Skull Base Research Articles

Artifact Assessment in the Skull Base Region of Head CT Images with Various Tilt Angles Relative to the Orbitomeatal Line

The aim of this study was to evaluate artifacts in the skull base region of head computed tomography (CT) images with various tilt angles relative to the orbitomeatal line. CT images of a head phantom acquired by helical and non-helical scanning with the tilt angles set from 0 to 20 degrees in 5-degree increments were evaluated in this study. Regions of interest (ROIs) were set at the cerebellum, temporal lobe, frontal lobe, and basal ganglia in the phantom images. Artifacts were evaluated by the coefficient of variation (CV) of the mean CT value between ROIs and the location parameter (β) of the Gumbel method. The CV and β values increased with increasing tilt angle for both helical and nonhelical images in the frontal lobes, but both decreased in the cerebellar region. In the temporal lobe and basal ganglia, there was no trend of change with tilt angle. Increasing the tilt angle relative to the OM line increased artifacts at the frontal lobes and decreased artifacts at the cerebellar region.

Narrative review of patient-specific 3D visualization and reality technologies in skull base neurosurgery: enhancements in surgical training, planning, and navigation

Recent advances in medical imaging, computer vision, 3-dimensional (3D) modeling, and artificial intelligence (AI) integrated technologies paved the way for generating patient-specific, realistic 3D visualization of pathological anatomy in neurosurgical conditions. Immersive surgical simulations through augmented reality (AR), virtual reality (VR), mixed reality (MxR), extended reality (XR), and 3D printing applications further increased their utilization in current surgical practice and training. This narrative review investigates state-of-the-art studies, the limitations of these technologies, and future directions for them in the field of skull base surgery. We begin with a methodology summary to create accurate 3D models customized for each patient by combining several imaging modalities. Then, we explore how these models are employed in surgical planning simulations and real-time navigation systems in surgical procedures involving the anterior, middle, and posterior cranial skull bases, including endoscopic and open microsurgical operations. We also evaluate their influence on surgical decision-making, performance, and education. Accumulating evidence demonstrates that these technologies can enhance the visibility of the neuroanatomical structures situated at the cranial base and assist surgeons in preoperative planning and intraoperative navigation, thus showing great potential to improve surgical results and reduce complications. Maximum effectiveness can be achieved in approach selection, patient positioning, craniotomy placement, anti-target avoidance, and comprehension of spatial interrelationships of neurovascular structures. Finally, we present the obstacles and possible future paths for the broader implementation of these groundbreaking methods in neurosurgery, highlighting the importance of ongoing technological advancements and interdisciplinary collaboration to improve the accuracy and usefulness of 3D visualization and reality technologies in skull base surgeries.

Finite element analysis of stresses on the skull base caused by trauma during sinus lift with mallet and osteotome

Finite element analysis of stresses on the skull base caused by trauma during sinus lift with mallet and osteotome

Foramen Magnum Meningioma: An Example of Integrated Virtual Reality, Skull Base Laboratory, and Surgical Approach: 2-Dimensional Operative Video.

Foramen Magnum Meningioma: An Example of Integrated Virtual Reality, Skull Base Laboratory, and Surgical Approach: 2-Dimensional Operative Video.

Heterozygous mutations in the straitjacket region of the latency-associated peptide domain of TGFB2 cause Camurati-Engelmann disease type II.

Camurati-Engelmann disease (CED) is an autosomal dominant bone dysplasia characterized by progressive hyperostosis of the skull base and diaphyses of the long bones. CED is further divided into two subtypes, CED1 and CED2, according to the presence or absence of TGFB1 mutations, respectively. In this study, we used exome sequencing to investigate the genetic cause of CED2 in three pedigrees and identified two de novo heterozygous mutations in TGFB2 among the three patients. Both mutations were located in the region of the gene encoding the straitjacket subdomain of the latency-associated peptide (LAP) of pro-TGF-β2. Structural simulations of the mutant LAPs suggested that the mutations could cause significant conformational changes and lead to a reduction in TGF-β2 inactivation. An activity assay confirmed a significant increase in TGF-β2/SMAD signaling. In vitro osteogenic differentiation experiment using iPS cells from one of the CED2 patients showed significantly enhanced ossification, suggesting that the pathogenic mechanism of CED2 is increased activation of TGF-β2 by loss-of-function of the LAP. These results, in combination with the difference in hyperostosis patterns between CED1 and CED2, suggest distinct functions between TGFB1 and TGFB2 in human skeletal development and homeostasis.

Neurotrauma and Cerebrospinal Fluid in Homer's Poems

AbstractHomer's Iliad, from the 8th century BC, remains the oldest record of Greek medicine and a unique source of surgical history. The Odyssey, also authored by Homer, narrates several medically significant events. Among the 148 war traumas described in the Iliad, over a quarter occurred in the craniocervical region. Studies on the Odyssey report at least 11 craniocervical traumas, 9 of which prove fatal. Is there any indication of the presence of cerebrospinal fluid (CSF) in the cases described by Homer, considering its last mention was 800 years prior in the Egyptian surgical papyrus of Edwin Smith? A passage in the Iliad suggests that the “tears” Homer mentions in the eyes of Eumelos, resulting from trauma, might be due to CSF oculorrhea secondary to a skull base fracture. In Odyssey Book IX, when the Cyclops strikes the heads of two sailors, and fluid and cranial contents emerge, it can be inferred that the poet was aware of fluid in the head (CSF), as there is no mention of blood. It is proposed that 800 years after the writing of the Edwin Smith papyrus, Homer probably provides the second human observation of CSF associated with traumatic situations involving direct head blows.

Pituitary neuroadenoma as an ‘Incidentaloma’ in a case of road traffic accident

: Pituitary adenomas are the most common tumors found in the Sella region. Functional pituitary adenomas exhibit a wide range of endocrine manifestations due to either hypo- or hyperfunction of the pituitary gland, as well as mass effect. They can have a slow but severe impact on vision due to compression of the optic nerves, optic chiasm and cavernous sinus.: A 42-year-old male, a security guard at a local dabha, was struck by a van while crossing the road. He sustained a head injury and unfortunately passed away during treatment at our tertiary case institute. At autopsy, upon examination of the skull, a mass measuring 5x5x3cm was discovered in the suprasellar area of base of skull. This mass was sent for histopathological examination, which confirmed it to be a "Pituitary neuroendocrine tumor possibly gonadotropic in nature." However, the cause of death in this case was opined as ‘Head injury’.: Forensic pathologists rarely encounter intracranial neoplasms that present as sudden and unexpected deaths. The incidence of undiagnosed fatal brain tumors detected at autopsy has been reported to range between 0.02% and 0.4%. Several studies have investigated the relationship between hormonally active pituitary adenomas and both mental health disorders and quality of life. One study by Johnson et al. found that patients with nonfunctional adenomas reported impairments in physical and emotional well-being compared to the normal population. Headache and visual symptoms are most commonly associated with pituitary adenomas.In the present case, although it was an incidental finding and not contributing to the cause of death, we cannot underestimate the effect of the tumor on the visual acuity of the decedent. Nonetheless, visual impairment due to the tumor could also have partially led to the road traffic accident.

Predictors of Operative Ischemic Cerebrovascular Complications in Skull Base Tumor Resections: Experience in Low Resource Setting

Abstract Background Ischemic cerebrovascular complications following skull base tumor resections remain a significant factor impacting both short-term and long-term patient outcomes. This study aims to improve risk stratification, surgical decision-making and postoperative care protocols. Methodology A retrospective cohort study on predictors of ischemic cerebrovascular complications among patients who underwent skull base tumor resection was conducted at two high-volume neurosurgical centers in Ethiopia from 2018 - 2023. Binary logistic analysis was performed to see the association of each predictor variable. Result The study included 266 patients, with 65.5% being female. The median age and tumor size were 37 (±IQR=17) years and 4.9cm (± IQR 1.5) respectively. Ischemic cerebrovascular complications occurred in 19.9% of patients. Middle cranial fossa tumors and tumors spanning both anterior & middle cranial fossa (AOR = 6.75, 95% CI 1.66-27.54, p < 0.008), grade 3-5 vascular encasement (AOR = 5.04, 95% CI 1.79-14.12, p < 0.002), near-total resection and gross total resection (AOR = 2.89, 95% CI 1.01-8.24, p <0.048), and difficult hemostasis (AOR = 9.37, 95% CI 3.19-27.52, p < 0.000) were significantly associated with iatrogenic vascular injury. Sub-arachnoid hemorrhage had a statistically significant association with vasospasm (AOR = 12.27, 95% CI: 1.99-75.37, p = 0.007). Conclusion Surgery-related ischemic cerebrovascular complications are common. Thorough perioperative risk stratification and proactive treatment planning are crucial to mitigate vascular insults associated with it. In low-resource settings, neurosurgical services are provided without advanced instruments, leading to more complications. Therefore, it's important to focus on improving neurosurgical setup to enhance patient outcomes.

Development and Validation of a Novel Human-Fixed Cadaveric Model Reproducing Cerebrospinal Fluid Circulation for Simulation of Endoscopic Endonasal Skull Base Surgery.

Endoscopic endonasal surgery is a well-established surgical approach to the skull base. Surgeons need a reusable long-lasting tool to acquire the skills needed for skull base reconstruction. The aim of this study was to elaborate and validate a human formalin-fixed cadaveric model that reproduces a realistic cerebrospinal fluid (CSF) circulation and that adequately renders a CSF leak. An external ventricular drain that connects with a peristaltic pump is placed in the subarachnoid space, which allows a water circulation that reproduces CSF circulation. Intracranial pressure is measured in real time. Endoscopic endonasal skull base approaches are performed, to create different skull base openings and CSF leaks. Participants were tasked with reconstruction of the defects using a standardized multilayered approach, with the goal of obtaining a watertight closure under normal intracranial pressure ranges. Compiled data included time of reconstruction, years of experience of participants, and success/failure to achieve a watertight reconstruction. A Likert questionnaire was also used. The cadaveric model reproduced CSF circulation in 4 types of dural defects: sellar, suprasellar, transcribriform, and transclival. Intracranial pressures were similar to physiological conditions and were reproducible. Each model was tested multiple times, over several months. Success rates concurred with training levels (r = .8282 and P = .0017). A strong inverse correlation was also found between years of experience and time of reconstruction (r = .4977 and P < .0001). Participants agreed that the model was realistic (median Likert score of 4), and they strongly agreed that it allowed for the improvement of their surgical skills (median Likert score of 5). This novel human-fixed cadaveric model for CSF circulation is efficient and adequately reproduces surgical conditions for skull base approaches. The model is unique, easy to reproduce, and reusable. It can be used as a tool for teaching and for research purposes.

Determination of the optimal imaging protocol for [18F]PSMA-PET-CT for the detection of bone metastases in prostate cancer patients.

Prostate-specific membrane antigen-positron emission tomography (PSMA-PET) is a widely used diagnostic tool in patients with prostate cancer (PC).However, due to the limited availability of PET scanners and relevant acquisition costs, it is important to consider the indications and acquisition time.The aim of this investigation was to determine whether a PET scan from the skull base to the proximal thigh is sufficient to detect the presence of bone metastases. A retrospective analysis was conducted on 1050 consecutive [18F]PSMA-1007-PET-CT scans from the head to the proximal lower leg.The PET scans were categorised according to the presence and amount of bone metastases: (1) 1-5, (2) 6-19 and (3) ≥20. Additionally, the PET scans were evaluated for the presence of bone metastases below the proximal thigh as well as bone metastases above the skull base.Imaging results were compared to patients PSA values. Of the 391 patients with bone metastases, 146 (37.3%) exhibited metastases located below the proximal thigh and 104 (26.6%) above the skull base.The majority of bone metastases located below the proximal thigh (145, 99.3%) and above the skull base (94, 90.4%) were identified in patients with more than five bone metastases. No solitary distal metastasis was detected.The PSA value correlated significantly with number of bone metastases (e. g., 1-5 vs. ≥20 bone metastases, P < 0.001) and was significantly higher in patients with distal bone metastases (P < 0.001).ROC analysis showed that a PSA value of 11.15 ng/mL is the optimal cut-off for detecting bone metastases located below the proximal thigh, with an AUC of 0.919 (95% CI: 0.892-0.945, sensitivity 87%, specificity 86%).Similarly, the PSA value of 12.86 ng/mL is the optimal cut-off for detecting bone metastases above the skull base with an AUC of 0.904 (95% CI: 0.874-0.935, sensitivity 87%, specificity 83%). CONCLUSION: PSMA-PET acquisition protocols from the skull base to the proximal femur may be sufficient to accurately detect bone metastatic disease in PC. PSA values can provide decision support for individual PET acquisition protocols.

Navigating the Intersection Between the Orbit and the Skull Base: The "Mirror" McCarty Keyhole During Transorbital Approach: An Anatomic Study With Surgical Implications.

McCarty keyhole (MCK) is the most important entry point during orbitocranial and cranio-orbital approaches; nevertheless, its anatomic coordinates have never been detailedly described from transorbital perspective. To provide the spatial coordinates for intraorbital projection of the "mirror" MCK by using the well-established main anatomic-surgical bony landmarks met along transorbital corridor. MCK was identified in 15 adult dry skulls (30 sides) on exocranial surface of pterional region based on the well-defined external bony landmarks: on the frontosphenoid suture, 5 to 6 mm behind the joining point (JP) of frontozygomatic suture (FZS), frontosphenoid suture (FSS), and sphenozygomatic suture (SZS). A 1-mm burr hole was performed and progressively enlarged to identify the intracranial and intraorbital compartments. Exit site of the intraorbital part of burr hole was referenced to the FZS on the orbital rim, the superior orbital fissure, and the inferior orbital fissure and to the JP of FZS, FSS, and SZS. To electronically validate the results, 3-dimensional photorealistic and interactive models were reconstructed with photogrammetry. Finally, for a further validation, McCarty mirror keyhole was also exposed, based on results achieved, through endoscopic transorbital approach in 10 head specimens (20 sides). Intraorbital projection of MCK was identified on the FSS on intraorbital surface, 1.5 ± 0.5 mm posterior to JP, 11.5 ± 1.1 mm posterior to the FZS on orbital rim following the suture, 13.0 ± 1.2 mm from most anterior end of superior orbital fissure, 15.5 ± 1.4 mm from the most anterior end of the inferior orbital fissure in vertical line, on measurements under direct macroscopic visualization (mean ± SD). These values were electronically confirmed on the photogrammetric models with mean difference within 1 mm. To be aware of exact position of intraorbital projection of MCK during an early stage of transorbital approaches provides several surgical, clinical, and aesthetic advantages.

American Rhinologic Society expert practice statement part 2: Postoperative precautions and management principles following endoscopic skull base surgery.

The goal of this American Rhinologic Society expert practice statement (EPS) is to summarize the best available evidence regarding postoperative precautions for patients following endoscopic skull base surgery for intradural pathology. These topics include the administration of postoperative nasal hygiene; patient mobilization and activity level; the resumption of continuous positive airway pressure in patients with obstructive sleep apnea; and the timing and capacity with which a patient may be subjected to barotrauma, such as air travel postoperatively. This EPS was developed following the recommended methodology and approval process as previously outlined. Given the diverse practices and limited agreement on the accepted principles regarding postoperative precautions for patients following skull base surgery, this EPS seeks to summarize the existing literature and provide clinically relevant guidance to bring clarity to these differing practice patterns. Following a modified Delphi approach, four statements were developed, all of which reached consensus. Because of the paucity of literature on these topics, these statements represent a summation of the limited literature and the experts' opinions. These statements and the accompanying evidence are summarized below, along with an assessment of future needs.

Mystery of the Muenke midface: spheno-occipital synchondrosis fusion and craniofacial skeletal patterns.

The spheno-occipital synchondrosis (SOS) is an important site of endochondral ossification in the cranial base that closes prematurely in Apert, Crouzon, and Pfeiffer syndromes, which contributes to varying degrees of midface hypoplasia. The facial dysmorphology of Muenke syndrome, in contrast, is less severe with low rates of midface hypoplasia. We thus evaluated the timing of SOS fusion and cephalometric landmarks in patients with Muenke syndrome compared to normal controls. Patients with Muenke syndrome who had at least one fine-cut head computed tomography scan performedfrom 2000 to 2020 were retrospectively reviewed. A case-control study was performed of patient scans and age- and sex-matched control scans. SOS fusion status was evaluated as open, partially closed, or closed. We included 28 patients and compared 77 patient scans with 77 control scans. Kaplan-Meier analysis demonstrated an insignificantly earlier timeline of SOS fusion in Muenke syndrome (p = 0.300). Mean sella-orbitale (SO) distance was shorter (44.0 ± 6.6 vs. 47.7 ± 6.7 mm, p < 0.001) and mean sella-nasion-Frankfort horizontal (SN-FH) angle was greater (12.1° ± 3.8° vs. 10.1° ± 3.2°, p < 0.001)in the Muenke group, whereas mean sella-nasion-A point (SNA) angle was similar and normal (81.1° ± 5.7° vs. 81.4° ± 4.7°, p = 0.762). Muenke syndrome is characterized by mild and often absent midfacial hypoplasia, with the exception of slight retropositioning of the infraorbital rim. Interestingly, SOS fusion patterns in these patientsare not significantly different from age- and sex-matched controls despite an increased odds of fusion. It is possible that differences in timing of SOS fusion may manifest phenotypically at the infraorbital rim rather than atthe maxilla.

Pilot Program in Surgical Anatomy Education for Complex Cranial and Skull Base Procedures: Curriculum Overview &amp; Initial 2-Year Experience at Mayo Clinic

Pilot Program in Surgical Anatomy Education for Complex Cranial and Skull Base Procedures: Curriculum Overview &amp; Initial 2-Year Experience at Mayo Clinic

Imaging features of pediatric meningiomas: emphasis on unusual locations.

This article aims to analyze pediatric meningioma's imaging characteristics, especially those in unusual locations. Pediatric patients with pathologically confirmed meningiomas at our hospital from January 2010 to January 2024 were enrolled. Meningiomas located in the cerebral convexity, parasagittal falcine region, anterior skull base, middle skull base, sphenoid ridge, cerebellopontine angle (CPA), olfactory groove, or juxtasella were considered in usual locations. Meningiomas found in other areas were considered in unusual locations. Clinical information, pathology results, and imaging features of pediatric meningiomas in usual and usual locations were analyzed and compared. A total of 18 patients (19 meningiomas) were enrolled, including 14 males and 4 females, with an average age of 14years (ranging from 6 to 18years). A total of 12 (63.2%) meningiomas were in the unusual location, including four (33.3%) were intraparenchymal, four (33.3%) were intraventricular, two (16.7%) were intraosseous, one (8.3%) case was in the paranasal sinus, and one (8.3%) was intraspinal. The meningiomas in unusual locations usually lacked the meningeal tail sign, and the misdiagnosis rate on preoperative imaging was significantly higher than that of meningiomas in usual locations. Pediatric meningiomas are prone to occur in unusual locations. When they occur in usual locations, they often lack typical radiographic features of meningiomas, leading to potential misdiagnosis before surgery. Recognition of the imaging characteristics of meningiomas in unusual locations in children may facilitate accurate preoperative imaging diagnosis.

Wartime penetrating skull base trauma with unpredictable internal fragment ricochet and migration: illustrative case.

Transnasal transsphenoidal penetrating craniocerebral injury is very rare even in wartime. Cases with good outcomes are even less common. A 20-year-old male sustained multiple fragment wounds to his head and face from a landmine explosion. One metal fragment entered his right nostril, traversed the nasal septum and anterior sphenoid sinus, and ricocheted superiorly off the clivus. The fragment then traveled almost to the surface of the left parietal lobe. Subsequently, under its own weight, it migrated back down its original track. The patient suffered cerebrospinal fluid rhinorrhea, pneumocephalus, and right-sided hemiparesis. Digital subtraction angiography was followed by microscopic transnasal skull base reconstruction supplemented by external lumbar drainage. Follow-up brain computed tomogrpahy showed further metallic fragment migration through the ventricular system. The fragment was removed through a transcortical approach. The patient's neurological examination and brain magnetic resonance imaging results demonstrated good recovery. The absence of external signs of deep injuries does not exclude the presence of a penetrating craniocerebral injury. Metal fragments may undergo ricochet and internal migration in both the brain parenchyma and the ventricular system. Timely diagnosis including three-dimensional reconstruction of a projectile's trajectory may facilitate appropriate surgical planning in complex cases. Intraventricular fragment migration may necessitate microsurgical removal. https://thejns.org/doi/10.3171/CASE24128.

Endoscopic and exoscopic surgery for brain tumors.

Nerves and blood vessels must be protected during brain tumor surgery, which has traditionally relied on microscopes. In the 2000s, endoscopes and related equipment were developed for neurosurgery. In this review, we aim to outline the role of endoscopes in brain tumor surgery and discuss the emerging use of exoscopes. The primary use of endoscopes in brain tumor surgery is in endoscopic endonasal surgery for pituitary tumors. By using the space within the sphenoid sinus, surgeons can insert an endoscope and instruments such as forceps or scissors through the nose to access and remove the tumor. Compared to microscopes, endoscopes can get closer to tumors, nerves, and blood vessels. They enable wide-angle observation of the skull base, making them valuable for skull base tumors as well as pituitary tumors. Endoscopes are also used in cases where a brain tumor is associated with hydrocephalus, allowing surgeons to correct obstructive hydrocephalus and perform tumor biopsies simultaneously. Exoscopy, a newer technique introduced in recent years, involves surgeons wearing special glasses and removing the tumor while viewing a three-dimensional monitor. This approach reduces surgeon fatigue and allows for more natural positioning during lengthy brain tumor surgeries. Future brain tumor surgeries will likely involve robotic surgery, which is already used for other organs. This is expected to make brain tumor removal safer and more accurate.

Radiological differentiation between bacterial orbital cellulitis and invasive fungal sino-orbital infections.

Invasive fungal orbital infections (IFOI) may be difficult to differentiate from sinogenic bacterial orbital cellulitis (OC). This study investigates the features differentiating OC from IFOI on magnetic resonance imaging (MRI). Retrospective study of adult patients with sinogenic OC and IFOI with pre-intervention MRI. Patients without post-septal involvement, non-sinogenic OC (e.g.: secondary to trauma) and poor-quality scans were excluded. Independent Sample's t test and Fisher's exact test were conducted with p < 0.05 deemed statistically significant. Eleven cases each of OC (Mean age: 41.6 ± 18.4years-old, Male: 10) and IFOI (Mean age: 65.0 ± 16.6years-old, Male: 9) between 2006 and 2023. IFOI patients were older, more likely immunocompromised and had a lower mean white-cell count (p value = 0.005, 0.035 and 0.017, respectively). The ethmoid and maxillary sinuses were most commonly involved in both entities. Pre-septal and lacrimal gland involvement were more common in OC (p = 0.001 and 0.008, respectively). Infiltrative OC orbital lesions were poorly demarcated, whilst those in IFOI were expansile/mass-like invading the orbit from the adjacent paranasal sinuses. Specific IFOI features included loss-of-contrast-enhancement (LoCE) of paranasal sinus tissues with orbital extension. Extra-orbital and -sinonasal extension indicative of IFOI included contiguous skull base or pterygopalatine fossa involvement, retro-antral and masticator space stranding and vasculitis. This study describes the key MRI features of IFOI including differentiating markers from OC. These specific features, such as LoCE of the paranasal and orbital soft tissues, the location and pattern of contiguous soft-tissue involvement, provide expedient identification of IFOI which necessitate early surgical intervention for microbiological confirmation of an invasive fungal pathology.

Surgical treatment of torticollis secondary to the presence of a congenital paracondylar process: illustrative case.

A paracondylar process is an abnormal bony exostosis arising from the skull base lateral to the occipital condyle and extending inferiorly toward the transverse process of the atlas. Paracondylar processes are typically identified incidentally and vary in size from a small protuberance to an elongated process. The authors present the first pediatric case of torticollis secondary to a congenital paracondylar process successfully treated with resection of the paracondylar process and sternocleidomastoid release. Cadaveric dissection, three-dimensional models, intraoperative imaging guidance, and multidisciplinary collaboration were paramount to a successful surgical outcome. https://thejns.org/doi/10.3171/CASE2447.

Surgical treatment of torticollis secondary to the presence of a congenital paracondylar process: illustrative case.

A paracondylar process is an abnormal bony exostosis arising from the skull base lateral to the occipital condyle and extending inferiorly toward the transverse process of the atlas. Paracondylar processes are typically identified incidentally and vary in size from a small protuberance to an elongated process. The authors present the first pediatric case of torticollis secondary to a congenital paracondylar process successfully treated with resection of the paracondylar process and sternocleidomastoid release. Cadaveric dissection, three-dimensional models, intraoperative imaging guidance, and multidisciplinary collaboration were paramount to a successful surgical outcome. https://thejns.org/doi/10.3171/CASE2447.