., the superior eyelid endoscopic transorbital approach, has been proposed to access the most lateral aspect of the skull base, including the petrous apex region. Our anatomic study aims to compare and combine such two endoscopic minimally invasive pathways to get full access to the petrous apex. Three-dimensional reconstructions and quantitative and morphometric data have been provided. MATERIAL AND METHODS: Five human cadaveric heads (10 sides) were dissected. The lab rehearsals were run as follows: (i) preliminary pre-operative CT scans of each specimen, (ii) pre-dissection planning of the petrous apex removal and its quantification, (iii) petrous apex removal via endoscopic endonasal route, (iv) post-operative CT scans, (v) petrous apex removal via endoscopic transorbital route, and (v) final post-operative CT scan with quantitative analysis. Neuronavigation was used to guide all dissections. RESULTS: The two endoscopic minimally invasive pathways allowed a different visualization and perspective of the petrous apex, and its surrounding neurovascular structures. After both corridors were completed, a communication between the surgical pathways was highlighted, in a so-called connection area, surrounded by the following important neurovascular structures: anteriorly, the internal carotid artery and the Gasserian ganglion; laterally, the internal acoustic canal; superiorly, the abducens nerve, the trigeminal root, and the tentorium cerebelli; inferomedially, the remaining clivus and the inferior petrosal sinus; and posteriorly, the exposed area of the brainstem. Used in a combined fashion, such multiportal approach provided a total of 97% of petrous apex removal. In particular, the transorbital route achieved a mean of 48.3% removal in the most superolateral portion of the petrous apex, whereas the endonasal approach provided a mean of 48.7% bone removal in the most inferomedial part. The difference between the two approaches was found to be not statistically significant (p = 0.67). CONCLUSION: The multiportal combined endoscopic endonasal and transorbital approach to the petrous apex provides an overall bone removal volume of 97% off the petrous apex. In this paper, we highlighted that it was possible to uncover a common path between these two surgical pathways (endonasal and transorbital) in a so-called connection area. Potential indications of this multiportal approach may be lesions placed in or invading the petrous apex and petroclival regions that can be inadequately reached via transcranial paths or via an endonasal endoscopic route alone.

The Posterior Lumbar Epidural Space: Three-Dimensional Reconstruction of High-Resolution MRI: Real and Potential Epidural Spaces and Their Content In Vivo.

OBJECTIVE: Our aim was to study the posterior lumbar epidural space with 3D reconstructions of magnetic resonance images (MRIs) and to compare and validate the findings with targeted anatomic microdissections. DESIGN: We performed 3D reconstructions of high-resolution MRIs from seven patients and normal-resolution MRIs commonly used in clinical practice from 196 other random patients. We then dissected and photographed the lumbar spine areas of four fresh cadavers. RESULTS: From the 3D reconstructions of the MRIs, we verified that the distribution of the posterior fat pad had an irregular shape that resembled a truncated pyramid. It spanned between the superior margin of the lamina of the caudad vertebra and beyond the inferior margin to almost halfway underneath the cephalad lamina of the cranial vertebra, and it was not longitudinally or circumferentially continuous. The 3D reconstructions of the high-definition MRI also consistently revealed a prelaminar fibrous body that was not seen in most of the usually used low-definition MRI reconstructions. Targeted microdissections confirmed the 3D reconstruction findings and also showed the prelaminar tissue body to be fibrous, crossing from side to side anterior to the cephalad half of each lamina, and spanning from the dural sac to the laminae. CONCLUSIONS: Three-dimensional reconstructions and targeted microdissection revealed the unique appearance of posterior fat pads and a prelaminar fibrous body. The exact consistency, presence, prevalence with age, presence in other regions, and function of this body are unknown and require further research.

Anatomical evaluation of the extent of spread in the erector spinae plane block: a cadaveric study.

PURPOSE: The erector spinae plane (ESP) block is an interfascial analgesic technique first described as an alternative for pain control at the thoracic level. The objective of this observational study was to determine the anatomical spread of dye following a T7 ESP block in a cadaveric model. METHODS: An ultrasound-guided ESP block was performed in four fresh human cadavers using an in-plane approach with a linear probe in a longitudinal orientation and a puncture in a craniocaudal direction. Twenty millilitres of an iodinated contrast/methylene blue solution was injected deep to the erector spinae muscle at the distal end of the T7 transverse process bilaterally in two of the specimens, and unilaterally in the other two (six ESP blocks in total). Subsequently, the specimens were subjected to a multi-slice computed tomography (CT) scan with three-dimensional reconstruction. Two of the specimens were dissected to evaluate the distribution of the contrast solution, and a sectional study was performed in the other two. RESULTS: In the six samples, evaluated by CT scan and anatomical dissection, a craniocaudal spread of the dye was observed in the dorsal region from T1-T11 with lateral extension towards the costotransverse region. No diffusion of contrast solution or dye to the anterior region (paravertebral space) was observed by CT scan or dissection. CONCLUSIONS: The results suggest that the ESP block reaches a wide range of the posterior rami of spinal nerves without diffusion into the paravertebral space or involvement of the anterior rami.

RéSUMé: OBJECTIF: Le bloc du plan des muscles érecteurs du rachis (ESP) est une technique analgésique interfasciale qui avait d'abord été décrite comme une alternative pour contrôler la douleur au niveau thoracique. L'objectif de cette étude observationnelle était de déterminer la propagation anatomique d'un colorant après la réalisation d'un bloc ESP au niveau T7 dans un modèle cadavérique. MéTHODE: Un bloc ESP a été réalisé sous échoguidage sur quatre cadavres humains frais en utilisant une approche dans le plan avec une sonde linéaire en orientation longitudinale et une ponction en direction cranio-caudale. Vingt millilitres d'une solution de contraste iodée / bleu de méthylène ont été injectés postérieurement aux muscles érecteurs du rachis à l'extrémité distale de l'apophyse transverse T7, bilatéralement dans deux des spécimens et unilatéralement dans les deux autres (soit six blocs ESP au total). Par la suite, les spécimens ont été soumis à une tomodensitométrie multicoupe avec reconstruction en 3D. Deux des spécimens ont été disséqués afin d'évaluer la distribution de la solution de contraste, et une étude sectionnelle a été réalisée sur les deux autres spécimens. RéSULTATS: Dans les six échantillons évalués par tomodensitométrie et dissection anatomique, une propagation cranio-caudale du colorant a été observée dans la région dorsale de T1­T11 avec une extension latérale vers la région costo-transverse. La tomodensitométrie et la dissection n'ont révélé aucune propagation de la solution de contraste ou du colorant à la région antérieure (espace paravertébral). CONCLUSION: Ces résultats suggèrent que le bloc ESP atteint de nombreux rameaux postérieurs des nerfs rachidiens sans diffusion dans l'espace paravertébral ou atteintes des rameaux antérieurs.

Endoscopic endo- and extra-orbital corridors for spheno-orbital region: anatomic study with illustrative case.

BACKGROUND AND OBJECTIVE: Management of selected spheno-orbital meningiomas via the endoscopic transorbital route has been reported. Surgical maneuverability in a narrow corridor as that offered by the orbit may be challenging. We investigate the additional use of an extra-orbital (EXO) path to be used in combination with the endo-orbital (EO) corridor. MATERIAL AND METHODS: Three human cadaveric heads (six orbits) were dissected at the Laboratory of Surgical Neuroanatomy at the University of Barcelona. The superior eyelid endoscopic transorbital approach was adopted, introducing surgical instruments via both corridors. Surgical freedom analysis was run to determine directionality of each corridor and to calculate the surgical maneuverability related to three anatomic targets: superior orbital fissure (SOF), foramen rotundum (FR), and foramen ovale (FO). We also reported of a 37-year-old woman with a spheno-orbital meningioma with hyperostosis of the lateral wall of the right orbit, treated with such combined endo-orbital and extra-orbital endoscopic approach. RESULTS: Combining both endo-orbital and extra-orbital corridors permitted a greater surgical freedom for all the targets compared with the surgical freedom of each corridor alone (EO + EXO to SOF: 3603.8 mm2 ± 2452.5 mm2; EO + EXO to FR: 1533.0 mm2 ± 892.2 mm2; EO + EXO to FO: 1193.9 mm2 ± 782.6 mm2). Analyzing the extra-orbital pathway, our results showed that the greatest surgical freedom was gained in the most medial portion of the considered area, namely the SOF (1180.5 mm2 ± 648.3 mm2). Regarding the surgical case, using both pathways, we gained enough maneuverability to nearly achieve total resection with no postoperative complications. CONCLUSION: An extra-orbital corridor may be useful to increase the instruments' maneuverability, during a pure endoscopic superior eyelid approach, and to reach the most medial portion of the surgical field from a lateral-to-medial trajectory. Further studies are needed to better define the proper indications for such strategy.

Application of PDF Software with 3D Functionalities in Radiological Models of the Skull Base: Characteristics, Experience and Solutions.

A widely known alternative for reading and exchanging digital files is the PDF file, by Adobe. This type of file has become the most used for the electronic exchange of files. It is platform-independent, suitable for the exchange of medical data in electronic academic publication. PDF can support additional resources such image, media, even, three-dimensional surface mesh models. A three-dimensional model of the base of the skull is generated from computed tomography images to provide an overview of the PDF file format, with emphasis on biomedical images. Three-dimensional representation in PDF files offers many advantages, as these images have more information than two-dimensional images, therefore, we consider this tool (3D PDF) a good alternative for the visualization, interaction and distribution of 3D content.

Computer Application of Ultrasound and Nuclear Magnetic Resonance Images for the Anatomical Learning of the Pelvis and the Female Pelvic Floor.

Computer applications have been incorporated as valuable components in teaching, especially thanks to the advancement and innovation of new technologies during the last decades. The implementation of these computer developments in medicine and in the field of medical teaching with different utilities has been a revolution. This is manifested with greater intensity in certain medical specialties and in different areas of medical education, for example in the study of human anatomy, especially in parts of the human body of great complexity such as the pelvis and the pelvic floor of women. New technologies are also important in the use, study and interpretation of radiological tests, including ultrasound and nuclear magnetic resonance. This implies a change in the study and learning techniques of students, resident doctors and specialists in gynecology, radiodiagnosis, urology and many other medical specialties, considering new computer developments as a good alternative or complement to existing teaching methods. For this reason, we consider that computer programs like the one we present in this work can be very useful in the future of education and more specifically in the training of specialists in medicine.

Endoscopic transorbital route to the petrous apex: a feasibility anatomic study.

BACKGROUND: While the subtemporal approach represents the surgical module milestone designed to reach the petrous apex, a novel ventral route, which is the superior eyelid endoscopic transorbital approach, has been proposed to access the skull base. Accordingly, we aimed to evaluate the feasibility of this route to the petrous apex, providing a qualitative and quantitative analysis of this relatively novel pathway. METHODS: Five human cadaveric heads were dissected at the Laboratory of Surgical NeuroAnatomy of the University of Barcelona. After proper dissection planning, anterior petrosectomy via the endoscopic transorbital route was performed. Specific quantitative analysis, as well as dedicated three-dimensional reconstruction, was done. RESULTS: Using the endoscopic transorbital approach, it was possible to reach the petrous apex with an average volume bone removal of 1.33 ± 0.21 cm3. Three main intradural spaces were exposed: cerebellopontine angle, middle tentorial incisura, and ventral brainstem. The first one was bounded by the origin of the trigeminal nerve medially and the facial and vestibulocochlear nerves laterally, the second extended from the origin of the oculomotor nerve to the entrance of the trochlear nerve into the tentorium free edge while the ventral brainstem area was hardly accessible through the straight, ventral endoscopic transorbital trajectory. CONCLUSION: This is the first qualitative and quantitative anatomic study concerning details of the lateral aspect of the incisura and ventrolateral posterior fossa reached via the transorbital window. This manuscript is intended as a feasibility anatomic study, and further clinical contributions are mandatory to confirm the effectiveness of this approach, defining its possible role in the neurosurgical armamentarium.

3D reconstruction of peripheral nerves from optical projection tomography images: A method for studying fascicular interconnections and intraneural plexuses.

The general microscopic characteristics of nerves are described in several textbooks of histology, but the specific microanatomies of most nerves that can be blocked by anesthesiologists are usually less well known. Our objective was to evaluate the 3D reconstruction of nerve fascicles from optical projection tomography images (OPT) and the ability to undertake an internal navigation exploring the morphology in detail, more specifically the fascicular interconnections. Median and lingual nerve samples were obtained from five euthanized piglets. OPT images of the samples were acquired and 3D reconstruction was performed. The OPT technique revealed the inner structure of the nerves at high resolution, including large and small fascicles, perineurium, interfascicular tissue, and epineurium. The fascicles were loosely packed inside the median nerve and more densely so in the lingual nerve. Analysis of the 3D models demonstrated that the nerve fascicles can show six general spatial patterns. Fascicular interconnections were clearly identified. The 3D reconstruction of nerve fascicles from OPT images opens a new path for research into the microstructure of the inner contents of fascicular nerve groups and their spatial disposition within the nerve including their interconnections. These techniques enable 3D images of partial areas of nerves to be produced and could became an excellent tool for obtaining data concerning the 3D microanatomy of nerves, essential for better interpretation of ultrasound images in clinical practice and thus avoiding possible neurological complications. Clin. Anat. 31:424-431, 2018. © 2017 Wiley Periodicals, Inc.

A Novel and Freely Available Interactive 3d Model of the Internal Carotid Artery.

We describe a new and freely available 3D interactive model of the intracranial internal carotid artery (ICA) and the skull base that also allows to display and compare its main segment classifications. High-resolution 3D human angiography (isometric voxel's size 0.36 mm) and Computed Tomography angiography images were exported to Virtual Reality Modeling Language (VRML) format for processing in a 3D software platform and embedding in a 3D Portable Document Format (PDF) document that can be freely downloaded at http://diposit.ub.edu/dspace/handle/2445/112442 and runs under Acrobat Reader on Mac and Windows computers and Windows 10 tablets. The 3D-PDF allows for visualisation and interaction through JavaScript-based functions (including zoom, rotation, selective visualization and transparentation of structures or a predefined sequence view of the main segment classifications if desired). The ICA and its main branches and loops, the Gasserian ganglion, the petrolingual ligament and the proximal and distal dural rings within the skull base environment (anterior and posterior clinoid processes, silla turcica, ethmoid and sphenoid bones, orbital fossae) may be visualized from different perspectives. This interactive 3D-PDF provides virtual views of the ICA and becomes an innovative tool to improve the understanding of the neuroanatomy of the ICA and surrounding structures.

Neuroanatomical correlates of stroke-associated infection and stroke-induced immunodepression.

BACKGROUND: Infections represent the most frequent medical complications in stroke patients. Their main determinants are dysphagia and a transient state of immunodepression. We analyzed whether distinct anatomical brain regions were associated with the occurrence of stroke-associated infections or immunodepression. MATERIALS AND METHODS: In 106 patients with acute ischemic stroke, we evaluated the incidence of pneumonia, urinary tract infection, or other infections together with the characterization of biomarkers of immunodepression. Twenty control subjects served to provide reference values. Using voxel-based lesion-symptom mapping, the involvement of gray and white matter structures was correlated with clinical and laboratory findings in crude analyses and in volume adjusted models to rule out associations reflecting differences in the size of the infarction. RESULTS: Stroke-associated infection occurred in 22 (21%) patients and prevailed in patients with larger infarcts. Volume adjusted voxel-based lesion-symptom mapping revealed the involvement of the superior and middle temporal gyri, the orbitofrontal cortex, the superior longitudinal fasciculus and the inferior fronto-occipital fasciculus amongst infected patients. These associations were similar for pneumonia but not for urinary tract infections. Lymphopenia was associated with lesions of the superior and middle temporal gyri. Laterality did not influence stroke-associated infections or the presence of immunodepressive traits after volume control. The greatest overlap in the neuroanatomical correlates occurred between pneumonia and dysphagia. CONCLUSION: Infarct volume plays a relevant role in the occurrence of stroke-associated infections, but lesions in specific brain locations such as the superior and lateral temporal lobe and the orbitofrontal cortex are also associated with increased infectious risk, especially pneumonia.

New Generation of Three-Dimensional Tools to Learn Anatomy.

We present a new generation tool based of interactive 3D models. This models are based on the radiological two-dimensional images by computed tomography imaging. Our article focuses on the anatomical region of the skull base. These new three-dimensional models offer a wide field of application in the learning, as they offer multiple visualization tools (rotation, scrolling, zoom…). In this way, understanding of the anatomical region is facilitated. A feature to be dismissed is that a professional workstation is not required to work with three-dimensional models, since a personal computer can be viewed and interacted with the models. Educational and clinical applications are also discussed.

Human Lumbar Ligamentum Flavum Anatomy for Epidural Anesthesia: Reviewing a 3D MR-Based Interactive Model and Postmortem Samples.

The ligamentum flavum (LF) forms the anatomic basis for the loss-of-resistance technique essential to the performance of epidural anesthesia. However, the LF presents considerable interindividual variability, including the possibility of midline gaps, which may influence the performance of epidural anesthesia. We devise a method to reconstruct the anatomy of the digitally LF based on magnetic resonance images to clarify the exact limits and edges of LF and its different thickness, depending on the area examined, while avoiding destructive methods, as well as the dissection processes. Anatomic cadaveric cross sections enabled us to visually check the definition of the edges along the entire LF and compare them using 3D image reconstruction methods. Reconstruction was performed in images obtained from 7 patients. Images from 1 patient were used as a basis for the 3D spinal anatomy tool. In parallel, axial cuts, 2 to 3 cm thick, were performed in lumbar spines of 4 frozen cadavers. This technique allowed us to identify the entire ligament and its exact limits, while avoiding alterations resulting from cutting processes or from preparation methods. The LF extended between the laminas of adjacent vertebrae at all vertebral levels of the patients examined, but midline gaps are regularly encountered. These anatomical variants were reproduced in a 3D portable document format. The major anatomical features of the LF were reproduced in the 3D model. Details of its structure and variations of thickness in successive sagittal and axial slides could be visualized. Gaps within LF previously studied in cadavers have been identified in our interactive 3D model, which may help to understand their nature, as well as possible implications for epidural techniques.

Pythagoras and Cosines: The skin-dural sac distance and optimal angles in paramedian spinal anesthesia.

The classical recommendation for paramedian approaches is needle insertion 1-2 cm paramedian and an angle of 10°-15° medial-cephalad to the plane of the back, but contact with vertebrae is frequent. A mathematical approach to individualizing punctures is proposed on the basis of skin-dural sac distance (d): Optimal angle ∼ inverse cosine [d/ √(1+d^2) ] and the distance covered by the needle ∼ √(1+d^2) for 1 cm paramedian punctures. The inferred angles were compared to optimal angles leading to the central dorsal part of the dural sac from 1 to 2 cm paramedian, measured by Magnetic Resonance Imaging (MRI) in seven cases and in a short stature volunteer (1.58 m, Body Mass Index (BMI) 23.2), to study supine and fetal positions using both closed MR and ultrasound. The average (d) decreased rostrally [6.8 cm (L4-L5)-4.3 cm (T11-T12)] while the mean optimal incidence angles increased [8.3°-16.5° (L4-L5) to 12.7°-24.1° (T11-T12) at 1-2 cm paramedian, respectively] and coincided with the estimated angles with a correlation coefficient = 0.98. In the volunteer, the optimal lateromedial angles increased from 14.4° to 26.7° (L3-L4) to 17.1°-30.3° (T11-T12) for a (d) = 3.7 cm (L3-L4)-3.1 cm (T11-T12) and increased ≤3.7° and ≤5.1° at 1 and 2 cm paramedian, respectively, in fetal positions in MR. Ultrasound yielded comparable figures. The range of possible angles for dural punctures is wider at 1 cm paramedian in lower approaches in lateral decubitus [from 3.6° at T12L1 (12.2°-15.8°) to 9° at L3L4 (8.8°-18.7°)]. The classically recommended angles of 10°-15° differ from the optimal angles, particularly in small patients, suggesting the need for ultrasound guidance or for inferring angles prior to spinal anesthesia. Clin. Anat. 29:1046-1052, 2016. © 2016 Wiley Periodicals, Inc.