Doo-Sik Kong

BACKGROUND AND OBJECTIVES: Tumors involving the cavernous sinus (CS) and Meckel's cave, such as trigeminal schwannomas and meningiomas, frequently displace the trigeminal nerve. This study aimed to classify displacement patterns of the trigeminal nerve using diffusion tensor imaging (DTI) tractography and evaluate its predictive accuracy compared with intraoperative findings. METHODS: We retrospectively reviewed 28 patients who underwent resection of CS- or Meckel's cave–involving tumors. Preoperative DTI tractography was compared with intraoperative nerve positioning. The correlation between displacement patterns and the selection of surgical approaches (lateral approach such as transcranial or transorbital, and medial approach like endonasal) was analyzed. RESULTS: Preoperative DTI tractography accurately predicted the trigeminal nerve position in 26 of 28 patients, yielding a concordance rate of 92.9%. Identified displacement patterns included medial (n = 7), lateral (n = 13), and encased (n = 8) configurations. In cases of medial displacement, a lateral approach was performed in all cases (100%), achieving an 85.7% favorable outcome rate. For lateral displacement, a medial approach (n = 4) resulted in a 100% favorable outcome rate, whereas a lateral approach (n = 9) yielded a 66.7% favorable outcome rate. All cases with an encased pattern (n = 8) were managed through a lateral approach, with a 25% favorable outcome rate observed. Although nerve displacement guided surgical planning, a lateral approach was often preferred to facilitate the technical manipulation of firm tumors. CONCLUSION: Preoperative DTI tractography is a reliable tool for predicting trigeminal nerve displacement. While displacement patterns guide the surgical route, the histological nature of the tumor, specifically the need for easier manipulation in firm tumors, often dictates a preference for lateral approaches over medial ones to ensure safer resection. DTI tractography should be regarded as a decision support tool that complements intraoperative assessment and microsurgical judgment in achieving maximal safe resection.

Intraoperative diagnosis is important for brain tumor surgery. Although frozen section (FS) remains the standard, its time demands and logistical limitations hinder real-time decision-making. Confocal laser endomicroscopy (CLE) offers rapid high-resolution imaging for efficient diagnosis. This multicenter prospective trial evaluated the diagnostic performance of CLE while developing a novel Swin Transformer–based AI diagnostic model. A total of 461 biopsies from 376 patients were analyzed. CLE demonstrated non-inferior diagnostic accuracy to FS (0.94 vs 0.92; P = 0.14), with comparable sensitivity (0.96 vs 0.95; P = 0.40) and specificity (0.79 vs 0.68; P = 0.31). CLE achieved a significantly faster median turnaround (5 m 56 s vs 20 m; P < 0.001). The AI model showed diagnostic accuracies of 0.94 for tumor detection and 0.88 for biopsy subtype diagnosis. Overall, CLE demonstrated diagnostic efficacy comparable to FS with significantly shorter turnaround. The AI diagnostic model also showed promising results supporting its potential integration with the CLE platform.

Background/Objectives: The endoscopic transorbital approach (ETOA) is a minimally invasive surgical route that provides access to the lateral skull base through the superior eyelid. Originally developed as an endoscopic procedure, ETOA has recently been explored using alternative visualization tools such as the exoscope. This study evaluates the effectiveness of exoscopic visualization across the different steps of transorbital surgery. Methods: Eight formalin-fixed cadaveric specimens (16 sides) were dissected by four teams of neurosurgeons trained in ETOA. The dissection protocol consisted of three stages: skin, orbital, and intracranial. The teams were assigned to four groups: the first performed a pure endoscopic ETOA (group A) and the second and third performed a combined exoscopic/endoscopic ETOA, using exoscopic visualization, respectively, for the skin phase only (group B) or for the skin and orbital phases (group C), while the fourth group performed a pure exoscopic ETOA All surgeons rotated across groups. Operative time was recorded. After each procedure, surgeons rated operative comfort, maneuverability, and image quality on a 0–5 scale. Pre- and postoperative CT scans were used for volumetric analysis, comparing surgical cavity size with and without the endoscope in place. In addition, an illustrative exoscopic case was included. Results: Exoscopic visualization proved to be more effective during the skin phase. In the orbital phase, it improved access and reduced crowding during lateral wall drilling. However, endoscopic visualization provided superior image clarity and magnification for deep and medial orbital structures. CT-based analysis confirmed that the exoscope significantly improves the working space during orbital dissection. Moreover, the combined approaches (Groups B and C) achieved shorter operative times and higher subjective ratings. Conclusions: The exoscope could be a valuable visualizing tool for transorbital surgery. While the skin phase benefits most from exoscopic visualization, the endoscope remains essential for the intracranial phase. The orbital phase can be effectively performed with either technique, each offering specific advantages and limitations.

BACKGROUND AND OBJECTIVES: The aim of this study was to elucidate the indications and technical intricacies of orbital rim removal (ORR) within the endoscopic transorbital approach (ETOA). In addition, it seeks to conduct a comparative analysis between cases using ORR and a control group to discern the associated clinical outcomes. METHODS: The study included consecutive patients who underwent ETOA between August 2016 and October 2023 in a single center. The anatomic exploration, involving 3 cadaveric specimens, uses 3-dimensional photogrammetry methodology to precisely showcase the ORR technique. Furthermore, our study introduced a novel anatomic demarcation—the “sphenoarcuate line” (SpAL)—which can serve as valuable metrics for surgical planning. RESULTS: A total of 121 patients were included. Pathological diagnoses included 56 patients (46.3%) of meningioma, 28 patients (23.1%) of schwannoma, 15 patients (12.4%) of other malignant tumors, and 22 patients (18.2%) of other benign tumors. ORR was performed in 54 patients (44.6%). Good outcomes—defined as gross total or near-total resection—were achieved in 90 patients (74.3%). No significant difference in good outcome rate was observed between the ORR group (73.1%) and the non-ORR group (75.9%; P = .83). However, ORR was associated with significantly improved good outcome rate in meningioma patients ( P = .04) and patients with tumors exhibiting lateral extension beyond the SpAL ( P = .03). 3-dimensional reconstructed volumes of surgical exposure using photogrammetry for ETOA revealed that the SpAL-demarcated volumes significantly expanded after ORR. CONCLUSION: This study establishes ORR as a pivotal advancement in ETOA, demonstrating its capacity to significantly enhance surgical outcomes, particularly in specific tumor scenarios. The anatomic study convincingly demonstrated the inclusion of ORR significantly expanded the surgical exposure during the ETOA. The combination of clinical insights and the feasibility of anatomic study demonstrates ORR as a valuable tool, augmenting outcomes and expanding the surgical armamentarium for complex cases in transorbital surgery.

Objective : This study aimed to compare the clinical outcomes and risk of two skull base reconstruction methods after expanded expanded endoscopic approach (EEA), viz. postoperative cerebrospinal fluid (CSF) lumbar drainage (L-method) and injectable hydroxyapatite cement without lumbar drainage (H-method).Methods : We enrolled 211 consecutive patients with grade 2 or 3 intraoperative CSF leakage during EEA. The most common preoperative diagnoses were pituitary adenoma (n=62, 29%), meningioma (n=50, 24%), and craniopharyngioma (n=28, 13%). Vascularized nasoseptal flaps were used in most cases (98%). We used the L-method and H-method in 83 (39%) and 103 patients (49%), respectively.Results : The overall reconstruction-related complication and postoperative CSF leakage rates were 8% (18/211) and 6% (12/211), respectively. The complications included postoperative CSF leakage (n=12), infection (n=4), postoperative optic nerve compression (n=1), and brain herniation (n=1). The postoperative complication and CSF leakage rates did not differ significantly between the L-method (12% and 10%, respectively) and H-method (8% and 4%, respectively) (p=0.326 and 0.112, respectively). Postoperative hospital stay was significantly shorter with the H-method (6.9 days) compared to the L-method (10.0 days) (p<0.001). However, the postoperative infection rate of the H-method (n=4) was higher than that of the L-method (n=0; p=0.070).Conclusion : Skull base reconstruction using hydroxyapatite effectively prevented postoperative CSF leakage and ensured patient comfort and shorter hospitalization without postoperative lumbar drainage, although postoperative infection requires consideration.

BACKGROUND AND OBJECTIVES: The superior eyelid endoscopic transorbital approach (ETOA) has recently emerged as a minimally invasive technique for treating selected skull base lesions. This study assesses the feasibility of transtentorial ETOA in accessing the perimesencephalic cisterns, following the course of the trochlear nerve and potentially transposing it depending on the pathology. METHODS: Anatomic dissections were conducted on 6 cadaveric specimens (12 orbits) using 0° and angled endoscopes. A stepwise anatomic description of the approach and visualized anatomic structures was provided. Furthermore, a quantitative analysis of the area of exposure (AoE) was conducted before (AoE1) and after (AoE2) the tentorial opening. A cadaveric dissection video and 3D model of the surgical corridor and targets were created to enhance the understanding of this complex region. RESULTS: Using the ETOA, the entire lateral wall of the cavernous sinus and middle cranial fossa floor were exposed through interdural dissection, with an average AoE1 of 336.17 mm ² (±SD 79.16). After the tentorial opening, complete exposure of the middle incisural space, cerebellomesencephalic fissure, and trigeminal root entry zone was achieved. The trochlear nerve was followed from its fissural segment to its exit point in the dorsal midbrain within the quadrigeminal cistern. The transtentorial ETOA allowed exposure of all 4 perimesencephalic cisterns, along with the oculomotor nerve, posterior cerebral artery, and superior cerebellar artery. The average AoE2 was 1059.25 mm ² (±SD 231.39, P = .00222). CONCLUSION: The transorbital approach, through a minimally invasive superior eyelid incision and a transtentorial corridor, provides an effective route to the perimesencephalic cisterns. Creating a tentorial flap window increases the exposed area by an average of 723.07 mm ² . By working between the cerebellum and the brainstem-cranial nerve complex and performing subarachnoid dissection through the cerebellomesencephalic fissure, the trochlear nerve exit point can be exposed.

BACKGROUND: Tinnitus is a common symptom in patients with vestibular schwannoma (VS). The impact of Gamma Knife radiosurgery (GKRS) on tinnitus and the health-related quality of life (HRQoL) of patients with VS remains unclear. This study evaluated the effect of GKRS on HRQoL affected by tinnitus. METHODS: From December 2020 to April 2022, spontaneous VS patients who had no prior history of treatment and underwent their first GKRS in this period were analyzed. Subjective distress from tinnitus was measured by the Tinnitus Handicap Inventory (THI) and their HRQoL by 36-Item Short Form Survey Version 2 (SF-36v2). Pre-GKRS THI and SF-36v2 were obtained, and after GKRS, consecutive THI and SF-36v2 were obtained during the follow-up period. Bowker’s test, paired Student’s t-test, and Spearman’s correlation were used to analyze the changes in THI grade, SF-36v2 score, and the correlation between THI grade and SF-36v2 score. Factors affecting the THI grade change and SF-36v2 score were evaluated through univariate and multivariate models. RESULTS: Twenty of 34 patients showed serviceable hearing before GKRS. The median radiation dose of GKRS was 12.75 Gy (range, 12-21 Gy). Twenty-two of 33 patients demonstrated no change or worse THI grade after GKRS, but the change was not statistically significant (P =.34). However, with age, the odds ratio of THI improvement is 0.905 (95% CI 0.83-0.98, P=.02). Patients with serviceable hearing before GKRS displayed THI grade improvement (OR = 6.721; P = .03). Compared to those with pre-GKRS THI grade 1, grades 3 and 4 exhibited lower odds of THI improvement (OR =0.095; P=.0449). No significant change was noted in SF-36v2 scores after GKRS. A high THI grade was correlated with a low physical component score (P =.03) and mental component score (P=.0002) of SF-36v2. CONCLUSION: Although THI grade and SF-36v2 change before and after GKRS did not show statistical significance, several factors affected THI grade change. Moreover, the THI grade and SF-36v2 score had a significant negative correlation. Factors that may aggravate tinnitus and further impact HRQoL of VS patients should be taken into account when planning treatment and providing counseling to VS patients.

Meningioma is the most prevalent primary brain tumor with extensive intra-tumoral heterogeneity and high recurrence rates, particularly in high-grade meningiomas. Despite advancements in understanding the molecular underpinnings of meningiomas, the longitudinal evolutionary trajectory and cellular diversity of recurrent tumors remain elusive. In this study, we perform single-nuclei sequencing of matched primary and recurrent meningiomas to explore the dynamic transcriptional heterogeneity and evolutionary trajectory of meningioma tumor cells, as well as their molecular interactions with tumor-associated immune cells that shape the complex milieu of the meningioma microenvironment. Our findings reveal that both primary and recurrent meningiomas constitute diverse cellular compositions and hierarchies, where recurrent tumor cells are characterized by enrichments of cell cycle activities and proliferative kinetics. Integrative RNA velocity and latent time uncover divergent transcriptional trajectories in recurrent tumors, demonstrating multidirectional transitions with the dominance of COL6A3, which confers higher risk vulnerability and treatment resistance. Tumor microenvironment analysis further reveals enrichments of COL6A3-mediated interactions between immunosuppressive macrophages and tumor cells in recurrent meningiomas. Collectively, these results provide profound insights into the complex evolutionary process of meningiomas and suggest potential therapeutic strategies for the treatment of recurrent tumors.