Sublabial transmaxillary approach to the inferior aspect of the orbit.

OBJECTIVE: The objective was to demonstrate the surgical steps and outcomes of the sublabial transmaxillary microsurgical approach with endoscopic assistance to treat lesions in the inferior aspect of the orbit, as well as to describe the use of patient-specific 3D models to facilitate surgical preparation and improve experience with the technique. METHODS: The authors' study evaluated data from patients who underwent an endoscope-assisted sublabial transmaxillary approach for inferior orbital lesions. For 2 patients, 3D models were created for preoperative planning and assessment of the approach. Surgical steps comprised osteotomy to access the maxillary sinus, bony resection of the orbital floor, opening of the periorbital fascia, and dissecting and removing the lesion, followed by closure. The neuroendoscope was used to inspect the surgical cavity between each step. RESULTS: The study included 5 patients with varying visual field defects and proptosis who underwent the sublabial transmaxillary microsurgical approach with endoscopic assistance. Complete resection was achieved in all, and all patients reported improvement in visual field defects and proptosis after the procedure. No complications were observed except for transient unilateral maxillary edema noted around the incision site in 3 patients during the early postoperative period, which resolved within a few days. Histopathological examination confirmed the diagnosis of cavernous malformation in all patients. CONCLUSIONS: The sublabial transmaxillary approach is a direct and safe method to resect cavernous malformations at the inferior aspect of the orbit. It reduces the risk of complications associated with lateral, transcranial, and transnasal approaches that may cross critical structures. The microsurgical approach provides the benefit of two-handed dissection for lesions embedded in orbital fat, which can be challenging because of adhesions to surrounding tissues. The use of 3D models can facilitate surgical planning and enhance familiarity with the approach.

Selective amygdalohippocampectomy via the paramedian supracerebellar-transtentorial approach for mediobasal temporal epilepsy.

Selective amygdalohippocampectomy via the pterional transsylvian approach is a feasible option for many patients with mediobasal temporal epilepsy. However, it may be insufficient for patients when the posterior hippocampal region is involved. The paramedian supracerebellar transtentorial approach offers precise anatomical orientation when exposing the entire length of the mediobasal temporal region, including the fusiform gyrus. In addition, this approach allows selective amygdalohippocampectomy without any neocortical damage. This video presents the successful treatment of a patient with posterior hippocampal sclerosis and mediobasal temporal epilepsy through the paramedian supracerebellar transtentorial approach.

Beyond nimodipine: advanced neuroprotection strategies for aneurysmal subarachnoid hemorrhage vasospasm and delayed cerebral ischemia.

The clinical management of aneurysmal subarachnoid hemorrhage (SAH)-associated vasospasm remains a challenge in neurosurgical practice, with its prevention and treatment having a major impact on neurological outcome. While considered a mainstay, nimodipine is burdened by some non-negligible limitations that make it still a suboptimal candidate of pharmacotherapy for SAH. This narrative review aims to provide an update on the pharmacodynamics, pharmacokinetics, overall evidence, and strength of recommendation of nimodipine alternative drugs for aneurysmal SAH-associated vasospasm and delayed cerebral ischemia. A PRISMA literature search was performed in the PubMed/Medline, Web of Science, ClinicalTrials.gov, and PubChem databases using a combination of the MeSH terms "medical therapy," "management," "cerebral vasospasm," "subarachnoid hemorrhage," and "delayed cerebral ischemia." Collected articles were reviewed for typology and relevance prior to final inclusion. A total of 346 articles were initially collected. The identification, screening, eligibility, and inclusion process resulted in the selection of 59 studies. Nicardipine and cilostazol, which have longer half-lives than nimodipine, had robust evidence of efficacy and safety. Eicosapentaenoic acid, dapsone and clazosentan showed a good balance between effectiveness and favorable pharmacokinetics. Combinations between different drug classes have been studied to a very limited extent. Nicardipine, cilostazol, Rho-kinase inhibitors, and clazosentan proved their better pharmacokinetic profiles compared with nimodipine without prejudice with effective and safe neuroprotective role. However, the number of trials conducted is significantly lower than for nimodipine. Aneurysmal SAH-associated vasospasm remains an area of ongoing preclinical and clinical research where the search for new drugs or associations is critical.

Microsurgical Resection of a Pediatric Tegmentum Tumor Through the Paramedian Supracerebellar Transtentorial Approach With the Tentorial Cut Technique: 2-Dimensional Operative Video.

The brainstem contains a highly complex group of nuclei and major white matter tracts within a small volume.1 The complex nature of its anatomy creates challenges for surgery in this area, impeding the standardization of approaches. Therefore, the concept of the "safe entry zone" should be considered with caution, and the strategy for each patient should be tailored based on the relevant subunit of the brainstem and individual patient characteristics. The critical parameter to target in patients is achieving the highest possible extent of resection while preserving function.1 The paramedian supracerebellar transtentorial approach is usually suitable for midbrain lesions. This approach allows for targeting tegmental tumors through the posterolateral midbrain surface.1 It is typically performed through a paramedian suboccipital craniotomy, ideally with the patient in the semisitting position, and is now considered a standard and safe approach.2 In patients with a spontaneous atrial right-to-left shunt, lateral or semilateral positions are viable alternatives, with the semilateral preferred for intraoperative magnetic resonance imaging.1 The cerebellar hemispheric tentorial bridging veins are usually located in the surgical route, narrowing the surgical corridor.3 Sacrifice or unintended rupture of these veins can sometimes lead to unexpected serious complications. Therefore, it is essential to preserve these veins during supracerebellar approaches.3 In this study, we demonstrate the resection of a pediatric tegmentum tumor through the left-sided paramedian supracerebellar transtentorial approach. In addition, we show the tentorial cut technique used to preserve the cerebellar hemispheric tentorial bridging veins. The patient's parents consented to the procedure and to the publication of his image.

Graftless Primary Dural Closure Following Retrosigmoid Approach: Doing More With less.

INTRODUCTION: Achieving watertight dural closure without grafts via the retrosigmoid approach can be challenging, contributing to a significant rate of postoperative cerebrospinal fluid (CSF) leaks. This study describes a dural incision technique for achieving primary dural closure without grafts following the retrosigmoid approach and presents clinical data from the authors' experience. METHODS: Clinical and surgical data of 227 patients who underwent the dural incision technique following the retrosigmoid approach for various pathologies were retrospectively reviewed. To achieve no-graft watertight dural closure, the dural incision involves 2 critical steps: a 1 cm transverse incision of the dura parallel to the foramen magnum to drain CSF from the cisterna magna, and a vertical linear opening of the retrosigmoid dura. Dural incisions were closed watertight with vicryl 4/0 running sutures, without the use of grafts, fibrin glue, hemostatic overlays, or dural substitutes. Pre- or postoperative lumbar drainage was not employed. RESULTS: Primary watertight dural closure was successfully achieved in all patients without the use of grafts or duraplasty. The average duration of dura closure was 17.7 minutes. During an average follow-up period of 49.3 months, there were no instances of CSF leaks or meningitis. CONCLUSIONS: In the authors' preliminary experience, the linear dural incision described herein was effective for achieving a no-graft, watertight primary dural closure in the retrosigmoid approach, with no CSF leaks or meningitis in our series. Validation of these preliminary data in a larger patient cohort is necessary.

Revisiting the microsurgical anatomy of the sagittal stratum and surgical implications: fiber microdissection and tractography study.

OBJECTIVE: The term "sagittal stratum" was coined by Heinrich Sachs in 1892 to define a parasagittally oriented white matter layer at the temporo-occipital cortex. Although this term has been widely used for more than 100 years, the description, classification, borders, and involved fibers of the structure vary among authors and remain imprecise. Through fiber microdissection and tractography, the authors aimed to define the sagittal stratum and resolve the uncertainty by revealing the relationship of this structure to other cerebral white matter pathways and the orientation of fibers in it. METHODS: Twenty postmortem human cerebral hemispheres were prepared according to Klingler's method. Fiber dissections were performed under a surgical microscope and with microsurgical techniques. The results of dissection at each step were photographed with 2D and 3D imaging techniques, and 3D photogrammetry techniques were used to create a 360° model. Diffusion tensor imaging and 7T high-resolution MRI were used to confirm the findings. RESULTS: This study revisited the 3D organization of white matter tracts in the sagittal stratum through fiber microdissection and tractography. The microneuroanatomical structure of the sagittal stratum and its special organization with fibers from all three fiber systems are demonstrated. The authors' findings revealed that the sagittal stratum has two layers consisting of four different fiber tracts. Its external layer consists of a long association fiber and a commissural fiber, while its internal layer consists of intertwined projection fibers, including temporo-parieto-occipitopontine fibers and the posterior thalamic peduncle. Detailed microdissection also showed the location of the posterior thalamic peduncle in the most medial site of all posterior hemispheric projection fibers. CONCLUSIONS: The structure of the sagittal stratum is distinctive in that it contains all three main fiber systems: association, commissural, and projection. Because of its expansive location in the temporal and occipital lobes, it can be damaged by most neurosurgical pathologies and procedures. The authors emphasize the significance of preserving the sagittal stratum during surgical interventions while also challenging the notion of a "silent" brain, suggesting that the current inability to fully comprehend cerebral function contributes to this misconception. Detailed knowledge of the complex white matter anatomy of the sagittal stratum can guide neurosurgeons in surgical planning and the selection of appropriate surgical approaches with intraoperative orientation for safe surgery and less comorbidity.

Creating a neuroanatomy education model with augmented reality and virtual reality simulations of white matter tracts.

OBJECTIVE: The utilization of digital technologies has experienced a notable surge, particularly in cases where access to cadavers is constrained, within the context of practical neuroanatomy training. This study evaluates augmented reality (AR)- and virtual reality (VR)-based educational models for neuroanatomy education. METHODS: Three-dimensional models were created using advanced photogrammetry. VR- and AR-based educational models were developed by arranging these 3D models to align with the learning objectives of neurosurgery residents and second-year medical students whose cadaveric training was disrupted due to an earthquake in Turkey. Participants engaged with and evaluated the VR- and AR-based educational models, followed by the completion of a 20-item graded user experience survey. A 10-question mini-test was given to assess the baseline knowledge level prior to training and to measure the achievement of learning objectives after training. RESULTS: Forty neurosurgery residents were trained with a VR-based educational model using VR headsets. An AR-based educational model was provided online to 200 second-year medical students for their practical neuroanatomy lesson. The average correct answer rates before the training were 7.5/10 for residents and 4.8/10 for students. These rates were significantly improved after the training to 9.7/10 for residents and to 8.7/10 for students (p < 0.001). Feedback from the users concurred that VR- and AR-based training could significantly enhance the learning experience in the field of neuroanatomy. CONCLUSIONS: VR/AR-based educational models have the potential to improve education. VR/AR-based training systems can serve as an auxiliary tool in neuroanatomy training, offering a realistic alternative to traditional learning tools.

Transorbital neuroendoscopic surgery for treatment of sphenoid wing meningiomas extending to the cavernous sinus: clinical implications and a technical illustration.

OBJECTIVE: The aim of this study was to evaluate the efficacy and safety of transorbital neuroendoscopic surgery (TONES) in the management of sphenoid wing meningiomas (SWMs) with cavernous sinus and orbital invasion. METHODS: The authors conducted a retrospective review of 32 patients with SWMs treated at Gazi University using TONES from October 2019 to May 2023. The study includes clinical applications to elucidate the endoscopic transorbital approach. Surgical techniques focused on safe subtotal resection, aiming to minimize residual tumor volume for subsequent radiosurgery. Data were collected on patient demographics, tumor characteristics, surgical procedures, complications, and postoperative outcomes, including radiological imaging and ophthalmological evaluations. RESULTS: Surgical dissections delineated a three-phase endoscopic transorbital approach: extraorbital, intraorbital, and intracranial. In the clinical application, gross-total resection was not achieved in any patient because of planned postoperative Gamma Knife radiosurgery. The mean follow-up period was 16.3 months. Of 30 patients with preoperative proptosis, 25 experienced postoperative improvement. No new-onset extraocular muscle paresis or visual loss occurred postoperatively. The average hospital stay was 1.15 days, with minimal complications and no significant morbidity or mortality. CONCLUSIONS: Total resection of SWMs invading the cavernous sinus and orbit is associated with substantial risks, particularly cranial nerve deficits. TONES offers a minimally invasive alternative, reducing morbidity compared with transcranial approaches, and represents a significant advancement in the surgical management of SWMs, especially those extending into the cavernous sinus and orbit. The approach provides a safe, effective, and patient-centric approach, prioritizing subtotal resection to minimize neurological deficits while preparing patients for adjunctive radiosurgery. This study positions TONES as a transformative surgical technique, aligning therapeutic efficacy with neurovascular preservation and postoperative recovery.

Human Adapted Prosomeric Model: A Future for Brainstem Tumor Classification.

This study reevaluates the conventional understanding of midbrain anatomy and neuroanatomical nomenclature in the context of recent genetic and anatomical discoveries. The authors assert that the midbrain should be viewed as an integral part of the forebrain due to shared genetic determinants and evolutionary lineage. The isthmo-mesencephalic boundary is recognized as a significant organizer for both the caudal midbrain and the isthmo-cerebellar area. The article adopts the prosomeric model, redefining the whole brain as neuromeres, offering a more precise depiction of brain development, including processes like proliferation, neurogenesis, cell migration, and differentiation. This shift in understanding challenges traditional definitions of the midbrain based on external brain morphology. The study also delves into the historical context of neuroanatomical models, including the columnar model proposed by Herrick in 1910, which has influenced our understanding of brain structure. Furthermore, the study has clinical implications, affecting neuroanatomy, neurodevelopmental studies, and the diagnosis and treatment of brain disorders. It emphasizes the need to integrate molecular research into human neuroanatomical studies and advocates for updating neuroanatomical terminology to reflect modern genetic and molecular insights. The authors propose two key revisions. First, we suggest reclassifying the isthmo-cerebellar prepontine region as part of the hindbrain, due to its role in cerebellar development and distinct location caudal to the genetically-defined midbrain. Second, we recommend redefining the anterior boundary of the genetically-defined midbrain to align with genetic markers. In conclusion, the authors highlight the importance of harmonizing neuroanatomical nomenclature with current scientific knowledge, promoting a more precise and informed understanding of brain structure, which is crucial for both research and clinical applications related to the human brain.

Neglected tracts of the brainstem: transverse peduncular tract of Gudden and taenia pontis.

OBJECTIVE: The anatomy and function of the brainstem have fascinated scientists for centuries; however, the brainstem remains one of the least studied regions of the human brain. As the authors delved into studying this structure, they observed a growing tendency to forget or neglect previously identified structures. The aim of this study was to describe two such structures: the transverse peduncular tract, also known as the Gudden tract, and the taenia pontis. The authors analyzed the potential effects of neglecting these structures during brainstem surgery and the implications for clinical practice. METHODS: After removal of the arachnoid and vascular structures, 20 human brainstem specimens were frozen and stored at -16°C for 2 weeks, according to the method described by Klingler. The specimens were then thawed and dissected with microsurgical techniques. The results of microsurgical fiber dissection at each step were photographed. RESULTS: This study revealed two previously neglected or forgotten structures within the brainstem. The first is the transverse peduncular tract of Gudden, which arises from the brachium of the superior colliculus. This tract follows an arcuate course along the lateral and ventral surfaces of the midbrain, perpendicular to the cerebral peduncle, and terminates in the nuclei of the transverse peduncular tract within the interpeduncular fossa. The second structure is the taenia pontis, which originates contralaterally in the interpeduncular fossa. It becomes visible at the level of the pontomesencephalic sulcus and extends to the base of the lateral mesencephalic sulcus, where it divides into several thin bundles. Along the interpeduncular sulcus, between the superior and middle cerebellar peduncles, it reaches the parabrachial recess and enters the cerebellum. CONCLUSIONS: Recently, with increasing understanding and expertise in brainstem research, surgical approaches to this area have become more common, emphasizing the importance of a detailed knowledge of the brainstem. The two structures mentioned in this paper are described in history books and were widely studied in the 19th century but have not been mentioned in modern literature. The authors propose that a deeper understanding of these structures may prove valuable in neurosurgical practice and help reduce patient comorbidity.

Ventral amygdalofugal pathway as an integrated surgically important network: microsurgical anatomy and segmentation based on fiber dissection.

OBJECTIVE: The ventral amygdalofugal pathway (VAFP) provides afferent and efferent connections to the amygdala and spans along some of the frequently traversed intra-axial surgical corridors as a dominant fiber bundle. This study aimed to reveal the frequently overlooked VAFP fibers by examining their courses and connections to the basal forebrain, septal region, hypothalamus, thalamus, tegmentum, and brainstem. METHODS: Ten postmortem human brains were used to display the characteristics of the VAFP, and fiber dissection results were compared with those of tractography. RESULTS: From anterior to posterior, the VAFP was separated into 5 different portions: 1) amygdala-substantia innominata; 2) amygdaloseptal (diagonal band of Broca); 3) amygdalo-thalamic; 4) amygdalo-hypothalamic, intermingling with the medial forebrain bundle and extending to the bed nucleus of stria terminalis; and 5) amygdalotegmental. The results of fiber dissections were confirmed with findings obtained from diffusion tensor tractography. CONCLUSIONS: This study supports the concept that interconnected forebrain, diencephalic, mesencephalic, and brainstem connections of the VAFP form an integrated surgically important network. The fiber dissection findings also provide the neuroanatomical basis for VAFP segmentation, which may help neurosurgeons better appreciate the complex microsurgical anatomy of the amygdalar connections. Amygdala-substantia innominata and amygdalotegmental connections are demonstrated for the first time and clarified within the structure of the VAFP.

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.

Microsurgical Resection of a Parachiasmatic Craniopharyngioma via a Left-Sided Pterional Transsylvian Approach.

Craniopharyngiomas are histologically benign tumors that originate from squamous rests along the pituitary stalk. They make up approximately 1.2% to 4.6% of all intracranial tumors and do not show significant differences in occurrence based on sex. Adamantinomatous craniopharyngiomas have 2 peaks of incidence, commonly observed in patients from ages 5 to 15 years and again from 45 to 60 years. In contrast, papillary craniopharyngiomas mainly affect adults in their fifth and sixth decades of life.1 The "malignancy" of craniopharyngiomas is attributed to their location and the challenges associated with achieving complete removal because they can manifest in the sellar, parachiasmatic, and intraventricular regions or a combination of these.2,3 Various approaches have been used to resect these tumors.4,5 Radical resection offers the most promising option for disease control, potential cure, and the ability to transform the disease from lethal to survivable in children, allowing for a functional adult life.2,3 Meticulous evaluation is crucial to determine the appropriate approach and side, with particular emphasis on closely examining the relationship between the tumor and optic pathways (nerve, chiasm, tract), which are frequently involved. This assessment should also include the tumor's relationship with other crucial structures, such as the hypothalamus and adjacent arteries, to ensure that the strategy is adjusted accordingly to further minimize the risk of postoperative morbidity. Video 1 demonstrates a left-sided pterional transsylvian approach to remove a parachiasmatic craniopharyngioma involving the left optic chiasm and tract.

Occipital Sinus-Sparing Linear Paramedian Dural Incision: A Technical Note and Case Series for Median Suboccipital Approach.

BACKGROUND: Durotomies, traditionally used during the midline suboccipital approach, involve sacrificing the occipital sinus (OS) with consequent shrinking of the dura, risk of venous complications, difficulty performing watertight closure, and a higher rate of postoperative cerebrospinal fluid (CSF) leaks. The present technical note describes the OS-sparing linear paramedian dural incision, which leads to a decrease in the risk of complications during the median suboccipital approach in our case series. METHODS: The OS-sparing linear incision technique involves a dural incision placed 1 cm lateral to the OS. The angle of view of the microscope is frequently changed to overcome the narrowed exposure of the linear durotomy. Copious irrigation with saline prevents drying of the dura. A running watertight closure of the dura is performed. The overall results of 5 cases are reviewed. RESULTS: The cases were 3 tumors and 2 cavernomas. The OS was preserved in all 5, and no duraplasty was needed. The average dura closure time was 16.8 minutes. No CSF leak occurred, and no wound complications were observed. A gross total resection of the lesion was achieved in all the patients. The mean follow-up was 10.2 months, and there were no late complications related to the dura closure. CONCLUSIONS: In comparison to the types of durotomies conventionally used for the midline suboccipital approach, the OS-sparing linear paramedian dural incision entails lower risks of bleeding, venous complications, CSF leaks, and infections by avoiding duraplasty. Validation of this technical note on a larger patient cohort is needed.

Thrombosed Posterior Inferior Cerebellar Artery Aneurysm Mimicking a Medulla Oblongata Cavernous Malformation: 2-Dimensional Operative Video.

The incidence of posterior inferior cerebellar artery (PICA) aneurysms is estimated to be between 0.5% and 3% of total aneurysm cases.1 Most patients with these aneurysms typically present with subarachnoid hemorrhage, although there are instances in which patients may present with symptoms resulting from mass effect exerted on the brain stem or lower cranial nerves.1,2 Treatment options for PICA aneurysms include endovascular procedures, surgical clipping, or bypass techniques.2 Surgical treatment is considered more effective for partially thrombosed aneurysms compared with endovascular approaches.3 In addition, endovascular coiling of these aneurysms carries the potential risk of coil migration and subsequent reopening of the aneurysm lumen.4 In certain instances, thrombosed PICA aneurysms have the potential to simulate the radiological characteristics of alternative pathologies, such as cavernous malformations or brainstem tumors.5-7 This situation can result in misdiagnosis and inappropriate management. We present the case of a patient who exhibited symptoms of imbalance and dysfunction in the lower cranial nerves. Magnetic resonance imaging findings indicated a possible cavernous malformation in the medulla oblongata. However, further investigation revealed that the underlying cause was a thrombosed PICA aneurysm. The patient was successfully treated through surgical clipping. The patient consented to the procedure and to the publication of his/her image.