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Purpose: The main anatomic variations should be taught along with the classical anatomy curriculum, since they can mislead both diagnosis and treatment. We report here a clinical and radiological case of left C6 cervicobrachial neuralgia recurrence due to a vertebral artery loop, we then describe 13 published cases of such neurovascular conflicts., Case: A 51-year-old woman suffered from recurrence of C6 cervicobrachial neuralgia after an initial C5-C6 decompression-fusion. Additional cervical angio-MR and CT scans found a tortuous aspect of the left vertebral artery that came into conflict with the left C6 spinal root, just after its emergence of the C5-C6 intervertebral foramen. A large posterior decompression was performed including a C5 and C6 left lateral mass resection to enlarge the foraminal space. The vertebral artery was kept in place. The patient reported a slow but consistent decrease in pain that disappeared after 3 months. Thirteen cases of a compressive vertebral loop are thereafter detailed., Conclusions and Discussion: Vascular precursors disarrangements can lead to a vertebral artery loop in contact with emerging cervical roots and potential clinical impact. This differential diagnosis should be considered for cervico-brachial neuralgia management. Moreover, the present case highlights the key role of a careful preoperative imaging assessment, as well as the need for robust knowledge of anatomy., (© 2022. The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature.)

Background: The anatomy of both the skull and the brain offers many landmarks that could lead surgery. Cranial "craniometric" key points were described many years ago, and then, cerebral key points-along sulci and gyri-were detailed more recently for microneurosurgical approaches that can reach deep structures while sparing the brain. Nonetheless, this anatomic knowledge is progressively competed by new digital devices, such as imaging guidance systems, although they can be misleading., Objective: To summarize cranial and sulcal key points and their related anatomic structures to renew their interest in modern neurosurgery and help surgical anatomy teaching., Methods: After a literature review collecting anatomic key points of skull and brain, specimens were prepared and images were taken to expose skull and brain from lateral, superior, posterior, and oblique views. A high-definition camera was used, and images obtained were modified, superimposing both key points and underlying anatomic structures., Results: From 4 views, 16 cranial key points were depicted: anterior and superior squamous point, precoronal and retrocoronal point, superior sagittal point, intraparietal point, temporoparietal point, preauricular point, nasion, bregma, stephanion, euryon, lambda, asterion, opisthocranion, and inion. These corresponded to underlying cerebral key points and relative brain parts: anterior and posterior sylvian point, superior and inferior rolandic point, supramarginal and angular gyri, parieto-occipital sulcus, and various meeting points between identifiable sulci. Stereoscopic views were also provided to help learning these key points., Conclusion: This comprehensive overview of the cranial and sulcal key points could be a useful tool for any neurosurgeon who wants to check her/his surgical route and make the surgery more "gentle, safe, and accurate.", (Copyright © Congress of Neurological Surgeons 2021. All rights reserved.)

Aggressive pituitary neuroendocrine tumors (APT) account for 10% of pituitary tumors. Their management is a rapidly evolving field of clinical research and has led pituitary teams to shift toward a neuro-oncological-like approach. The new terminology "Pituitary neuroendocrine tumors" (PitNet) that was recently proposed to replace "pituitary adenomas" reflects this change of paradigm. In this narrative review, we aim to provide a state of the art of actual knowledge, controversies, and recommendations in the management of APT. We propose an overview of current prognostic markers, including the recent five-tiered clinicopathological classification. We further establish and discuss the following recommendations from a neurosurgical perspective: (i) surgery and multi-staged surgeries (without or with parasellar resection in symptomatic patients) should be discussed at each stage of the disease, because it may potentialize adjuvant medical therapies; (ii) temozolomide is effective in most patients, although 30% of patients are non-responders and the optimal timeline to initiate and interrupt this treatment remains questionable; (iii) some patients with selected clinicopathological profiles may benefit from an earlier local radiotherapy and/or chemotherapy; (iv) novel therapies such as VEGF-targeted therapies and anti-CTLA-4/anti-PD1 immunotherapies are promising and should be discussed as 2nd or 3rd line of treatment. Finally, whether neurosurgeons have to operate on "pituitary adenomas" or "PitNets," their role and expertise remain crucial at each stage of the disease, prompting our community to deal with evolving concepts and therapeutic resources., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

The brainstem is one of the most densely packed areas of the central nervous system in terms of gray, but also white, matter structures and, therefore, is a highly functional hub. It has mainly been studied by the means of histological techniques, which requires several hundreds of slices with a loss of the 3D coherence of the whole specimen. Access to the inner structure of the brainstem is possible using Magnetic Resonance Imaging (MRI), but this method has a limited spatial resolution and contrast in vivo. Here, we scanned an ex vivo specimen using an ultra-high field (11.7T) preclinical MRI scanner providing data at a mesoscopic scale for anatomical T2-weighted (100 µm and 185 µm isotropic) and diffusion-weighted imaging (300 µm isotropic). We then proposed a hierarchical segmentation of the inner gray matter of the brainstem and defined a set of rules for each segmented anatomical class. These rules were gathered in a freely accessible web-based application, WIKIBrainStem (https://fibratlas.univ-tours.fr/brainstems/index.html), for 99 structures, from which 13 were subdivided into 29 substructures. This segmentation is, to date, the most detailed one developed from ex vivo MRI of the brainstem. This should be regarded as a tool that will be complemented by future results of alternative methods, such as Optical Coherence Tomography, Polarized Light Imaging or histology… This is a mandatory step prior to segmenting multiple specimens, which will be used to create a probabilistic automated segmentation method of ex vivo, but also in vivo, brainstem and may be used for targeting anatomical structures of interest in managing some degenerative or psychiatric disorders., (Copyright © 2021. Published by Elsevier Inc.)

Chordomas are rare sarcomas that are usually treated by surgery and/or radiotherapy since these are chemo-resistant tumors, but immunotherapy could be a possible option for chordoma patients. However, few reports investigating the composition of the chordoma immune microenvironment exist. We immunohistochemically studied 81 chordomas regarding their immune microenvironment factors and compared them with clinicopathological data. Macrophages and CD4 cells were the most prominent inflammatory cell populations, followed by CD8 T cells, while CD20 B cells and high endothelial venules (MECA-79+) were less frequently found. PD-L1 (22C3) expression by inflammatory cells was found in 21 (26%) tumors and was associated with a larger tumor size. None of the cases showed the expression of PD-L1 by tumor cells. Survival analysis showed that younger patients had a better overall survival. Considering the immunohistochemical factors studied, higher CD8, the presence of PD-L1+ immune cells, and higher vascular density were adverse prognostic factors, but in multivariate analysis, only PD-L1+ immune cells retained prognostic significance. To conclude, chordoma tumor cells do not express PD-L1, but PD-L1+ immune cells seem to play a negative prognostic role, supporting the need for further studies in this field and the possible beneficial role of immunotherapy in these patients.

Chordomas are notably resistant to chemotherapy. One of the cytoprotective mechanisms implicated in chemoresistance is autophagy. There are indirect data that autophagy could be implicated in chordomas, but its presence has not been studied in chordoma tissues. Sixty-one (61) chordomas were immunohistochemically studied for autophagic markers and their expression was compared with the expression in notochords, clinicopathological data, as well as the tumor immune microenvironment. All chordomas strongly and diffusely expressed cytoplasmic p62 (sequestosome 1, SQSTM1/p62), whereas 16 (26.2%) tumors also showed nuclear p62 expression. LC3B (Microtubule-associated protein 1A/1B-light chain 3B) tumor cell expression was found in 44 (72.1%) tumors. Autophagy-related 16‑like 1 (ATG16L1) was also expressed by most tumors. All tumors expressed mannose-6-phosphate/insulin-like growth factor 2 receptor (M6PR/IGF2R). LC3B tumor cell expression was negatively associated with tumor size, while no other parameters, such as age, sex, localization, or survival, were associated with the immunohistochemical factors studied. LC3B immune cell expression showed a significant positive association with programmed death-ligand 1 (PD-L1)+ immune cells and with a higher vascular density. ATG16L1 expression was also positively associated with higher vascular density. Notochords ( n = 5) showed different immunostaining with a very weak LC3B and M6PR expression, and no p62 expression. In contrast to normal notochords, autophagic factors such as LC3B and ATG16L1 are often present in chordomas, associated with a strong and diffuse expression of p62, suggesting a blocked autophagic flow. Furthermore, PD-L1+ immune cells also express LC3B, suggesting the need for further investigations between autophagy and the immune microenvironment.

The spinal cord (SC) is a dense network of billions of fibers in a small volume surrounded by bones that makes tractography difficult to perform. We aim to provide a review collecting all technical settings of SC tractography and propose the optimal set of parameters to perform a good SC tractography rendering. The MEDLINE database was searched for articles reporting "spinal cord" "tractography" in "humans". Studies were selected only when tractography rendering was displayed and MRI acquisition and tracking parameters detailed. From each study, clinical context, imaging acquisition settings, fiber tracking parameters, region of interest (ROI) design, and quality of the tractography rendering were extracted. Quality of tractography rendering was evaluated by several objective criteria proposed herein. According to the reported studies, to obtain a good tractography rendering, diffusion tensor imaging acquisition should be performed with 1.5 or 3 Tesla MRI, in the axial plane, with > 20 directions; b value: 1000 s mm -2 ; right-left phase-encoding direction for cervical SC; isotropic voxel size; and no slice gap. Concerning the tracking process, it should be performed with determinist approach, fractional anisotropy threshold between 0.15 and 0.2, and curvature threshold of 40°. ROI design is an essential step for providing good tractography rendering, and their placement has to consider partial volume effects, magnetic susceptibility effects, and motion artifacts. The review reported herein highlights that successful SC tractography depends on many factors (imaging acquisition settings, fiber tracking parameters, and ROI design) to obtain a good SC tractography rendering.

Purpose: The anatomy of both the brain and the skull is particularly difficult to learn and to teach. Since their anatomical structures are numerous and gathered in a complex tridimensional (3D) architecture, classic schematical drawing or photography in two dimensions (2D) has difficulties in providing a clear, simple, and accurate message. Advances in photography and computer sciences have led to develop stereoscopic 3D visualization, firstly for entertainment then for education. In the present study, we report our experience of stereoscopic 3D lecture for neuroanatomy teaching to early medical school students., Methods: High-resolution specific pictures were taken on various specimen dissections in the Anatomy Laboratory of the University of Lyon, France. Selected stereoscopic 3D views were displayed on a large dedicated screen using a doubled video projector. A 2-h stereoscopic neuroanatomy lecture was given by two neuroanatomists to third-year medicine students who wore passive 3D glasses. Setting up lasted 30 min and involved four people. The feedback from students was collected and analyzed., Results: Among the 483 students who have attended the stereoscopic 3D lecture, 195 gave feedback, and all (100%) were satisfied. Among these, 190 (97.5%) reported a better knowledge transfer of brain anatomy and its 3D architecture. Furthermore, 167 (86.1%) students felt it could change their further clinical practice, 179 (91.8%) thought it could enhance their results in forthcoming anatomy examinations, and 150 (76.9%) believed such a 3D lecture might allow them to become better physicians. This 3D anatomy lecture was graded 8.9/10 a mean against 5.9/10 for previous classical 2D lectures., Discussion-Conclusion: The stereoscopic 3D teaching of neuroanatomy made medical students enthusiastic involving digital technologies. It could improve their anatomical knowledge and test scores, as well as their clinical competences. Depending on university means and the commitment of teachers, this new tool should be extended to other anatomical fields. However, its setting up requires resources from faculties and its impact on clinical competencies needs to be objectively assessed.

Background: Metastases to the pituitary (MP) are uncommon, accounting for 0.4% of intracranial metastases. Through advances in neuroimaging and oncological therapies, patients with metastatic cancers are living longer and MP may be more frequent. This review aimed to investigate clinical and oncological features, treatment modalities and their effect on survival., Methods: A systematic review was performed according to PRISMA recommendations. All cases of MP were included, excepted primary pituitary neoplasms and autopsy reports. Descriptive and survival analyses were then conducted., Results: The search identified 2143 records, of which 157 were included. A total of 657 cases of MP were reported, including 334 females (50.8%). The mean ± standard deviation age was 59.1 ± 11.9 years. Lung cancer was the most frequent primary site (31.0%), followed by breast (26.2%) and kidney cancers (8.1%). Median survival from MP diagnosis was 14 months. Overall survival was significantly different between lung, breast and kidney cancers (P < .0001). Survival was impacted by radiotherapy (hazard ratio (HR) 0.49; 95% confidence interval (CI) 0.35-0.67; P < .0001) and chemotherapy (HR 0.58; 95% CI 0.36-0.92; P = .013) but not by surgery. Stereotactic radiotherapy tended to improve survival over conventional radiotherapy (HR 0.66; 95% CI 0.39-1.12; P = .065). Patients from recent studies (≥ 2010) had longer survival than others (HR 1.36; 95% CI 1.05-1.76; P = .0019)., Conclusion: This systematic review based on 657 cases helped to better identify clinical features, oncological characteristics and the effect of current therapies in patients with MP. Survival patterns were conditioned upon primary cancer histologies, the use of local radiotherapy and systemic chemotherapy, but not by surgery.

Background: Skull base chondrosarcomas are rare tumors often invading the petrous apex and cavernous sinus, and many surgical approaches have been described. For most of them, these tumors grow slowly and their partial removal can be a first option before complementary radiotherapy. We described herein a minimally invasive approach that could be useful for soft non-calcified chondrosarcomas., Method and Results: We report a case of right parasellar chondrosarcoma, for which an extra-intradural extracavernous subtemporal approach allowed a safe effective partial removal., Conclusion: This surgical approach is indicated in selected cases to obtain good decompression or partial removal of lesions involving the parasellar space and the petrous apex.

Objective: The goal in this study was to describe the overall organization of the spinal arachnoid mater and spinal subarachnoid space (SSAS) as well as its relationship with surrounding structures, in order to highlight spinal cord arachnoid cisterns., Methods: Fifteen spinal cords were extracted from embalmed adult cadavers. The organization of the spinal cord arachnoid and SSAS was described via macroscopic observations, optical microscopic views, and scanning electron microscope (SEM) studies. Gelatin injections were also performed to study separated dorsal subarachnoid compartments., Results: Compartmentalization of SSAS was studied on 3 levels of axial sections. On an axial section passing through the tips of the denticulate ligament anchored to the dura, 3 subarachnoid cisterns were observed: 2 dorsolateral and 1 ventral. On an axial section passing through dural exit/entrance of rootlets, 5 subarachnoid cisterns were observed: 2 dorsolateral, 2 lateral formed by dorsal and ventral rootlets, and 1 ventral. On an axial section passing between the two previous ones, only 1 subarachnoid cistern was observed around the spinal cord. This compartmentalization resulted in the anatomical description of 3 elements: the median dorsal septum, the arachnoid anchorage to the tip of the denticulate ligament, and the arachnoid anchorage to the dural exit/entrance of rootlets. The median dorsal septum already separated dorsal left and right subarachnoid spaces and was described from C1 level to 3 cm above the conus medullaris. This septum was anchored to the dorsal septal vein. No discontinuation was observed in the median dorsal arachnoid septum. At the entrance point of dorsal rootlets in the spinal cord, arachnoid trabeculations were described. Using the SEM, numerous arachnoid adhesions between the ventral surface of the dorsal rootlets and the pia mater over the spinal cord were observed. At the ventral part of the SSAS, no septum was found, but some arachnoid trabeculations between the arachnoid and the pia mater were present and more frequent than in the dorsal part. Laterally, arachnoid was firmly anchored to the denticulate ligaments' fixation at dural points, and dural exit/entrance of rootlets made a fibrous ring of arachnoidodural adhesions. At the level of the cauda equina, the arachnoid mater surrounded all rootlets together-as a sac and not individually., Conclusions: Arachnoid cisterns are organized on each side of a median dorsal septum and compartmentalized in relation with the attachments of denticulate ligament and exit/entrance of rootlets.

Background: Predicting the displacement of cranial nerves by tumors could make surgery safer and the outcome better. Recent advances in imaging and processing have overcome some of the limits associated with cranial nerve tractography, such as spatial resolution and fiber crossing. Among others, probabilistic algorithms yield to a more accurate depiction of cranial nerve trajectories., Objective: To report how cranial nerve probabilistic tractography can help the surgical strategy in a series of various skull base tumors., Methods: After distortion correction and region of interest seeding, a probabilistic tractography algorithm used the constrained spherical deconvolution model and attempted the reconstruction of cranial nerve trajectories in both healthy and displaced conditions., Results: Sixty-two patients were included and presented: vestibular schwannomas (n = 33); cerebellopontine angle meningiomas (n = 15); arachnoid or epidermoid cysts (n = 6); cavernous sinus and lower nerves schwannomas (n = 4); and other tumors (n = 4). For each patient, at least one 'displaced' cranial nerve was not clearly identified on classical anatomical MRI images. All 372 cranial nerves were successfully tracked on each healthy side; among the 175 cranial nerves considered 'displaced' by tumors, 152 (87%) were successfully tracked. Among the 127 displaced nerves of operated patients (n = 51), their position was confirmed intraoperatively for 118 (93%) of them. Conditions that led to tractography failure were detailed. On the basis of tractography, the surgical strategy was adjusted for 44 patients (71%)., Conclusion: This study reports a cranial nerve probabilistic tractography pipeline that can: predict the position of most cranial nerves displaced by skull base tumors, help the surgical strategy, and thus be a pertinent tool for future routine clinical application., (Copyright © 2018 by the Congress of Neurological Surgeons.)

Objective: Diffusion imaging tractography has allowed the in vivo description of brain white matter. One of its applications is preoperative planning for brain tumor resection. Due to a limited spatial and angular resolution, it is difficult for fiber tracking to delineate fiber crossing areas and small-scale structures, in particular brainstem tracts and cranial nerves. New methods are being developed but these involve extensive multistep tractography pipelines including the patient-specific design of multiple regions of interest (ROIs). The authors propose a new practical full tractography method that could be implemented in routine presurgical planning for skull base surgery., Methods: A Philips MRI machine provided diffusion-weighted and anatomical sequences for 2 healthy volunteers and 2 skull base tumor patients. Tractography of the full brainstem, the cerebellum, and cranial nerves was performed using the software DSI Studio, generalized-q-sampling reconstruction, orientation distribution function (ODF) of fibers, and a quantitative anisotropy-based generalized deterministic algorithm. No ROI or extensive manual filtering of spurious fibers was used. Tractography rendering was displayed in a tridimensional space with directional color code. This approach was also tested on diffusion data from the Human Connectome Project (HCP) database., Results: The brainstem, the cerebellum, and the cisternal segments of most cranial nerves were depicted in all participants. In cases of skull base tumors, the tridimensional rendering permitted the visualization of the whole anatomical environment and cranial nerve displacement, thus helping the surgical strategy., Conclusions: As opposed to classical ROI-based methods, this novel full tractography approach could enable routine enhanced surgical planning or brain imaging for skull base tumors.

Background: Learning surgical anatomy of the petrous pyramid can be a challenge, especially in the beginning of the training process. Providing an easier, holistic approach can be of help to everyone with interest in learning and teaching skull base anatomy. We present the complex organization of petrous pyramid anatomy using a new compartmental approach that is simple to understand and remember., Methods: The surfaces of the petrous pyramid of two temporal bones were examined; and the contents of the petrous pyramid of 8 temporal bones were exposed through progressive drilling of the superior surface., Results: The petrous pyramid is made up of a bony container, and its contents were grouped into 4 compartments (mucosal, cutaneous, neural, and vascular). Two reference lines were identified (mucosal and external-internal auditory canal lines) intersecting at the level of the middle ear. The localization of contents relative to these reference lines was then described, and 2 methods of segmentation (the X method and the V method) were then proposed. This description was then used to describe middle ear relationships, facial nerve anatomy, and air cell distribution., Conclusions: This new compartmental approach allows a comprehensive understanding of the distribution of petrous pyramid contents. Dividing it into anatomic compartments, and then navigating this mental map along specific reference points, lines, spaces, and segments, could create a useful tool to teach or learn its complex tridimensional anatomy., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Peri-tumoral edema in intracranial meningiomas occurs frequently and obviously impacts the morbidity and mortality of these predominantly benign neoplasms. Several causative factors (age, gender, volume, location…) have been unsuccessfully investigated. Despite recent progresses in metabolic imaging and molecular biology, the pathogenesis of peri-tumoral edema remains debated. Hypotheses include vascular endothelial growth factor, metalloproteinases and interleukins among many others. It is probable that this pathogenesis encompasses all these factors with different levels. The current review aims to shed the light on the investigated factors involved in the pathogenesis of peri-tumoral edema in meningiomas and identify the potential therapeutic targets.

Background: Diffusion imaging tractography caught the attention of the scientific community by describing the white matter architecture in vivo and noninvasively, but its application to small structures such as cranial nerves remains difficult. The few attempts to track cranial nerves presented highly variable acquisition and tracking settings., Objective: To conduct and present a targeted review collecting all technical details and pointing out challenges and solutions in cranial nerve tractography., Methods: A "targeted" review of the scientific literature was carried out using the MEDLINE database. We selected studies that reported how to perform the tractography of cranial nerves, and extracted the following: clinical context; imaging acquisition settings; tractography parameters; regions of interest (ROIs) design; and filtering methods., Results: Twenty-one published articles were included. These studied the optic nerves in suprasellar tumors, the trigeminal nerve in neurovascular conflicts, the facial nerve position around vestibular schwannomas, or all cranial nerves. Over time, the number of MRI diffusion gradient directions increased from 6 to 101. Nine tracking software packages were used which offered various types of tridimensional display. Tracking parameters were disparately detailed except for fractional anisotropy, which ranged from 0.06 to 0.5, and curvature angle, which was set between 20° and 90°. ROI design has evolved towards a multi-ROI strategy. Furthermore, new algorithms are being developed to avoid spurious tracts and improve angular resolution., Conclusion: This review highlights the variability in the settings used for cranial nerve tractography. It points out challenges that originate both from cranial nerve anatomy and the tractography technology, and allows a better understanding of cranial nerve tractography.

Magnetic resonance imaging tractography permits in vivo visualization of white matter structures. Aside from its academic value, tractography has been proven particularly useful to neurosurgeons for preoperative planning. Preoperative tractography permits both qualitative and quantitative analyses of tumor effects upon surrounding white matter, allowing the surgeon to specifically tailor their operative approach. Despite its benefits, there is controversy pertaining to methodology, implementation, and interpretation of results in this context. High-definition fiber tractography (HDFT) is one of several non-tensor tractography approaches permitting visualization of crossing white matter trajectories at high resolutions, dispensing with the well-known shortcomings of diffusion tensor imaging (DTI) tractography. In this article, we provide an overview of the advantages of HDFT in a neurosurgical context, derived from our considerable experience implementing the technique for academic and clinical purposes. We highlight nuances of qualitative and quantitative approaches to using HDFT for brain tumor surgery planning, and integration of tractography with complementary operative adjuncts, and consider areas requiring further research.

A 37-year-old man came to our neurosurgical department with a 2-month history of a progressive invalidating balance disorder. Cerebral magnetic resonance imaging found a T2-weighted hypersignal lesion of the right cerebellopontine angle that severely compressed the brainstem, however the position of cranial nerves was not clearly identified. The new MRI diffusion tool, tractography, allowed to reconstruct the trajectory of cranial nerves that were displaced by the tumor. As such, the acoustic facial bundle was severely flattened posteriorly and superiorly, while the lower nerves were pushed inferiorly. Effective neurosurgical decompression was performed and confirmed the position of cranial nerves V-XII. The patient was discharged and returned home without any cranial nerve deficit. This case illustrates how advances in imaging can now better describe the anatomy surrounding brain tumors and make surgery safer to the benefit of patients., (Copyright © 2018 Elsevier Inc. All rights reserved.)

The human inferior longitudinal fasciculus (ILF) is a ventral, temporo-occipital association tract. Though described in early neuroanatomical works, its existence was later questioned. Application of in vivo tractography to the neuroanatomical study of the ILF has generally confirmed its existence, however, consensus is lacking regarding its subdivision, laterality and connectivity. Further, there is a paucity of detailed neuroanatomic data pertaining to the exact anatomy of the ILF. Generalized Q-Sampling imaging (GQI) is a non-tensor tractographic modality permitting high resolution imaging of white-matter structures. As it is a non-tensor modality, it permits visualization of crossing fibers and accurate delineation of close-proximity fiber-systems. We applied deterministic GQI tractography to data from 30 healthy subjects and a large-volume, averaged diffusion atlas, to delineate ILF anatomy. Post-mortem white matter dissection was also carried out in three cadaveric specimens for further validation. The ILF was found in all 60 hemispheres. At its occipital extremity, ILF fascicles demonstrated a bifurcated, ventral-dorsal morphological termination pattern, which we used to further subdivide the bundle for detailed analysis. These divisions were consistent across the subject set and within the atlas. We applied quantitative techniques to study connectivity strength of the ILF at its anterior and posterior extremities. Overall, both morphological divisions, and the un-separated ILF, demonstrated strong leftward-lateralized connectivity patterns. Leftward-lateralization was also found for ILF volumes across the subject set. Due to connective and volumetric leftward-dominance and ventral location, we postulate the ILFs role in the semantic system. Further, our results are in agreement with functional and lesion-based postulations pertaining to the ILFs role in facial recognition.

Background: Traumatic spinal subarachnoid hematoma, associated or not with a concurrent subdural hematoma, has rarely been described. The evolution of such hematomas is heterogeneous. This study aims at defining the most accurate management, which is currently not standardized., Case Description: A 20-year-old man, victim of a high-kinetic road accident 5 days before and with several nonneurologic nonsurgical vertebral fractures, experienced a sudden dorsolumbar pain radiating to his lower limbs. A rapidly progressive asymmetric paraparesis with loss of reflexes was noticed, associated with bilateral global hypoesthesia of the lower limbs and with acute urinary retention, whereas the anal tonicity was preserved (American Spinal Injury Association C). Magnetic resonance imaging scan revealed a conus medullaris compression at the level of the L1-L2 vertebrae by an intradural expansive mass. Immediate surgical decompression revealed a strictly subarachnoid hematoma. Venous bleeding was seen at the level of the conus medullaris and controlled. Pathologic examination of the clot excluded an underlying tumor or vascular abnormality. The complete coagulation profile was normal., Conclusion: Six weeks after surgery, the neurologic examination revealed only a slight tactile hypoesthesia of the left thigh. With only 4 reported cases, purely subarachnoid spinal hematomas remain widely rarer than epidural hematomas. The reported case possesses a certain number of peculiarities: young age, pure subarachnoid location, lumbar location, occurrence after a car accident, subacute onset, and excellent neurologic recovery. In our opinion, a symptomatic subarachnoid spinal hematoma should be surgically evacuated at the early phase so neurologic recovery can be expected., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Background: Liponeurocytoma is a very rare tumor classified as grade II (neuronal and mixed neuronal-glial tumors) according to 2016 World Health Organization classification of tumors of the central nervous system. The median age at detection is 50 years, and the most frequent location is the posterior cranial fossa, especially within the cerebellar hemispheres; liponeurocytomas arising in the cerebellopontine angle (CPA) are exceptional., Case Description: Here we report the clinical, radiological, and pathological characteristics of a CPA liponeurocytoma in a 35-year-old woman, as well as a review of the literature. This unusual cisternal location raises the issue of the differential imaging diagnosis with much more common CPA tumors (e.g., meningiomas, vestibular schwannomas, ependymomas, epidermoid cyst, hemangioblastomas, medulloblastomas)., Conclusion: To the best of our knowledge, 59 cases of cerebellar liponeurocytomas have been reported to date, which include only 6 cases of CPA liponeurocytomas. Treatment relies on total removal whenever possible, with an excellent prognosis, but a high MIB-1 index (>10%) and/or incomplete tumor resection are the main adverse prognostic factors., (Copyright © 2018 Elsevier Inc. All rights reserved.)

A 24-year-old woman was hit by a bus and suffered an isolated complete oculomotor nerve palsy. Computed tomography scan did not show a skull base fracture. T2*-weighted magnetic resonance imaging revealed petechial cerebral hemorrhages sparing the brainstem. T2 constructive interference in steady state suggested a partial sectioning of the left oculomotor nerve just before entering the superior orbital fissure. Diffusion tensor imaging fiber tractography confirmed a sharp arrest of the left oculomotor nerve. This recent imaging technique could be of interest to assess white fiber damage and help make a diagnosis or prognosis., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Skull base architecture is tough to understand because of its 3D complex shape and its numerous foramen, reliefs or joints. It is especially true for the sphenoid bone whom central location hinged with most of skull base components is unique. Recently, technological progress has led to develop new pedagogical tools. This way, we bought a new real-time three-dimensional insight of the sphenoid bone that could be useful for the teacher, the student and the surgeon. High-definition photography was taken all around an isolated dry skull base bone prepared with Beauchêne's technique. Pictures were then computed to provide an overview with rotation and magnification on demand. From anterior, posterior, lateral or oblique views and from in out looks, anatomical landmarks and subtleties were described step by step. Thus, the sella turcica, the optic canal, the superior orbital fissure, the sphenoid sinus, the vidian canal, pterygoid plates and all foramen were clearly placed relative to the others at each face of the sphenoid bone. In addition to be the first report of the 360 Photography tool, perspectives are promising as the development of a real-time interactive tridimensional space featuring the sphenoid bone. It allows to turn around the sphenoid bone and to better understand its own special shape, numerous foramen, neurovascular contents and anatomical relationships. This new technological tool may further apply for surgical planning and mostly for strengthening a basic anatomical knowledge firstly introduced.

Background: Delayed intraventricular pneumocephalus is a very rare and potentially serious complication of ventriculoperitoneal shunt. It can occur several months or years after shunting. Its pathogenesis is unclear. We herein discuss the underlying mechanisms and particularly the possible role of positive pressure ventilation., Case Description: A 60 year-old man presented with a lateral ventricle neurocytoma microsurgically resected complicated by a late-onset (15 months) postoperative hydrocephalus requiring an adjustable ventriculoperitoneal (VP) shunt. One month later, the patient was diagnosed with a sleep apnea and required a continuous positive airway pressure (CPAP) device. A few weeks afterward the patient presented with headaches and alteration of consciousness. CT-Scan revealed a massive intraventricular pneumocephalus associated with a millimetric left petrous bone defect. A transient breakout of the positive ventilation and a subtemporal surgical repair of the defect led to the rapid resolution of the pneumocephalus., Discussion: Delayed intraventricular pneumocephalus requires two conditions: a VP shunt and an osteodural defect. The CPAP may play an important trigger role in the pathogenesis of this complication through a ball valve mechanism. The management relies on transient suspension of the positive ventilation and the surgical repair of the identified defect with or without pressure adjustments of the valve., Conclusion: Intraventricular pneumocephalus is a potentially serious complication of patients with a VP shunt and receiving positive pressure ventilation. The introduction of a CPAP device must be discussed with the neurosurgeon beforehand in shunted patients., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Purpose: Since the petroclival region is deep-seated with close neurovascular relationships, the removal of petroclival tumors still represents a fascinating surgical challenge. Although the classical anterior petrosectomy (AP) offers a meaningful access to this petroclival region, the expanded endoscopic endonasal approach (EEEA) recently leads to overcome difficulties from trans-cranial approaches. Herein, we present an anatomic comparison of AP versus EEEA. We aim to describe the limits of these both approaches helping the choice of the optimal surgical route for petroclival tumors., Methods: Six fresh cadaveric heads were harvested and injected with colored latex. Each approach was step-by-step detailed until its final surgical exposure., Results: The AP provided a narrow direct supero-lateral access to the petroclival area that can also reach the cavernous sinus, the retrochiasmatic region and perimesencephalic cisterns. However, this corridor anterior to the internal acoustic meatus passed on each side of the trigeminal nerve. Moreover, tumor extensions toward the foramen jugularis, inside the clivus or behind the internal acoustic meatus were difficult to control. The EEEA brought a straightforward access to the clivus but the petrous apex was hidden behind the internal carotid artery. Several variants were described: a medial transclival, a lateral through the Meckel's cave and an inferior trans-pterygoid route. Elsewhere, tumor extension behind the internal acoustic meatus or above the tentorium could not be satisfactorily assessed., Discussion and Conclusion: PA and EEEA have their own limits in reaching the petroclival region in accordance with the tumor characteristics. The AP should be preferred for radical removal of middle-sized petrous apex intradural tumors like meningiomas. The EEEA would be of interest for extradural midline tumors like chordomas or for petrous apex cysts drainage.

Objective: Petroclival tumors remain a surgical challenge. Classically, the retrosigmoid approach (RSA) has long been used to reach such tumors, whereas the anterior petrosectomy (AP) has been proposed to avoid crossing cranial nerves. More recently, the endoscopic endonasal approach has been "expanded" (i.e., EEEA) to the petroclival region. We aimed to compare these 3 approaches to help in the surgical management of petroclival tumors., Methods: Petroclival approaches were performed on 5 specimens after they were prepared with formaldehyde colored via latex injection., Results: The EEEA provides a simple straightforward route to the clivus, but reaching the petrous apex requires the surgeon to circumvent the internal carotid artery either via a medial transclival, an inferior transpterygoid, or a lateral variant through the Meckel's cave. In contrast, the AP offers a narrow direct superolateral access to the petroclival region crossed by the trigeminal nerve. Finally, the RSA provides a wide simple and quick exposure of the cerebellopontine angle, but access to the petroclival region needs the surgeon to deal with the V(th) to XI(th) cranial nerves., Discussion/conclusion: The EEEA should be preferred for extradural midline tumors (chordomas, chondrosarcomas) or for cystic lesions when drainage is essential. The AP could be optimal for the radical removal of intradural vascularized tumors (meningiomas) with intrapetrous or supratentorial extensions. The RSA retains an advantage for small or cystic tumors near the internal acoustic meatus. The skull base surgeon has to master all of these routes to choose the more appropriate one according to the surgical objective, the tumor characteristics, and the patient's medical status., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Background: Because of their deep location surrounded by closed numerous neurovascular structures, skull base tumors of the cavernous sinus are still difficult to manage. Recently, the endoscopic endonasal approach commonly used for pituitary tumor resection has been "expanded" to the parasellar, infratemporal and orbital compartments with some advantages compared to the intracranial route., Methods: The authors reported the case of a 49-year-old male presenting a large extradural tumor of the left cavernous sinus with extensions toward the orbit, sphenoid sinus and infratemporal fossa. His ophthalmological examination was normal, and the body CT scan revealed no primary neoplasm., Results: In this operative video, the approach is described step by step with surgical nuances. The endoscopy provided a close-up panoramic view and various angles of vision. Also, it avoided an invasive craniotomy, cerebral retraction and cranial nerves damages. Thus, it allowed the total removal of this tumor originating from the maxillary branch of the trigeminal nerve. The pathologic examination confirmed a schwannoma., Conclusion: The expanded endoscopic endonasal approach provides an interesting corridor to cavernous sinus tumors with satisfactory control of extensions inferiorly toward the infratemporal fossa, anteriorly via the superior orbital fissure and medially within the sphenoid. Finally, the skull base surgeon has to master this anterior endoscopic route as well as all the other "open" transcranial skull base approaches to propose the best surgical route fitting the tumor characteristics.

Many benign and malignant tumors as well as other inflammatory or vascular diseases may be located in the areas of Meckel's cave or the cavernous sinus. Except for typical features such as for meningiomas, imaging may not by itself be sufficient to choose the best therapeutic option. Thus, even though modern therapy (chemotherapy, radiotherapy, or radiosurgery) dramatically reduces the field of surgery in this challenging location, there is still some place for surgical biopsy or tumor removal in selected cases. Until recently, the microscopic subtemporal extradural approach with or without orbitozygomatic removal was classically used to approach Meckel's cave but with a non-negligible morbidity. Percutaneous biopsy using the Hartel technique has been developed for biopsy of such tumors but may fail in the case of firm tumors, and additionally it is not appropriate for anterior parasellar tumors. With the development of endoscopy, the endonasal route now represents an interesting alternative approach to Meckel's cave as well as the cavernous sinus. Through our experience, we describe the modus operandi and discuss what should be the appropriate indication of the use of the endonasal endoscopic approach for Meckel's cave disease in the armamentarium of the skull base surgeon., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Background: With the refinement of the technique, endoscopic endonasal surgery increases its field of indications. The orbital compartment is among the locations easily reached through the nostril. This anteromedial approach has been described primarily for inflammatory or traumatic diseases, with few data for tumoral diseases., Method: Since 2010, this route has been used at our institution either for decompression or for biopsy of orbital tumoral diseases., Findings/conclusions: Even if further studies are warranted, this strategy proved to be beneficial for patients, with improvements in visual outcome. In this article, the authors summarize their technique and their experience with endonasal endoscopic orbital decompression., Key Points: Nasal and sphenoidal anatomies determine the feasibility and risks for doing an efficient medial optic or orbit decompression. • Techniques and tools used are those developed for pituitary surgery. • A middle turbinectomy and posterior ethmoidectomy are mandatory to expose the medial wall of the orbit. • The Onodi cell is a key marker for the optic canal and must be opened up with caution. • The lamina papyracea is opened first with a spatula and the optic canal opened up by a gentle drilling under continuous irrigation from distal to proximal. • Drilling might always be used under continuous irrigation to avoid overheating of the optic nerve. An ultrasonic device can be used as well. • The nasal corridor is narrow and instruments may hide the infrared neuronavigation probe. To overcome this issue, a magnetic device could be useful. • Doppler control could be useful to locate the ICA. • The optic canal must be opened up from the tuberculum of the sella to the orbital apex and from the planum (anterior cranial fossa) to the lateral OCR or ICA canal • At the end of the procedure, the optic nerve becomes frequently pulsatile, which is a good marker of decompression.

Purpose: For intramedullary tumor (IMT) surgery, a balance has to be found between aggressively resecting the tumor and respecting all the sensory and motor pathways. The most common surgical approach is through the dorsal median sulcus (DMS) of the spinal cord. However, the precise organization of the meningeal sheats in the DMS remains obscure in the otherwise well-described anatomy of the spinal cord. A better understanding of this architecture may be of benefit to IMT surgeon to spare the spinal cord., Methods: Three spinal cords were studied. The organization of the spinal cord meninges in the DMS was described via macroscopic, microsurgical and optical microscopic views. A micro dissection of the DMS was also performed., Results: No macroscopic morphological abnormalities were observed. With the operative magnifying lens, the dura was opened, the arachnoid was removed and the pia mater was cut to access the DMS. The histological study showed that the DMS was composed of a thin rim of capillary-carrying connective tissue extending from the pia mater and covering the entire DMS. There was no true space between the dorsal columns, no arachnoid or crossing axons either., Conclusion: Our work indicates that the DMS is not a sulcus but a thin blade of collagen extending from the pia mater. Its location is given by tiny vessels coming from the surface towards the deep. Thus, the surgical corridor has to follow the DMS as closely as possible to prevent damage to the spinal cord during midline IMT removal.

Object: While several approaches have been described for optic nerve decompression, the endoscopic endonasal route is gaining favor because it provides excellent exposure of the optic canal and the orbital apex in a minimally invasive manner. Very few studies have detailed the experience with nontraumatic optic nerve decompressions, whereas traumatic cases have been widely documented. Herein, the authors describe their preliminary experience with endoscopic endonasal decompression for nontraumatic optic neuropathies (NONs) to determine the procedure's efficacy and delineate its potential indications and limits., Methods: The medical reports of patients who had undergone endoscopic endonasal optic nerve and orbital apex decompression for NONs at the Lyon University Neurosurgical Hospital in the period from January 2012 to March 2014 were reviewed. For all cases, clinical and imaging data on the underlying pathology and the patient, including demographics, preoperative and 6-month postoperative ophthalmological assessment results, symptom duration, operative details with video debriefing, as well as the immediate and delayed postoperative course, were collected from the medical records., Results: Eleven patients underwent endoscopic endonasal decompression for NON in the multidisciplinary skull base surgery unit of the Lyon University Neurosurgical Hospital during the 27-month study period. The mean patient age was 53.4 years, and there was a clear female predominance (8 females and 3 males). Among the underlying pathologies were 4 sphenoorbital meningiomas (36%), 3 optic nerve meningiomas (27%), and 1 each of trigeminal neuroma (9%), orbital apex meningioma (9%), ossifying fibroma (9%), and inflammatory pseudotumor of the orbit (9%). Fifty-four percent of the patients had improved visual acuity at the 6-month follow-up. Only 1 patient whose sphenoorbital meningioma had been treated at the optic nerve atrophy stage continued to worsen despite surgical decompression. The 2 patients presenting with preoperative papilledema totally recovered. One case of postoperative epistaxis was successfully treated using balloon inflation, and 1 case of air swelling of the orbit spontaneously resolved., Conclusions: Endoscopic endonasal optic nerve decompression is a safe, effective, and minimally invasive technique affording the restoration of visual function in patients with nontraumatic compressive processes of the orbital apex and optic nerve. The timing of decompression remains crucial, and patients should undergo such a procedure early in the disease course before optic atrophy.

Background: The purely endoscopic eyebrow supraorbital approach is an alternative to both the endoscopic endonasal and eyebrow microsurgical routes to the anterior and middle cranial base. It combines an enhanced visualization provided by the endoscope and the absence of cerebrospinal fluid (CSF) leaks and nasal complications., Methods: A trans-eyebrow 2-cm craniotomy is designed to allow the placement of a straight endoscope and visualize the skull base from the cribriform plate to the mesiotemporal lobe., Result: Visualization is considerably improved, while the keyhole mini-invasive concept is respected., Conclusion: The purely endoscopic eyebrow supraorbital keyhole approach is a valuable and alternative minimally invasive route to anterior and middle skull base lesions.