Erdheim-Chester disease of brain parenchyma without any systemic involvement: A case report and review of literature.

Erdheim-Chester disease is a non-Langerhans cell histiocytosis syndrome characterised by histiocytic infiltration of different organs and systems in the body. Erdheim-Chester disease with isolated central nervous system (CNS) involvement causes diagnostic difficulties due to the absence of systemic findings and may result in misdiagnosis and inaccurate treatment choices. The case discussed in this report exemplifies how challenging it is to diagnose Erdheim-Chester disease with isolated CNS involvement. This case, which presented with progressive pyramidocerebellar syndrome, was clinically and radiologically resistant to all immunosuppressive and immunomodulatory treatments administered. The presence of false negative results in repeated histopathological investigations and the absence of evidence for systemic disease hindered the diagnosis and treatment work-up. In this study, we reviewed and discussed the prominent features of the presented case in light of the relevant literature.

Creation of a microsurgical neuroanatomy laboratory and virtual operating room: a preliminary study.

OBJECTIVE: A comprehensive understanding of microsurgical neuroanatomy, familiarity with the operating room environment, patient positioning in relation to the surgery, and knowledge of surgical approaches is crucial in neurosurgical education. However, challenges such as limited patient exposure, heightened patient safety concerns, a decreased availability of surgical cases during training, and difficulties in accessing cadavers and laboratories have adversely impacted this education. Three-dimensional (3D) models and augmented reality (AR) applications can be utilized to depict the cortical and white matter anatomy of the brain, create virtual models of patient surgical positions, and simulate the operating room and neuroanatomy laboratory environment. Herein, the authors, who used a single application, aimed to demonstrate the creation of 3D models of anatomical cadaver dissections, surgical approaches, patient surgical positions, and operating room and laboratory designs as alternative educational materials for neurosurgical training. METHODS: A 3D modeling application (Scaniverse) was employed to generate 3D models of cadaveric brain specimens and surgical approaches using photogrammetry. It was also used to create virtual representations of the operating room and laboratory environment, as well as the surgical positions of patients, by utilizing light detection and ranging (LiDAR) sensor technology for accurate spatial mapping. These virtual models were then presented in AR for educational purposes. RESULTS: Virtual representations in three dimensions were created to depict cadaver specimens, surgical approaches, patient surgical positions, and the operating room and laboratory environment. These models offer the flexibility of rotation and movement in various planes for improved visualization and understanding. The operating room and laboratory environment were rendered in three dimensions to create a simulation that could be navigated using AR and mixed reality technology. Realistic cadaveric models with intricate details were showcased on internet-based platforms and AR platforms for enhanced visualization and learning. CONCLUSIONS: The utilization of this cost-effective, straightforward, and readily available approach to generate 3D models has the potential to enhance neuroanatomical and neurosurgical education. These digital models can be easily stored and shared via the internet, making them accessible to neurosurgeons worldwide for educational purposes.

Assessment the neurodegenaration process of post-geniculate optic pathway in thalamic tumors using optical coherence tomography: Post-geniculate optic pathway in thalamic tumors.

PURPOSE: To investigate the effect of thalamic tumors related to post-geniculate optic pathway and those of microsurgical removal on neurodegeneration process of visual pathway using OCT. METHODS: This cross-sectional study included 30 eyes of 15 patients with thalamic tumors and data compiled from 45 eyes of 45 healthy participants. The analysis of variables was divided into ipsilateral and contralateral eye depends on the laterality of brain tumors. The data gained at baseline, postoperative 3rd and postoperative 6th month period was analyzed in One-Way Repeated Measures ANOVA. RESULTS: The mean superior quadrant retinal nerve fiber layer (RNFL) thickness of ipsilateral eye was significantly thicker (p = 0.02), while inferior hemifield ganglion cell-inner plexiform layer (GC-IPL) thickness of contralateral eye was significantly higher compared to control groups (p = 0.02). Significant negative correlations were found between the mean preop. mean deviation (MD) and tumor volume and time interval between initial diagnosis and surgery (r = - 0.730, p = 0.002 and r = - 0.680, p = 0.005, respectively) in the ipsilateral eye. In repeated measure analysis, there was no unfavourable effect of thalamic microsurgery on peripapillary average RNFL thickness on both ipsilateral and contralateral eyes (Ipsilateral eye; f (1.5,21.7) 0.76 p = 0.51 and contralateral eye; f (1.4,20.4) 0.42 p = 0.59). CONCLUSION: This study suggests that thalamic tumors affecting post-geniculate optic pathway may lead to significant increase in RNFL and GC-IPL thicknesses and changes in VF parameters. Timely intervention in thalamic tumors may prevent irreversible loss of retinal axons secondary to neurodegeneration process.

Microsurgical Treatment of Deep and Eloquent AVMs.

Over the past 30 years, the treatment of deep and eloquent arteriovenous malformations (AVMs) has moved away from microneurosurgical resection and towards medical management and the so-called minimally invasive techniques, such as endovascular embolization and radiosurgery. The Spetzler-Martin grading system (and subsequent modifications) has done much to aid in risk stratification for surgical intervention; however, the system does not predict the risk of hemorrhage nor risk from other interventions. In more recent years, the ARUBA trial has suggested that unruptured AVMs should be medically managed. In our experience, although these eloquent regions of the brain should be discussed with patients in assessing the risks and benefits of intervention, we believe each AVM should be assessed based on the characteristics of the patient and the angio-architecture of the AVM, in particular venous hypertension, which may guide us to treat even high-grade AVMs when we believe we can (and need to) to benefit the patient. Advances in imaging and intraoperative adjuncts have helped us in decision making, preoperative planning, and ensuring good outcomes for our patients. Here, we present several cases to illustrate our primary points that treating low-grade AVMs can be more difficult than treating high-grade ones, mismanagement of deep and eloquent AVMs at the behest of dogma can harm patients, and the treatment of any AVM should be tailored to the individual patient and that patient's lesion.

Cottonoid-guided intraoperative ultrasonography in neurosurgery: a proof-of-concept single surgeon case series.

Ultrasonography was introduced into neurosurgery in the 1950s, but its successful utilization as an intraoperative tool dates from the early 1980s. However, it was not used widely because of limited technology, a lack of specific training, and, most importantly, the concurrent evolution of computerized tomography and magnetic resonance imaging. The intraoperative use of cottonoid patties as acoustical markers was first described in 1984, but the practice did not gain acceptance, and no articles have been published since. Herein, we reconsider the echogenic properties of the surgical cottonoid patty and demonstrate its usefulness with intraoperative ultrasonography (ioUS) in neurosurgical practice as a truly real-time neuronavigation tool. We also discuss its advantages and compare it with other intraoperative image guidance tools. The echogenic properties of the handmade cottonoid patties in various sizes used with ioUS are described. Details of our cottonoid-guided ioUS technique and its advantages with illustrated cases are also described. As an echogenic marker, cottonoid patties can be easily recognized with ioUS. Their usage with ultrasonography provides truly real-time anatomical orientation throughout the surgery, allowing easy access to intraparenchymal pathologies, and precise and safer resection. Cottonoid-guided ioUS helps not only to localize intraparenchymal pathologies but also to delineate the exact surgical trajectory for each type of lesion. Furthermore, it is not affected by brain shift and distortion. Thus, it is a truly real-time, dynamic, cost-effective, and easy-to-use image guidance tool. This technique can be used safely for every intraparenchymal pathology and increases the accuracy and safety of the surgeries.

The extreme anterior interhemispheric transcallosal approach for pure aqueduct tumors: surgical technique and case series.

Purely aqueductal tumors represent a rare but distinct entity of neoplasms with characteristic morphology and clinical presentation. This study aims to describe the extreme anterior interhemispheric transcallosal approach as a surgical option for purely aqueductal tumors in the upper part of the cerebral aqueduct and present the surgical results. Prospectively collected data of 4 patients undergoing the extreme anterior interhemispheric transcallosal approach for purely aqueductal tumors in the upper cerebral aqueduct was analyzed. The technique is a variation of the anterior interhemispheric transcallosal approach. The callosotomy is placed at the transition between the body and genu of the corpus callosum, allowing an approach steep enough to reach through the foramen of Monro to the upper cerebral aqueduct without opening the choroidal fissure. All patients had preoperative, and intraoperative or immediate postoperative 3-T magnetic resonance imaging, and underwent examination at admission, after surgery, at discharge, and 3 months postoperatively. Patient data are reported according to common descriptive statistics. All patients harbored low-grade gliomas causing hydrocephalus. Complete resection was achieved without mortality or morbidity. All patients recovered and presented neurologically intact at the 3-month postoperative follow-up. None had recurrence or needed adjuvant therapy. The extreme anterior interhemispheric transcallosal approach proved to be effective and safe. This approach does not require manipulation of the choroidal fissure or disrupt healthy brain parenchyma (except for a small callosotomy). We propose it as an option for removing a purely aqueductal tumor in the upper cerebral aqueduct with associated hydrocephalus.

The historical evolution of the fornix and its terminology: a review.

The historical evolution of the fornix has not been sufficiently reviewed in the literature. In this article, we follow this evolution from the first mention of the fornix in animal dissections of the second century AD, to the legalization of cadaver dissection in the 1300 s, to the introduction of neural staining techniques and the microscope in the seventeenth century, to today. We summarize the focus of fornix studies on memory to reveal its relationship with the hippocampus. We then cover the detection of the fornix and its neural connections noninvasively with the advancement of radiological imaging techniques. Finally, we discuss the prominence of the fornix as a target for deep brain stimulation in Alzheimer's disease and post-traumatic brain injury memory disorders.

The posterior interhemispheric transparieto-occipital fissure approach to the atrium of the lateral ventricle: a fiber microdissection study with case series.

The surgical approach to the atrium of the lateral ventricle remains a challenge because of its deep location and close relationship to important neurovascular structures. We present an alternative and safer approach to lesions of the atrium using a natural pathway through the parieto-occipital fissure. We demonstrate this approach through cadaveric anatomical microdissection and a case series. Five formalin-fixed brain specimens (10 hemispheres) were dissected with the Klingler technique. Transillumination was used to show the trajectory of the approach in cadaveric specimens. Clinical data from five patients who underwent this approach were reviewed. This data included intraoperative ultrasound images, operative images, pre- and postoperative magnetic resonance imaging, MR tractography, and visual field examination. The parieto-occipital fissure is a constant, uninterrupted fissure that can be easily identified in cadavers. Our anatomical dissection study revealed that the atrium of the lateral ventricle can be approached through the parieto-occipital fissure with minor damage to the short association fibers between the precuneus and cuneus, and a few fibers of the forceps major. In our series, five patients underwent total resection of their atrial lesions via the posterior interhemispheric transparieto-occipital fissure. No morbidity or mortality was observed, and the disruption of white matter was minimal, as indicated on postoperative tractography. The postoperative visual fields were normal. The posterior interhemispheric transparieto-occipital fissure approach is an alternative to remove lesions in the atrium of the lateral ventricle, causing the least damage to white matter tracts and preserving visual cortex and optic radiation.

Changes in the peripapillary and subfoveal choroidal vascularity index after transsphenoidal surgery for pituitary macroadenoma.

PURPOSE: To investigate the changes in peripapillary and subfoveal choroidal vascular indexes (CVI) before and after pituitary macroadenoma surgery by using a binarization method. METHOD: In this cross-sectional study, we examined 17 eyes in 9 patients with pituitary macroadenomas who had undergone transsphenoidal pituitary surgery due to chiasmal compression. We also compiled data from 17of in 17 healthy subjects. ImageJ 1.51 software processing (National Institutes of Health, Bethesda, Maryland, USA) was used for binarization of optical coherence tomography scans. The CVI was computed as the ratio of luminal area to total choroidal areal. The CVI, OCT and VF parameters were analyzed in One-Way Repeated Measures ANOVA to determine significant changes in measurements during the postoperative course. RESULTS: The mean peripapillary inferior and temporal quadrant CVIs were significantly lower in the eyes of patients with pituitary macroadenoma compared to controls (46.0 ± 0.03 versus. 42.8 ± 0.04, p = 0.02; 45.8 ± 0.03 Versus. 42.3 ± 0.04, p = 0.02). In repeated measure analysis, there was a significant effect of transsphenoidal microscobic pituitary surgery on peripapillary inferior quadrant CVI and BCVA, F(1.3, 21.5) = 6.62, p = 0.01 and F (1.8, 29.7) = 7.8, p < 0.005, respectively. CONCLUSION: This study suggests that PMa with chiasmal compression may lead to significant changes in the peripapillary CVI. Pituitary surgery had a favorable significant effect on peripapillary choroidal vascular network and BCVA. Furthermore, optical coherence tomography is a helpful technique for quantifying the alterations of peripapillary CVI during the preoperative and postoperative course.

Primary intracranial intraventricular leiomyoma: a literature review.

Leiomyomas, benign tumors of well-differentiated smooth muscle and vascular collagenous tissue, usually occur in the uterus but can develop wherever smooth muscle is present. Primary intracranial leiomyomas are rare tumors. We present the case of a 40-year-old woman with a primary intraventricular leiomyoma. She consulted us for headache, dizziness, and black spots in her vision. Magnetic resonance images (MRI) disclosed a mass rooted in the posterior septum pellucidum. The tumor was totally excised by the senior author with no residual seen on intraoperative MRI. Pathological examination showed it to be a benign spindle-cell neoplasm. On the 6th month control MRI, there was no recurrence. We also reviewed articles relevant to primary intracranial leiomyomas.

Limited positive predictive value of diffusion tensor tractography in determining clinically relevant white matter damage in brain stem cavernous malformations: A retrospective study in a single center surgical cohort.

PURPOSE: Diffusion tensor tractography (DTT) might reflect the postoperative clinical outcome of the patients with brain stem (BS) tumors correlating well with the neurological symptoms, but cavernous malformation (CM) is a hemorrhagic tumor prone to artifacts that may limit DTT. We set out to determine the correlation of DTT findings with the neurological examination before and after surgical resection in patients with BSCMs. MATERIALS AND METHODS: DTT findings were evaluated bilaterally for fiber tract displacement or deviation, deformation and interruption in every patient before and after the surgery. Neurological examination was performed at admission, discharge and outpatient follow-up visit. The sensitivity, specificity, positive and negative predictive values of DTT were calculated both pre- and post-operatively. RESULTS: There were 25 patients (9 men 16 women) with a mean age of 39.5±13.9 years. The mean size of the CMs was 6909±8374mm3 (range: 180-38,220mm3) The mean follow-up time was 42.7±23.2 months (range: 8 to 112 months). Preoperatively, the sensitivity, specificity, positive and negative predictive values of DTT for corticospinal tracts (CST) and medial lemnisci (ML) were 100%, 60%, 38.4%, 100% and 87.5%, 11.7%, 31.8%, 66.6%, respectively. Postoperatively, the sensitivity, specificity, positive and negative predictive values of DTT for CSTs and ML were 100%, 64.7%, 40%, 100% and 100%, 0%, 33.3%, 66.6%, respectively. CONCLUSION: Positive findings on DTT such as fiber tract deviation, deformation, disruption or interruption should be taken cautiously before drawing conclusions of a clinically relevant damage of white matter tracts.

Distinctive role of dysregulated miRNAs in chordoma cancer stem-like cell maintenance.

Chordoma is a rare, slow-growing tumor thought to arise from remnants of embryonic notochord associated with an aggressive outcome. Cancer stem-like cells (CSCs) are related to tumorigenesis, recurrence, and resistance in cancers. Therefore, chordoma CSCs are possible targets for chordoma treatment. In this study, dysregulated miRNAs were determined in chordoma CSCs and identified their role in chordoma. Dysregulated miRNAs were determined via miRNA microarray and validated through qPCR. miRNAs were transiently transfected to the chordoma cell lines and their roles in proliferation, apoptosis, migration and invasion capacities and stem-like properties were identified. Finally, a relationship between clinicopathological features and dysregulated miRNAs has been evaluated among 21 chordoma patients. CD133+CD15+ cells exhibited CSC phenotype with increased CSC- and Epithelial-Mesenchymal Transition (EMT)-related gene expression, invasion, migration, tumorosphere- and colony-forming abilities. In addition, WNT5A, TGF-α, BTG2 and MYCBP genes involved in CSC-related pathways, were targets of miR-140-3p, miR-148a-3p, miR-210-5p and miR-574-5p, respectively. Transfection of CSC-related miRNAs also increased migration and invasion along with stem cell phenotype. Finally, we determined that miR-140-3p and miR-148a-3p expressions correlated with Ki67 while miR-140-3p and TGF-α expressions were correlated with p53. Moreover, MYCBP expression was positively correlated with tumor volume, and metastasis was associated with the expression of miR-210-5p and TGF-α in our patient cohort. Through these findings, we conclude that chordoma CSCs have distinctive miRNA profile, which can regulate stem-like properties of chordoma CSCs.

Historical controversies about the thalamus: from etymology to function.

The authors report on and discuss the historical evolution of the 3 intellectual and scientific domains essential for the current understanding of the function of the human thalamus: 1) the identification of the thalamus as a distinct anatomical and functional entity, 2) the subdivision of thalamic gray matter into functionally homogeneous units (the thalamic nuclei) and relative disputes about nuclei nomenclature, and 3) experimental physiology and its limitations.Galen was allegedly the first to identify the thalamus. The etymology of the term remains unknown although it is hypothesized that Galen may have wanted to recall the thalamus of Odysseus. Burdach was the first to clearly and systematically define the thalamus and its macroscopic anatomy, which paved the way to understanding its internal microarchitecture. This structure in turn was studied in both nonhuman primates (Friedemann) and humans (Vogt and Vogt), leading to several discrepancies in the findings because of interspecies differences. As a consequence, two main nomenclatures developed, generating sometimes inconsistent (or nonreproducible) anatomo-functional correlations. Recently, considerable effort has been aimed at producing a unified nomenclature, based mainly on functional data, which is indispensable for future developments. The development of knowledge about macro- and microscopic anatomy has allowed a shift from the first galenic speculations about thalamic function (the "thalamus opticorum nervorum") to more detailed insights into the sensory and motor function of the thalamus in the 19th and 20th centuries. This progress is mostly the result of lesion and tracing studies. Direct evidence of the in vivo function of the human thalamus, however, originates from awake stereotactic procedures only.Our current knowledge about the function of the human thalamus is the result of a long process that occurred over several centuries and has been inextricably intermingled with the increasing accumulation of data about thalamic macro- and microscopic anatomy. Although the thalamic anatomy can currently be considered well understood, further studies are still needed to gain a deeper insight into the function of the human thalamus in vivo.

Characterization of stem-like cells in a new astroblastoma cell line.

Cell lines established from tumors are the most commonly used models in cancer research, and their use in recent years has enabled a greater understanding of the biology of cancer and the means to develop effective treatment strategies. Astroblastomas are uncommon neuroepithelial tumors of glial origin, predominantly affecting young people, mainly teenagers and children, predominantly females. To date, only a single study has reported that astroblastomas contain a large number of neural stem-like cells, which had only a partial proliferation capacity and differentiation. Our objective was to establish an astroblastoma cell line to investigate the presence of astroblastic cells and cancer stem-like cells. The migratory and invasion abilities of the cells were quantified with invasion and migration assays and compared to a glioblastoma cell line. The presence of stem cells was detected with surface-marker analysis by using flow cytometry, and measuring the differentiation ability with a differentiation assay and the self-renewal capacity with a sphere-forming assay. These characteristics may determine whether this novel cell line is a model for astroblastomas that may have stem-cell characteristics. With this novel cell line, scientists can investigate the molecular pathways underlying astroblastomas and develop new therapeutic strategies for patients with these tumors.

Simultaneous analysis of miRNA-mRNA in human meningiomas by integrating transcriptome: A relationship between PTX3 and miR-29c.

BACKGROUND: Although meningioma is a common disease, there is a lack of understanding of the underlying molecular mechanisms behind its initiation and progression. We used combined miRNA-mRNA transcriptome analysis to discover dysregulated genes and networks in meningiomas. METHODS: Fourteen fresh-frozen meningioma samples and one human meningeal cell line were analyzed by using miRNA and whole transcriptome microarray chips. Data was filtered and analyzed. Candidate miRNAs and mRNAs were selected for validation in fifty-eight patient samples. miRNA and target mRNA relationships were assessed by inhibiting miRNA in meningioma cells. Apoptosis and viability assays were also used as functional tests. RESULTS: With the whole transcriptome microarray, 3753 genes were found to be dysregulated, and 891 miRNAs were found to be dysregulated as a result of miRNA microarray. Results were combined and analyzed with bioinformatics tools. Top differential pathways included those of inflammation, cancer, and cellular growth and survival. The oncosupressor PTX3 was constitutively low in meningioma samples. Moreover, PTX3 negatively correlated with miR-29c in our samples. Inhibiting miR-29c upregulated the PTX3 level, induced apoptosis of meningioma cells, and decreased cell viability. CABIN1, miR-29c, TMOD1, PTX3, RPL22, SPARCL1 and RELA were correlated with clinicopathological features in patient samples. CONCLUSIONS: Our results present the first integrated mRNA-miRNA analysis in meningiomas. miR-29c-3p and PTX3 are inversely correlated in tissues and meningioma cells, hinting that PTX3 can be regulated by miR-29c-3p. Furthermore, we determined potential clinicopathological markers.

The paramedian supracerebellar-transtentorial approach to remove a posterior fusiform gyrus arteriovenous malformation.

This is the case of a 14-year-old female who presented with headache and seizures. Cranial magnetic resonance imaging revealed an arteriovenous malformation (AVM) located at the posterior portion of the right-sided fusiform gyrus. Cerebral angiography showed that the AVM was fed mainly by branches from the inferior temporal trunk of the posterior cerebral artery. The main venous drainage was to the right transverse sinus through the tentorial vein. The AVM was totally excised through the paramedian supracerebellar-transtentorial approach with the patient in a semisitting position. Postoperative MRI and cerebral angiography confirmed the total resection. The patient was discharged on the 5th postoperative day without neurological deficit. The video can be found here: https://youtu.be/QPrUl8AP7G8 .

The molecular aspects of chordoma.

Chordomas are one of the rarest bone tumors, and they originate from remnants of embryonic notochord along the spine, more frequently at the skull base and sacrum. Although they are relatively slow growing and low grade, chordomas are highly recurrent, aggressive, locally invasive, and prone to metastasize to the lungs, bone, and the liver. Chordomas highly and generally show a dual epithelial-mesenchymal differentiation. These tumors resist chemotherapy and radiotherapy; therefore, radical surgery and high-dose radiation are the most used treatments, although there is no standard way to treat the disease. The molecular biology process behind the initiation and progression of a chordoma needs to be revealed for a better understanding of the disease and to develop more effective therapies. Efforts to discover the mysteries of these molecular aspects have delineated several molecular and genetic alterations in this tumor. Here, we review and describe the emerging insights into the molecular landscape of chordomas.

Unilateral axis facet hypertrophy--a rare case of irreducible rotatory atlantoaxial dislocation and a review of the literature.

Fixed atlantoaxial dislocations are difficult to treat and there is no consensus in the treatment protocol. Unilateral enlargement of the atlas-axis facet complex in fixed atlantoaxial dislocations is a very rare condition. These pathologies are usually quite unstable and surgical treatment is necessary in unreductable cases. A 52-year-old woman with a diagnosis of irreducible-fixed rotatory atlantoaxial dislocation presented with acute onset of dizziness, loss of balance, and tetraparesis. She was under 8 years of conservative follow-up. Review of radiology revealed unilateral C2 superior facet hypertrophy compressing the medulla and obstructing the vertebral artery. To treat this condition, we have used a posterior midline approach and removed the lateral portions of the posterior rim of the foramen magnum and the assimilated posterior arch of C1. The V3 segments of the vertebral arteries were exposed bilaterally. The atlantoaxial joint complex on the left was hypertrophied compressing V3. We have removed hypertrophied lateral mass of the atlas and the hypertrophic superior articular facet of C2 for decompression. Patency of both vertebral arteries were checked intraoperatively by Doppler and indocyanine green angiography. We have fixated craniocervical junction on the same session. Patient was neurologically intact and she had confirmed fusion on the surgical site after three years of follow-up. This is a rare case of unilateral hypertrophy of the C2 superior articular facet in a fixed atlantoaxial rotatory dislocation. Progressive compression of medulla and the left vertebral artery leaded to clinical worsening of neurology in this case after 8 years of follow-up. Surgical treatment was necessary for neurological decompression and to establish stability.

Posterior Interhemispheric Transtentorial Subsplenial Approach for Posterior Thalamic Tumors: 2-Dimensional Operative Video.

INDICATIONS CORRIDOR AND LIMITS OF EXPOSURE: The posterior interhemispheric transtentorial subsplenial approach provides a direct corridor to posterior thalamic lesions without a cortical or callosal incision. 1. ANATOMIC ESSENTIALS NEED FOR PREOPERATIVE PLANNING AND ASSESSMENT: This corridor is through the posterior interhemispheric fissure along the medial surface of the cuneus and allows the subsplenial region to be explored. Evaluating the tumor's size and extension is crucial to determining the suitability of this approach. The deep venous system may be displaced from mass effect, requiring preoperative venous examination. ESSENTIALS STEPS OF THE PROCEDURE: A 34-year-old male patient was admitted elsewhere with blurred vision and imbalance. MRI revealed a right-sided posterior thalamic tumor with heterogeneous contrast enhancement. The patient was followed-up after placement of a ventriculoperitoneal shunt. Seven months later, he was admitted to our clinic because the tumor had grown. The patient underwent surgical intervention. The patient was placed in the prone oblique position. After dural opening, the quadrigeminal cistern was opened to release cerebrospinal fluid, allowing significant gravity relaxation of the ipsilateral hemisphere. The tentorium was cut and retracted to achieve the necessary exposure. PITFALLS/AVOIDANCE OF COMPLICATIONS: The most serious complications of this approach occur from vascular injuries. Gravitational retraction of the occipital lobe protects the optic radiation, and anatomic landmarks help the surgeon maintain anatomic orientation. VARIANTS AND INDICATIONS FOR THEIR USE: The perimedian supracerebellar transtentorial approach is an alternative to the posterior interhemispheric transtentorial subsplenial approach for lesions in this area; however, the indications and limits of these approaches have some differences.The patient consented to the procedure and to the publication of his/her image.Images at 0:29 reused from Serra et al, 1 with permission from Elsevier.

Revealing the confusion of the evolution of the term sagittal stratum. Historical overview and systematic literature review.

The fiber dissection technique is one of the earliest methods used to demonstrate the internal structures of the brain, but until the development of fiber tractography, most neuroanatomy studies were related to the cerebral cortex and less attention was given to the white matter. During the historical evolution of white matter dissection, debates have arisen about tissue preservation methods, dissection methodology, nomenclature, and efforts to adopt findings from primates to the human brain. Since its first description, the sagittal stratum has been one of the white matter structures subject to controversy and has not been sufficiently considered in the literature. With recent functional studies suggesting potential functions of the sagittal stratum, the importance of attaining a precise understanding of this structure and its constituent fiber tracts is further highlighted. This study revisits the historical background of white matter dissection, unveils the early synonymous descriptions of the sagittal stratum, and provides a systematic review of the current literature. Through evaluation of the historical statements about the sagittal stratum, we provide an understanding of the divergence and explain the reasons for the ambiguity. We believe that acquiring such an understanding will lead to further investigations on this subject, which has the potential to benefit in addressing various neuropsychiatric conditions, maintaining functional connectivity, and optimizing surgical outcomes.