Exo- and endoscopic lateral orbital wall approach for the medial temporal lobe glioma: how I do it.

BACKGROUND: The endoscopic transorbital approach provides a direct access to the medial temporal lobe (MTL). However, when excising a highly vascular tumour, a wider access route that enables the concurrent use of standard neurosurgical instruments with both hands is preferable. METHOD: We described the concept and technique of the lateral orbital wall approach (LOWA), which comprises orbitotomy and mini-craniotomy to treat MTL lesions using an exoscope and endoscope. CONCLUSION: The LOWA provides a safe and natural surgical corridor to the MTL and enables 2- or 3-hand surgery. Hence, LOWA can potentially improve safety and efficiency to treat MTL lesions.

Exo- and endoscopic two-step approach for meningeal tumours invading the lateral wall of large dural venous sinuses: how I do it.

BACKGROUND: Treating meningeal tumours invading the large dural venous sinuses is a subject of debate regarding the approach for removing the intra-sinus components. Additionally, directly observing the invasion site of tumours invading the lateral wall of the sinus is difficult. METHOD: We describe our exo- and endoscopic two-step approach (EETA): an exoscope is used to remove the extra-sinus component, while an endoscope is used to observe the invaded lateral wall and remove the intra-sinus component. CONCLUSION: EETA can be a viable option for treating meningeal tumours invading the venous sinus owing to its high resection rate and low invasiveness.

Suprapterional keyhole approach for anteromedial skull base lesions: How I do it.

BACKGROUND: For a minimally invasive treatment approach to the anteromedial part of the anterior cranial fossa (ACF), a small incision and craniotomy of the posterolateral part of the ACF are preferable. METHOD: We described the concept and technique of suprapterional keyhole approach (SPKA), which uses an exoscope and endoscope to treat ACF lesions. CONCLUSION: The SPKA enables ACF observation from the lateral direction; the endoscope's extended viewing angles enable the observation of the anteromedial part of the ACF, including the bilateral olfactory groove. Facial skin and large scalp incisions are avoided, making this approach efficient for ACF lesions.

A Combined Exoscopic and Endoscopic Approach for Radical Temporal Bone Resection and Usefulness of the Endoscopic Approach to the Medial Aspect of the Temporal Bone.

Radical temporal bone resection (TBR) for lateral skull base malignancies is technically challenging because of the vital anatomical structures located at the medial part of the temporal bone and their limited exposure. A possible solution is to adopt an additional endoscopic approach for medial osteotomy to reduce blind spots. The authors aimed to describe a combined exoscopic and endoscopic approach (CEEA) for cranial dissection in radical TBR and to determine the usefulness of the endoscopic approach to the medial aspect of the temporal bone. Having utilized the CEEA in for cranial dissection in radical TBR since 2021, the authors included 5 consecutive patients who underwent the procedure between 2021 and 2022. All surgeries were successful and resulted in no significant complications. The additional use of an endoscope improved visualization of the middle ear in 4 patients and that of the inner ear and carotid canal in 1 patient, enabling precise and safe cranial dissection. Furthermore, surgeons experienced reduced intraoperative postural stress with CEEA than with a microscopic approach. The main advantage of CEEA in radical TBR was the extension of the viewing angles of the endoscope, which allowed observation of the medial aspect of the temporal bone and limited tumor exposure and injury to vital structures. Given the other benefits of exoscopes and endoscopes, including compact size, ergonomics, and surgical field accessibility, CEEA proved to be an efficient treatment option for cranial dissection in radical TBR.

Feasibility of underwater microvascular decompression for hemifacial spasm: a technical note.

BACKGROUND: We present a case series of underwater microvascular decompression (MVD) for hemifacial spasm (HFS) and an evaluation of its feasibility and safety. METHODS: This retrospective study was conducted at a single institution and included 20 patients with HFS who underwent underwater MVD between September 2019 and January 2021. Surgery was performed in 3 steps, as follows: exoscopic wound opening (soft tissue, bone, dura, and arachnoid around the cerebellomedullary cistern), underwater endoscopic surgery (decompression of the facial nerve), and exoscopic wound closure. In underwater endoscopic surgery, the surgical field was continuously irrigated with artificial cerebrospinal fluid. Abnormal muscle response and brainstem auditory evoked potentials (BAEPs) were monitored. RESULTS: Neurovascular conflicts were clearly observed in all patients without fogging and soiling of the endoscope lens. HFS was completely relieved in 19 patients (95%). An amplitude reduction of wave V of BAEPs of more than 50% was not observed in any of the cases. In 5 cases (25%), the latency of wave V of BAEPs was prolonged for more than 1.0 ms; these changes completely or near completely returned to baseline values at dural closure in all 5 cases. A postoperative complication of transient facial palsy was observed in 1 patient (5%) during postoperative days 10-30. There were no other complications. CONCLUSIONS: Our findings suggest that underwater MVD is a safe and feasible option for the treatment of HFS. However, it did not show advantages over conventional endoscopic MVD when the protective effect on the eighth cranial nerve was evaluated.

Histological outcome evaluation of selected brain preparation protocols for white fiber dissection.

BACKGROUND: White fiber dissection is essential for studying brain connections.　However, preparation protocols have not been validated. METHODS: We microstructurally analyzed Klingler's brain preparation method and freezing process and assessed changes under two protocols:freeze-only and freeze-thaw.　The microstructure changes of these protocols were evaluated by measuring the ratio of the total gap area to the white matter area and determining the mean eccentricity value to assess the degree of anisotropy. RESULTS: Sixty hemispheres were allocated to ten different freezing protocols.　In the freeze-only protocols, the total gap area ratio was significantly higher compared to that of specimens fixed with only formaldehyde, particularly after continuous freezing for 3-4 weeks;however, the difference in eccentricity was not significant.　In the freeze-thaw protocols, both the area ratio and eccentricity were significantly higher compared to the freeze-only.　The optimum degree of fiber separation in the freeze-thaw protocols reached its peak with four cycles of 1-week freezing periods interrupted by six hours of thawing. CONCLUSION: The Klingler method assists in the separation of the white fibers through the gaps formed by ice crystals, but an appropriate degree of anisotropy is reached when the freezing protocol is interrupted by at least four thawing cycles.

Platelet-derived Growth Factor Activates Pericytes in the Microvessels of Chronic Subdural Hematoma Outer Membranes.

Angiogenesis is one of the growth mechanisms of chronic subdural hematoma (CSDH). Pericytes have been implicated in the capillary sprouting during angiogenesis and are involved in brain ischemia and diabetic retinopathy. This study examined the pericyte expressions in CSDH outer membranes obtained during trepanation surgery. Eight samples of CSDH outer membranes and 35 samples of CSDH fluid were included. NG2, N-cadherin, VE-cadherin, Tie-2, endothelial nitric oxide synthase (eNOS), platelet-derived growth factor (PDGF) receptor-ß (PDGFR-ß), a well-known marker of pericytes, phosphorylated PDGFR-ß at Tyr751, and ß-actin expressions, were examined using western blot analysis. PDGFR-ß, N-cadherin, and Tie-2 expression levels were also examined using immunohistochemistry. The concentrations of PDGF-BB in CSDH fluid samples were measured using enzyme-linked immunosorbent assay kits. NG2, N-cadherin, VE-cadherin, Tie-2, eNOS, PDGFR-ß, and eNOS expressions in CSDH outer membranes were confirmed in all cases. Furthermore, phosphorylated PDGFR-ß at Tyr751 was also detected. In addition, PDGFR-ß, N-cadherin, and Tie-2 expressions were localized to the endothelial cells of the vessels within CSDH outer membranes by immunohistochemistry. The concentration of PDGF-BB in CSDH fluids was significantly higher than that in cerebrospinal fluid. These findings indicate that PDGF activates pericytes in the microvessels of CSDH outer membranes and suggest that pericytes are crucial in CSDH angiogenesis through the PDGF/PDGFR-ß signaling pathway.

A hypoxia-inducible factor (HIF)-3α splicing variant, HIF-3α4 impairs angiogenesis in hypervascular malignant meningiomas with epigenetically silenced HIF-3α4.

Hypoxia inducible factor is a dominant regulator of adaptive cellular responses to hypoxia and controls the expression of a large number of genes regulating angiogenesis as well as metabolism, cell survival, apoptosis, and other cellular functions in an oxygen level-dependent manner. When a neoplasm is able to induce angiogenesis, tumor progression occurs more rapidly because of the nutrients provided by the neovasculature. Meningioma is one of the most hypervascular brain tumors, making anti-angiogenic therapy an attractive novel therapy for these tumors. HIF-3α has been conventionally regarded as a dominant-negative regulator of HIF-1α, and although alternative HIF-3α splicing variants are extensively reported, their specific functions have not yet been determined. In this study, we found that the transcription of HIF-3α4 was silenced by the promoter DNA methylation in meningiomas, and inducible HIF-3α4 impaired angiogenesis, proliferation, and metabolism/oxidation in hypervascular meningiomas. Thus, HIF-3α4 could be a potential molecular target in meningiomas.

Endoscopic transnasal transsphenoidal management of sellar/suprasellar arachnoid cyst: A case report and literature review.

Background: Arachnoid cysts (ACs) are collections of cerebrospinal fluids (CSFs) that develop within the arachnoid layer of the meninges. Sellar ACs are comparatively rare. In general, ACs account for approximately 1% of all intracranial mass lesions, and sellar ACs are 3% of all intracranial ACs. An endoscopic transnasal transsphenoidal approach for the treatment of ACs by fenestrating the cyst's wall and connecting with the subarachnoid space is the most optimal option. Case Description: A 74-year-old woman whose sellar AC was diagnosed on magnetic resonance imaging a year ago was admitted to our hospital with complaints of bitemporal hemianopia and diminished visual acuity in the past 2 months. Sellar AC was diagnosed based on the clinical history and presentation, as well as neurologic, endocrinologic, and ophthalmologic examinations, including visual acuity and visual field examination, and additional imaging findings. The patient with a sellar/suprasellar AC was treated by an endoscopic transnasal transsphenoidal approach with cyst drainage and perforation of the lamina terminalis. Postoperatively, the visual disturbances improved markedly. No surgery-related complications occurred. Conclusion: The endoscopic transnasal transsphenoidal approach remains a minimally invasive and preferred approach for the treatment of sellar/suprasellar ACs. Hermetically reconstructing the sellar floor is an effective method to prevent CSF leakage.

Mixed Germ Cell Tumor with a Yolk Sac Tumor Component in the Medulla Oblongata of a 50-year-old Patient: A Case Report and Literature Review.

Yolk sac tumor (YST) is a rare primary brain tumor that occurs almost exclusively in patients under 30 years old. Intracranial germ cell tumors are most frequently located in the pineal and suprasellar region. Medulla oblongata YSTs are particularly rare. Extragonadal YSTs may be difficult to diagnose because of their characteristics, such as the rarity and variety of growth patterns. Furthermore, they are known to have a very poor prognosis. We herein report a case of YST of the medulla oblongata in a 50-year-old woman. She was followed up for 18 months without any tumor recurrence.

Angiogenesis in the Outer Membrane of Chronic Subdural Hematomas through Thrombin-Cleaved Osteopontin and the Integrin α9 and Integrin ß1 Signaling Pathways.

BACKGROUND: A chronic subdural hematoma (CSDH) is considered to be an inflammatory and angiogenic disease. The CSDH outer membrane, which contains inflammatory cells, plays an important role in CSDH development. Osteopontin (OPN) is an extracellular matrix protein that is cleaved by thrombin, generating the N-terminal half of OPN, which is prominently involved in integrin signal transduction. We explored the expression of the N-terminal half of OPN in CSDH fluid and the expression of integrins α9 and ß1 and the downstream components of the angiogenic signaling pathways in the outer membrane of CSDHs. METHODS: Twenty samples of CSDH fluid and eight samples of CSDH outer membrane were collected from patients suffering from CSDHs. The concentrations of the N-terminal half of OPN in CSDH fluid samples were measured using ELISA kits. The expression levels of integrins α9 and ß1, vinculin, talin-1, focal adhesion kinase (FAK), paxillin, α-actin, Src and ß-actin were examined by Western blot analysis. The expression levels of integrins α9 and ß1, FAK and paxillin were also examined by immunohistochemistry. We investigated whether CSDH fluid could activate FAK in cultured endothelial cells in vitro. RESULTS: The concentration of the N-terminal half of OPN in CSDH fluid was significantly higher than that in the serum. Western blot analysis confirmed the presence of these molecules. In addition, integrins α9 and ß1, FAK and paxillin were localized in the endothelial cells of vessels within the CSDH outer membrane. FAK was significantly phosphorylated immediately after treatment with CSDH fluid. CONCLUSION: Our data suggest that the N-terminal half of OPN in CSDH fluid promotes neovascularization in endothelial cells through integrins α9 and ß1. The N-terminal half of OPN, which is part of the extracellular matrix, plays a critical role in the promotion of CSDHs.

Surgical Strategy for Squamous Cell Carcinoma of the External Auditory Canal: Management of Locally Advanced Cases with Skull Base Involvement.

Objective Surgical indications for advanced-stage squamous cell carcinoma (SCC) of the external auditory canal (EAC) are highly dependent on the skull base surgery team. The aim of this study was to evaluate the surgical outcomes in patients with SCC of the EAC and to clarify the surgical indication of far advanced cases using the T4 subclassification. Methods Patients with SCC of the EAC who underwent curative treatment from 2002 to 2021 at our hospital were retrospectively reviewed. Clinical and surgical results, including operative data, overall survival (OS), and disease-specific survival (DSS), were analyzed. To clarify the surgical indication for advanced-stage tumors, we proposed the T4 subclassification. Results In the 46 patients included in the study, 8 patients had T1 tumors, 10 had T2 tumor, 5 had T3 tumors, and 23 had T4 tumors. The 5-year DSS with T1, T2, T3, and T4 tumors were 100, 85.7, 100, and 61.7%, respectively. No prognostic impacts for margin status were found between the 5-year OS and DSS ( p = 0.23 and 0.13, respectively). Patients with far-advanced-stage (T4b) tumors were significantly associated with shorter DSS than those with early-stage (T1/T2) and advanced-stage (T3/T4a) tumors ( p = 0.007 and 0.03, respectively). Conclusion The present study focused on patients with SCC of the EAC at a university hospital over a period of 20 years, especially with skull base involvement, and a T4 subclassification was proposed. Complete tumor resection in an en bloc fashion could help achieve a good survival rate even in patients with locally advanced tumors.

Peptide-pulsed dendritic cell vaccination targeting interleukin-13 receptor α2 chain in recurrent malignant glioma patients with HLA-A*24/A*02 allele.

BACKGROUND AIMS: Dendritic cell (DC)-based vaccination targeting tumor-associated antigens is an attractive approach to overcoming the limitations of current treatments for malignant gliomas (MG). Interleukin-13 receptor α2 chain (IL-13Rα2) is a promising target because of its abundant and specific expression in MG. We conducted a phase I trial of DC vaccination in patients with recurrent MG using two IL-13Rα2-derived peptides restricted to HLA-A*0201 and -A*2402. The objective was to evaluate the safety and clinical and immunologic responses. METHODS: Eight recurrent MG patients were enrolled. DC were generated from peripheral blood and pulsed with HLA-matched peptide; 1 × 10(7) DC were administered every 2 weeks for a maximum of six immunizations. The T-cell response in peripheral blood was evaluated by tetramer and ELISPOT assays in HLA-A*2402 patients. RESULTS: All enrolled patients except one completed at least four DC vaccinations. No severe adverse events were observed. A positive T-cell response was detected in two out of three evaluable HLA-A*2402 patients. One patient achieved stable disease for 16 months and another patient showed a dramatic regression for one lesion for 4 months. CONCLUSIONS: The regimen was feasible and safe, and the HLA-A*24-restricted peptide exhibited a capacity to induce immune responses. These results warrant further studies to evaluate whether add-on regimens to post-operative chemoradiotherapy delays recurrence in newly diagnosed MG patients.

Combined Exoscopic and Endoscopic Two-Step Keyhole Approach for Intracranial Meningiomas.

The advantages of neuroendoscopic surgery are the wide viewing angle and the freedom of an axis of view with minimal surgical trauma. With the advent of the exoscope, which has similar advantages to endoscopy, such as a small body and ergonomically superior heads-up surgery, it has become possible to add a field of view that is similar to that of microsurgery to endoscopic surgery. By taking advantage of the features of these scopes, we report the usefulness of the minimally invasive combined exoscopic and endoscopic two-step keyhole approach (EEKA) for various types of meningiomas. We reviewed data from 34 consecutive cases of EEKA for various types of intracranial meningiomas compared with that of conventional microsurgery. All of the tumors were resected as planned without severe complications. Significantly better outcome data were obtained in terms of the blood loss and the surgical time in the EEKA group, in addition to the craniotomy size. The well-illuminated fine vision in the deep corners by the endoscope enabled radical resection of the tumors with minimum burden on the patients. This technique has the potential for minimally invasive surgery in intracranial meningioma patients, including the older population.

A rapid and durable response to larotrectinib in a patient with NTRK fusion-positive secretory carcinoma originating from the external auditory canal.

For decades, no clear consensus existed on the standard treatment option for malignant tumors of the external auditory canal, an extremely rare disease. Here we report the case of a 55-year-old female patient with secretory carcinoma that originated from the left external auditory canal. Magnetic resonance imaging (MRI) at baseline showed that the tumor had extended to the medulla oblongata despite surgical and radiation treatments for more than 20 years from the initial diagnosis. Based on the results of a next-generation sequencing test of a formalin-fixed paraffin-embedded surgical specimen indicating that the tumor harbored ETV6-NTRK3 fusion, the patient was enrolled in a global basket study of larotrectinib, an oral selective tropomyosin receptor kinase (TRK) inhibitor. Three weeks after the start of larotrectinib treatment, MRI showed only small remnants of the tumor in the medulla oblongata and the patient's headache before the treatment had disappeared. Subsequent MRI after 12 weeks of treatment confirmed the complete disappearance of the tumor. The patient repeated grade 2 flu-like symptoms related to treatment, but did not experience any other grade 2 or worse treatment-related adverse events. TRK inhibitors, such as larotrectinib, exert potent antitumor activity against neurotrophic tyrosine receptor kinase (NTRK) fusion-positive tumors in a tumor-agnostic manner. To the best of our knowledge, this is the first report on NTRK fusion-positive secretory carcinoma of the external auditory canal, and this report provides a valuable insight into the management of the extremely rare but now treatable malignancy.

Cytokine networks in glioma.

Glioma is the most frequently occurring brain tumor, but the prognosis of patients with gliomas remains poor despite advances in surgery, radiotherapy, and chemotherapy. Therefore, great efforts have been made to develop improved therapeutic strategies. Cytokines are a heterogeneous group of soluble small polypeptides or glycoproteins that exert pleiotropic and redundant effects that promote the growth, differentiation, and activation of normal cells. Cytokines have either pro- or anti-inflammatory activity and immunosuppressive activity, depending on the microenvironment surrounding the tumor. The microenvironment consists of heterogeneous tumor cells, immune cells, and extracellular matrix. Modulation of the microenvironment by the tumor is essential for its growth and progress. Cytokine production acts as a means of communication in the tumor microenvironment. In this article, we review the cross-talk between cytokines in the tumor microenvironment and the cytokine therapies that have been used till date for glioma treatment.

Sequential expression of neutrophil chemoattractants in cerebrospinal fluid after subarachnoid hemorrhage.

OBJECTIVE: Neutrophils induce inflammation through the exocytosis of cytotoxic granule proteins. Recently, neutrophils have been reported to be an independent parameter associated with unfavorable outcomes after subarachnoid hemorrhage (SAH). However, the mechanism by which neutrophils accumulate within the CSF after SAH remains undetermined. METHODS: Concentrations of C5a, epithelial neutrophil activating peptide 78 (ENA-78), interleukin-8 (IL-8), growth-regulated oncogene-α (GRO-α), neutrophil gelatinase-associated lipocalin (NGAL) and myeloperoxidase (MPO) were measured serially until day 14 in the CSF of 10 patients with SAH. CSF samples obtained from patients suffering from unruptured aneurysms were used as controls. RESULTS: The concentrations of C5a and ENA-78 were significantly increased on day 1, while those of IL-8 and GRO-α significantly increased during days 3-7 compared with those of the control samples. The levels of NGAL and MPO, components of neutrophil granules, significantly increased during days 1-5 and days 1-3, respectively, after SAH and gradually decreased thereafter. The correlations between ENA-78 and C5a on day 1, IL-8 and GRO-α on days 3-7, and NGAL and MPO on days 1-3 were significant. CONCLUSION: These neutrophil chemoattractants might be serially involved in the infiltration of neutrophils into the CSF after SAH. Migrated neutrophils play an important role in inflammatory reactions in the central nervous system after SAH.

Sequential Expression of Chemokines in Chronic Subdural Hematoma Fluids after Trepanation Surgery.

Chronic subdural hematoma (CSDH) is considered an angiogenic and inflammatory disease. Chemokines attract leukocytes, and invading neutrophils and monocytes/macrophages play important roles in wound healing. However, no studies have been reported regarding changes in expression of chemokines in CSDH fluid after trepanation surgery. We randomly divided patients who underwent trepanation surgery into two groups. One was the irrigation group, in which irrigation of CSDH fluids was performed and a drainage tube was placed (n = 10). The other was the non-irrigation group, in which a drainage tube was inserted without irrigation (n = 10). CSDH fluids were collected during the trepanation surgery, immediately after surgery and on day 1 through the drainage tube. The concentrations of interleukin-8 (IL-8), growth-regulated oncogene-α (GRO-α), epithelial neutrophil-activating peptide 78 (ENA-78), monocyte chemoattractant protein-1 (MCP-1), interferon-γ-induced protein-10 (IP-10), tissue plasminogen activator (tPA), von Willebrand factor (vWF), eotaxin-3, and myeloperoxidase (MPO) in each CSDH fluid sample were measured using enzyme-linked immunosorbent assay kits. After irrigation, concentrations of all chemokines decreased. However, concentrations of IL-8, GRO-α, ENA-78, MCP-1, and MPO were significantly increased on day 1 compared with concentrations during surgery with or without irrigation. In contrast, there were no changes in concentrations of IP-10, eotaxin-3, tPA, or vWF after trepanation surgery. Moreover, there were significant relationships among concentrations of IL-8, GRO-α, ENA-78, and MCP-1 during the surgery and on day 1. In CSDH fluids, chemokines that attract neutrophils, such as IL-8, GRO-α, ENA-78, and macrophage-attracting MCP-1, appear first after trepanation surgery, whereas lymphocyte-attracting IP-10 and eosinophil-attracting eotaxin-3 levels do not change within 1 day of surgery. These findings suggest that neutrophils and macrophages may play important roles in the healing process of CSDH at an early stage.

Skull Base Reconstruction Using a Temporoparietal Galeal Flap in Simultaneous Transnasal and Transcranial Surgery for the Prevention of Carotid Blowout Syndrome: A Report of 3 Cases.

Background Carotid blowout syndrome (CBS) is a rare complication that usually occurs after removal of head and neck tumors. Since transnasal skull base surgery allows a wide exposure of the ventral skull base, neurosurgeons should pay attention to prevent this devastating complication. We present, three cases involving exposure of the internal carotid artery (ICA) at the skull base during the simultaneous transnasal and transcranial approach. Case Description The first patient was a 69-year-old man with a recurrent chordoma. The exposed ICA was covered by an abdominal fat graft and nasoseptal flap, but he experienced CBS 2 months later and died. The second patient was a 66-year-old man with an intraosseous cavernous angioma of the petrous bone. The exposed ICA was covered by a temporoparietal galeal flap (TPGF), abdominal fat graft, and nasoseptal flap. The third patient was a 73-year-old man with skull base radiation necrosis and intracerebral abscess after proton beam therapy for orbital adenoid cystic carcinoma. The exposed ICA was covered by TPGF. The second and third patients' postoperative courses were uneventful. Conclusion Based on our experience, a nasoseptal flap alone may be insufficient to protect ICA. TPGF is therefore another available reconstruction option that may help prevent CBS.

Combined Exoscopic and Endoscopic Technique for Craniofacial Resection.

We determined the feasibility of the combined exoscopic-endoscopic technique (CEE) as an alternative to the microscope in craniofacial resection (CFR). This retrospective study was conducted at a single institution and included eight consecutive patients with head and neck tumors who underwent CFR between September 2019 and July 2021. During the transcranial approach, microsurgery was performed using an exoscope in the same manner as in traditional microscopic surgery, and an endoscope was used at the blind spot of the exoscope. The exoscope provided images of sufficient quality to perform microsurgery, while the sphenoid sinus lumen was the blind spot of the exoscope during anterior (n = 3) and anterolateral CFR (n = 2), and the medial aspect of the temporal bone was the blind spot of the exoscope during temporal bone resection (n = 2). These blind spots were visualized by the endoscope to facilitate accurate transection of the skull base. The advantages of the exoscope and endoscope include compact size, ergonomics, surgical field accessibility, and equal visual experience for neurosurgeons and head and neck surgeons, which enabled simultaneous transcranial and transfacial surgical procedures. All the surgeries were successful without any relevant complications. CEE is effective in transcranial skull base surgery, especially CFR involving simultaneous surgical procedures.