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During intraoperative monitoring of motor evoked potentials (MEP), heterogeneity across studies in terms of study populations, intraoperative settings, applied warning criteria, and outcome reporting exists. A scoping review of MEP warning criteria in supratentorial surgery was conducted in accordance with the Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR). Sixty-eight studies fulfilled the eligibility criteria. The most commonly used alarm criteria were MEP signal loss, which was always a major warning sign, followed by amplitude reduction and threshold elevation. Irreversible MEP alterations were associated with a higher number of transient and persisting motor deficits compared with the reversible changes. In almost all studies, specificity and Negative Predictive Value (NPV) were high, while in most of them, sensitivity and Positive Predictive Value (PPV) were rather low or modest. Thus, the absence of an irreversible alteration may reassure the neurosurgeon that the patient will not suffer a motor deficit in the short-term and long-term follow-up. Further, MEPs perform well as surrogate markers, and reversible MEP deteriorations after successful intervention indicate motor function preservation postoperatively. However, in future studies, a consensus regarding the definitions of MEP alteration, critical duration of alterations, and outcome reporting should be determined.

ObjectiveSpinal cerebrospinal fluid (CSF) leaks cause spontaneous intracranial hypotension (SIH). Microsurgery can sufficiently seal spinal CSF leaks. Yet, some patients suffer from residual symptoms. Aim of the study was to assess predictors for favorable outcome after surgical treatment of SIH.MethodsWe included consecutive patients with SIH treated surgically from January 2013 to May 2020. Subjects were surveyed by a questionnaire. Primary outcome was resolution of symptoms as rated by the patient. Secondary outcome was postoperative headache intensity on the numeric rating scale (NRS). Association between variables and outcome was assessed using univariate and multivariate regression. A cut-off value for continuous variables was calculated by a ROC analysis.ResultsSixty-nine out of 86 patients (80.2%) returned the questionnaire and were analyzed. Mean age was 46.7 years and 68.1% were female. A significant association with the primary and secondary outcome was found only for preoperative symptom duration (p = 0.001 and p < 0.001), whereby a shorter symptom duration was associated with a better outcome. Symptom duration remained a significant predictor in a multivariate model (p = 0.013). Neither sex, age, type of pathology, lumbar opening pressure, nor initial presentation were associated with the primary outcome. ROC analysis yielded treatment within 12 weeks as a cut-off for better outcome.ConclusionShorter duration of preoperative symptoms is the most powerful predictor of favorable outcome after surgical treatment of SIH. While an initial attempt of conservative treatment is justified, we advocate early definitive treatment within 12 weeks in case of persisting symptoms.

BackgroundDue to its complexity and to existing treatment alternatives, exposure to intracranial aneurysm microsurgery at the time of neurosurgical residency is limited. The current state of the art includes training methods like assisting in surgeries, operating under supervision, and video training. These approaches are labor-intensive and difficult to fit into a timetable limited by the new work regulations. Existing virtual reality (VR)–based training modules lack patient-specific exercises and haptic properties and are thus inferior to hands-on training sessions and exposure to real surgical procedures.Materials and methodsWe developed a physical simulator able to reproduce the experience of clipping an intracranial aneurysm based on a patient-specific 3D-printed model of the skull, brain, and arteries. The simulator is made of materials that not only imitate tissue properties including arterial wall patency, thickness, and elasticity but also able to recreate a pulsatile blood flow. A sample group of 25 neurosurgeons and residents (n = 16: early residency with less than 4 years of neurosurgical exposure; n = 9: late residency and board-certified neurosurgeons, 4–15 years of neurosurgical exposure) took part to the study. Participants evaluated the simulator and were asked to answer questions about surgical simulation anatomy, realism, haptics, tactility, and general usage, scored on a 5-point Likert scale. In order to evaluate the feasibility of a future validation study on the role of the simulator in neurosurgical postgraduate training, an expert neurosurgeon assessed participants’ clipping performance and a comparison between groups was done.ResultsThe proposed simulator is reliable and potentially useful for training neurosurgical residents and board-certified neurosurgeons. A large majority of participants (84%) found it a better alternative than conventional neurosurgical training methods.ConclusionThe integration of a new surgical simulator including blood circulation and pulsatility should be considered as part of the future armamentarium of postgraduate education aimed to ensure high training standards for current and future generations of neurosurgeons involved in intracranial aneurysm surgery.

Background Given the changes in the current learning environment health professionals are facing major challenges to keep up with current and updated information with the rapidly growing clinical and scientific knowledge base. Being able to identify relevant, high-quality articles, adapt or adopt to new learning strategies with an already intense workload are just a few of the main challenges. Self-directed learning is a key skill of competent health professionals and describes the process by which individuals evaluate their learning needs, goals and the resources needed for learning, however the emerging problems for professionals practicing SDL are manifold. Design A qualitative, exploratory approach based on four research questions was used to understand how skilled neurosurgeons maintain and update their professional knowledge. Twenty-six neurosurgeons within the University Hospital of Bern completed a semi-structured interview. Results One of the main findings concerns the differences between neurosurgeons regarding the SDL strategies they employ, which is compounded by their level of experience. All participants recognized that new or alternative learning approaches are necessary to manage the learning landscape, and for many this concerned their use of learning digital tools. Many, however, were unsure how to change their current behavior. Conclusion The results highlight that positive factors influencing SDL in the workplace include learning leadership and support in identifying new or alternative strategies, an internal culture committed to learning as well as digital learning tools and networks. All are vital in managing the continuously evolving learning environment.

Abstract BACKGROUND Spinal cerebrospinal fluid (CSF) leaks are the cause of spontaneous intracranial hypotension (SIH). OBJECTIVE To propose a surgical strategy, stratified according to anatomic location of the leak, for sealing all CSF leaks around the 360° circumference of the dura through a single tailored posterior approach. METHODS All consecutive SIH patients undergoing spinal surgery were included. The anatomic site of the leak was exactly localized. We used a tailored hemilaminotomy and intraoperative neurophysiological monitoring (IOM) for all cases. Neurological status was assessed before and up to 90 d after surgery. RESULTS Forty-seven SIH patients had an identified CSF leak between the levels C6 and L1. Leaks, anterior to the spinal cord, were approached by a transdural trajectory (n = 28). Leaks lateral to the spinal cord by a direct extradural trajectory (n = 17) and foraminal leaks by a foraminal microsurgical trajectory (n = 2). The transdural trajectory necessitated cutting the dentate ligament accompanied by elevation and rotation of the spinal cord under continuous neuromonitoring (spinal cord release maneuver, SCRM). Four patients had transient defiticts, none had permanent neurological deficits. We propose an anatomic classification of CSF leaks into I ventral (77%, anterior dural sac), II lateral (19%, including nerve root exit, lateral, and dorsal dural sac), and III foraminal (4%). CONCLUSION Safe sealing (with IOM) of all CSF leaks around the 360° surface of the dura is feasible through a single posterior approach. The exact surgical trajectory is selected according to the anatomic category of the leak.

Intraoperative neurophysiological monitoring (IONM) guides the surgeon in ensuring motor pathway integrity during high-risk neurosurgical and orthopedic procedures. Although motor-evoked potentials (MEPs) are valuable for predicting motor outcomes, the key features of predictive signals are not well understood, and standardized warning criteria are lacking. Developing a muscle identification prediction model could increase patient safety while allowing the exploration of relevant features for the task. The aim of this study is to expand the development of machine learning (ML) methods for muscle classification and evaluate them in a bicentric setup. Further, we aim to identify key features of MEP signals that contribute to accurate muscle classification using explainable artificial intelligence (XAI) techniques. This study used ML and deep learning models, specifically random forest (RF) classifiers and convolutional neural networks (CNNs), to classify MEP signals from routine supratentorial neurosurgical procedures from two medical centers according to muscle identity of four muscles (extensor digitorum, abductor pollicis brevis, tibialis anterior, and abductor hallucis). The algorithms were trained and validated on a total of 36,992 MEPs from 151 surgeries in one center, and they were tested on 24,298 MEPs from 58 surgeries from the other center. Depending on the algorithm, time-series, feature-engineered, and time-frequency representations of the MEP data were used. XAI techniques, specifically Shapley Additive Explanation (SHAP) values and gradient class activation maps (Grad-CAM), were implemented to identify important signal features. High classification accuracy was achieved with the RF classifier, reaching 87.9% accuracy on the validation set and 80% accuracy on the test set. The 1D- and 2D-CNNs demonstrated comparably strong performance. Our XAI findings indicate that frequency components and peak latencies are crucial for accurate MEP classification, providing insights that could inform intraoperative warning criteria. This study demonstrates the effectiveness of ML techniques and the importance of XAI in enhancing trust in and reliability of artificial intelligence-driven IONM applications. Further, it may help to identify new intrinsic features of MEP signals so far overlooked in conventional warning criteria. By reducing the risk of muscle mislabeling and by providing the basis for possible new warning criteria, this study may help to increase patient safety during surgical procedures.

Clazosentan, an endothelin receptor antagonist, significantly and dose-dependently reduced angiographic vasospasm after aneurysmal subarachnoid haemorrhage (aSAH). We investigated whether clazosentan reduced vasospasm-related morbidity and all-cause mortality. In this randomised, double-blind, placebo-controlled, phase 3 study, we randomly assigned patients with aSAH secured by surgical clipping to clazosentan (5 mg/h, n=768) or placebo (n=389) for up to 14 days (27 countries, 102 sites, inpatient and outpatient settings) using an interactive web response system. The primary composite endpoint (week 6) included all-cause mortality, vasospasm-related new cerebral infarcts, delayed ischaemic neurological deficit due to vasospasm, and rescue therapy for vasospasm. The main secondary endpoint was dichotomised extended Glasgow outcome scale (GOSE; week 12). This trial is registered with ClinicalTrials.gov, number NCT00558311. In the all-treated dataset, the primary endpoint was met in 161 (21%) of 764 clazosentan-treated patients and 97 (25%) of 383 placebo-treated patients (relative risk reduction 17%, 95% CI −4 to 33; p=0·10). Poor functional outcome (GOSE score ≤4) occurred in 224 (29%) clazosentan-treated patients and 95 (25%) placebo-treated patients (−18%, −45 to 4; p=0·10). Lung complications, anaemia, and hypotension were more common with clazosentan. Mortality (week 12) was 6% in both groups. Clazosentan at 5 mg/h had no significant effect on mortality and vasospasm-related morbidity or functional outcome. Further investigation of patients undergoing endovascular coiling of ruptured aneurysms is needed to fully understand the potential usefulness of clazosentan in patients with aSAH. Actelion Pharmaceuticals.

Based on the current guidelines, there is no consensus on inpatient treatment including cerebral vasospasm prophylaxis and follow-up imaging for perimesencephalic nonaneurysmal subarachnoid hemorrhage (NASAH). To evaluate the daily practice of neurosurgeons within the Vascular Section of the European Association of Neurosurgical Societies (EANS) an online survey was performed from February 2023 to June 2023. Thirty-two questionnaires were answered from eighteen different countries. Most answers were provided from employees of University Hospitals ( n  = 27; 84.4%). Up to five NASAH cases per year were reported by 10 (31.3%), another 12 (37.4%) treat more than 20 cases. The majority of contributors (65.6%) estimate the complication rates in NASAH to be less than 2%. Inpatient monitoring was significantly influenced by the initial presentation and the distribution of blood observed in the CT scan, with significantly more patients being admitted to the intensive care unit in case 3 ( p  = 0.011) compared to case 1. Further, the therapeutic approaches differ in the blood pressure monitoring ( p  = 0.08). However, this finding did not achieve statistical significance. In case 1 and case 2 neither cerebral vasospasm prophylaxis nor transcranial doppler sonography is performed in 11 centers (34.4%) which decreases statistically significantly in case 3 ( n  = 2; 6.3%; p  = 0.0014). This study confirms that, the amount of blood in the first native CT scan influences the treatment decision. However, clear intercontinental differences cannot be evaluated due to the small number of participants.

Purpose Spontaneous spinal epidural hematoma (SSEH) is a rare pathology characterized by a hemorrhage in the spinal epidural space without prior surgical or interventional procedure. Recent literature reported contradictory findings regarding the clinical, radiological and surgical factors determining the outcome, hence the objective of this retrospective analysis was to re-assess these outcome-determining factors. Methods Patients surgically treated for SSEH at our institution from 2010 – 2022 were screened and retrospectively assessed regarding management including the time-to-treatment, the pre-and post-treatment clinical status, the radiological findings as well as other patient-specific parameters. The outcome was assessed using the modified McCormick Scale. Statistical analyses included binary logistic regression and Fisher’s exact test. Results In total, 26 patients (17 men [65%], 9 women [35%], median age 70 years [interquartile range 26.5]) were included for analysis. The SSEHs were located cervically in 31%, cervicothoracically in 42% and thoracically in 27%. Twenty-four patients (92%) improved after surgery. Fifteen patients (58%) had a postoperative modified McCormick Scale grade of I (no residual symptoms) and 8 patients (31%) had a grade of II (mild symptoms). Only 3 (12%) patients remained with a modified McCormick Scale grade of IV or V (severe motor deficits / paraplegic). Neither time-to-treatment, craniocaudal hematoma expansion, axial hematoma occupation of the spinal canal, anticoagulation or antiplatelet drugs, nor the preoperative clinical status were significantly associated with the patients’ outcomes. Conclusion Early surgical evacuation of SSEH generally leads to favorable clinical outcomes. Surgical hematoma evacuation should be indicated in all patients with symptomatic SSEH.

Background The technique of 5-aminolevulinic acid (5-ALA) tumor fluorescence is increasingly used to improve visualization of tumor tissue and thereby to increase the rate of patients with gross total resections. In this study, we measured the resection volumes in patients who underwent 5-ALA-guided surgery for non-eloquent glioblastoma and compared them with the preoperative tumor volume. Methods We selected 13 patients who had received a complete resection according to intraoperative 5-ALA induced fluorescence and CRET according to post-operative T1 contrast-enhanced MRI. The volumes of pre-operative contrast enhancing tissue, post-operative resection cavity and resected tissue were determined through shift-corrected volumetric analysis. Results The mean resection cavity (29 cm 3 ) was marginally smaller than the pre-operative contrast-enhancing tumor (39 cm 3 , p  = 0.32). However, the mean overall resection volume (84 cm 3 ) was significantly larger than the pre-operative contrast-enhancing tumor (39 cm 3 , p  = 0.0087). This yields a mean volume of resected 5-ALA positive, but radiological non-enhancing tissue of 45 cm 3 . The mean calculated rim of resected tissue surpassed pre-operative tumor diameter by 6 mm (range 0–10 mm). Conclusions Results of the current study imply that (i) the resection cavity underestimates the volume of resected tissue and (ii) 5-ALA complete resections go significantly beyond the volume of pre-operative contrast-enhancing tumor bulk on MRI, indicating that 5-ALA also stains MRI non-enhancing tumor tissue. Use of 5-ALA may thus enable extension of coalescent tumor resection beyond radiologically evident tumor. The impact of this more extended resection method on time to progression and overall survival has not been determined, and potentially puts adjacent and functionally intact tissue at risk.