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Background: Transnasal endoscopic decompression of the optic nerve is increasingly gaining acceptance among ear, nose, and throat (ENT) surgeons, however neither strict indications for the procedure nor the precise extent of effective decompression have been firmly established to date. This study aimed to determine the distance between endoscopically visible, anatomical structures within the sphenoid sinus and the posterior (i.e. intracranial) endpoint of decompression. The lateral optico-carotid recess (LOCR) is proposed as a reference for the undertaken measurements., Methods: The precise localizations of the LOCR and the point at which the optic nerve is covered by bone only for 180° of its circumference were determined using high-resolution computed tomography performed in 30 subjects (60 orbits). Reformed high-resolution computed tomography scans, perpendicular to the optic canal, were used for all measurements., Results: The point at which optic nerve decompression can be safely terminated was identified in proximity to the medial edge of the LOCR: in all cases, no further than 2.5 mm anterior to this landmark (assigned a negative value) and no further than 1.3 mm posterior (assigned positive values), with a mean of -0.4±1.3 mm. When measured from the orbital apex, the distance ranged from 4.8 to 14.4 mm, with a mean of 8.7±2.5 mm., Conclusions: The LOCR can be directly discernible by the endoscopic surgeon and identified on the reconstructed high-resolution computed tomography scans, offering a reliable landmark for designating the required extent of decompression. Measurements related to the orbital apex proved less credible, and additionally, this landmark is challenging to identify during surgery., Competing Interests: Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://qims.amegroups.com/article/view/10.21037/qims-24-1125/coif).The authors have no conflicts of interest to declare., (2024 AME Publishing Company. All rights reserved.)

Proline metabolism has been identified as a significant player in several neoplasms, but knowledge of its role in gliomas is limited despite it providing a promising line of pursuit. Data on proline metabolism in the brain are somewhat historical. This study aims to investigate alterations of proline metabolism in gliomas of WHO grade 4 (GG4) in the context of the brain. A total of 20 pairs of samples were studied, consisting of excised tumor and unaffected brain tissue, obtained when partial brain resection was required to reach deep-seated lesions. Levels of proline oxidase/proline dehydrogenase (POX/PRODH), Δ 1 -pyrroline-5-carboxylate reductases (PYCR1/2/3), prolidase (PEPD), and metalloproteinases (MMP-2, MMP-9) were assessed, along with the concentration of proline and proline-related metabolites. In comparison to normal brain tissue, POX/PRODH expression in GG4 was found to be suppressed, while PYCR1 expression and activity of PEPD, MMP-2, and -9 were upregulated. The GG4 proline concentration was 358% higher. Hence, rewiring of the proline metabolism in GG4 was confirmed for the first time, with a low-POX/PRODH/high-PYCR profile. High PEPD and MMPs activity is in keeping with GG4-increased collagen turnover and local aggressiveness. Further studies on the mechanisms of the interplay between altered proline metabolism and the GG4 microenvironment are warranted.

Purpose: While Ruptured Arteriovenous Malformation Grading Scale (RAGS) has recently been validated in children, the literature lacks validation on adults exclusively. Therefore, we aimed to determine the validity of RAGS on the external multicenter adult cohort and compare its accuracy with other scales., Methods: A retrospective analysis was performed in five neurosurgical departments to extract patients who presented with the first episode of acute brain arteriovenous malformation (bAVM) rupture between 2012 and 2019. Standard logistic regression and area under the receiver operating curve (AUROC) calculations were performed to determine the value of the following scales: intracerebral hemorrhage (ICH), AVM-associated ICH (AVICH), Spetzler-Martin (SM), Supplemented SM (Supp-SM), Hunt and Hess (HH), Glasgow Coma Scale (GCS), World Federation of Neurological Surgeons (WFNS), and RAGS to predict change in categorical and dichotomized modified Rankin Scale (mRS) across three follow-up periods: within the 6 months, 6 months to 1 year, and above 1 year., Results: Sixty-one individuals with a mean age of 43.6 years were included. The RAGS outperformed other grading scales during all follow-up time frames. It showed AUROC of 0.78, 0.74, and 0.71 at the first 6 months, between 6 and 12 months, and after 12 months of follow-up, respectively, when categorized mRS was applied, while corresponding values were 0.79, 0.76, and 0.73 for dichotomized mRS, respectively., Conclusion: The RAGS constitutes a reliable scale predicting clinical outcomes following bAVM rupture among adults. Furthermore, the RAGS proved its generalizability across medical centers with varying treatment preferences., (© 2022. The Author(s).)

Purpose: We aimed to study brain tissue oxygenation during the period of controlled reduction of arterial blood pressure - a maneuver often used in extended endoscopic skull base surgery for bloodless operative field., Methods: Intracranial pressure, arterial blood pressure and the resultant cerebral perfusion pressure were measured during extended endoscopic skull base surgery in 5 patients with diagnosed tumors of the skull base and arterial hypertension. Simultaneously, in those patients, we measured partial pressure of oxygen in the brain parenchyma (PbtO 2 )., Results: Values of PbtO 2 lower than 15 mm Hg (risk of brain ischemia) were observed in 3 patients for periods of 40 min, 110 min and 123 min, respectively. In 2 of these patients, no hypotension (mean arterial pressure <65 mm Hg) was necessary for bloodless operative field. Another 2 patients had PbtO 2 above 30 mm Hg at the time when their mean arterial pressure was below 65 mm Hg. The time course of PbtO 2 followed that of cerebral perfusion pressure with a time lag of 40-60 s in all patients., Conclusion: Moderate reduction of arterial pressure, often used to obtain bloodless operative field during extended endoscopic skull base surgery, may in patients with the medical history of arterial hypertension be associated with critically low values of partial oxygen pressure in brain tissue., Competing Interests: Declaration of competing interest The authors declare no conflict of interests., (Copyright © 2020 The Authors. Published by Elsevier B.V. All rights reserved.)