Category: Vascular

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Impact of Clinical Variables and Aneurysm Morphology on Hemorrhage Volume and Clinical Outcomes

Neurosurgery 98:394–403, 2026

This study investigates determinants of aneurysmal subarachnoid hemorrhage (aSAH) volume and its effect on early clinical outcomes using objective, semiautomated CT quantification in 200 ruptured intracranial aneurysms. Multivariate analysis identified older age, higher Hunt and Hess score, and bifurcation aneurysm location as independent predictors of larger aSAH volume, while sex (female) correlated with lower volumes.

Outcome analysis stratified by age showed that in patients 18–64 years greater aSAH volume increased risk of delayed cerebral ischemia, clinical vasospasm, and 7-day mortality; in patients ≥65 years larger volume was associated only with 7-day mortality. The authors recommend multicenter studies using objective quantification to validate age-specific clinical implications.

Hemorrhage Volume Predictors: Larger aneurysmal subarachnoid hemorrhage (aSAH) volumes are associated with older age, higher Hunt and Hess (HH) scores at admission, and ruptured aneurysms located at arterial bifurcations, especially the basilar tip; women have lower hemorrhage volumes than men.

Aneurysm Morphology: Aneurysm size, aspect ratio (AR), size ratio (SR), and irregular morphology do not significantly influence aSAH volume, although bifurcation location is a strong predictor of increased hemorrhage volume.

Hemodynamics Over Morphology: Hemorrhage volume appears to be more influenced by cerebral flow dynamics and aneurysm location (bifurcation vs. sidewall) than by traditional morphological parameters such as size or shape.

Age-Dependent Outcomes: In patients aged 18–64 years, larger aSAH volume is linked to increased risk of delayed cerebral ischemia (DCI), clinical vasospasm, and 7-day mortality; in patients ≥65 years, larger volume is only associated with increased 7-day mortality, not DCI or vasospasm.

Elderly Population Specifics: Lower risk of vasospasm and DCI in elderly patients may be due to arteriosclerotic changes and larger cisternal spaces, which allow greater blood accumulation without corresponding clinical symptoms.

Objective Measurement: Use of semiautomated, machine learning-based tools (e.g., MATLAB segmentation) provides more reliable and reproducible quantification of hemorrhage volume compared to subjective grading systems.

Clinical Implications: Objective hemorrhage quantification could improve risk stratification, facilitate personalized treatment, and enhance understanding of blood clearance and outcomes after aSAH.

Research Recommendations: Multicenter studies using objective quantification methods are needed for validation and to refine management strategies for ruptured aneurysms, considering age-specific differences

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Natural History of Sporadic Cerebral Cavernous Malformations by Zabramski Classification: Hemorrhage Risk and Functional Outcomes Over 5 Years

Neurosurgery 98:376–383, 2026

This prospective cohort study examines sporadic cerebral cavernous malformations (CCMs) categorized by Zabramski MRI types I–IV, reporting lesion features, presentation, hemorrhage rates, and mRS outcomes over a mean follow-up of 4.7 years. Type I lesions had the highest symptomatic presentation, largest size, brainstem predominance, and elevated hemorrhage risks.

Functional outcomes improved for some patients, but Type I had the poorest outcomes. Severe symptomatic hemorrhage was the strongest predictor of sustained disability (mRS ≥3). Types III and IV had low hemorrhage rates and favorable prognoses, supporting conservative management and tailored follow-up imaging.

Zabramski Classification: Stratifies cerebral cavernous malformations (CCMs) into Types I–IV based on MRI features, which correlate with clinical presentation, hemorrhage risk, and functional outcomes.

Type I Lesions: Show the highest annual symptomatic hemorrhage (SH) rate (13.9%), a 5-year cumulative risk of 50.6%, are mostly symptomatic at presentation, often located in the brainstem, and have the poorest long-term functional outcomes (mRS ≥2 in 35.4% at last follow-up).

Type II and III Lesions: Exhibit lower annual hemorrhage rates (2.9% and 1.8%, respectively), more frequently present with seizures or focal neurological deficits rather than hemorrhage, and have better long-term functional outcomes (Type II: mRS ≥2 in 11.2%; Type III: mRS ≥2 in 7.5% at last follow-up).

Type IV Lesions: Are exclusively asymptomatic, detected incidentally, have no observed hemorrhagic events during follow-up, and show no functional impairment (no cases of mRS ≥2).

Severe Symptomatic Hemorrhage: Is the strongest independent predictor of poor functional outcome (mRS ≥3), outweighing lesion type, age, location, or surgical intervention in multivariate analysis (HR 10.88, P < .001).

Dynamic Lesion Evolution: Zabramski type can change over time, particularly for Type I lesions, highlighting the need for longitudinal imaging and dynamic risk assessment rather than reliance on a single timepoint classification.

Clinical Management Implications: Conservative management is appropriate for most Type III and IV lesions due to their benign natural history, while Type I lesions require closer monitoring and individualized intervention strategies due to higher risk.

Study Limitations: Small sample sizes for Types III and IV, potential MRI protocol variability, and single-center design may limit generalizability; multicenter studies are needed for broader validation.

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Single-Session Middle Meningeal Artery Embolization With Concomitant Evacuation Surgery for Chronic Subdural Hematomas: A Multicenter Assessment of Feasibility, Safety, and Efficacy

Operative Neurosurgery 30:270–277, 2026

This multicenter retrospective cohort assesses feasibility, safety, and short-term efficacy of performing middle meningeal artery embolization (MMAE) concurrently with surgical evacuation for chronic subdural hematoma in a single anesthetic session. Among 157 patients, technical success was 97.4%, radiographic improvement occurred in 91.7%, and 63.1% achieved ≥50% hematoma reduction, with a 10.8% overall complication rate and 0.6% procedure-related mortality.

The report compares outcomes to recent randomized trials and existing series, noting similar intraprocedural complication rates and favorable reintervention and functional-independence outcomes (83.9% mRS ≤2 at median 54 days). Authors highlight potential resource and LOS advantages, acknowledge retrospective limitations, and call for prospective studies to define long-term benefit, cost impact, and selection criteria.

Single-session MMAE plus evacuation: Performing middle meningeal artery embolization (MMAE) and surgical evacuation for chronic subdural hematoma (cSDH) in a single anesthetic session is feasible and technically successful in 97.4% of cases, with no major intraprocedural failures reported.

Safety profile: The overall complication rate for the combined procedure is 10.8%, with a low intraprocedural complication rate of 2.5% and a procedure-related mortality of 0.6%, comparable to or better than staged approaches and recent randomized trials.

Radiographic and functional outcomes: Radiographic improvement is observed in 91.7% of patients, with 63.1% achieving at least a 50% reduction in hematoma thickness; 83.9% of patients maintain or achieve functional independence (mRS ≤2) at short-term follow-up.

Hospital length of stay (LOS): The median hospital LOS is 6 days, which is slightly shorter than reported in comparable studies using staged procedures, suggesting potential for reduced resource utilization.

Reintervention rates: Unplanned reoperations during the index hospitalization are low (2.5%), including for recurrent hematomas and subdural empyema, which favorably compares to other large studies and randomized trials.

Patient selection and anesthesia: Most procedures use general anesthesia (92%), but monitored anesthesia care (MAC) or conscious sedation may further streamline care in selected patients and reduce anesthesia-related risks.

Applicability to complex cases: The single-session approach is effective and safe even in patients with bilateral cSDH, who are often considered more complex.

Future directions: Prospective studies are needed to assess long-term outcomes, cost-effectiveness, ideal patient selection, and whether this approach reduces recurrence and enhances recovery compared to staged strategies.

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Added Value of Adjunctive Middle Meningeal Embolization to Surgical Evacuation for Chronic Subdural Hematoma: Comprehensive Meta-Analysis Based on Controlling Confounders

Neurosurgery 98:303–317, 2026

This meta-analysis evaluates whether adding middle meningeal artery embolization (MMAE) to surgical evacuation improves outcomes in patients with chronic subdural hematoma (CSDH).

Key Insights and Themes

Chronic subdural hematoma (CSDH) is a common neurological disorder with high recurrence rates after surgical evacuation, ranging from 2% to 37%.

Middle meningeal artery embolization (MMAE) has emerged as an adjunct or alternative to surgery, aiming to reduce CSDH recurrence by targeting the vascular supply of the hematoma membranes.

Systematic review and meta-analysis included 17 studies (1814 patients; 939 MMAE+S, 1440 S), comprising randomized trials, matched, and unmatched cohorts, with a mean follow-up of 3 months.

Baseline comparability between MMAE+S and surgery-alone groups was achieved except for higher antithrombotic use in the MMAE+S group (34.9% vs 22.4%).

Recurrence rates were significantly lower in the MMAE+S group compared to surgery alone (4.7% vs 17.7%; relative risk [RR] 0.31, P < .01), a benefit confirmed in randomized and matched studies.

Radiological outcomes (postoperative hematoma thickness, volume, and midline shift) were all significantly reduced in the MMAE+S group.

Functional outcomes, complications, mortality, and hospital stay were similar between groups, indicating no increased risk with adjunctive MMAE.

Timing of embolization affected outcomes: postoperative MMAE was associated with lower recurrence, while preoperative MMAE did not show significant benefit.

Embolic agent selection mattered: liquid embolic agents (e.g., Onyx, Squid) led to better outcomes than particles, with recurrence reduction seen only with liquid agents.

Antithrombotic use, a known risk factor for recurrence, was higher in the MMAE+S group, yet recurrence rates remained lower, suggesting a robust effect of adjunctive MMAE.

Surgical technique variability (burr-hole craniostomy, craniotomy, twist-drill) existed across studies, potentially influencing heterogeneity in outcomes.

Complication rates were low and comparable between groups; most complications were minor, and serious adverse events were rare.

Length of hospital stay did not differ significantly between groups, though some previous studies suggested longer stays with MMAE+S, possibly due to worse initial clinical status.

Cost-effectiveness may favor MMAE+S in the long term, as reduced recurrence and reoperation rates can offset higher initial costs.

Ongoing clinical trials (e.g., CHESS, MEMBRANE, EMPROTECT) are expected to clarify optimal timing, patient selection, and cost-effectiveness of adjunctive MMAE.

Limitations include heterogeneity in surgical and embolization techniques, retrospective study designs, and reliance on aggregate rather than individual patient data.

Areas for future research include optimal timing and materials for MMAE, patient selection, and cost-benefit analyses.

Conclusion

Adjunctive MMAE with surgical evacuation significantly reduces CSDH recurrence and improves radiological outcomes without increasing complications or mortality, supporting its use in high-risk patients.

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Long-Term Outcomes of Surgical Clipping of Woven EndoBridge-Eligible Middle Cerebral Artery Bifurcation Aneurysms

Operative Neurosurgery 30:18–25, 2026

This clinical study evaluates long-term outcomes of microsurgical clipping for middle cerebral artery (MCA) wide-neck bifurcation aneurysms that meet radiographic criteria for treatment with the Woven EndoBridge (WEB) device. Using a retrospective review of a prospectively maintained registry, the authors compare functional outcomes, complication rates, recurrence, and retreatment against published WEB and clipping cohorts.

Results show high surgical efficacy: 99% treatment success, 94.1% of unruptured cases achieving final mRS ≤2, a 4.9% morbidity rate, and 0% mortality, with lower retreatment and higher complete occlusion rates than reported WEB series. The authors conclude microsurgical clipping remains a reliable option for MCA WNBAs and recommend location-specific subgroup analyses in future WEB studies.

Microsurgical Clipping Outcomes: Surgical clipping of WEB-eligible middle cerebral artery (MCA) wide-necked bifurcation aneurysms (WNBAs) achieved a 99% treatment success rate, 4.9% morbidity, 0% mortality, and 94.1% good functional outcomes (mRS ≤2) in unruptured cases, with low recurrence and retreatment rates.

Comparison to WEB Device: Clipping resulted in higher complete occlusion rates, lower retreatment rates, and lower thromboembolic complication rates compared to endovascular treatment with the Woven EndoBridge (WEB) device for MCA WNBAs.

Functional Outcomes: Both ruptured and unruptured aneurysms treated surgically showed excellent or improved functional status at follow-up, with 91.8% of unruptured and 94.1% of ruptured cases experiencing stable or improved mRS scores.

Complication Profile: Thromboembolic complications occurred in 5.9% of unruptured cases, with permanent neurological deficits in 4.9% and no surgical mortality; intraoperative rupture was rare (2.0%).

Limitations of WEB Evidence: Most WEB studies pooled multiple aneurysm locations, making it difficult to assess location-specific efficacy; at the MCA, WEB showed higher retreatment and thromboembolic rates than clipping, and lower rates of complete occlusion.

Treatment Selection: MCA aneurysms are often suitable for surgical clipping due to their accessible location and favorable anatomy, especially at experienced centers, supporting a “clip-first” approach for many MCA WNBAs.

Study Limitations: Findings are based on a retrospective, single-center cohort at a high-volume academic institution, limiting generalizability and direct comparison to randomized or multicenter WEB trials.

Clinical Recommendation: Both clipping and WEB are effective for MCA WNBAs, but surgical clipping may offer superior durability and occlusion; treatment choice should be individualized through shared decision-making, not solely based on minimally invasive appeal.

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Artificial intelligence–based deep learning model for evaluating procedural consistency in microvascular anastomosis

J Neurosurg 144:1–10, 2026

This study presents an LSTM-based deep learning model that objectively evaluates microvascular anastomosis performance by predicting hand-motion trajectories from MediaPipe-derived hand landmarks. It quantifies consistency using Kullback-Leibler divergence and validates complementary metrics—economy and flow of motion—comparing two expert neurosurgeons (repeat sessions) and one trainee in simulated end-to-side anastomoses.

Results show low KL divergence for experts versus higher divergence for the trainee, reflecting greater consistency and efficiency. The authors discuss methodology, model architecture choices, limitations in generalizability, and potential integration into microsurgical training workflows for objective skill assessment.

Deep Learning Model: An LSTM-based neural network was developed to objectively assess consistency and precision in microvascular anastomosis by predicting and comparing suturing hand movements using video-based hand landmark tracking, eliminating the need for physical sensors.

Hand Tracking Technology: The model utilized MediaPipe Hand Landmarker, a CNN-based system that detects 21 hand landmarks from standard video, enabling detailed, sensor-free motion analysis during microsurgical simulation.

Performance Metrics: Three primary metrics were used: Kullback-Leibler (KL) divergence for consistency, economy of motion (mean Euclidean distance of hand movement), and flow of motion (median time per suture), providing quantitative, objective evaluation of surgical skill.

Experimental Setup: Two expert neurosurgeons performed microanastomosis simulations (interrupted and continuous suturing) in two sessions one year apart, and a trainee performed the same task for comparison; all sessions were recorded and analyzed using the AI pipeline.

Results and Interpretation: Experts showed low KL divergence (high consistency) and efficient, rhythmic motion, while the trainee had higher KL divergence, longer suture intervals, and more variable motion, reflecting less developed skill.

Model Application: The approach enables rapid, automated assessment of multiple trainees using standard video equipment, supporting objective tracking of skill progression and facilitating feedback in training environments.

Model Rationale: LSTM architecture was chosen for its ability to model long-term temporal dependencies in sequential hand movement data, making it suitable for predicting surgical motion patterns over extended timeframes.

Limitations and Future Directions: Current findings are based on a small sample of experts and one trainee in a simulated environment; broader validation, metric standardization (especially for KL divergence), and extension to real operative settings are needed for generalizability.

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Guidelines for the Diagnosis and Clinical Management of Cavernous Malformations of the Brain and Spinal Cord

Neurosurgery 98:3–22, 2026

These guidelines present updated, evidence-based recommendations for diagnosing and managing cavernous malformations (CMs) of the brain and spinal cord, produced by an expert multidisciplinary panel convened by the Alliance to Cure Cavernous Malformation. The document summarizes systematic literature review methods, evidence ratings, and 53 consensus recommendations across epidemiology, genetics, imaging, neurosurgery, and neurology.

Key clinical guidance addresses diagnostic MRI protocols, genetic testing for familial CM (KRIT1/CCM2/PDCD10), surgical/radiosurgical indications including pediatric and geriatric considerations, seizure and headache management, and lifestyle and medication factors potentially affecting hemorrhage risk. Recommendations highlight evidence limitations and prioritize further research.

Diagnosis: MRI with susceptibility-weighted sequences is the gold standard for diagnosing cavernous malformations (CMs); CT may be used in emergencies, but MRI is preferred for follow-up and detailed assessment.

Genetic Testing: Genetic testing for KRIT1 (CCM1), CCM2, and PDCD10 (CCM3) is recommended for individuals with multiple CMs, a family history, or suspected familial CM (FCM); founder mutations exist in certain populations.

Hemorrhage Risk: Annual risk of symptomatic intracranial hemorrhage (ICH) from CMs ranges from 0.7% to 7.5%, with higher risk for recurrent bleeds and in familial cases, especially with CCM3 mutations.

Surgical Management: Surgery is generally reserved for symptomatic, accessible CMs or those causing drug-resistant epilepsy; conservative management is preferred for asymptomatic or deep/eloquent area lesions unless recurrent bleeds occur.

Medical Management: Antiseizure medication is recommended after a first CM-related seizure; standard migraine therapy applies for nonhemorrhagic CMs, and nonaspirin NSAIDs can be used cautiously.

Pregnancy: Pregnancy does not increase the risk of CM hemorrhage compared to nonpregnant states; MRI without contrast is advised for new neurological symptoms during pregnancy.

Medication Risks: Antithrombotic agents (e.g., aspirin) do not increase and may actually lower CM hemorrhage risk, while female hormones may increase risk; thrombolytic use remains controversial and should be considered on a case-by-case basis.

Lifestyle and Emerging Therapies: Vitamin D supplementation, aerobic activity, and a diet low in processed foods are reasonable lifestyle recommendations; propranolol and statins show potential but lack definitive evidence for reducing hemorrhage risk.

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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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