Modified Skin Incision and Location of Burr-Hole Surgery via a Retrosigmoid Approach: An Anatomical Study

Objective This study aims to reduce the tissue damage during craniotomy with retrosigmoid approach. A modified sickle-shaped skin incision was developed, and a new burr-hole positioning method was proposed. Methods Five adult cadaveric heads (10 sides) were used in this study. The sickle-shaped skin incision was performed during craniotomy. The nerves, blood vessels, and muscles were observed and measured under a microscope. Additionally, 62 dry adult skull specimens (left sided, n = 35; right sided, n = 27) were used to measure the distance between the most commonly used locating point (asterion [Ast] point) and the posteroinferior point of the transverse sigmoid sinus junction (PSTS) (Ast-PSTS), as well as the distance between the new locating O point and the PSTS (O-PSTS). Then, the reliability of the new locating O point was validated on the same five adult cadaveric heads (10 sides) used for the sickle-shaped skin incision. Results The sickle-shaped skin incision reduced the damage to the occipital nerves, blood vessels, and muscles during the surgery via a retrosigmoid approach. The dispersion and variability of O-PSTS were smaller than those of Ast-PSTS. Conclusion The sickle-shaped skin incision of the retrosigmoid approach can reduce the tissue damage and can completely expose the structures in the cerebellopontine angle. The modified O point is a more reliable locating point for a burr-hole surgery than the Ast point.

Interpretable Machine Learning–Based Prediction of Intraoperative Cerebrospinal Fluid Leakage in Endoscopic Transsphenoidal Pituitary Surgery: A Pilot Study

Purpose Transsphenoidal surgery (TSS) for pituitary adenomas can be complicated by the occurrence of intraoperative cerebrospinal fluid (CSF) leakage (IOL). IOL significantly affects the course of surgery predisposing to the development of postoperative CSF leakage, a major source of morbidity and mortality in the postoperative period. The authors trained and internally validated the Random Forest (RF) prediction model to preoperatively identify patients at high risk for IOL. A locally interpretable model-agnostic explanations (LIME) algorithm is employed to elucidate the main drivers behind each machine learning (ML) model prediction. Methods The data of 210 patients who underwent TSS were collected; first, risk factors for IOL were identified via conventional statistical methods (multivariable logistic regression). Then, the authors trained, optimized, and audited a RF prediction model. Results IOL reported in 45 patients (21.5%). The recursive feature selection algorithm identified the following variables as the most significant determinants of IOL: Knosp's grade, sellar Hardy's grade, suprasellar Hardy's grade, tumor diameter (on X, Y, and Z axes), intercarotid distance, and secreting status (nonfunctioning and growth hormone [GH] secreting). Leveraging the predictive values of these variables, the RF prediction model achieved an area under the curve (AUC) of 0.83 (95% confidence interval [CI]: 0.78; 0.86), significantly outperforming the multivariable logistic regression model (AUC = 0.63). Conclusion A RF model that reliably identifies patients at risk for IOL was successfully trained and internally validated. ML-based prediction models can predict events that were previously judged nearly unpredictable; their deployment in clinical practice may result in improved patient care and reduced postoperative morbidity and healthcare costs.

Comparative Analysis of Surgical Exposure among Endoscopic Endonasal Approaches to Petrosectomy: An Experimental Study in Cadavers

Objectives Endoscopic endonasal approaches (EEAs) for petrosectomies are evolving to reduce perioperative brain injuries and complications. Surgical terminology, techniques, landmarks, advantages, and limitations of these approaches remain ill defined. We quantitatively analyzed the anatomical relationships and differences between EEA exposures for medial, inferior, and inferomedial petrosectomies. Design This study presents anatomical dissection and quantitative analysis. Setting Cadaveric heads were used for dissection. EEAs were performed using the medial petrosectomy (MP), the inferior petrosectomy (IP), and the inferomedial petrosectomy (IMP) techniques. Participants Six cadaver heads (12 sides, total) were dissected; each technique was performed on four sides. Main Outcomes and Measures Outcomes included the area of exposure, visible distances, angles of attack, and bone resection volume. Results The IMP technique provided a greater area of exposure (p < 0.01) and bone resection volume (p < 0.01) when compared with the MP and IP techniques. The IMP technique had a longer working length of the abducens nerve (cranial nerve [CN] VI) than the MP technique (p < 0.01). The IMP technique demonstrated higher angles of attack to specific neurovascular structures when compared with the MP (midpons [p = 0.04], anterior inferior cerebellar artery [p < 0.01], proximal part of the cisternal CN VI segment [p = 0.02]) and IP (flocculus [p = 0.02] and the proximal [p = 0.02] and distal parts [p = 0.02] of the CN VII/VIII complex) techniques. Conclusion Each of these approaches offers varying degrees of access to the petroclival region, and the surgical approach should be appropriately tailored to the pathology. Overall, the IMP technique provides greater EEA surgical exposure to vital neurovascular structures than the MP and the IP techniques.

Subtemporal Approach and Its Infratentorial Extension: Review and a Comparative Analysis of Different Techniques

Introduction Surgical resection of lesions occupying the incisural space is challenging. In a comparative fashion, we aimed to describe the anatomy and surgical approaches to the tentorial incisura and to the rostral brainstem via the intradural subtemporal approach and its infratentorial extensions. Methods Six fresh human head specimens (12 sides) were prepared for the microscopic dissection of the tentorial incisura using the intradural subtemporal approach and its infratentorial extensions. Endoscope was used to examine the anatomy of the region inadequately exposed with the microscope. Image-guided navigation was used to confirm bony structures visualized around the petrous apex. Results Standard subtemporal approach provides surgical access to the supratentorial brainstem above the pontomesencephalic sulcus and to the lateral surface of the cerebral peduncle. The linear or triangular tentorial divisions can provide access to the infratentorial space below the pontomesencephalic sulcus. The triangular tentorial flap in comparison with the linear incision obstructs the exposure of anterior incisural space and of the prepontine cistern. Visualization of the brainstem below the trigeminal nerve can be achieved by the anterior petrosectomy. Conclusion Infratentorial extension of the intradural subtemporal approach is technically demanding due to critical neurovascular structures and a relatively narrow corridor. In-depth anatomical knowledge is essential for the selection of the appropriate operative approach and safe surgical resections of lesions.

Anterior Skull Base Meningioma: Surgical approach and complication avoidance

Background: Endoscopic endonasal approach (EEA) and keyhole transcranial approaches are being increasingly used in anterior skull base meningioma (ASBM) surgery. Objective: We compare tumor resection rates and complication profiles of EEA and supraorbital key hole approach (SOKHA) against conventional transcranial approaches (TCA). Methods: Fifty-four patients with ASBM [olfactory groove (OGM), n=19 and planum sphenoidale/tuberculum sellae (PS/TSM), n=35) operated at a single centre over 7 years were retrospectively analyzed. Results: The overall rate of GTR was higher in OGM (15/19, 78.9%) than PS-TSM group (23/35, 65.7%, p=0.37). GTR rate with OGM was 90% and 75% with TCA and EEA. Death (n=1) following medical complication (TCA) and CSF leak requiring re-exploration (n=2, one each in TCA and EEA) accounted for the major complications in OGM. For the PS/TSM group, the GTR rates were 73.3% (n=11/15), 53.8% (n=7/13) and 71.4% (n=5/7) with TCA, EEA and SOKHA respectively. Seven patients (20%) of PS-TSM developed major postoperative complications including 4 deaths (one each in TCA, SOKHA and 2 in EEA group) and 3 visual deteriorations. Direct and indirect vascular complications were common in lesser invasive approaches to PS-TSM especially if the tumor has encased intracranial arteries. Conclusions: No single approach is applicable to all ASBMs. TCA is still the best approach to obtain GTR but has tissue trauma related problems. SOKHA may be a good alternative to TCA in selected PS-TSMs while EEA may be an alternate option in some OGMs. A meticulous patient selection is needed to derive reported results of EEA for PS-TSM.

Sinonasal Neuroendocrine Carcinoma: 15 Years of Experience at a Single Institution

Objectives Sinonasal neuroendocrine carcinomas (SNECs) are among the rarest paranasal sinus cancers. Consensus guidelines for therapy are difficult to develop due to limited data regarding the natural history and successful treatment of these tumors. This study presents 15 years of experience treating SNEC at a single institution and a review of the literature. Design Retrospective review. Setting Academic medical center in the United States. Participants Patients diagnosed with primary SNEC. Main Outcome Measures Overall survival. Results Thirteen patients were identified and included. Overall estimated survival was 74.6% at 5 years. Ten of 13 (76.9%) patients were diagnosed with high-grade neuroendocrine carcinoma and three (23.1%) with intermediate or low grade. All three patients with low- or intermediate-grade cancer survived more than 10 years from their initial diagnosis (median survival: 11.6 years) and are currently alive. The four patients who died had high-grade carcinoma, and estimated overall 5-year survival for all patients with high-grade carcinomas was 65.6%. Five patients, all with high-grade carcinoma, of seven who completed primary chemoradiation therapy (CRT) required salvage resection, and 60% are alive without disease. Conclusion This cohort has a higher overall rate of survival than many recent case series and reviews. There is consensus that multimodal therapy is preferred over monotherapy, but approaches to treatment vary widely. Our approach of surgical resection as primary therapy for low-grade tumors and primary CRT for high-grade SNEC has been successful, and could indicate hope for improved survival among these patients.

Impact of Treatment Modalities Upon Survival Outcomes in Skull Base and Clival Chordoma: An NCDB Analysis

Objectives: Skull base chordomas are locally aggressive malignant tumors derived from the notochord remnant. There are limited large-scale studies examining the role and extent of surgery and radiation therapy. Design: Analysis of the National Cancer Database (NCDB) was performed to evaluate the survival outcomes of various treatments, and to assess for predictors of overall survival (OS). Participants: Retrospective, population-based cohort study of patients diagnosed with a clival/skull base chordoma between 2004-2015 in the NCDB. Main Outcome Measures: The primary outcome was overall survival (OS). Results: 468 cases were identified. 49% of patients received surgery and 20.7% had positive margins. Mean age at diagnosis was 48.4 years in the surgical cohort, and 55% were male. Of the surgical cohort, 33.8% had negative margins, 20.7% had positive margins, and 45.5% had unknown margin status. Age ≥ 65 (HR 3.07, 95% CI 1.63-5.76, p<0.001), diagnosis between 2010-2015 (HR 0.49, 95% CI 0.26-0.90, p=0.022), tumor size >5 cm (HR 2.29, 95% CI 1.26-4.15, p=0.007) and government insurance (HR 2.28, 95% CI 1.24-4.2, p=0.008) were independent predictors of OS. When comparing surgery with or without adjuvant radiation, no survival differences were found, regardless of margin status (P=0.66). Conclusions: Surgery remains the mainstay of therapy. Advanced age over 65, large tumor size, and government insurance were predictors of worse OS. While negative margins and the use of adjuvant radiation did not appear to impact OS, these may very well reduce local recurrences. A multidisciplinary approach is critical in achieving optimal outcomes in this challenging disease.

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 2002-2021 were retrospectively reviewed at our hospital. 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, we proposed the T4-subclassification. Results In 46 patients, the tumors were in T1 stage in 8 patients, T2 in 10, T3 in 5, and T4 in 23. 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 p = 0.13). 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 p = 0.03). 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 to achieve a good survival rate even in patients with locally advanced tumors.

Dispersed Bone Spicules as a Cause of Postoperative Headache after Retrosigmoid Vestibular Schwannoma Surgery: A Myth?

Objectives Dispersion of bone dust in the posterior fossa during retrosigmoid craniectomy for vestibular schwannoma (VS) resection could be a source of meningeal irritation and lead to development of persistent postoperative headaches (POH). We aim to determine risk factors, including whether the presence of bone spicules that influence POH after retrosigmoid VS resection. Design Present study is a retrospective case series. Setting The study was conducted at a tertiary skull-base referral center. Participants Adult patients undergoing VS resection via a retrosigmoid approach between November 2017 and February 2020 were included for this study. Main Outcome Measures Development of POH lasting ≥ 3 months is the primary outcome of this study. Results Of 64 patients undergoing surgery, 49 had complete data (mean age, 49 years; 53% female). Mean follow-up time was 2.4 years. At latest follow up, 16 (33%) had no headaches, 14 (29%) experienced headaches lasting <3 months, 19 (39%) reported POH lasting ≥3 months. Twenty-seven (55%) patients had posterior fossa bone spicules detectable on postoperative computed tomography (CT). Age, gender, body mass index, length of stay, tumor diameter, size of craniectomy, the presence of bone spicules, or the amount of posterior petrous temporal bone removed from drilling did not differ significantly between patients with POH and those without. On multivariate logistic regression, patients with POH were less likely to have preoperative brainstem compression by the tumor (odds ratio [OR] = 0.21, p = 0.028) and more likely to have higher opioid requirements during hospitalization (OR = 1.023, p = 0.045). Conclusion The presence of bone spicules in the posterior fossa on postoperative CT did not contribute to headaches following retrosigmoid craniectomy approach for VS resection.

Impact of Race, Ethnicity, and Socioeconomic Status on Nasopharyngeal Carcinoma Disease-Specific and Conditional Survival

Introduction Race, ethnicity, and socioeconomic status (SES) are complex, interconnected social determinants of health outcomes. This study uses multivariable analysis on a combination of large national datasets to examine the effects of these factors on 5-year disease-specific survival (DSS) and conditional DSS (CDSS) for nasopharyngeal carcinoma (NPC). Methods A retrospective study of adults with NPC between 2000 and 2017 from the Surveillance, Epidemiology, End Results (SEER) registry was performed, using the National Cancer Institute Yost Index, a census tract–level composite score of SES to categorize patients. Kaplan–Meier analysis and Cox's regression for DSS and CDSS were stratified by SES. Logistic regression was conducted to identify risk factors for advanced cancer stage at time of diagnosis and receiving multimodal therapy. Results Our analysis included 5,632 patients. DSS was significantly associated with race and SES (p < 0.01). Asian/Pacific Islander patients exhibited increased survival when controlling for other variables (hazard ratio [HR] = 0.73, p < 0.01). Although Black patients were more likely to be diagnosed with advanced disease (Black odds ratio [OR] = 1.47, p < 0.01), Black patients were also less likely to receive multimodal therapy; however, this relationship lost statistical significance once SES was incorporated into the multivariable analysis. DSS was decreased among the lowest (first) and middle (second) tertiles of SES (first HR = 1.34, p < 0.01; second HR = 1.20, p < 0.01) compared with the highest (third). Conclusion Our results indicate that race, ethnicity, and SES significantly affect survival, stage at diagnosis, and treatment of NPC. An interplay of tumor biology and inequalities in access to care likely drives these disparities.