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The α-synuclein seed amplification assay: Interpreting a test of Parkinson\u27s pathology
No full textThe α-synuclein seed amplification assay (αSyn-SAA) sensitively detects Lewy pathology, the amyloid state of α-synuclein, in the cerebrospinal fluid (CSF) of patients with Parkinson\u27s disease (PD). The αSyn-SAA harnesses the physics of seeding, whereby a superconcentrated solution of recombinant α-synuclein lowers the thermodynamic threshold (nucleation barrier) for aggregated α-synuclein to act as a nucleation catalyst ( seed ) to trigger the precipitation (nucleation) of monomeric α-synuclein into pathology. This laboratory setup increases the signal for identifying a catalyst if one is present in the tissue examined. The result is binary: positive, meaning precipitation occurred, and a catalyst is present, or negative, meaning no precipitation, therefore no catalyst. Since protein precipitation via seeding can only occur at a concentration many-fold higher than the human brain, laboratory-elicited seeding does not mean human brain seeding. We suggest that a positive αSyn-SAA reveals the presence of pathological α-synuclein but not the underlying etiology for the precipitation of monomeric α-synuclein into its pathological form. Thus, a positive αSyn-SAA supports a clinical diagnosis of PD but cannot inform disease pathogenesis, ascertain severity, predict the rate of progression, define biology or biological subtypes, or monitor treatment response
Extra-axial cavernous malformation of the cerebellopontine angle: illustrative case
No full textBACKGROUND: Extra-axial cavernous malformations (CMs) in the cerebellopontine angle (CPA) are rare, typically affect cranial nerves (CNs), and present significant therapeutic challenges. This report discusses the case of a patient with an extra-axial CM in the CPA involving the CN VII/VIII complex, alongside a systematic review of similar cases. OBSERVATIONS: A literature search of the PubMed and Embase databases identified 216 articles, with 18 meeting the inclusion criteria, encompassing 21 cases (average age 42.6 years). The most common symptoms were hearing loss (86%), facial palsy (43%), and facial numbness (33%). After surgery, hearing improved in 26% of patients and facial palsy improved in 37%. Overall, 32% of patients experienced postoperative improvement. One death was reported. LESSONS: These lesions can cause significant symptoms, often leading to unfavorable clinical outcomes despite surgical intervention. Gross-total resection with CN preservation is the goal, but more data with earlier intervention and longer follow-up are needed to refine treatment strategies. https://thejns.org/doi/10.3171/CASE24528
Microanatomy of the Temporal Division of the Facial Nerve in the Periorbital Region Applied to Minimally Invasive Keyhole Approaches
No full textBACKGROUND: Minimally invasive keyhole approaches to the anterior skull base and circle of Willis require small incisions near distal branches of the temporal division (TD) of the facial nerve. Few studies have focused on planning the incision to avoid the TD branches and maximize exposure in these approaches. This study aimed to define a safe zone away from the TD branches for skin incision during minimally invasive keyhole approaches using reliable and practical skin landmarks. METHODS: In 5 cadaveric heads (10 sides), a Cartesian system was established with the orbitomeatal line connecting the lateral canthus and the external acoustic meatus (x-axis). A perpendicular line was drawn to the x-axis at the lateral canthus (y-axis). TD branches were dissected proximally to distally until the nerve-muscle junction of the orbicularis oculi and fronto-occipitalis muscles. Nerve-muscle junction points were registered in the Cartesian system. Probabilistic heat maps were generated to define a periorbital safe zone. RESULTS: A median of 3 branches each innervated the orbicularis oculi and fronto-occipitalis. A semicircular area centered on the lateral canthus with a radius of 10 mm was found to have low (\u3c10%) chance of containing a TD branch. This safe zone could be extended posteriorly to 15 mm inferior to the orbitomeatal line. CONCLUSIONS: Identifying a safe zone for preserving TD branches is crucial for surgical incisions planned in the superolateral region of the orbit. This study provides a clinically applicable and reproducible landmark for planning incisions commonly used during minimally invasive keyhole approaches
Prediction of Postoperative Segmental Lordosis at L5 to S1 After Single-Level Anterior Lumbar Interbody Fusion
No full textBACKGROUND: Anterior lumbar interbody fusion (ALIF) is used to improve spinopelvic alignment, most commonly by increasing segmental lordosis (SL) at L5 to S1. Achieving certain radiographic parameters is critical for good patient outcomes. However, the relationships between pre- and postoperative SL and interbody dimensions are inexact and have not been well studied. This study investigated the relationships between postoperative SL at L5 to S1, ALIF cage angle, and preoperative radiographic measurements to improve the predictability of surgical radiographic outcomes after L5 to S1 ALIF. METHODS: A single-center database was retrospectively reviewed for patients who underwent L5 to S1 ALIF from January 2017 to December 2022. Patients with posterior percutaneous instrumentation were included in the study, but patients with posterior decompression or facetectomies at L5 to S1 were excluded. Pre- and postoperative scoliosis films and patient surgical data were analyzed. A multilinear regression analysis was performed to create a predictive model of postoperative L5 to S1 SL. RESULTS: This study evaluated 46 single-level L5 to S1 ALIFs. Using mixed-effects linear regression analysis, postoperative L5 to S1 SL can be predicted with statistical significance (P \u3c 0.001) and power of 0.98 if the cage angle and preoperative L5 to S1 SL are known using the following formula: SL = 8.741 + (0.454 × C) + (0.595 × SL), where SL is postoperative L5 to S1 SL in degrees, C is cage angle in degrees, and SL is preoperative L5 to S1 SL in degrees. CONCLUSIONS: Cage angle and preoperative L5 to S1 SL were predictive of postoperative SL after L5 to S1 ALIF. The ability to predict postoperative radiographic values is critically important for good patient outcomes, and efforts should be made to develop more sophisticated mathematical models
Geographic Disparities in Neurosurgery Workforce Adequacy Across the United States: Projections to 2037
No full textBACKGROUND AND OBJECTIVES: Studies on the adequacy of the neurosurgery workforce have been limited. The objectives of this study were to assess the supply, demand, and adequacy of the neurosurgery workforce in the United States. METHODS: This was a cross-sectional study of US neurosurgeons using data from the Health Workforce Simulation Model. Supply was defined as the number of full-time neurosurgeons working in the United States. Demand was defined as the number of full-time neurosurgeons needed to meet healthcare needs under status quo and improved access scenarios. Workforce adequacy was defined as the ratio of supply and demand. Linear regression was used to analyze workforce trends. RESULTS: From 2025 to 2037, the supply of neurosurgeons was projected to increase from 7030 to 7230 (2.8% increase, P \u3c .001). Over the same period, demand was projected to increase under status quo (7310 to 8310, 13.7% increase, P \u3c .001) and improved access (10 210 to 11 830, 15.9% increase, P \u3c .001) scenarios. Accordingly, neurosurgery workforce adequacy was projected to decrease under status quo (96.2% to 87.0%, P \u3c .001) and improved access (68.9% to 61.1%, P \u3c .001) scenarios. In 2025, neurosurgery workforce adequacy was lower in nonmetropolitan areas compared with metropolitan areas under the status quo (30.8% vs 101%, P \u3c .001) and improved access (10.7% vs 78.8%, P \u3c .001) scenarios. In 2025, the states with the lowest neurosurgery workforce adequacy were Nevada (42.9%), New Jersey (66.7%), and Indiana (73.3%). By 2037, the states with the lowest projected neurological surgery workforce adequacy were Delaware (33.3%), Nevada (37.5%), New Hampshire (50.0%), and Vermont (50.0%). CONCLUSION: Projected inadequacies exist for the neurosurgery workforce, which are greatest in nonmetropolitan areas and certain US states. Future research is needed to develop strategies that improve neurosurgery workforce adequacy including training opportunities to increase the supply of future neurosurgeons
Pterional craniotomy for occlusion of a basal temporal arteriovenous fistula
No full textAtypical arteriovenous fistulas (AVFs) lack the parenchymal nidus observed in arteriovenous malformations (AVMs) and are not dural-based lesions supplied by meningeal arteries, unlike true dural AVFs. Atypical AVFs are parenchymally based with a nondural arterial supply. This video presents a man in his 50s with a remote carotid takedown for flow reduction of a described temporal AVM. Imaging showed a basal temporal AVF supplied by middle cerebral artery branches, coalescence of arterial feeders onto a large venous varix, and no intervening nidus. Dearterialization of the venous varix eliminated the shunting lesion. Atypical AVFs are often misdiagnosed but can be cured with microsurgical interruption. The video can be found here: https://stream.cadmore.media/r10.3171/2025.7.FOCVID2587
Pterional vs. mini-pterional craniotomy for intracranial aneurysms: a systematic review and meta-analysis
No full textThe mini-pterional craniotomy (mPT) was designed to be a minimally invasive alternative to the standard pterional (PT) approach. However, it remains unclear which technique produces better results. Thus, we aimed to perform a meta-analysis comparing functional, surgical, and aesthetic outcomes between mPT and PT in intracranial aneurysms. We searched PubMed, EMBASE, Web of Science, and Cochrane Library for studies comparing mPT to PT in patients who underwent clipping of brain aneurysms until June 2024. Outcomes were modified Rankin Scale (mRS) or Glasgow Outcome Scale (GOS), surgical complications, operation time, length of stay, and patients\u27 aesthetic satisfaction. Statistical analysis was performed using the R software (version 4.4.0). Heterogeneity was assessed with I statistics. We included 6 studies with a total of 1011 patients, of whom 696 (63.1%) underwent mPT. The mean age was 59.0 ± 2.8 years, 67.6% were female, and 68.2% of all aneurysms were located in the middle cerebral artery. Unfavorable functional outcome (mRS ≥ 3 or GOS ≤ 3) at discharge (OR 0.21, 95% CI: 0.07-0.59; I = 0%), overall surgical complications (OR 0.45, 95% CI: 0.21-0.99; I = 72%), and operation time (MD - 54.42 min, 95% CI: -60.78 to - 48.06; I = 0%) were significantly lower in mPT compared to PT. Moreover, patients\u27 aesthetic satisfaction was statistically higher in mPT (OR 2.91, 95% CI: 1.06-8.00; I = 0%). However, there was no significant difference in length of stay between groups (MD - 1.52 days, 95% CI: -3.75 to 0.72; I = 72%). Mini-pterional craniotomy is associated with better functional outcomes at discharge, fewer surgical complications, and a shorter operation time. Therefore, our results might suggest that mPT is a promising and preferable alternative to standard PT
Risk Models for Adverse Events in Microsurgery for Intracranial Unruptured Aneurysms
No full textBACKGROUND AND OBJECTIVES: Preventive treatment of unruptured intracranial aneurysms (UIAs) requires assessment of treatment risks vs expected benefit. Although established scores exist to estimate rupture and growth risk, currently, no externally validated tools exist to estimate the risks of microsurgical treatment of UIAs. Clinical prediction models based on machine learning enable generation of personalized risk estimates for each individual patient based on their specific patient and aneurysm characteristics. METHODS: Using data from 20 international centers from the prediction of adverse events after microsurgery for intracranial unruptured aneurysms study on patients treated microsurgically for UIAs, we developed and externally validated clinical prediction models for 3 outcomes measured at hospital discharge: poor neurological outcome (modified Rankin Score ≥3), new sensorimotor neurological deficits, and all-cause adverse events (Clavien-Dindo Grade ≥1). RESULTS: A total of 3705 patients were included. Data from 13 centers (2881, 78%) were used for model development. Fully trained models were evaluated on 824 patients (22%) from 7 additional centers. Average age was 56 ± 12 years, and 1049 (28%) were male. At discharge, poor neurological outcome was seen in 514 patients (14%). New sensorimotor deficits were observed in 534 patients (14%), and 894 patients (24%) experienced adverse events until discharge. At external validation, prediction of poor neurological outcome was achieved with good calibration and an area under the curve (AUC) = 0.70 (95% CI: 0.63-0.75). Similarly, new neurological deficits were predicted with good calibration and with an AUC = 0.69 (95% CI: 0.63-0.74). Prediction of all-cause adverse events only achieved an AUC = 0.59 (95% CI: 0.55-0.64) with fair calibration. The prediction model was integrated into a web application accessible at https://neurosurgery.shinyapps.io/PRAEMIUM/. CONCLUSION: The developed models for prediction of poor neurological outcome and new sensorimotor neurological deficits at discharge exhibit good calibration and fair discrimination based on a multinational external validation, indicating that the predicted probabilities correspond well to real-world risks and may thus be clinically useful in more objectively estimating the risk of microsurgical treatment
The Complexities of Aeronautical Transfer of Acutely Unwell Neurosurgical Patients
No full textOBJECTIVE: Neurosurgical care is difficult to access in many scenarios. Aeromedical evacuation of acutely unwell neurosurgical patients from remote, isolated, or poorly equipped locations can be considered. This article aims to provide a framework of logistical factors that deserve special consideration in the preparation of these patients for transfer. METHODS: We searched all relevant medical literature, military reports, and travel industry documents on transfer of neurosurgical patients. This review was combined with a senior author\u27s (M.J.) extensive relevant experience, to present important factors for neurosurgeons to consider during planning of aeromedical evacuation, highlighting potential preventable causes of deterioration en route. RESULTS: Several criteria must be met for a transfer to be considered. The safe transfer of patients with craniospinal pathology requires efficient collaboration between the referring teams, the receiving units/departments, and the medical transfer service. Clear communication, qualified personnel, and appropriate transportation equipment must be available for the transfer. One must consider unique stressors during the air transfer, including the risk of hypoxia on certain types of flights. Vibration, loud noise, acceleration, and changes in barometric pressure en route may negatively affect the patient during transfer. Patient stabilization before transfer is a priority. Medical conditions that can potentially worsen in-flight should be corrected before transfer. The use of a checklist before departure is highly recommended and is included herein. The timing of transfer concerning the postoperative patient deserves special consideration. CONCLUSIONS: Although there is little published information, this review provides useful criteria and parameters needed for safe aeromedical evacuation of neurosurgical patients