INTRODUCTION:The pineal region is located at the posterior part of the incisural space. This region includes the pineal body within the quadrigeminal arachnoidal cistern. This article reviews the anatomic features of this region, with particular emphasis on those of interest for surgical access to the pineal region. MATERIAL AND METHODS:Five cadaver heads fixed in 10% formalin and injected with colored latex were used for anatomic dissection. RESULTS:The pineal body is surrounded by the following structures: posterior part of the third ventricle, tectum, the complex of the great cerebral vein of Galen, pulvinar nuclei of the thalamus, and splenium of corpus callosum. CONCLUSION:The surgical approach of the pineal body, whatever the way or the technique used (microsurgical, endoscopic, or stereotactic), creates a great challenge for the neurosurgeons by its location in the deep of the brain and its closed relationships with complex surrounding structures.

OBJECTIVE:Skull base tumors are difficult to approach because of their deep location and their entrapment by cranial nerves (CNs), arteries, and veins. CN trajectories can be challenging to describe by conventional MRI when they are deformed by skull base tumors. High-resolution (HR) T2-weighted MRI (T2) has been able to depict normal CN cisternal paths; however, tractography has demonstrated value in CN reconstruction when the nerves are displaced by skull base tumors. In the present study, the authors aimed to compare HR T2 to tractography in the detection of CNs displaced by skull base tumors. METHODS:From a case series of various complex skull base tumors managed between July 2015 and December 2023 in a single department, HR T2 scans were acquired, as were diffusion images with dedicated postprocessing, including distortion correction, region of interest design, probabilistic fiber tracking, and three-plane visualization. The positions of CNs displaced by skull base tumors were then compared between HR T2 and tractography. RESULTS:A total of 132 patients were included in the study. They presented with various skull base tumors: vestibular schwannomas (n = 47), cerebellopontine angle (CPA) meningiomas (n = 46), CPA epidermoid cysts (n = 12), cavernous sinus schwannomas (n = 8), cavernous sinus meningiomas (n = 3), and 16 less frequent histological types. A total of 442 CNs were identified as being displaced by skull base tumors. Of these nerves, 236 (53.4%) were identifiable using HR T2, and 358 (81.0%) were successfully reconstructed using tractography (p < 0.001, McNemar test), although not significantly for the abducens nerve, lower nerves, and hypoglossal nerve. Interestingly, the identification rate of the abducens nerve was higher on HR T2 than tractography (43.5% vs 34.8%). CONCLUSIONS:The present study revealed that tractography is more effective in predicting the position of most nerves displaced by skull base tumors, whereas HR T2 can identify the smallest CNs such as the abducens nerve.

OBJECTIVE:Skull base tumor surgery remains challenging because these tumors are deeply seated and trapped within numerous cranial nerves and vessels. Accurate histopathological analysis of skull base tumors will strongly impact their further management. Yet, currently there is no noninvasive validated method to confirm their diagnosis. In a recent study of MRI tractography, the authors used fiber orientation distribution (FOD) and noted that this diffusion model formed a pattern that could correspond to the histopathological type of skull base tumors. The aim of this study was to propose a new imaging method for skull base tumors that can detect the diagnosis according to the FOD pattern. METHODS:From an 81-case series of skull base tumors, MRI diffusion images were investigated by 3 independent observers. Diffusion patterns were classified as centrifugal, wrapped, and chaotic, corresponding to meningiomas, schwannomas, and epidermoid cysts, respectively. RESULTS:The overall identification rate was 80.7%, with an excellent concordance between the 3 observers (Fleiss's κ coefficient = 0.765, p < 0.0001). The identification rate increased along with the observers' anatomoradiological expertise (72.8%, 77.8%, and 91.4%, for observer 1 [low expertise], 2 [average expertise], and 3 [extensive expertise], respectively) and was higher for schwannomas (88.6%), than meningiomas (72.6%) and epidermoid cysts (66.7%). CONCLUSIONS:This new imaging tool could assist in complex skull base tumor identification and characterization, as well as surgical management.

The surgery of skull base epidermoid cysts can be challenging because of intracerebral extensions and the encasement of cranial nerves and internal carotid artery branches.1-3 Advances in magnetic resonance imaging, particularly tractography, may help to visualize the trajectory of displaced cranial nerves,4,5 and thus reduce the surgical risks. We report here the case of a 59-year-old woman who presented with diplopia, left ataxia, and cognitive impairment, which revealed a large right skull base epidermoid cyst with infra-, supra-, and latero-sellar extensions (Video 1). The optic chiasma was pushed superiorly, and the oculomotor nerves were unidentifiable within the tumor. The internal carotid artery termination was stretched by the tumor and the first segment of the middle cerebral artery. Tractography was used to identify the position of the optic, oculomotor, and trigeminal nerves, which were encased within the tumor. A transsylvian approach allowed us to reach the tumor components using interoptic, opticocarotid, and laterocarotid triangles. This multiple window method gave access to most of the tumor's supratentorial component, which was removed using various size suction. Mirrors were useful to enhance the resection. Finally, a near-total removal of the tumor was achieved including the decompression of the brainstem, cranial nerves, and vessels. The capsule was kept in place to preserve critical anatomic structures; however, it should be removed when possible depending on tumor configuration. The patient, who consented to the procedure and to the publication of her images, recovered within a few days.

Robust and continuous in vivo differentiation of spinal tracts along the brain–spinal cord axis is limited. We stitched brain and spinal cord diffusion tensor imaging (DTI) to create continuity between the brain and cervical spinal cord, enabling tractography along the central nervous system, producing an atlas of the spinal cord white matter. This prospective pilot study included four healthy subjects. Brain and cervical spinal cord 3-T DTI acquisitions were performed. Distortions were corrected using the Functional magnetic resonance imaging of the brain Software Library (FSL) software package. A semiautomatic stitching process was achieved using cross-correlation. Once the highest correlation peak was identified, rigid registration allowed accurate image alignment and fusion. Regions of interest were drawn in the brainstem according to atlas-guided projection tracts. Fiber tracking was performed using a deterministic approach with Diffusion Spectrum Imaging (DSI) Studio. The median fiber length from stitched-image tractography (192 mm) was significantly greater than that from both the brain (111.5 mm) and spinal cord (115 mm) fields of view. The white matter fiber atlas described: the corticospinal tract in the medial part of the lateral funiculus; the rubrospinal tract in the lateral funiculus, overlapped with the corticospinal tract; the gracilis and cuneatus tracts in the dorsal columns; the spinothalamic tract in the ventrolateral part of the spinal cord, around the ventral horn; and the spinocerebellar tracts overlapping them, in the lateral funiculus. Stitching brain and spinal cord DTI fields of view provided an in vivo spinal cord white matter atlas in humans. This study provides a detailed and individualized mapping of spinal tracts, serving as a potential tool for neurosurgical planning, particularly in procedures involving intramedullary tumors. It also may enhance the accuracy of prognostic assessments in patients with spinal cord injury, multiple sclerosis, or degenerative myelopathy.

Meningiomas are the second most common type of tumor associated with Neurofibromatosis Type 2 Schwannomatosis (NF2-SWN). While the characteristics of intracranial meningiomas have been extensively studied, data on the epidemiological and histological features of spinal meningiomas (SM) remain limited. An observational, retrospective study was conducted on NF2-SWN patients who underwent surgical resection of SMs at three NF2-SWN reference centers. Data were compared to a cohort of patients operated on for sporadic SM at Pitié-Salpêtrière Hospital. To evaluate the prevalence of spinal meningiomas in NF2-SWN, we analyzed the craniospinal MRIs of NF2-SWN patients followed at the Pitié-Salpêtrière Hospital. Nineteen NF2-SWN patients who underwent surgery for 29 SMs between 1996 and 2024 were included (median age at surgery: 22 years; IQR:10–43). The most common location was the thoracic spine (22 cases, 76

BackgroundThe role of middle meningeal artery (MMA) embolization as an adjunct to standard treatment in chronic subdural hematoma (CSDH) is debated. Further randomized trials are needed to establish MMA embolization as an essential therapeutic option for CSDH. The OTEMACS study aims to assess the adjunctive benefit of MMA embolization in patients undergoing either conservative or surgical treatment for CSDH.MethodsOTEMACS is a multicenter, prospective, randomized controlled clinical trial with an open-label and blinded endpoint evaluation (PROBE) design. Patients with symptomatic CSDH treated either with conservative or surgical treatment are randomized 1:1 to receive MMA embolization within 72 h (experimental arm) or standard of care alone (control arm). The primary efficacy outcome is a composite of clinical and radiological events, including surgical rescue or revision surgery within 90 ± 14 days postrandomization or radiological remaining of the CSDH thickness >10 mm at 90 ± 14 days postrandomization. The primary safety outcome included all-cause mortality. Secondary outcomes included the modified Rankin scale, Barthel index, EuroQol-5, and Mini Mental State Examination. The number of patients to be included is 440.ResultsThe trial debuted in October 2021 in six centers, in France. A preplanned interim analysis was performed after the enrollment and completion of the follow-up of 220 patients, and the Data Safety Monitoring Board decided to stop the trial for efficacy. The final results will be made available upon completion of the enrollment.ConclusionsOTEMACS will provide additional evidence for the clinical and radiological efficacy and safety of MMA embolization in patients with CSDH.

Here, we report a very rare case of spontaneous intraventricular tension pneumocephalus. This case concerns a 40-year-old patient with medical history of a tumor of the pineal region and a secondary hydrocephalus treated by multiple ventriculoperitoneal shunts. He presented in the emergency room because of unusual headaches, nausea, and visual loss. In addition, he reported slight rhinorrhea in the past few weeks. The initial brain computed tomography scan revealed a spontaneous intraventricular tension pneumocephalus. There was no history of recent head trauma and no sign of disconnection of the shunt system. A complementary radiologic assessment including a thin-slice bone computed tomography scan and a radioisotope cisternography revealed an osseous defect and an isotope leakage at the junction between the tegmen tympani and the squamous part of the left temporal bone. A middle cranial fossa surgery was performed to repair the osteo-meningeal breach.

The use of diffusion tensor imaging (DTI) has seen significant development over the last two decades, in particular with the development of the tractography of association tracts for preoperative planning of surgery. However, projection tracts are difficult to differentiate from one another and tractography studies have failed to reconstruct these ascending/descending pathways from/to the spinal cord. The present study proposes an atlas of regions of interest (ROIs) designed specifically for projection tracts tractography. Forty-nine healthy subjects were included in this prospective study. Brain DTI was acquired using the same 3 T MRI scanner, with 32 diffusion directions. Distortions were corrected using the FSL software package. ROIs were drawn using the anterior commissure (AC)-posterior commissure (PC) line on the following landmarks: the pyramid for the corticospinal tract, the medio-caudal part of the red nucleus for the rubrospinal tract, the pontine reticular nucleus for corticoreticular tract, the superior and inferior cerebellar peduncles for, respectively, the anterior and posterior spinocerebellar tract, the gracilis and cuneatus nucleus for the dorsal columns, and the ventro-posterolateral nucleus for the spinothalamic tract. Fiber tracking was performed using a deterministic algorithm using DSI Studio software. ROI coordinates, according to AC-PC line, were given for each tract. Tractography was obtained for each tract, allowing tridimensional rendering and comparison of tracking metrics between tracts. The present study reports the accurate design of specific ROIs for tractography of each projection tract. This could be a useful tool in order to differentiate projection tracts at the spinal cord level.

This pilot study aimed to investigate the interest of high angular resolution diffusion imaging (HARDI) and tractography of the spinal cord (SC) in the management of patients with intramedullary tumors by providing predictive elements for tumor resection. Eight patients were included in a prospective study. HARDI images of the SC were acquired using a 3T MRI scanner with a reduced field of view. Opposed phase-encoding directions allowed distortion corrections. SC fiber tracking was performed using a deterministic approach, with extraction of tensor metrics. Then, regions of interest were drawn to track the spinal pathways of interest. HARDI and tractography added value by providing characteristics about the microstructural organization of the spinal white fibers. In patients with SC tumors, tensor metrics demonstrated significant changes in microstructural architecture, axonal density, and myelinated fibers (all, p < 0.0001) of the spinal white matter. Tractography aided in the differentiation of tumor histological types (SC-invaded vs. pushed back by the tumor), and differentiation of the spinal tracts enabled the determination of precise anatomical relationships between the tumor and the SC, defining the tumor resectability. This study underlines the value of using HARDI and tractography in patients with intramedullary tumors, to show alterations in SC microarchitecture and to differentiate spinal tracts to establish predictive factors for tumor resectability.

This study aimed to characterize spinal cord microstructure in healthy subjects using high angular resolution diffusion imaging (HARDI) and tractography. Forty-nine healthy subjects (18–50 years, divided into 2 age groups) were included in a prospective study. HARDI of the cervical spinal cord were acquired using a 3T MRI scanner with: 64 directions, b‑value: 1000s/mm2, reduced field-of-view (zonally magnified oblique multi-slice), and opposed phase-encoding directions. Distortions were corrected using the FSL software package. Fiber tracking was performed using a deterministic approach with DSI-Studio software. Tensor metrics—fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), radial diffusivity (RD)—and tractography statistics were then extracted, at each spine level, and after grey-white matter segmentation. The microstructural organization of the spinal cord differed between upper and lower cervical spine levels: FA, and AD significantly decreased (p < 0.001); and RD significantly increased (p < 0.05) in lower levels, demonstrating changes in axonal density and myelinated fibers according to a cranio-caudal axis. FA, MD, AD, and RD values were significantly higher in spinal cord white matter (p < 0.0001), compared to grey matter. Age was not associated with a significant change in FA, while there is for MD, AD and RD (p < 0.05). Spinal cord tractography may provide information on the architectural organization of fibers and spinal tracts. This study proposes a database in cervical spinal cord HARDI, allowing to study the microstructural organization of the spinal cord in healthy subjects, and providing a foundation for comparison with patients presenting spinal cord pathologies.

Trigeminal schwannoma (TS), though a rare and benign tumor, becomes a significant surgical challenge due to its intricate location. This study aims to detail the long-term functional outcomes and tumor control post-surgical resection. We analyzed a multicentric retrospective cohort of 39 patients operated on for a TS in five tertiary centers between January 1993 and July 2022. Six TS (15

BACKGROUND AND OBJECTIVES: Neurosurgical resection of brain tumors is a technically demanding task with a steep initial learning curve. Experience has been shown to improve surgical performance and increase the rates of resection. High-grade gliomas (HGG) are responsible for 65% of all primary malignant central nervous system tumors and are the commonest surgically treated brain tumor worldwide. There is increasing evidence that maximal safe surgical resection of HGG impacts on overall survival. The delineation of tumor tissue (and hence the extent of resection) is improved by the use of intraoperative tumor fluorescence, which is achieved by preoperative oral administration of 5-aminolevulinic acid. This however relies on the surgeon developing a skillset of operating under different light conditions for which specific training and experience are required. METHODS: We propose a novel, affordable, and highly adaptable model for recreating these surgical conditions and thus simulate fluorescence-guided HGG resection outside the operating theater for trainee neuro-oncological surgeons. We present a model incorporating plant-based polysaccharides, doped with protoporphyrin IX (PpIX), into cadaveric brains of animals. RESULTS: We show that the concentrations of polymer and PpIX can be titrated (using previously published data) to produce mechanical and fluorescence properties that model tumor tissue. We validate the simulation in a neurosurgical skills laboratory. Furthermore, we used a mini spectrometer with handheld probe to collect fluorescence signals and validate the spectroscopic signal from the PpIX. CONCLUSION: It is hoped that this model system will be useful in neurosurgical teaching and training courses and to neurosurgeons who want to try out new techniques or equipment in anatomy laboratories.

Diffusion tensor imaging (DTI) is commonly used to establish three-dimensional mapping of white-matter bundles in the supraspinal central nervous system. DTI has also been the subject of many studies on cranial and peripheral nerves. This non-invasive imaging technique enables virtual dissection of nerves in vivo and provides specific measurements of microstructural integrity. Adverse effects on the lumbosacral plexus may be traumatic, compressive, tumoral, or malformative and thus require dedicated treatment. DTI could lead to new perspectives in pudendal neuralgia diagnosis and management. We performed a systematic review of all articles or posters reporting results and protocols for lumbosacral plexus mapping using the DTI technique between January 2011 and December 2023. Twenty-nine articles published were included. Ten studies with a total of 351 participants were able to track the lumbosacral plexus in a physiological context and 19 studies with a total of 402 subjects tracked lumbosacral plexus in a pathological context. Tractography was performed on a 1.5T or 3T MRI system. DTI applied to the lumbosacral plexus and pudendal nerve is feasible but no microstructural normative value has been proposed for the pudendal nerve. The most frequently tracking parameters used in our review are: 3T MRI, b-value of 800 s/mm2, 33 directions, 3 × 3 × 3 mm3, AF threshold of 0.1, minimum fiber length of 10 mm, bending angle of 30°, and 3DT2 TSE anatomical resolution. Increased use of DTI could lead to new perspectives in the management of pudendal neuralgia due to entrapment syndrome, whether at the diagnostic, prognostic, or preoperative planning level. Prospective studies of healthy subjects and patients with the optimal acquisition parameters described above are needed to establish the accuracy of MR tractography for diagnosing pudendal neuralgia and other intrapelvic nerve entrapments.

The aim was to identify predictors of progression in a series of patients managed for an intracranial hemangioblastoma, in order to guide the postoperative follow-up modalities. The characteristics of 81 patients managed for an intracranial hemangioblastoma between January 2000 and October 2022 were retrospectively analyzed. The mean age at diagnosis was of 48 ± 16 years. Eleven (14%) patients had von Hippel–Lindau disease. The most frequent tumor location was the cerebellar hemispheres (n = 51, 65%) and 11 (14%) patients had multicentric hemangioblastomas. A gross total resection was achieved in 75 (93%) patients. Eighteen (22%) patients had a local progression, with a median progression-free survival of 56 months 95% CI [1;240]. Eleven (14%) patients had a distant progression (new hemangioblastoma and/or growth of an already known hemangioblastoma). Local progression was more frequent in younger patients (39 ± 14 years vs. 51 ± 16 years; p = 0.005), and those with von Hippel–Lindau disease (n = 8, 44% vs. n = 3, 5%, p < 0.0001), multiple cerebral locations (n = 3, 17% vs. n = 2, 3%, p = 0.02), and partial tumoral resection (n = 4, 18% vs. n = 1, 2%, p = 0.0006). Therefore, it is advisable to propose a postoperative follow-up for at least 10 years, and longer if at least one predictor of progression is present.

Understanding and teaching the three-dimensional architecture of the brain remains difficult because of the intricate arrangement of grey nuclei within white matter tracts. Although cortical area functions have been well studied, educational and three-dimensional descriptions of the organization of deep nuclei and white matter tracts are still missing. We propose herein a detailed step-by-step dissection of the lateral aspect of a left hemisphere using the Klingler method and provide high-quality stereoscopic views with the aim to help teach medical students or surgeons the three-dimensional anatomy of the brain. Three left hemispheres were extracted and prepared. Then, according to the Klingler method, dissections were carried out from the lateral aspect. Photographs were taken at each step and were modified to provide stereoscopic three-dimensional views. Gray and white structures were described: cortex, claustrum, putamen, pallidum, caudate nucleus, amygdala; U-fibers, external and internal capsules, superior longitudinal fasciculus, frontal aslant fasciculus, uncinate fasciculus, inferior fronto-occipital fasciculus, inferior longitudinal fasciculus, corticospinal fasciculus, corona radiata, anterior commissure, and optic radiations. This educational stereoscopic presentation of an expert dissection of brain white fibers and basal ganglia would be of value for theoretical or hands-on teaching of brain anatomy; labeling and stereoscopy could, moreover, improve the teaching, understanding, and memorizing of brain anatomy. In addition, this could be also used for the creation of a mental map by neurosurgeons for the preoperative planning of brain tumor surgery.

SummaryThe frontal aslant tract (FAT) is a crucial neural pathway of language and speech, but little is known about its connectivity and segmentation differences across populations. In this study, we utilized diffusion MRI automatic tractography to investigate the probabilistic coverage of the FAT in a large sample of 1065 young adults. Our primary goal was to reveal individual variability and lateralization of FAT and its structure-function correlations in language processing. Our results showed that the left anterior FAT exhibited the most substantial individual differences, particularly in the superior and middle frontal gyrus, with greater variability in the superior than the inferior region. Furthermore, we found significant left lateralization in FAT, with a greater difference in innervation coverage in the inferior and posterior portions. Additionally, our analysis revealed a significant correlation between the size of left FAT inferior innervation areas and Picture Vocabulary function, highlighting the structural and functional importance of the left FAT in language processing. In comparison, the anisotropy of FAT did not show significant correlation. Overall, our study provides valuable insights into individual and population differences in FAT connectivity and segmentation and sheds light on its critical role in language functions.

Abstract Objective Central pontine myelinolysis (CPM) is a rare demyelinating disease that affects the pons and which can cause extreme disabilities such as locked‐in syndrome (LIS) in the initial phase. The aim of the study was to describe the evolution over a 12‐month period of two patients with CPM causing an initial LIS. Method We retrospectively report the unexpected clinical outcome of these two patients in relation with the anatomical damages documented by brain MRI, associated with diffusion tensor imaging and reconstruction of corticospinal tracts in tractography. The following clinical parameters systematically assessed at 3, 6, 9, and 12 months: muscle testing on 12 key muscles (Medical Research Council), prehension metrics (box and block test and purdue pegboard), and independence for acts of daily living (functional independence measure). Results Both patients showed a progressive recovery beginning between 2 and 3 months after the onset of symptoms, leading to almost complete autonomy at 12 months (FIM > 110), with motor strength greater than 4/5 in all joint segments (MRC > 50/60). On brain MRI with tractography, CST appeared partially preserved at pons level. Interpretation The possibility of a near‐complete functional recovery at 12 months is important to consider given the ethical issues at stake and the discussions about limiting care that may take place initially. It seems to be the consequence of reversible myelin damage combined with partially preserved neurons. Development of collateral pathways or resolution of conduction block may explain this recovery. MRI comprising DTI and tractography could play a key role in the prognosis of motor recovery.