Category: Vascular

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Role of surgical treatment of intracranial aneurysms in the era of endovascular therapy: a review

Neurosurg Focus 59(6):E2, 2025

This review evaluates the contemporary role of microsurgical clipping versus endovascular treatment (EVT) for intracranial aneurysms, comparing long-term durability, complication profiles, and anatomical or patient factors that guide modality selection. It synthesizes trial data (ISAT, BRAT), meta-analyses, and location-specific outcomes to highlight differences in occlusion, retreatment, and morbidity.

The article also outlines practical considerations—hybrid strategies, cerebral bypass, training needs, economics, and global disparities—arguing for individualized, multidisciplinary decision-making and preserving microsurgical expertise despite growing EVT adoption.

Treatment Goals: Exclusion of intracranial aneurysms from circulation while preserving parent vessels and neural function remains the primary objective; both endovascular treatment (EVT) and microsurgical clipping are core modalities.

Long-term Outcomes: Microsurgical clipping offers greater durability and lower rates of recurrence, rebleeding, and retreatment compared to EVT, which has higher retreatment rates despite lower short-term morbidity.

Procedure Selection: EVT is generally preferred for older patients and posterior circulation aneurysms, while microsurgery is favored in younger patients, those with hematomas, mass effect, and aneurysms of the middle cerebral and pericallosal arteries.

Aneurysm Location: Surgical clipping achieves higher occlusion and lower recurrence, especially for anterior circulation, middle cerebral artery, and complex aneurysms; EVT is more suitable for posterior circulation and anatomically challenging cases.

Complications and Adjuncts: Microsurgery allows for evacuation of hematomas and cisternal blood (reducing vasospasm and hydrocephalus), while EVT avoids craniotomy risks but may induce mechanical vasospasm and requires antiplatelet therapy.

Hybrid and Advanced Techniques: Hybrid approaches (combining EVT and surgery) and cerebral bypass remain essential for complex, giant, or recurrent aneurysms not amenable to standard treatments.

Cost and Access: Microsurgical treatment incurs lower overall healthcare costs than EVT; global disparities exist, with surgical clipping dominating in low-resource settings due to limited endovascular infrastructure.

Decision-Making: Optimal management requires individualized, multidisciplinary evaluation considering patient factors, aneurysm characteristics, and resource availability; no single factor should solely dictate treatment choice

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Recurrence of initial angiographic occlusion in intracranial dural arteriovenous fistulas

J Neurosurg 143:1530–1538, 2025

This clinical study analyzes recurrence after angiographic cure of intracranial dural arteriovenous fistulas (DAVFs) using a single-center DREAM-INI cohort of 510 patients. It reports an overall recurrence rate of 8.0%, estimated cumulative recurrence of 13.9% at 36 months and 24.1% at 105 months, and an annual recurrence risk of 6.2%, with most recurrences occurring within 15 months but some delayed beyond 10 years.

The paper identifies independent risk factors including age <45 years, transverse–sigmoid sinus location, multiple fistulae, pial arterial supply, and venous congestion, distinguishes in situ versus remote-site recurrence, explores pathophysiologic mechanisms (venous hypertension, incomplete embolization, angiogenesis), and recommends angiographic follow-up beyond one year for high-risk cured patients.

Recurrence Rate: The overall recurrence rate of intracranial dural arteriovenous fistulas (DAVFs) after initial angiographic cure was 8.0%, with estimated recurrence rates of 13.9% at 36 months and 24.1% at 105 months; the annual recurrence risk was 6.2%.

Types of Recurrence: DAVF recurrence can be classified as in situ recurrence (at the original site) or remote site recurrence (at a different location); both are closely linked to unresolved venous hypertension and previously masked portions of the fistula.

Timing of Recurrence: Most recurrence events (76.6%) occurred within 15 months after initial cure, but delayed recurrences were observed, including cases more than 3 years and up to 10 years later.

Risk Factors: Key risk factors for recurrence included age younger than 45 years, transverse–sigmoid sinus location, multiple fistulae, pial arterial supply, and venous congestion.

Borden Classification: Recurrence was more frequently observed in Borden type II DAVFs, whereas Borden type III DAVFs had a lower recurrence rate when complete occlusion of the proximal draining vein was achieved.

Treatment Implications: Almost all recurrences occurred after endovascular therapy, highlighting the importance of ensuring complete occlusion of the draining vein to minimize recurrence risk.

Clinical Symptoms: There was no clear correlation between clinical symptoms and DAVF recurrence; many recurrences were asymptomatic, emphasizing the need for routine angiographic follow-up.

Follow-Up Recommendation: All patients with cured DAVFs, especially those with identified risk factors, should undergo angiographic follow-up beyond 1 year to detect and manage possible recurrences.

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Optimal imaging follow-up strategies for conservatively managed cerebral cavernous malformations: a cost-effectiveness analysis

J Neurosurg 143:1555–1566, 2025

This study evaluates cost-effectiveness of MRI surveillance intervals for conservatively managed cerebral cavernous malformations (CCMs) using a Markov model and Monte Carlo simulations. It compares 0.5-, 1-, 2-, and 3-year follow-up strategies for brainstem versus nonbrainstem CCMs, calculating lifetime costs, QALYs, and net monetary benefit from a US societal perspective.

Results indicate annual MRI is most cost-effective for brainstem CCMs, while a 3-year MRI interval is preferred for nonbrainstem CCMs, with findings robust to sensitivity analyses that varied hemorrhage rates, mortality, and MRI costs. The authors emphasize individualized follow-up based on symptoms, Zabramski grade, family history, and lesion multiplicity, and note model limitations and US-centric cost data.

Optimal MRI Follow-up for Brainstem CCM: Annual MRI follow-up (every 1 year) is the most cost-effective strategy for conservatively managed, unruptured brainstem cerebral cavernous malformations (CCM), balancing cost and quality-adjusted life years (QALYs).

Optimal MRI Follow-up for Nonbrainstem CCM: MRI follow-up every 3 years is the most cost-effective approach for nonbrainstem CCM, with less frequent imaging justified by lower rupture and rehemorrhage rates.

Markov Model and Monte Carlo Simulation: A decision-analytic Markov model with Monte Carlo simulations was used to compare different MRI follow-up intervals (0.5, 1, 2, and 3 years) for both brainstem and nonbrainstem CCM, incorporating costs, effectiveness (QALYs), and net monetary benefit (NMB).

Key Drivers of Cost-effectiveness: The cost-effectiveness of follow-up strategies is highly sensitive to annual rates of CCM rupture, mortality after rupture, and the cost of MRI; higher hemorrhage or mortality rates favor more frequent imaging.

Individualization of Follow-up: Follow-up intervals should be tailored based on lesion location, symptoms, prior hemorrhage, Zabramski grade, family history, and multiplicity, as higher-risk patients may benefit from closer surveillance.

Brainstem Lesion Risks: Brainstem CCMs have higher annual rupture (2.8%) and rehemorrhage rates (32.3%) compared to nonbrainstem lesions, resulting in greater disability and loss of quality of life, justifying more vigilant follow-up.

MRI Cost Thresholds: As the annual MRI cost increases above $6,581 for brainstem CCM and $8,995 for nonbrainstem CCM, less frequent MRI follow-up (every 2 years) becomes more cost-effective than the previously optimal intervals.

Limitations: The model does not distinguish between cerebellar and supratentorial nonbrainstem lesions, does not account for comorbidities or detailed imaging findings (e.g., Zabramski grade), and uses US-based cost data, which may limit generalizability to other healthcare settings.

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Institutional experience using the endoscopic endonasal approach for the treatment of 40 intracranial aneurysms: indications, outcomes, and technical considerations

J Neurosurg 143:1575–1587, 2025

This clinical series reviews 40 intracranial aneurysms treated via the endoscopic endonasal approach (EEA) over 20 years, outlining patient selection, operative techniques, reconstruction evolution, and outcomes. It emphasizes indications where EEA provides superior ventral access for paraclinoid and selected posterior circulation aneurysms, especially when endovascular therapy is unsuitable.

The report details complication rates—notably CSF leaks—and their temporal improvement, intraoperative adjuncts, follow-up imaging, illustrative cases, and statistical correlations identifying posterior location, age, and SAH as risk factors.

Endoscopic Endonasal Approach (EEA) Indications: EEA is reserved for carefully selected intracranial aneurysms—primarily medially projecting paraclinoidal/cavernous internal carotid artery (ICA) and posterior circulation aneurysms—especially when endovascular treatment is unsuitable and open surgery would risk cranial nerve or brain injury.

Advantages of EEA: Provides a direct ventral surgical corridor, enabling superior proximal/distal vascular control, avoiding brain retraction and cranial nerve manipulation, and facilitating treatment of concomitant sellar pathologies or multiple lesions in a single procedure.

Patient Selection and Outcomes: Out of 34 patients (40 aneurysms) over 20 years, most aneurysms treated were in the paraclinoid/cavernous ICA or posterior circulation; EEA was only used if it was considered safer than open or endovascular approaches, with less than 1% of aneurysm patients treated annually by EEA.

Complication Profile: The main complication was cerebrospinal fluid (CSF) leak (8 cases), particularly in posterior circulation or post-subarachnoid hemorrhage (SAH) cases; other complications included meningitis, clip exposure, lacunar infarcts, and transient cranial nerve palsies. No permanent cranial nerve deficits, visual loss, or procedure-related mortalities occurred since 2019.

Technical Evolution: Advancements in reconstruction techniques and instrumentation (e.g., dedicated endonasal clip appliers, multilayer closure) have reduced complications such as clip exposure and improved overall safety and outcomes over time.

Limitations of EEA: Not suitable for most anterior communicating artery (AcomA) aneurysms due to limited exposure and control; not feasible for revascularization procedures; requires a highly experienced, multidisciplinary team for optimal results.

Comparative Morbidity: EEA appears to reduce the risk of cranial nerve deficits and parenchymal injury compared to lateral (open) approaches, especially for midline lesions, but CSF leak remains the main limitation.

Clinical Recommendation: EEA should be considered only for selected cases where endovascular and open approaches are suboptimal, and only by experienced teams aware of the risks and reconstruction challenges, with all treatment options discussed in a multidisciplinary setting.

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Nighttime surgery increases complication risk in chronic subdural hematoma: a population‑based cohort study

Acta Neurochirurgica (2025) 167:311

This population-based retrospective cohort study of 2,860 adults undergoing chronic subdural hematoma (CSDH) evacuation at a tertiary neurosurgical center (2006–2023) examines whether nighttime procedures increase postoperative risk. Nighttime surgery—defined by local shift boundaries—was independently associated with higher moderate-to-severe complications (OR 1.58), with risk peaking during final night-shift hours, while adjusted recurrence differences were not statistically significant.

The paper details standardized surgical protocols, staffing patterns, sensitivity analyses using alternative nighttime definitions, and multivariable models adjusting for comorbidity and neurological status. Authors conclude that when clinical stability permits, deferring CSDH evacuation to daytime hours may reduce significant complications, while acknowledging retrospective limitations and potential residual confounding.

Nighttime surgery: Undergoing chronic subdural hematoma (CSDH) surgery at night is independently associated with a higher risk of moderate-to-severe postoperative complications compared to daytime surgery (OR 1.58; 95% CI 1.04–2.37; p = 0.028).

Complication risk timing: The risk of complications increases gradually overnight and peaks during the final hours of the night shift, suggesting a circadian or fatigue-related effect.

Absolute risk increase: Nighttime surgery results in a 1.6% absolute increase in moderate-to-severe complications, with a number needed to harm (NNH) of 63, indicating a modest but clinically meaningful risk.

CSDH recurrence: Although recurrence rates were higher after nighttime surgery in unadjusted analysis, this difference was not statistically significant after adjusting for confounders (adjusted OR 1.28; 95% CI 0.98–1.65; p = 0.067).

Complication types: The most common moderate-to-severe complications include subdural empyema (1.4%), surgical site infection requiring revision (0.3%), and cerebral herniation (0.3%).

Clinical recommendation: When feasible and the patient is stable, deferring CSDH surgery to daytime hours is advised to minimize complication risk.

Prior research limitations: Previous studies were often underpowered, used inconsistent nighttime definitions, and found mixed results regarding the safety of nighttime CSDH surgery.

Study limitations: Retrospective design, possible unmeasured confounding, small differences in baseline severity, and limited generalizability to other healthcare settings with different resources or scheduling practices.

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Lumbar Puncture or External Ventricular Drainage as Initial Treatment for Acute Hydrocephalus in Aneurysmal Subarachnoid Hemorrhage

Neurosurgery 97:1308–1315, 2025

This two-center cohort study compares lumbar puncture (LP) versus external ventricular drainage (EVD) as initial treatments for acute hydrocephalus after aneurysmal subarachnoid hemorrhage, analyzing rates of permanent ventriculoperitoneal shunts (VPS), procedure-related complications, and 3-month functional outcomes. Patients eligible for LP had similar admission severity, and outcomes were adjusted for baseline predictors to compare strategies across centers.

Results show markedly fewer permanent VPS implantations (10% vs 68%) and lower short-term complication rates with LP, while unfavorable functional outcomes at 3 months did not differ significantly. The authors conclude LP is a viable initial option for selected patients, recommending future studies on cognitive and quality-of-life effects.

Initial Treatment: Lumbar puncture (LP) as initial treatment for acute hydrocephalus after aneurysmal subarachnoid hemorrhage (SAH) resulted in significantly fewer patients requiring permanent ventriculoperitoneal shunt (VPS) implantation compared to external ventricular drainage (EVD) (10% vs 68%).

Complication Rates: LP was associated with lower short-term complication rates than EVD (21% vs 38%), including lower rates of intracerebral hemorrhage and infection, especially when LP alone was sufficient.

Functional Outcomes: No statistically significant difference was observed in unfavorable functional outcomes (Glasgow Outcome Scale 1-3 at 3 months) between LP and EVD groups, though the trend favored LP (40% vs 49%).

Patient Selection: LP is suitable as first-line treatment only for selected patients (e.g., GCS ≥7, no space-occupying hematoma, no intraventricular obstruction), while EVD remains necessary for those with contraindications to LP or requiring intracranial pressure monitoring.

Volume of CSF Drainage: Lower cerebrospinal fluid (CSF) volumes drained with LP (typically 25-30 mL per procedure) compared to EVD (hundreds of mL over days) may contribute to reduced VPS dependency.

Study Limitations: Differences in overall management strategies, patient selection, and treatment protocols between centers limit the ability to attribute outcomes solely to the initial hydrocephalus treatment modality; results should not be interpreted as definitive evidence that LP is superior to EVD.

Implications for Practice: LP can be considered as an initial treatment for acute hydrocephalus after SAH in eligible patients, but there is currently no evidence that it improves long-term functional outcomes; further research is needed to assess effects on cognition and quality of life.

Research Needs: More robust, prospective studies are required to clarify optimal patient selection, CSF drainage strategies, and comparative benefits of LP versus EVD in post-SAH hydrocephalus management.

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Minimally invasive surgical evacuation confers a mortality benefit in patients with moderate-sized putaminal hemorrhages

J Neurosurg 143:1514–1521, 2025

Minimally invasive surgical (MIS) evacuation of moderate-sized putaminal intracerebral hemorrhages (pICH, 10–50 mL) was retrospectively compared with matched maximal medical management in a single-center cohort. The study found similar utility-weighted functional outcomes but a marked reduction in 1-year mortality (3% surgical vs 24% medical) and shorter ICU length of stay for surgically treated patients, with an incremental cost-effectiveness ratio of ~$68,463 per QALY.

Detailed stereotactic volumetric mapping revealed that hemorrhage spatial distribution predicts outcome differently by treatment: anteromedial extension (caudate/anterior limb internal capsule) associated with worse surgical outcomes, while posterior/superior extension (corona radiata/frontal lobe) predicted worse medical outcomes. The authors propose imaging-based selection criteria for MIS candidacy and recommend validation in larger, multicenter studies.

• Mortality Benefit: Minimally invasive surgical (MIS) evacuation of moderate-sized putaminal intracerebral hemorrhages (pICHs, 10–50 mL) significantly reduced 1-year mortality compared to medical management (3% vs 24%, p = 0.010).

• Functional Outcome: Functional outcomes (utility-weighted modified Rankin Scale) were statistically similar between surgical and medical cohorts, with no significant difference detected (mean uw-mRS 0.44 vs 0.33, p = 0.174), possibly due to limited sample size.

• ICU Stay: MIS evacuation resulted in a shorter median ICU length of stay by 3 days compared to medical management (4 vs 7 days, p = 0.045).

• Cost-Effectiveness: Surgical evacuation was cost-effective with an incremental cost-effectiveness ratio of $68,462.55 per quality-adjusted life year (QALY), under the commonly accepted $100,000/QALY threshold.

• Anatomical Predictors: Poor functional outcomes after MIS were associated with anteromedial hemorrhage extension (anterior limb of internal capsule/caudate), while poor outcomes after medical management were linked to posterior/superior extension (frontal lobe/corona radiata).

• Patient Selection: Imaging-based spatial distribution of pICH can help predict which patients may benefit most from surgical versus medical management, suggesting a role for CT-based anatomical biomarkers in clinical decision-making.

• Study Limitations: Retrospective, single-center design, small sample size, and potential selection bias limit generalizability and statistical power, especially regarding functional outcome differences.

• Guideline Context: Current evidence and guidelines do not define optimal selection criteria for surgery in basal ganglia ICH, highlighting the need for further prospective, multicenter research to refine indications for MIS evacuation

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Detailed Analysis of Late Adverse Effects of Stereotactic Radiosurgery for Dural Arteriovenous Fistulas

Neurosurgery 97:1368–1376, 2025

This single-center retrospective study evaluates long-term late radiation-induced complications (LRICs) after stereotactic radiosurgery (SRS) for dural arteriovenous fistulas (DAVFs) in 30 patients over a median 99-month follow-up, reporting obliteration rates, post-SRS T2 signal changes, and incidence of chronic encapsulated hematoma (CEH). Findings show high DAVF obliteration (79.6% at 5 years) with rare but notable LRICs (11.1% at 10 years), and an association between post-SRS signal changes and CEH occurrence.

The report details radiosurgical techniques, diagnostic criteria, case courses of two asymptomatic CEHs managed conservatively, and discusses pathophysiology linking radiation, VEGF-mediated permeability, and lesion expansion. The authors recommend prolonged imaging surveillance, heightened monitoring for patients with post-SRS T2 changes, and call for larger multicenter studies to refine predictive models and management strategies.

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Tentorial Dural Arteriovenous Fistulas: A Retrospective Cohort Study

Operative Neurosurgery 29:678–685, 2025

This single-center retrospective cohort study analyzes 275 patients with tentorial dural arteriovenous fistulas (TDAVFs) treated between 2001 and 2022, detailing demographic, angiographic, and treatment data across six Lawton-classified subtypes. Results highlight a predominance of middle-aged male patients, high immediate occlusion rates with endovascular techniques, and subtype-specific differences in venous drainage patterns and complication rates.

The manuscript compares treatment modalities and outcomes, noting superior petrosal sinus TDAVFs more often require microsurgery, while Galenic and torcular subtypes showed lower immediate cure rates and higher complications or new fistula formation. Follow-up angiographic and clinical data emphasize favorable functional recovery for most patients despite treatment-related risks.

• Patient Demographics: Tentorial dural arteriovenous fistulas (TDAVFs) predominantly affect middle-aged men, with 85.8% of cases occurring in males and a mean age of 51.1 years.

• Subtype Distribution: The most common TDAVF subtype is superior petrosal sinus (34.9%), followed by tentorial sinus (31.6%), Galenic (15.6%), torcular (7.3%), incisural (5.5%), and straight sinus (5.1%).

• Aggressiveness and Presentation: TDAVFs are less common than other DAVFs but are the most aggressive, frequently presenting with hemorrhage or progressive neurological deficits; more than half of patients present with intracranial hemorrhage or nonhemorrhagic neurological deficits (NHNDs).

• Treatment Approach: Most TDAVFs (83.0%) can be effectively treated with endovascular embolization, but superior petrosal sinus TDAVFs more often require microsurgical intervention (31.6% in this group).

• Immediate Occlusion and Complications: Immediate complete occlusion was achieved in 92.8% of treated cases, with Galenic TDAVFs showing a lower occlusion rate and both Galenic and superior petrosal sinus TDAVFs exhibiting higher complication rates (12.5% overall).

• Outcomes: Favorable clinical outcomes (mRS <3) were achieved in 82.6% of patients, with torcular and tentorial sinus TDAVFs associated with better outcomes compared to other subtypes.

• Recurrence and New Fistulas: Recurrence after complete occlusion was rare (0.9%), but torcular TDAVFs had a higher tendency to develop new fistulas post-treatment (2.6% of cases).

• Key Technical Considerations: Endovascular treatment is preferred when feasible, but surgical approaches are indicated for lesions with unfavorable arterial access or higher risk of complications, particularly in superior petrosal sinus TDAVFs.

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Machine Learning–Based Rupture Risk Prediction for Intracranial Aneurysms: A Systematic Review and Meta-Analysis

Neurosurgery 97:1072–1082, 2025

This systematic review and meta-analysis evaluates machine learning (ML) applications for predicting intracranial aneurysm rupture, comparing 124 ML models across 36 retrospective studies (22,462 patients) with the PHASES score. Results show ML—especially deep learning and SVM—achieves higher AUC and specificity than PHASES, with hemodynamic inputs improving test-set specificity but not external validation.

The authors highlight methodological heterogeneity, risks of bias, and overfitting concerns from retrospective single‑center data, urging prospective, standardized studies and external validation before clinical integration of ML rupture‑risk tools.

Machine Learning (ML) Models: ML techniques, including deep learning (DL), support vector machines (SVM), and regression models, show higher specificity and overall diagnostic accuracy than the traditional PHASES score for predicting intracranial aneurysm rupture risk, with comparable sensitivity.

• Deep Learning Performance: DL models achieved the highest sensitivity (up to 0.87), specificity (up to 0.86), and area under the curve (AUC-ROC up to 0.92) among all ML families, indicating strong discriminative ability in rupture risk prediction.

• PHASES Score Limitations: The PHASES score, though widely used, demonstrates lower specificity (0.51) and modest overall discriminative ability (AUC-ROC 0.66), and does not incorporate important risk factors like aneurysm morphology or family history.

• Hemodynamic Parameters: Incorporating hemodynamic variables (e.g., wall shear stress, flow patterns) into ML models improves specificity and accuracy in test sets, but benefits are less pronounced in external validation, possibly due to sample size and generalizability issues.

• Retrospective Data and Overfitting: All included ML models were trained on retrospective, post-rupture data, raising concerns about overfitting and the applicability of these models to pre-rupture clinical decision-making.

• Generalizability Concerns: ML models often perform less well on external validation data due to biases in patient selection, single-center data, and differences in imaging or clinical protocols, while the PHASES score maintains more consistent performance across settings.

• Need for Prospective Validation: There is a critical need for prospective studies and standardized protocols to confirm the clinical utility and reliability of ML-based rupture risk prediction models before integration into routine practice.

• Clinical Implications: ML approaches, especially DL and SVM, have the potential to enhance individualized risk stratification and reduce overtreatment, but methodological challenges and validation in diverse populations remain essential for safe clinical adoption.

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Comparative effectiveness of standalone middle meningeal artery embolization versus surgical evacuation in noncritical patients with nonacute subdural hematomas

Neurosurg Focus 59(4):E8, 2025

This retrospective propensity score–matched cohort study compares standalone middle meningeal artery embolization (sMMAE) with standard surgical evacuation for nonacute subdural hematomas (NASDH) in noncritical patients treated from 2017–2024. Primary outcome was reintervention for recurrence; secondary outcomes included hospital length of stay (LOS), new neurological deficits, and adverse events.

After matching 85 patients per group, reintervention rates did not differ significantly (IRR 1.38, p=0.41). sMMAE was associated with shorter median LOS (4 vs 6 days, p=0.003) and fewer noncardiorespiratory medical adverse events, suggesting sMMAE may be a less-invasive option in selected patients while larger trials are needed.

• Standalone Middle Meningeal Artery Embolization (sMMAE) vs. Surgery: sMMAE for nonacute subdural hematoma (NASDH) showed no significant difference in reintervention rates due to hematoma recurrence compared to surgical evacuation (incidence rate ratio [IRR] 1.38, p = 0.41).

• Hospital Length of Stay: Patients treated with sMMAE had a significantly shorter hospital stay (median 4 days) compared to those who underwent surgical evacuation (median 6 days, p = 0.003).

• Adverse Events: sMMAE was associated with a lower risk of other medical (non-neurological, non-cardiorespiratory) adverse events (1.1% vs 15.2%; relative risk [RR] 0.07, p = 0.013), with no significant differences in new neurological deficits or cardiorespiratory/neurological adverse events between groups.

• Patient Selection: The findings apply to noncritical NASDH patients (midline shift < 10 mm, no coma) who are eligible for either intervention; results do not extend to patients with larger or rapidly deteriorating hematomas.

• Propensity Score Matching: Groups were balanced for key confounders (age, sex, comorbidities, hematoma characteristics) using propensity score matching, enhancing comparability of outcomes.

• Mortality: Mortality rates during follow-up were similar between groups and deaths were unrelated to the primary outcome of recurrence.

• Study Limitations: Limitations include retrospective design, moderate sample size, incomplete long-term clinical outcome data, and potential residual confounding by indication or procedural heterogeneity.

• Clinical Implication: sMMAE may offer a less invasive alternative to surgery with shorter hospitalization and fewer medical complications for selected NASDH patients, but larger studies are needed to confirm noninferiority and guide patient selection.

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Decreasing delayed cerebral infarction after aneurysmal subarachnoid hemorrhage using active blood clearance and prevention of delayed cerebral ischemia: results of a 16-year patient registry

J Neurosurg 143:928–938, 2025

Active blood clearance and prevention of delayed cerebral ischemia (ABCD) after aneurysmal subarachnoid hemorrhage significantly reduced delayed cerebral infarction rates and improved outcomes in high-risk patients, using methods like intrathecal irrigation, urokinase, and nimodipine, according to a 16-year registry study.

Active blood clearance and prevention of delayed cerebral ischemia (ABCD) was introduced for patients with aneurysmal subarachnoid hemorrhage (aSAH) to reduce delayed cerebral infarction (DCI) using methods like intrathecal irrigation, fibrinolysis with urokinase, and intrathecal nimodipine.

• Four ABCD methods were developed: stereotactic catheter ventriculocisternostomy (STX-VCS), intraoperative cisternoventricular catheter (CVC), ventriculolumbar irrigation (VLI), and lumbo-lumbar irrigation (LLI).

• Implementation of ABCD in high-risk patients led to a significant reduction in DCI rates from 21.2% to 7.7% and a 70% decrease in per-patient DCI burden.

• Patients selected for ABCD had higher initial blood load and worse clinical status, but still showed improved outcomes, especially those with high Hijdra scores (≥30).

• Pressure-controlled VLI and intraoperative CVC emerged as the most practical and widely applicable ABCD techniques.

• Complication rates were low and ABCD was considered safe, with rare adverse events and no increase in infection rates.

• The study suggests ABCD outperforms previous DCI prevention strategies and recommends multicenter trials for further validation.

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Novel Delivery System Significantly Improves Technical Success and Safety of the Endovascular Clip System (eCLIPs) While Maintaining Efficacy for the Treatment of Wide-Necked Bifurcation Aneurysms

Neurosurgery 97:963–970, 2025

A prospective registry study found that the new eCLIPs electrolytic bifurcation system (eB) for wide-necked bifurcation aneurysms significantly improved technical success and safety over the prior generation, while maintaining high efficacy, with 96% satisfactory occlusion and low rates of neurological complications and retreatment.

• The eCLIPs device is an endovascular implant designed to treat wide-necked bifurcation aneurysms (WNBAs).

• This study compares two generations: the first-generation eCLIPs bifurcation remodeling system (eBRS) and the newer eCLIPs electrolytic bifurcation system (eB).

• A prospective registry included 280 patients; the eB system showed higher implantation success (92% vs 81% for eBRS, P = .007).

• Both systems achieved high rates of satisfactory aneurysm occlusion (mRROC 1+2: 96%).

• The eB system had lower all-cause (1.1%) and neurological (0.5%) death rates compared to eBRS (7% and 5%, respectively).

• Stroke and repeat procedure rates were low for both devices, with eB performing better (stroke: ~1.7%, repeat procedure: 2.2% vs 8.9% for eBRS).

• eCLIPs compares favorably in safety and efficacy to other devices like WEB and stent-assisted coiling.

• The eB system offers improved procedural success and safety, making eCLIPs a strong option for WNBAs; further studies are recommended.

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Microsurgical management of 883 previously coiled intracranial aneurysms

J Neurosurg 143:654–667, 2025

This systematic review and meta-analysis found that microsurgical management of previously coiled intracranial aneurysms is effective and safe in well-selected patients, achieving high complete occlusion and good functional outcomes, especially with delayed direct clipping, small aneurysm size, and anterior location.

• Microsurgical management of previously coiled intracranial aneurysms (IAs) is effective and safe in well-selected patients.

• Meta-analysis included 874 patients with 883 previously coiled IAs; most underwent direct clipping.

• Complete occlusion rate was 97.2%, good functional outcome 82.9%, and perioperative mortality 3.7%.

• Direct clipping had the best safety and efficacy, with the lowest rates of complications and highest rates of good outcomes.

• Smaller, anteriorly located, and unruptured aneurysms were associated with the most favorable outcomes.

• Early microsurgery (within 1 month of coiling) and Gurian group C IAs had higher perioperative death rates.

• Key management factors: IA size, location, rupture status, indication, and timing/type of microsurgery.

• Most studies were retrospective case series, limiting subgroup analysis and introducing some heterogeneity.

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Predictive models for assessing the risk of brain aneurysm rupture

J Neurosurg 143:607–614, 2025

This study evaluated predictive models for brain aneurysm rupture risk using clinical, morphological, and advanced MRI radiomics data. Models combining these factors, especially radiomics, significantly improved accuracy in identifying symptomatic aneurysms, supporting a comprehensive, personalized approach for aneurysm risk stratification and treatment decisions.

• The study evaluated predictive models for assessing the risk of brain aneurysm rupture using high-resolution MRI, clinical, morphological, and radiomic data.

• 129 intracranial aneurysms were analyzed; 26% were symptomatic (ruptured or with warning symptoms).

• The PHASES score alone had low predictive ability (AUC 0.61–0.62) for symptomatic aneurysms.

• Adding morphological metrics (especially size ratio) and smoking status improved prediction (AUC up to 0.79).

• Incorporating aneurysm wall enhancement (AWE) metrics further increased model performance (AUC 0.82).

• The best model included age and radiomics features, achieving the highest predictive accuracy (AUC 0.87, 88% sensitivity).

• Younger age, current smoking, larger size ratio, and higher wall enhancement were associated with symptomatic aneurysms.

• A comprehensive approach using clinical, morphological, and advanced imaging/radiomics data improves aneurysm risk stratification.

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Conservative management of 661 patients with unruptured intracranial aneurysms: an observational study over 4 decades

J Neurosurg 143:641–653, 2025

This retrospective study of 661 patients with unruptured intracranial aneurysms found a 4.4% aneurysm-related mortality and 0.6% annual rupture rate. No ruptures occurred with PHASES <8 or ELAPSS <15, highlighting these thresholds for risk stratification and the importance of close follow-up, especially in the first 10 years.

• A retrospective study analyzed 661 patients with 767 unruptured intracranial aneurysms (UIAs) managed conservatively over 4 decades.

• The overall aneurysm-related mortality rate was 4.4%, with 3.5% of patients experiencing rupture; annual hemorrhage rate was 0.6%.

• Most ruptures (87%) occurred within the first 5 years after diagnosis; no ruptures were observed after 10 years.

• No ruptures or aneurysm-related deaths occurred in patients with PHASES score <8 or ELAPSS score <15.

• Independent predictors of rupture included aneurysm size, PHASES and ELAPSS scores, posterior circulation location, and age ≥70 years.

• Aneurysms <7 mm in diameter did not rupture in this cohort, but this may reflect selection bias.

• Lifelong regular follow-up is recommended for conservatively managed UIAs, especially in the first 10 years.

• PHASES and ELAPSS score thresholds can help identify high-risk patients who may benefit from treatment.

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An Algorithm for the Microsurgical Resection of Cerebellar Cavernomas

Operative Neurosurgery 29:238–246, 2025

This study retrospectively analyzes cerebellar cavernous malformations (cCMs), presenting a tailored microsurgical treatment algorithm. Nearly half of cCM patients required surgery, with individualized approaches improving outcomes. The study highlights the rarity, management challenges, and need for further research into optimal surgical strategies for cCMs.

• Cerebellar cavernous malformations (cCMs) are rare vascular brain lesions, representing 6.5% of all CMs in a large cohort.

• Almost half (49%) of cCM patients underwent surgical treatment, with approaches tailored to lesion location using a specific algorithm.

• Surgical strategies included supracerebellar-infratentorial, telovelar, suboccipital transcortical, and retrosigmoid approaches.

• Surgically treated patients showed significant improvement in functional outcomes, with no mortality and a 27.5% morbidity rate.

• No significant risk factors for postoperative morbidity were identified, including lesion location or associated developmental venous anomalies.

• Conservative management was chosen for asymptomatic or mildly symptomatic patients; about half of cCM patients were managed this way.

• The study provides an individualized surgical algorithm and highlights the need for further research and minimally invasive techniques.

• Main limitations include retrospective single-center design, small surgical sample size, and lack of pediatric or radiation therapy cases.

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Open Microsurgical Versus Endovascular Management of Unruptured and Ruptured Brain Aneurysms

Operative Neurosurgery 29:171–180, 2025

This review compares open microsurgical clipping and endovascular techniques for treating unruptured and ruptured brain aneurysms, discussing their respective risks, benefits, and outcomes. It emphasizes individualized treatment decisions based on aneurysm characteristics, patient factors, and advances in both surgical and endovascular modalities.

• Microsurgical clipping and endovascular techniques are the main treatments for intracranial aneurysms, each with distinct risks and benefits.

• Clipping offers more durable repairs and lower retreatment rates but is more invasive and has higher short-term morbidity, especially in ruptured aneurysms.

• Endovascular treatments (coiling, stenting, flow diverters) are less invasive, have shorter recovery, and are preferred for older patients or those with comorbidities, but have higher recurrence and retreatment rates.

• Aneurysm characteristics such as size, location, morphology, and patient age/comorbidities are critical in selecting the optimal treatment.

• Posterior circulation aneurysms and wide-necked or complex aneurysms often favor endovascular approaches due to surgical risks.

• Clipping is particularly advantageous for younger patients, anterior circulation, and when hematoma evacuation or fenestration is needed.

• New endovascular devices (flow diverters, WEB) expand treatment options but require further study for long-term outcomes.

• Treatment decisions should be individualized, ideally at centers with expertise in both techniques, considering rupture status, anatomy, and patient factors.

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Relationship of blood flow, angioarchitecture, and rupture in cerebral arteriovenous malformations

J Neurosurg 143:499–504, 2025

Patients with ruptured cerebral AVMs were more likely to have deep location, deep venous drainage, lower flow, smaller nidal volume, smaller arterial feeders, and fewer draining veins than unruptured AVMs. These findings highlight the complex interplay between angioarchitecture, hemodynamics, and rupture risk.

• Lower AVM flow, smaller nidus volume, deep location, deep venous drainage, smaller arterial feeders, and fewer draining veins are associated with ruptured AVMs compared to unruptured ones.

• Male sex and deep AVM location significantly increase the risk of hemorrhagic presentation.

• AVM size and flow are not independent predictors when other variables are considered.

• Fewer draining veins, but not venous stenosis, are linked to rupture, suggesting venous outflow restriction may play a role.

• Findings support previous smaller QMRA-based studies showing lower flow is associated with rupture, despite some conflicting literature.

• Prerupture flow data are lacking; rupture itself may alter measured hemodynamics.

• Further research is needed to clarify the role of hemodynamics and venous occlusion in AVM rupture risk.

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Outcomes After Standardized Burr-Hole Surgery for Chronic Subdural Hematomas: A Population-Based Consecutive Cohort Study of 2655 Patients

Neurosurgery 97:298–309, 2025

This large population-based study of 2655 chronic subdural hematoma patients treated with mostly single burr-hole craniotomy found an 11% recurrence and complication rate, 12% 1-year mortality, and identified male sex, diabetes, antithrombotic use, midline shift, and bilateral surgery as independent recurrence predictors.

• Large cohort study (n=2655) analyzed outcomes after standardized burr-hole craniotomy (BHC) for chronic subdural hematoma (CSDH) at a single center (2006–2022).

• Reoperation for hematoma recurrence occurred in 11% of patients, with most recurrences happening within 23 days.

• Independent predictors of recurrence included male sex, diabetes, preoperative antithrombotic therapy, midline shift, and bilateral hematomas.

• Postoperative complications occurred in 11% (3.9% moderate-to-severe); urinary tract infections, subdural empyema, and seizures were most common.

• 1-year postoperative mortality was 12%.

• Higher Charlson Comorbidity Index and lower Glasgow Coma Scale score were independent predictors of moderate-to-severe complications.

• Minicraniotomy was used in 9.3% of cases, with similar recurrence but slightly higher complication rates compared to BHC.

• Predictive models for recurrence and complications had low performance, suggesting other unmeasured factors are important.

 

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