Improved optic nerve visualization and treatment planning through a dedicated optic nerve MRI protocol.

OBJECTIVE: This study describes an innovative optic nerve MRI protocol for better delineating optic nerve anatomy from neighboring pathology. METHODS: Twenty-two patients undergoing MRI examination of the optic nerve with the dedicated protocol were identified and included for analysis of imaging, surgical strategy, and outcomes. T2-weighted and fat-suppressed T1-weighted gadolinium-enhanced images were acquired perpendicular and parallel to the long axis of the optic nerve to achieve en face and in-line views along the course of the nerve. RESULTS: Dedicated optic nerve MRI sequences provided enhanced visualization of the nerve, CSF within the nerve sheath, and local pathology. Optic nerve sequences leveraged the "CSF ring" within the optic nerve sheath to create contrast between pathology and normal tissue, highlighting areas of compression. Tumor was readily tracked along the longitudinal axis of the nerve by images obtained parallel to the nerve. The findings augmented treatment planning. CONCLUSIONS: The authors present a dedicated optic nerve MRI protocol that is simple to use and affords improved cross-sectional and longitudinal visualization of the nerve, surrounding CSF, and pathology. This improved visualization enhances radiological evaluation and treatment planning for optic nerve lesions.

Surgical management of symptomatic hemangioma of the geniculate ganglion: fascicular-sparing resection or grafting?

Geniculate ganglion hemangioma (GGH) is rarely presented in the neurosurgical literature. It extends extradurally on the middle fossa floor and displaces the intratemporal part of the facial nerve. Surgical treatment is advisable at early symptoms. Proposed techniques include fascicular-sparing resection or nerve interruption with grafting. No definitive conclusions exist about the superiority of a certain technique in preserving facial nerve integrity and function. Through the description of a surgically managed symptomatic GGH, we herein discuss literature data about the surgical results of fascicular-sparing resection versus grafting. A PRISMA-based literature search was performed on the PubMed database. Only articles in English and published since 1990 were selected and furtherly filtered based on the best relevance. Statistical comparisons were performed with ANOVA. One hundred sixteen GGHs were collected, 56 were treated by fascicular-sparing resection, and 60 were treated by grafting. The facial function was improved, or unchanged, in 53 patients of the fascicular-sparing group and 30 patients of the grafting one. Sixty-five patients achieved a good (House-Brackmann (HB) grade III) postoperative facial outcome, of which 47 and 18 belonged to the fascicular-sparing and grafting group, respectively. Greater efficacy of the fascicular-sparing technique in the achievement of a better facial outcome was found (p = 0.0014; p = 0.0022). A surgical resection at the earliest symptoms is critical to preserve the facial nerve function in GGHs. Fascicular-sparing resection should be pursued in symptomatic cases with residual facial function (I-III HB). Conversely, grafting has a rationale for higher HB grades (V-VI). Broader studies are required to confirm these findings and turn them into new therapeutic perspectives.

Creation of a novel trigeminal tractography atlas for automated trigeminal nerve identification.

Diffusion MRI (dMRI) tractography has been successfully used to study the trigeminal nerves (TGNs) in many clinical and research applications. Currently, identification of the TGN in tractography data requires expert nerve selection using manually drawn regions of interest (ROIs), which is prone to inter-observer variability, time-consuming and carries high clinical and labor costs. To overcome these issues, we propose to create a novel anatomically curated TGN tractography atlas that enables automated identification of the TGN from dMRI tractography. In this paper, we first illustrate the creation of a trigeminal tractography atlas. Leveraging a well-established computational pipeline and expert neuroanatomical knowledge, we generate a data-driven TGN fiber clustering atlas using tractography data from 50 subjects from the Human Connectome Project. Then, we demonstrate the application of the proposed atlas for automated TGN identification in new subjects, without relying on expert ROI placement. Quantitative and visual experiments are performed with comparison to expert TGN identification using dMRI data from two different acquisition sites. We show highly comparable results between the automatically and manually identified TGNs in terms of spatial overlap and visualization, while our proposed method has several advantages. First, our method performs automated TGN identification, and thus it provides an efficient tool to reduce expert labor costs and inter-operator bias relative to expert manual selection. Second, our method is robust to potential imaging artifacts and/or noise that can prevent successful manual ROI placement for TGN selection and hence yields a higher successful TGN identification rate.

Brachytherapy with surgical resection as salvage treatment for recurrent high-grade meningiomas: a matched cohort study.

PURPOSE: To evaluate surgical resection with brachytherapy placement as a salvage treatment in patients with recurrent high-grade meningioma who exhausted prior external beam treatment options. METHODS: Single-center retrospective review of our institutional experience of brachytherapy implantation from 2012 to 2018. The primary outcome of the study was progression free survival (PFS). Secondary outcomes included overall survival (OS) and complications. A matched cohort of patients not treated with brachytherapy over the same time period was evaluated as a control group. All patients had received prior radiation treatment and underwent planned gross total resection (GTR) surgery. RESULTS: A total of 27 cases were evaluated. Compared with prior treatment, brachytherapy implantation demonstrated a statistically significant improvement in tumor control [HR 0.316 (0.101 - 0.991), p = 0.034]. PFS-6 and PFS-12 were 92.3% and 84.6%, respectively. Compared with the matched control cohort, brachytherapy treatment demonstrated improved PFS [HR 0.310 (0.103 - 0.933), p = 0.030]. Overall survival was not statistically significantly different between groups [HR 0.381 (0.073 - 1.982), p = 0.227]. Overall postoperative complications were comparable between groups, although there was a higher incidence of radiation necrosis in the brachytherapy cohort. CONCLUSION: Brachytherapy with planned GTR improved PFS in recurrent high-grade meningioma patients who exhausted prior external beam radiation treatment options. Future improvement of brachytherapy dose delivery methods and techniques may continue to prolong control rates and improve outcomes for this challenging group of patients.

Clinical applications of dynamic CT angiography for intracranial lesions.

BACKGROUND: Dynamic CT angiography (dCTA) augments traditional CTA with temporal resolution and has been demonstrated to influence operative planning in skull base surgery. METHODS: Three hundred twenty-five dynamic CTA cases from a single institution were reviewed for indication of study, findings, and comparison to other modalities of imaging. RESULTS: The most frequent application of dCTA was pre-operative surgical planning (59.4%); resection of skull base tumors represented the majority of these pre-operative studies (93.3%). It was also used to evaluate new neurological symptoms (20.9%). Of these, the most common symptoms prompting a dCTA study included headache (22.1%) and visual field deficit (11.8%). The most commonly visualized vascular lesions were partial (22.9%) and complete vascular occlusions (9.0%). Dynamic CTA has also been useful in post-operative imaging for vascular malformations (9.5%) and tumors (2.5%). Finally, dCTA was employed to evaluate ambiguous abnormal findings observed on other imaging modalities (7.7%). Cerebral dCTA ruled out inconclusive abnormal vascular findings visualized on other imaging modalities (64.0%) more frequently than it confirmed them (32.0%), and was inconclusive in a singular case (4.0%). CONCLUSIONS: Cerebral dCTA is an evolving new technology with a diverse spectrum of potential applications. In addition to its role in guiding pre-operative planning for skull base surgical cases, dynamic CTA offers excellent spatial and temporal resolution for assessment of vascular lesions.

Combined petrosal approach for petroclival meningioma.

The authors present the case of a 56-year-old patient who presented with a large petroclival meningioma and clinical symptoms of brainstem compression and hydrocephalus. The authors describe a two-stage combined petrosal approach for complete resection of the tumor. The nuances of the approach and microsurgical technique are discussed, as well as the radiographic and clinical outcomes. The video can be found here: https://youtu.be/JxoTXS-uiHM .

The frequency and severity of intracranial hypotension post-intraoperative lumbar drainage using a Tuohy needle and the traditional needle.

Background Intraoperative lumbar cerebrospinal fluid (CSF) drainage is a well-recognised technique in cranial and vascular surgery. The goal of the study was to assess the frequency and severity of intracranial hypotension post-intraoperative lumbar drainage performed using two different techniques, a 14G Tuohy needle versus an 18G traditional needle. Methods The medical records and imaging studies of 94 patients who had undergone open cranial operation were retrospectively studied: 47 patients had intraoperative lumbar drainage and 47 patients did not. A 14G Tuohy needle was employed in 27 (57.4%) patients and an 18G traditional needle was employed in 20 (42.6%) patients. Results There were signs of intracranial hypotension on MR images in nine (19.1%) patients who had intraoperative lumbar CSF drainage; none of the patients in the control group exhibited the MR signs of intracranial hypotension. A 14G needle was used in 6/9 patients and resulted in severe complications: one patient developed a delayed intracranial epidural hematoma that required emergency evacuation and a blood patch. Another patient developed somnolence that required two epidural blood patches and a third patient had protracted headaches. The 18G needle was used in the remaining 3/9 patients who were asymptomatic or presented with mild headaches. Conclusion The use of the smaller 18G traditional needle was associated with better outcomes with regards to intracranial hypotension, and the frequency of severe complications was higher with the use of the 14G Tuohy needle.

Extent of resection and overall survival for patients with atypical and malignant meningioma.

BACKGROUND: The prognosis for patients with atypical and malignant meningioma is guarded; whether the extent of resection is associated with survival-based outcomes in this population remains poorly defined. This study investigated the association between gross total resection (GTR) and all-cause mortality in patients with atypical and malignant meningioma. METHODS: The Surveillance, Epidemiology, and End Results program was used to identify 575 and 64 patients betweens the ages of 18 and 70 years who were diagnosed with atypical and malignant meningioma, respectively, between 2004 and 2009. Multivariate Cox proportional hazards regression was used to assess the adjusted impact of GTR versus subtotal resection on all-cause mortality. RESULTS: Baseline patient characteristics were similar for patients who did undergo GTR and patients who did not undergo GTR. The 5-year overall survival rates were 91.3% (95% confidence interval [CI], 86.2%-94.5%) and 78.2% (95% CI, 70.0%-84.3%) for patients with atypical meningioma who did and did not undergo GTR, respectively, and 64.5% (95% CI, 45.9%-78.1%) and 41.1% (95% CI, 17.9%-63.1%) for patients with malignant meningioma who did and did not undergo GTR, respectively. After adjustments for available, pertinent confounding variables, GTR was associated with lower all-cause mortality in patients with atypical (hazard ratio, 0.39; 95% CI, 0.23-0.67; P < .001) and malignant meningioma (hazard ratio, 0.35; 95% CI, 0.15-0.81; P = .01). CONCLUSIONS: The extent of resection is a powerful predictor of outcome for patients with atypical and malignant meningioma. These data highlight the hazard associated with the presence of gross tumor bulk after surgery and suggest a value for more extensive resections that should be balanced against the additional potential morbidity.

Brachytherapy in the treatment of recurrent aggressive falcine meningiomas.

Recurrent aggressive falcine meningiomas are uncommon tumors that recur despite receiving extensive surgery and radiation therapy (RT). We have utilized brachytherapy as a salvage treatment in two such patients with a unique implantation technique. Both patients had recurrence of WHO Grade II falcine meningiomas despite multiple prior surgical and RT treatments. Radioactive I-125 seeds were made into strands and sutured into a mesh implant, with 1 cm spacing, in a size appropriate to cover the cavity and region of susceptible falcine dura. Following resection the vicryl mesh was implanted and fixed to the margins of the falx. Implantation in this interhemispheric space provides good dose conformality with targeting of at-risk tissue and minimal radiation exposure to normal neural tissues. The patients are recurrence free 31 and 10 months after brachytherapy treatment. Brachytherapy was an effective salvage treatment for the recurrent aggressive falcine meningiomas in our two patients.

Supracerebellar "Flyover" Approach to Dumbbell Falcotentorial Meningioma Encasing the Galenic Venous System.

Falcotentorial meningiomas involve the tentorial apex and straight sinus, posing challenges when encasing the galenic venous system.1 Microneurosurgery is considered the best treatment option for large falcotentorial meningiomas because it provides a definitive cure.2 In contrast, Gamma Knife surgery mainly allows the control of smaller or residual tumors after microsurgical resection.3 Approach selection between interhemispheric supratentorial versa supracerebellar transtentorial is dictated by the displacement of the Galen vein.1,4-8Video 1 describes the critical surgical steps of the supracerebellar "flyover" approach for a Bassiouni type II dumbbell falcotentorial meningiomas encasing the galenic venous system. Preoperative embolization was ruled out due to potential additional morbidity and mortality risks.9,10 A perimedian supracerebellar infratentorial transtentorial approach was performed with the patient in ¾ prone Concorde position. After early devascularization and division of the tentorium, the meningioma was internally debulked while preserving the arachnoid plane. The posterior choroidal arteries, internal cerebral veins, basal veins of Rosenthal, and vein of Galen were carefully dissected, and the tumor was completely resected. The patient was discharged on postoperative day 3 with no deficits. Postoperative magnetic resonance imaging confirmed a Simpson grade 1 resection. Pathology revealed a grade 2 meningioma. The patient remained asymptomatic with no recurrence at a 10-year follow-up. The reported case demonstrates that the most critical factor in the choice of approach to midline dumbbell falcotentorial meningiomas is the relationship of the tumor to the galenic venous system and its tributaries.

neuroGPT-X: toward a clinic-ready large language model.

OBJECTIVE: The objective was to assess the performance of a context-enriched large language model (LLM) compared with international neurosurgical experts on questions related to the management of vestibular schwannoma. Furthermore, another objective was to develop a chat-based platform incorporating in-text citations, references, and memory to enable accurate, relevant, and reliable information in real time. METHODS: The analysis involved 1) creating a data set through web scraping, 2) developing a chat-based platform called neuroGPT-X, 3) enlisting 8 expert neurosurgeons across international centers to independently create questions (n = 1) and to answer (n = 4) and evaluate responses (n = 3) while blinded, and 4) analyzing the evaluation results on the management of vestibular schwannoma. In the blinded phase, all answers were assessed for accuracy, coherence, relevance, thoroughness, speed, and overall rating. All experts were unblinded and provided their thoughts on the utility and limitations of the tool. In the unblinded phase, all neurosurgeons provided answers to a Likert scale survey and long-answer questions regarding the clinical utility, likelihood of use, and limitations of the tool. The tool was then evaluated on the basis of a set of 103 consensus statements on vestibular schwannoma care from the 8th Quadrennial International Conference on Vestibular Schwannoma. RESULTS: Responses from the naive and context-enriched Generative Pretrained Transformer (GPT) models were consistently rated not significantly different in terms of accuracy, coherence, relevance, thoroughness, and overall performance, and they were often rated significantly higher than expert responses. Both the naive and content-enriched GPT models provided faster responses to the standardized question set than expert neurosurgeon respondents (p < 0.01). The context-enriched GPT model agreed with 98 of the 103 (95%) consensus statements. Of interest, all expert surgeons expressed concerns about the reliability of GPT in accurately addressing the nuances and controversies surrounding the management of vestibular schwannoma. Furthermore, the authors developed neuroGPT-X, a chat-based platform designed to provide point-of-care clinical support and mitigate the limitations of human memory. neuroGPT-X incorporates features such as in-text citations and references to enable accurate, relevant, and reliable information in real time. CONCLUSIONS: The present study, with its subspecialist-level performance in generating written responses to complex neurosurgical problems for which evidence-based consensus for management is lacking, suggests that context-enriched LLMs show promise as a point-of-care medical resource. The authors anticipate that this work will be a springboard for expansion into more medical specialties, incorporating evidence-based clinical information and developing expert-level dialogue surrounding LLMs in healthcare.

Fascicular-Sparing Technique for Resection of Cerebellopontine Angle Facial Nerve Schwannoma.

Surgery of cerebellopontine angle (CPA) facial nerve schwannoma (FNS) in patients with good facial nerve function is a challenge.1-10Video 1 highlights the fascicular-sparing technique for resection of a CPA FNS. A 41-year-old male patient symptomatic with persistent headaches and tinnitus underwent a retrosigmoid approach for a right cystic CPA tumor, presumed vestibular schwannoma. Intraoperatively, the facial nerve was identified as fine multiple strands splayed around the perimetry of the tumor, which elicited a motor response at a low threshold stimulation. This finding led to the intraoperative diagnosis of FNS according to the reported criteria.5 Neuromonitoring-assisted fascicular-sparing resection technique was performed. It involved the gradual separation of the uninvolved nerve fibers using a fine-stimulating dissector at a threshold of 0.2 mA. Entry into the tumor was at a stimulation silent cyst. The tumor was debulked with preservation of the endoneurium and pulse irrigation hemostasis. A near-total resection was performed. The patient was discharged on the second postoperative day with a House-Brackman III facial nerve deficit. The deficit remained stable during the following annual follow-up visits. Resection of CPA FNS is indicated at the earliest sign of deficit. However, it might be encountered as masquerading at the surgery of an acoustic tumor. The fascicular-sparing technique is critical in avoiding injuries to the endoneurium during the resection and with the ability to preserve function. The sparing of endoneurium avoids collagenization, fibrosis, and ischemia of the nerve, which are known to be the pathologic substrate of worse functional outcomes.

The Party Wall: Redefining the Indications of Transcranial Approaches for Giant Pituitary Adenomas in Endoscopic Era.

The evolution of endoscopic trans-sphenoidal surgery raises the question of the role of transcranial surgery for pituitary tumors, particularly with the effectiveness of adjunct irradiation. This narrative review aims to redefine the current indications for the transcranial approaches for giant pituitary adenomas in the endoscopic era. A critical appraisal of the personal series of the senior author (O.A.-M.) was performed to characterize the patient factors and the tumor's pathological anatomy features that endorse a cranial approach. Traditional indications for transcranial approaches include the absent pneumatization of the sphenoid sinus; kissing/ectatic internal carotid arteries; reduced dimensions of the sella; lateral invasion of the cavernous sinus lateral to the carotid artery; dumbbell-shaped tumors caused by severe diaphragm constriction; fibrous/calcified tumor consistency; wide supra-, para-, and retrosellar extension; arterial encasement; brain invasion; coexisting cerebral aneurysms; and separate coexisting pathologies of the sphenoid sinus, especially infections. Residual/recurrent tumors and postoperative pituitary apoplexy after trans-sphenoidal surgery require individualized considerations. Transcranial approaches still have a critical role in giant and complex pituitary adenomas with wide intracranial extension, brain parenchymal involvement, and the encasement of neurovascular structures.

Comparative Anatomic Study Between Intradural Suboccipital Retrosigmoid and Extradural Transzygomatic Middle Fossa Approaches to Expose the Trigeminal Nerve.

BACKGROUND: Meckel cave tumors are relatively rare, especially trigeminal nerve (TN) schwannomas. These tumors frequently project through the trigeminal pore, occupying the middle and posterior fossae. The most used routes to this region are the suboccipital retrosigmoid intradural approach (SORSA) and the transzygomatic middle fossa approach (TZMFA). Both approaches allow further exposure by adding intraoperative techniques, such as removing the suprameatal tubercle (retrosigmoid intradural suprameatal approach [RISA]) and the petrous apex (TZMFA-PA), respectively. This study aims to understand how TN exposure differs between both surgical approaches and how it increases by adding specific surgical maneuvers to these techniques. METHODS: Five formalin-fixed adult cadaver heads were submitted to high-resolution computed tomography and their images were loaded into the neuronavigation device. Anatomic key points were defined along the outline of the TN, and their three-dimensional spatial locations were collected following each surgical approach. This process allowed the calculation of the TN exposed area obtained through each technique. RESULTS: The mean areas of exposure of the TN were 125.9 mm2 with SORSA and 208.9 mm2 with RISA, which represents an additional mean gain of 61.92% (P = 0.047). Using TZMFA, a mean exposure of 419.24 mm2 was obtained. When TZMFA-PA was used, the mean exposed area was 486.03 mm2, representing a mean gain in the exposure area of 16.81% (P = 0.072). CONCLUSIONS: Our study suggests that TZMFA allows better exposure of TN ganglionic and postganglionic segments, and the removal of the PA adds the preganglionic segment visualization, although with less TN exposed area compared with RISA. With SORSA, the additional suprameatal tubercle removal shows the trigeminal pore and the medial margin of the central portion of the TN ganglionic segment, making it possible to expose the mouth of the Meckel cave and part of its contents.

Petrosal approaches to brainstem cavernous malformations.

OBJECT: Although they provide excellent ventral and lateral exposure of the brainstem, petrosal approaches to brainstem cavernous malformations (CMs) are infrequently reported. METHODS: The authors reviewed their experience with petrosal approaches to brainstem CMs in combination with a comprehensive review of the literature to elucidate resection rates, complication rates, and outcomes. RESULTS: Including their own results, the authors found 65 cases in 20 reports of brainstem CMs treated with petrosal approaches. The specific approaches were posterior petrosal in 37 cases (57%), anterior petrosal in 17 (26%), extended posterior petrosal in 10 (15%), and a combined petrosal approach in 1 case (2%). For 50 cases in 16 reports with detailed outcome information, the overall complete resection rate was 90%, with early postoperative morbidity reported in 30% of cases and permanent morbidity in 14%. The rate of CSF leakage was 6%. CONCLUSIONS: The versatile petrosal approaches to brainstem CMs are associated with good outcomes and an acceptable morbidity rate. More expansive lesions can be approached using a combination of the standard anterior and posterior petrosal approach, preserving hearing and avoiding the greater complication rates associated with extended posterior petrosal approaches.

Evolution of the posterior petrosal approach.

In this article, the authors review the history of the posterior petrosal approach. The early foundation of the retrolabyrinthine lateral petrosectomy has its roots in the otolaryngology literature. These early approaches were limited in exposure by the tentorium superiorly and the sigmoid sinus posteriorly. Although the concept of a transtentorial approach was originally combined with a complete labyrinthectomy, Hakuba and colleagues described the expansive exposure afforded by sectioning the tentorium and superior petrosal sinus and mobilizing a skeletonized sigmoid sinus. This maneuver serves as the key step in allowing for the full, combined supra- and infratentorial exposure that the posterior petrosal approach provides. In contrast to Hakuba et al.'s approach, which used a partial labyrinthectomy, modern approaches often preserve the entire labyrinth (retrolabyrinthine approach). For added exposure, the latter can be combined with the anterior petrosal approach, allowing for the preservation of hearing and an enhanced view of the surgical target. The authors review the evolution of the petrosal approach and highlight its applicability.

Petrosal approaches to posterior circulation aneurysms.

Complex posterior circulation aneurysms are formidable lesions with an abysmal natural history. Their management continues to present a challenge to both endovascular and open microsurgical approaches. Affording an expansive, combined supra- and infratentorial exposure, the petrosal approaches are well suited for these challenging lesions when located along the basilar trunk or at a low-lying basilar apex. This report evaluates the evolution and application of petrosal approaches to these lesions. Excluding transsigmoid, infratentorial, or labyrinth-sacrificing approaches, the authors found 23 reports with 61 posterior circulation aneurysms treated via a petrosal approach. Although early morbidity was not negligible, rates of aneurysm occlusion (95% overall) and long-term outcome were quite laudable in light of the challenge posed by these lesions. Moreover, with accumulating experience with petrosal approaches, rates of complications are likely to wane, as neurosurgeons capitalize on the expansive exposure afforded by these indispensable approaches.

The Utilization of the Cranio-Orbital Zygomatic Approach for the Resection of Juvenile Nasopharyngeal Angiofibroma: 2-Dimensional Operative Video.

Juvenile angiofibroma is a rare benign expansive lesion typically affecting young men. Surgery is the current mainstay of treatment. Because it is a very vascular lesion, preoperative transarterial embolization can decrease intraoperative bleeding.1,2 Transmaxillary or transpalatal approaches were used for totally extracranial lesions. Endonasal endoscopic resection became wildly used for radical excision with limited morbidity.2 In large lesions with intracranial extension and cavernous sinus involvement (Fisch type 4), purely anterior approaches (endoscopic or transmaxillary) can be associated with significant carotid artery and cranial nerves injuries and excessive hemorrhage from internal carotid artery supply that cannot be eliminated by preoperative embolization.3 Subtotal resection has been preconized in such cases, but tumor progression, cranial nerves and vision compromise, and major nasal postoperative bleeding could ensue. Radiotherapy of residual tumor has been associated with long-term complications, particularly given the young age of these patients.2 The cranio-orbital zygomatic approach provides an excellent exposure to the extensions into the middle fossa, anterior fossa, cavernous sinus, paranasal sinus, and infratemporal fossa components of large angiofibromas.4-6 It is particularly advantageous in the early interruption of the cavernous carotid feeders that are not amenable to safe embolization, rendering the tumor devascularized and bloodlessly resected. This article demonstrates the details and the advantages of this approach in a 13-year-old adolescent boy operated in 1997 for giant juvenile angiofibroma with extension in the middle fossa and the parasellar space with major vascularization from the cavernous carotid artery. The guardian consented to the procedure and publication of images. Image at 3:05 reprinted with permission from Al-Mefty O, Operative Atlas of Meningiomas. Vol 1, © LWW, 1998. Image at 3:25 from Arnautovic KI, Al-Mefty O, Angtuaco E. A combined microsurgical skull-base and endovascular approach to giant and large paraclinoid aneurysms. Surg Neurol. 1998;50(6):504-520; © Elsevier, 1998. Used with permission. Image at 9:21 reprinted from Kempe LG and Krekorian EA,6 with permission from John Wiley and Sons, © 1969 The Triological Society.