Category: Vascular

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Drainage Volume, Drainage Time, and Irrigation Volume in Chronic Subdural Hematoma

Neurosurgery 99:537–544, 2026

Postoperative drainage is an important component of chronic subdural hematoma surgery, yet the interpretation of drainage volume and duration remains clinically relevant to the prevention of recurrence. This analysis of the FINISH trial examines their association with reoperation, alongside the volume of intraoperative irrigation. Its findings invite a critical appraisal of the assumption that greater drainage necessarily reflects more effective evacuation, while emphasizing the distinction between observational associations and evidence sufficient to establish a standardized drainage protocol.

Objective

To examine whether drainage and irrigation measurements relate to recurrence requiring reoperation.

Methods

This post hoc analysis used 546 patients from the multicenter FINISH irrigation trial. Logistic regression assessed drainage volume, duration and irrigation volume against outcomes.

Main results

Reoperation occurred in 84 patients (15.4%). Median drainage was 70 mL over 48 hours. Each additional 100 mL was associated with higher reoperation odds (OR 1.15, 95% CI 1.02–1.31). Reoperation rates were 18.2% with drainage under 48 hours and 12.1% at 48 hours or longer. Irrigation volume was not associated with reoperation.

Interpretation — operative relevance

The practical decision is how to interpret the postoperative drain within the evacuation strategy. The study does not justify deliberately increasing or restricting output. A high output may identify a different clinical situation rather than cause recurrence.

Similarly, these comparisons do not establish that extending every drain beyond 48 hours improves outcome. The duration comparison was not randomized, even though the parent trial was. More irrigation should not be equated automatically with a better operation.

Limitations

Drainage exposures were observational. Clinical decisions and unmeasured factors may explain part of the associations. The abstract does not provide a validated output-based removal algorithm or enough procedural detail to compare drain position, suction or irrigation technique.

Clinical takeaway

Document output and elapsed drainage time together, and interpret them alongside clinical recovery. This paper is useful for reviewing a unit’s drain protocol; it does not supply a new mandatory removal threshold or irrigation dose.

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Third Ventricular Cavernous Malformations: Approach Selection for Minimally Invasive Resection and Systematic Review

Operative Neurosurgery 31:399–409, 2026

Third-ventricular cavernous malformations are rare lesions in an unforgiving anatomical corridor. This paper combines three institutional operations with a systematic review to examine how lesion position should guide the route of access. Two patients underwent endoscope-assisted supraorbital trans–lamina terminalis resection and one a port-based transsulcal exoscopic procedure. In the literature, transcallosal and transcortical transventricular craniotomies remained the most commonly reported routes. The main message is not that one minimally invasive approach is universally preferable, but that the shortest safe trajectory must be individualized around the fornices, hypothalamus, thalamus, deep veins and ventricular anatomy.

Objective

To describe minimally invasive surgical strategies for symptomatic third-ventricular cavernous malformations and synthesize the published experience to support anatomical approach selection.

Methods

The investigators reviewed a prospectively maintained institutional database and identified three symptomatic patients with imaging evidence of hemorrhage. Demographic, clinical, anatomical and surgical outcome data were analyzed. A PRISMA-based PubMed and Embase search identified the available reports of surgically treated third-ventricular cavernous malformations and the approaches used.

Main results

The institutional group included two men and one woman; all were symptomatic, none had hydrocephalus and all had signs of intralesional hemorrhage. Two lesions were removed through a supraorbital keyhole, endoscope-assisted trans–lamina terminalis route. The third was treated through a right frontal keyhole with a port-based transsulcal, exoscope-assisted route.

The review assembled 54 reported surgical cases. The most frequent routes were interhemispheric transcallosal in 26 cases (48.1%) and transcortical transventricular in 16 (29.6%). The combined experience demonstrates substantial heterogeneity in lesion origin, ventricular size and surface presentation, all of which alter the safest corridor.

Interpretation

“Minimally invasive” should describe limited tissue disruption, not merely a smaller opening. A trans–lamina terminalis route may suit an anterior or inferior lesion with favorable line of sight, whereas a transsulcal or transventricular route may better address a superior or lateral target. High-quality multiplanar and susceptibility imaging, neuronavigation and planned conversion options are more important than allegiance to a single approach.

Limitations

The institutional experience contains only three patients. The systematic review is dominated by case reports and small series, with publication bias, incomplete outcome reporting and no valid comparative groups. Some historical cases predate modern endoscopy, exoscopy, tract-informed planning and contemporary postoperative imaging.

Clinical takeaway

Select the route from the lesion’s precise relationship to the ventricular walls, foramina, fornices, hypothalamus, thalamus and deep venous structures. Use the corridor that offers direct visualization with the least neural transgression, and counsel patients that the evidence for approach superiority remains low level.

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Evaluating Conscious Sedation Versus General Anesthesia for Venous Sinus Stenting for Idiopathic Intracranial Hypertension and Implications for Outpatient Management

Neurosurgery 99:700–709, 2026

Venous sinus stenting for idiopathic intracranial hypertension is commonly separated into diagnostic manometry under conscious sedation and later stenting under general anesthesia. This cohort asks whether conscious sedation and a more streamlined pathway can deliver comparable safety and efficacy. After propensity matching, outcomes did not differ significantly between conscious sedation and general anesthesia. Same-admission diagnosis and treatment were associated with more repeat stenting, although this group included every fulminant presentation. The work supports outpatient feasibility but not indiscriminate conversion to a single-session pathway.

Objective

To compare venous sinus stenting under conscious sedation and general anesthesia and to evaluate single-session diagnostic venography plus stenting versus staged procedures, with particular attention to outpatient management.

Methods

The retrospective cohort included 114 adults treated for idiopathic intracranial hypertension at one comprehensive cerebrovascular center from January 2017 through December 2024. Clinical presentation, procedural characteristics, symptom resolution and restenosis were compared between general anesthesia and conscious sedation and between same-admission and staged pathways. Propensity-score matching was used for both comparisons.

Main results

Thirty-six patients underwent general anesthesia and 78 conscious sedation. After matching, 36 patients remained in each group, with no significant difference in the measured safety or clinical outcomes. One major complication—acute visual loss caused by cerebral venous thrombosis—occurred in the conscious-sedation cohort.

Thirty-seven patients underwent same-admission venography and stenting, compared with 77 staged procedures. All 17 fulminant cases belonged to the same-admission group. Apparent differences in time to recurrent headache and visual symptoms were no longer significant after matching, but restenosis requiring repeat stenting remained more frequent after the same-admission strategy.

Interpretation

Conscious sedation appears technically feasible for venous sinus stenting in selected patients and could remove a barrier to outpatient care. The increased repeat-stenting signal after same-admission treatment may reflect the biological and clinical severity of fulminant disease, residual confounding or differences in pressure measurement and selection; it should not be attributed automatically to workflow.

Limitations

This was a retrospective single-center study with only 114 patients and one major complication, limiting safety comparisons. Anesthetic and admission strategies were chosen clinically rather than randomly. Propensity matching cannot correct unmeasured confounding, especially because every fulminant case entered the same-session group.

Clinical takeaway

Conscious sedation and staged outpatient venography followed by outpatient stenting may be reasonable in carefully selected, stable adults. Fulminant presentations still require expedited individualized treatment, and same-session stenting should not become routine until predictors of restenosis and the effect of anesthetic conditions on manometry are better defined.

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Microsurgical Management of Tentorial Dural Arteriovenous Fistula: An Analysis From CONDOR

Journal of Neurosurgery 2026;145(2):424–435

Tentorial dural arteriovenous fistulas frequently have cortical venous drainage and an aggressive natural history. This international multicenter series focuses on microsurgery, often after embolization has failed. Tailored approaches achieved angiographic success in 90% with a low rate of permanent neurological morbidity. Results were similar whether surgery was the primary or salvage strategy. The study reinforces microsurgery as a durable option when endovascular cure is incomplete or anatomically unfavorable.

Objective

To describe surgical approaches, obliteration rates, complications and longer-term durability after microsurgical treatment of tentorial dural arteriovenous fistulas.

Methods

CONDOR retrospectively collected dural fistula data from 16 international centers between 1990 and 2021. Of 161 patients with a tentorial fistula, 44 underwent microsurgery; 23 received surgery as salvage treatment after failed embolization. Success required angiographically confirmed complete obliteration or, for a high-grade lesion, elimination of cortical venous drainage.

Main results

Aggressive presentation was present in 91% of the surgical cohort: 64% presented with hemorrhage and 27% with a nonhemorrhagic neurological deficit. The retrosigmoid approach was most common (44%), followed by midline suboccipital (24%) and occipital (15%) approaches.

Surgical success was achieved in 38 of 42 assessable patients (90%). Perioperative complications occurred in 11%, while permanent neurological deficit occurred in 2%. During a mean 3-year follow-up, 2 of 38 successfully treated fistulas (5%) recurred. Primary and salvage microsurgery had similar outcomes.

Interpretation

Microsurgery provides high and durable disconnection rates for tentorial fistulas that cannot be cured safely by embolization. The range of approaches reflects anatomical heterogeneity; operative planning should target the fistulous point and cortical venous outflow rather than apply a uniform exposure.

Limitations

This retrospective registry spans three decades, with substantial evolution in angiography, embolic agents and surgical practice. Only 44 patients underwent surgery, treatment selection was nonrandom and imaging follow-up was not necessarily uniform. Outcomes from experienced referral centers may not be reproduced in lower-volume units.

Clinical takeaway

Discuss high-grade tentorial dural fistulas in a multidisciplinary cerebrovascular team. When embolization cannot provide safe definitive disconnection—or has already failed—an anatomically tailored microsurgical approach offers a high likelihood of cure with acceptable morbidity in experienced hands.

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Real-Time Remote Telerobotic Magnetic Navigation for Endovascular Simulated Stroke Thrombectomy Across 5700 Miles

Operative Neurosurgery. 2026;31(2):355–360

This preclinical study explores whether robotic neuroendovascular procedures can be performed safely across intercontinental distances. A neurosurgeon in Arizona remotely navigated aspiration catheters through a vascular phantom located in Switzerland. The system reached every simulated intracranial target and demonstrated a rapid learning curve. Although still far from clinical application, the experiment represents an important step toward remotely delivered mechanical thrombectomy.

Objective
To test whether a neurointerventionalist could remotely perform magnetic robotic navigation and simulated aspiration thrombectomy across an intercontinental distance.

Methods
A magnetic-field generator, mechanical catheter advancer and vascular phantom were installed in an interventional suite in Switzerland. Through a wireless connection, a neurosurgeon operating from Arizona navigated a guidewire and aspiration catheter to simulated middle cerebral artery and basilar artery occlusions.

Twenty consecutive navigation procedures were performed: 10 targeting the M1 segment and 10 the basilar artery. Aspiration was attempted in four trials.

Main results
All 20 vascular targets were reached successfully from more than 5,700 miles away. Mean navigation time was 114 seconds for the M1 segment (SD 44.4) and 134 seconds for the basilar artery (SD 65.8).

All four attempted clot aspirations were successful. Navigation time decreased by an average of 77% between the initial and final trials, suggesting a rapid operator learning curve. The absence of haptic feedback did not prevent completion of the simulated procedures.

Interpretation
This preclinical experiment demonstrates the technical feasibility of intercontinental robotic neuroendovascular navigation. If validated in progressively more realistic models and ultimately in patients, this technology could help extend thrombectomy expertise to hospitals without on-site neurointerventional coverage.

The study establishes feasibility—not clinical safety, effectiveness or readiness for routine use.

Limitations
Procedures were performed in a silicone phantom rather than living vascular anatomy. The model could not reproduce arterial tortuosity, vasospasm, vessel-wall injury, thrombus variability or unexpected patient movement. Only four aspiration attempts were performed, and the study did not test the consequences of network interruption or equipment failure. Full-text verification was access-limited, but the complete indexed abstract and numerical results were available.

Clinical takeaway
Remote robotic thrombectomy is technically possible over intercontinental distances, but substantial preclinical and clinical validation, redundant communication systems and clearly defined emergency-conversion protocols will be required before human application.

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Association of monotherapy intervention with long-term outcomes in Spetzler-Martin grade I and II arteriovenous malformations

Journal of Neurosurgery. 2026;145(2):443–453

Objective
To compare long-term hemorrhagic stroke and mortality after conservative management, microsurgery, stereotactic radiosurgery or embolization alone in patients with low-grade brain arteriovenous malformations.

Methods
Nationwide multicenter prospective observational cohort of patients with Spetzler-Martin grade I or II AVMs. Outcomes were evaluated according to the initial monotherapy strategy.

Main results
Interventional treatment was associated with lower long-term hemorrhagic risk than conservative management, although outcomes varied according to treatment modality and AVM characteristics. Microsurgery offered immediate obliteration but carried an upfront procedural risk; radiosurgery delayed protection until obliteration, while embolization results were strongly dependent on anatomical selection.

Interpretation
Low-grade AVMs should not be treated as a homogeneous group. The balance between natural-history risk and treatment morbidity depends on presentation, eloquence, venous drainage, patient age and the likelihood of complete obliteration.

Limitations
Despite prospective follow-up, treatment was not randomized. The intervention selected was influenced by anatomy, center experience and clinical presentation, leaving a substantial risk of confounding by indication.

Clinical takeaway
For carefully selected Spetzler-Martin grade I–II AVMs, intervention may provide durable protection, but modality selection should be individualized in a multidisciplinary cerebrovascular team.

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Surgical revascularization versus nonsurgical management in children with symptomatic moyamoya arteriopathy: a North American multicenter cohort study

Journal of Neurosurgery: Pediatrics. 2026;38(2):205–214.

Objective
To compare recurrent ischemic events after surgical revascularization or conservative treatment in children with symptomatic moyamoya arteriopathy.

Methods
Retrospective comparison of 49 children treated at two North American institutions: 24 received nonsurgical management and 25 underwent predominantly indirect revascularization. Median age was 6 years.

Main results
Ipsilateral ischemic event–free survival at 12, 24 and 60 months was 52.8%, 52.8% and 31.7% with nonsurgical management, compared with 87.7%, 83.0% and 83.0% after surgery. Surgical revascularization was associated with a substantially longer time to recurrence (HR 0.15; 95% CI 0.04–0.51).

Interpretation
The findings strongly favor revascularization for children with symptomatic disease. Nevertheless, treatment strategy was closely linked to the institution, making residual confounding likely.

Limitations
Small retrospective cohort, center-dependent treatment allocation and differences in patient selection. The observed association involving race should not be interpreted as causal.

Clinical takeaway
In symptomatic pediatric moyamoya, timely referral for surgical revascularization appears preferable to observation alone.

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Prospective untreated outcomes in patients with cerebral cavernous malformation

J Neurosurg 144:1344–1352, 2026

This prospective cohort study quantifies long-term functional outcomes in 332 untreated patients with cerebral cavernous malformation (CCM), using modified Rankin Scale (mRS) scores to evaluate disability over a mean 6.6-year follow-up. It reports incidence of symptomatic hemorrhage (SH), temporal patterns of recovery after a first SH, and external validation of published predictive nomograms.

Key findings identify brainstem location, a history of self-reported psychiatric disorder, and two or more SHs as independent predictors of long-term disability; most patients improved within one year after a first hemorrhage, and ten-year disability risk for nonbrainstem CCM was under 8%.

Objective Elucidate long-term morbidity and disability risk in adults with untreated cerebral cavernous malformation (CCM).

Methods Prospectively followed registry cohort; functional outcome tracked using mRS, with disability defined as mRS ≥ 3; time-to-disability analyzed via Kaplan–Meier and risk factors via Cox models; previously published morbidity nomograms were externally validated.

Cohort 332 patients (58.4% female; mean age 44.5); 19.8% familial CCM; 28.0% brainstem location; 38.3% presented with symptomatic hemorrhage (SH).

Recovery after first SH Among patients with SH who had no further SH and no surgery (n=48), disability (mRS ≥ 3) was 27.1% at diagnosis, improving to 6.2% at 1 year and 4.7% at 5 years, with most improvement in year 1.

Hemorrhage burden Over mean 6.6 years, 31.0% had ≥1 prospective SH and 14.5% had multiple prospective SHs; disability rose sharply with each SH (mRS ≥ 3: 2.3% with 0 SH up to 100% after 5 SHs in untreated follow-up).

Location risk Brainstem CCM carried substantially higher disability risk (18.8% at 5 years; 35.4% at 10 years) versus nonbrainstem locations (4.1% at 5 years; 7.5% at 10 years).

Predictors Multivariate predictors of disability included brainstem location, self-reported psychiatric disorder, and ≥2 SHs.

Nomogram validation Prior nomograms showed high specificity but limited sensitivity; AUC 0.687 for predicting mRS ≥ 2 and 0.783 for predicting mRS ≥ 3.

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Basilar artery perforator rupture as the cause of perimesencephalic subarachnoid hemorrhage

J Neurosurg 144:1271–1277, 2026

This clinical study evaluates the etiology of perimesencephalic subarachnoid hemorrhage (pmSAH) by applying high-resolution cone-beam CT (CBCT) during catheter angiography to detect basilar artery perforator outpouchings. The retrospective analysis of 22 pmSAH patients found that CBCT identified basilar perforator pseudoaneurysms in a substantial subset, with conservative management yielding excellent outcomes.

The authors argue that many pmSAHs may be arterial rather than venous in origin when imaged with modern high-resolution CBCT protocols. They recommend heightened suspicion for an arterial source and detailed angiographic CBCT acquisition, while acknowledging limits of retrospective design, variable imaging quality, and unresolved management questions.

Objective High-resolution CBCT performed during catheter angiography was used to better identify the etiology of perimesencephalic SAH (pmSAH), challenging the historical assumption of a venous source.

Methods Retrospective review of pmSAH cases (Jan 2023–Dec 2024) requiring catheter angiography with available, diagnostic-quality CBCT; images were interpreted by two experienced neuroangiographers to consensus.

Cohort Of 152 spontaneous SAH presentations, 22 met Rinkel criteria for pmSAH; after exclusions (alternative causes found, missing/low-quality CBCT), 13 patients remained for CBCT-based imaging analysis.

Key finding In 8/13 (61.5%) analyzed pmSAH cases, CBCT showed a basilar artery perforator focal outpouching consistent with a rupture site (submillimeter, 0.4–0.8 mm).

Anatomy distribution Among the 8 identified perforator lesions, 6 were rostral basilar perforators, with 1 midbasilar and 1 caudal perforator involvement.

Outcomes All pmSAH patients—including those with identified basilar perforator outpouchings—had excellent recovery, with no re-rupture events and no clinically significant vasospasm reported in the series.

Follow-up imaging In patients who underwent follow-up DSA with CBCT, the basilar perforator finding resolved on follow-up imaging.

Conclusion/implication pmSAH should be approached with high suspicion for an arterial etiology (basilar perforator pseudoaneurysm frequently detectable with high-resolution CBCT), and conservative management was associated with excellent outcomes in this cohort.

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A 7-Year Experience in Microsurgical Treatment of Unruptured Intracranial Aneurysms in Older Patients

Neurosurgery 98:1325–1338, 2026

This article reports a 7-year single-center retrospective analysis comparing one-year neurological outcomes after microsurgical clipping of unruptured intracranial aneurysms in patients >65 years versus younger adults. It details patient selection, aneurysm characteristics, statistical methods, and primary endpoint assessment using the modified Rankin Scale.

Findings indicate similar favorable 1-year outcomes between older and younger cohorts, with diabetes and de novo aneurysm formation/growth identified as independent predictors of poor outcome in the older group. The discussion contextualizes results against endovascular options, comorbidity considerations, and limitations of retrospective single-center data.

Question addressed Whether to treat unruptured intracranial aneurysms (UIAs) in patients >65 remains controversial because of frailty/comorbidities and procedural risk vs rupture risk under conservative management.

Study design Retrospective review of UIA patients treated with microsurgical clipping (single quaternary center, 2014–2020), including only those with admission mRS ≤2; primary endpoint was 1-year mRS, with poor outcome defined as mRS >2.

Cohort 390 total surgically treated patients; 132 (34%) were >65 with mean age 71±4 years.

Main outcome No significant difference in poor neurological outcome at 1 year between older vs younger patients (11% vs 9.3%, P=.82), indicating comparable functional outcomes after microsurgery in selected older adults.

Aneurysm differences with age Older patients had larger aneurysm dimensions and more calcification (e.g., calcification 15% vs 2.8%) and higher PHASES/ELAPSS scores than younger patients.

Univariate risk factors (older group) Factors associated with poor 1-year outcome included diabetes, higher Charlson Comorbidity Index, calcification, treating multiple aneurysms, de novo formation/growth, and higher aspect ratio.

Independent predictors On multivariable analysis in older patients, only diabetes (OR 19.1, P=.02) and de novo formation or growth (OR 12.7, P=.02) predicted poor neurological outcome.

Clinical implication Chronological age alone is not a stand-alone contraindication to microsurgical treatment; individualized selection and comorbidity/risk stratification (notably diabetes and aneurysm growth patterns) are key.

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Clinical Outcomes of Subarachnoid Hemorrhage in Patients With Nicotine Dependence

Neurosurgery 98:1095–1102, 2026

This retrospective, population-based study analyzes clinical outcomes after nontraumatic subarachnoid hemorrhage (SAH) among 43,315 patients with documented nicotine dependence versus patients without substance use disorders. Using the TriNetX network with propensity score matching, primary endpoints included mortality, vasospasm, hydrocephalus, and delayed cerebral ischemia (DCI), with nicotine dependence associated with significantly higher hazards for all outcomes.

The manuscript details methods, matching variables, statistical analyses, mechanistic discussion of nicotine’s vascular effects, and limitations inherent to large electronic health record databases. Conclusions emphasize that nicotine dependence predicts worse SAH outcomes and support prioritizing smoking cessation counseling as part of long-term patient management.

Study focus: Clinical outcomes after nontraumatic subarachnoid hemorrhage (SAH) in adults with nicotine dependence versus those with no substance use disorder diagnoses.

Data source & cohort: TriNetX electronic medical record network analysis of adults (≥18) with ICD-10 I60 (nontraumatic SAH) from 2004–2024; 43,315 had nicotine dependence (F17) out of ~210k+ SAH patients.

Methods: Used 1:1 propensity score matching to balance demographics, comorbidities, lab/substance testing, and SAH severity (NIS-SAH Severity Score elements), then applied Cox proportional hazards and Kaplan–Meier survival analyses.

Mortality risk: Nicotine dependence associated with higher post-SAH mortality hazard (HR ≈ 1.24–1.25, statistically significant).

Vasospasm risk: Nicotine dependence associated with higher hazard of vasospasm (HR ≈ 1.47–1.49, statistically significant).

DCI risk: Nicotine dependence associated with higher hazard of delayed cerebral ischemia (DCI) (HR reported ≈ 1.30–1.35, statistically significant).

Hydrocephalus risk: Nicotine dependence associated with higher hazard of newly diagnosed hydrocephalus (HR ≈ 1.27, statistically significant).

Clinical implication: Elevated risks linked to nicotine dependence underscore the importance of smoking cessation counseling for long-term management after SAH.

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Chronic Oculomotor Nerve Palsy Presentation From Posterior Communicating Artery Aneurysm

Operative Neurosurgery 30:703–710, 2026

This case series analyzes 17 patients with subacute to chronic oculomotor nerve palsy (ONP) caused by posterior communicating artery (PCoA) aneurysms treated between 1991 and 2024. Demographics, aneurysm characteristics, treatment modalities (clipping vs endovascular), and follow-up outcomes are reported, highlighting that only a minority presented with rupture.

The report finds that complete ONP recovery occurred exclusively in patients treated within five weeks of symptom onset, supporting early definitive management to maximize functional nerve recovery despite chronic ONP not reliably predicting imminent aneurysm rupture.

Clinical question: The natural history of chronic oculomotor nerve palsy (ONP) from posterior communicating artery (PCoA) aneurysm is unclear, especially regarding rupture risk and likelihood of nerve recovery when symptoms persist beyond 1 week.

Cohort & design: Case series from a prospectively accrued institutional database (1991–2024) including patients with ≥1 week ONP attributed to PCoA aneurysm; patients with <1 week onset, inadequate follow-up, or other causes of ONP were excluded.

Patient profile: 17 patients; predominantly female (94.1%), median age 56; ONP duration ranged 1 week to 10 years; 29.4% presented with aneurysm rupture.

Treatment approaches: Most were treated with microsurgical clipping (64.7%) or endovascular therapy (29.4%); one patient was managed conservatively due to comorbidities/limited life expectancy.

ONP recovery outcomes: Complete ONP recovery occurred in 23.5% (4/17); all complete recoveries were in patients with symptom duration <5 weeks.

Timing signal: Subacute ONP (<5 weeks) was associated with better recovery (including complete recovery), while chronic ONP (≥5 weeks) had no complete recoveries in this cohort.

Rupture implication: Chronic ONP appeared not to indicate imminent rupture, with only about one-third presenting ruptured and an example of 10 years of stable ONP preceding rupture in the longest-duration case.

Management takeaway: Even if chronic ONP may not predict near-term rupture, early definitive aneurysm treatment is still recommended to maximize the chance of functional ONP recovery.

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The role of surveillance MRI scans in patients with sporadic cerebral cavernous malformations

J Neurosurg 144:1017–1023, 2026

This clinical study assesses the diagnostic value of routine versus symptom-driven MRI follow-up in patients with sporadic cerebral cavernous malformations (CCMs), analyzing radiographic changes at the first postdiagnosis scan in a prospective single-center cohort. Results show that new or worsening focal neurological deficit (FND) strongly predicts symptomatic hemorrhage, while routine surveillance rarely detects acute hemorrhage.

Imaging progression—including lesion growth, Zabramski classification changes, T1 hyperintensity, and edema—occurred across indications but had limited impact on management when patients were asymptomatic. The authors recommend symptom-driven MRI, reserving routine surveillance for select cases and early posthemorrhage confirmation.

Objective Evaluate whether routine surveillance MRI vs symptom-driven MRI better detects hemorrhage in patients with sporadic, brain-only cerebral cavernous malformations (CCMs), and what radiographic changes appear at first follow-up.

Cohort/Design Prospective single-center registry analysis of 236 sporadic brain-only CCM patients who had ≥1 follow-up MRI after diagnosis; MRI indications categorized as routine vs symptom-driven (e.g., new/worsening focal neurological deficit [FND], headache, seizure).

Hemorrhage yield Radiographic hemorrhage at first follow-up occurred in 19.1% (13/68) of symptom-driven MRIs vs 1.2% (2/168) of routine/non–CCM-related surveillance MRIs.

Routine progression In routine/non–CCM-related surveillance (n=168), 10.1% showed radiologic progression (growth ≥3 mm, more aggressive Zabramski type, or hemorrhage), but acute hemorrhage was only 1.2%; 88.2% of progression events occurred within 2 years.

Imaging correlates of SH Symptomatic hemorrhage (SH) was associated with lesion growth, moderate-to-severe T1-hyperintensity, and edema at follow-up; baseline lesion size and location did not predict hemorrhage.

Symptom predictors New or worsening FND predicted hemorrhage, while seizure or headache alone did not; in multivariate analysis, only new/worsening FND remained independently associated with hemorrhage (OR 13.73, p<0.001).

Clinical implication Follow-up MRI is most justified when there is new or worsening FND; routine surveillance in asymptomatic patients has limited diagnostic yield but may be reasonable in select situations.

Special cases MRI may still be considered for atypical, prolonged headaches distinct from baseline and not responsive to over-the-counter medication, or for changing/new seizure patterns based on clinical judgment.

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Microsurgery Versus Embolization for Spinal Cord Arteriovenous Malformations: A Proposed Grading System

Neurosurgery 98:786–798, 2026

This study proposes a four-parameter grading system to stratify angioarchitectural complexity of spinal cord arteriovenous malformations (SCAVMs) and compares clinical outcomes of microsurgery versus endovascular embolization across five grades in a 714-patient multicenter cohort. The grade sums points for metameric manifestation, lesion diameter ≥2 cm, anterior sulcal artery supply, and lesion depth, predicting incomplete resection with strong ROC (receiver-operating characteristic) performance.

Results show embolization as the preferred primary treatment owing to lower immediate risk, while microsurgery achieves higher complete obliteration for low-grade lesions (scores 0–1) but carries greater treatment-related deterioration and worse long-term prognosis for higher grades (scores 2–4). Recommendations prioritize embolization, reserving microsurgery for select low-grade or high-risk patients when embolization fails.

Study aim Compare outcomes of microsurgery vs endovascular embolization for SCAVMs by introducing a grading system that stratifies angioarchitectural complexity to enable fairer comparisons.

Cohort & design Retrospective multicenter analysis of 714 SCAVM patients treated (2007–2022); 308 received microsurgery (often after failed/partial embolization) and 406 received exclusive embolization.

Grading system (0–4 points) One point each for anterior sulcal artery supply, metameric manifestations, maximum lesion diameter ≥2 cm, and embedded (deep) lesion depth; total score defines grade.

Predictors basis & performance The four grading variables were independent predictors of incomplete resection in microsurgical cases, and the score showed strong ROC discrimination in modeling and validation groups (AUC ≈ 0.83).

Overall treatment tradeoff Microsurgery achieved a higher complete obliteration rate (61.7% vs 24.4%) but had higher treatment-related deterioration (19.8% vs 4.2%) and higher poor prognosis at last follow-up (52.3% vs 36.2%) than exclusive embolization.

Low grades (0–2) obliteration For scores 0–2, microsurgery produced significantly higher complete obliteration than embolization; for scores 3–4, complete obliteration rates were similar between methods.

Long-term deterioration & prognosis by grade Long-term clinical deterioration after embolization was higher for score 1 (significant) and also higher for score 0 (not significant); for scores 2–4, long-term deterioration risk was comparable, while poor prognosis was generally worse with microsurgery except score 0 (similar).

Treatment strategy Embolization should be the primary approach for SCAVMs; microsurgery is an alternative if embolization fails to fully obliterate lesions in score 0 (recommended) and selected 1-point patients (optional, especially higher clinical risk), but not first-line for scores 2–4.

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Treatment strategies, complications, and outcomes in spontaneous cerebellar hemorrhage

Acta Neurochirurgica (2026) 168:99

This single-center observational study examines treatment strategies, complications, and outcomes in 194 adults with spontaneous cerebellar hemorrhage (sCH) managed at a Swedish neurointensive care unit between 2008–2024. It compares conservative care, external ventricular drainage (EVD) alone, and combined hematoma evacuation with suboccipital decompression plus EVD, reporting short- and long-term mortality, functional outcome at discharge, and procedure-related complications.

Key findings show that conservative management often succeeds for neurologically stable patients with moderate hematomas (>15 mL), while combined evacuation/decompression with EVD is safe and effective for more severe presentations; EVD alone can suffice for selected hydrocephalus-predominant cases. Age, admission neurological status (GCS M), and hematoma volume independently predict 6-month mortality and functional outcome.

Study design Retrospective single-center cohort of adults with primary spontaneous cerebellar hemorrhage treated in a neurointensive care unit in Uppsala, Sweden (2008–2024), comparing conservative vs surgical management and analyzing predictors of 6‑month mortality and discharge functional outcome (GODS).

Treatment selection About half of 194 patients underwent surgery; surgically treated patients typically had worse neurological status, larger hematoma volumes, and more posterior fossa mass effect (e.g., fourth ventricle compression/hydrocephalus/IVH).

Conservative strategy for stable moderate-large bleeds In awake/stable patients with hematomas >15 mL initially managed conservatively, 78% did not need delayed surgery and most achieved favorable outcomes.

Surgical approach and safety Combined hematoma evacuation with suboccipital decompression plus EVD was associated with low complication rates and low early mortality in this cohort.

EVD-only option in selected cases Some patients with hydrocephalus and smaller hemorrhages were successfully treated with EVD alone, suggesting this may suffice when hydrocephalus predominates without dominant infratentorial mass effect.

Outcomes Overall mortality was 11% at discharge and 28% at 6 months; discharge outcomes differed by treatment group (higher early mortality but higher favorable discharge outcome in conservatively managed patients), while 6‑month mortality was similar between groups.

Key prognostic factors Age, neurological status (GCS motor score), and hematoma volume independently predicted 6‑month mortality; GCS motor score and hematoma volume independently predicted favorable discharge outcome (GODS > 3).

Clinical implication Favorable outcomes were achievable even in elderly patients; conservative care fit neurologically stable patients with moderate volumes, while surgery/EVD pathways were used for more severe presentations or deterioration.

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Neuropsychological profile and risk factors for poor cognitive outcomes in survivors of aneurysmal subarachnoid hemorrhage

J Neurosurg 144:517–525, 2026

This clinical study characterizes long-term neuropsychological outcomes in 156 survivors of aneurysmal subarachnoid hemorrhage (aSAH), using MoCA-22, digit span, and verbal fluency tests. Findings show that 34% scored below the 25th percentile despite largely favorable functional recovery, with deficits concentrated in executive function, working memory, and language.

Multivariable analysis identified modified Fisher grade 4 on admission and new radiological infarction during hospitalization as independent predictors of poor cognitive outcomes. Secondary assessments revealed frequent depressive symptoms and acquired personality disturbances, implicating impacts on work productivity and social relationships.

Objective Characterize neuropsychological deficits in aneurysmal subarachnoid hemorrhage (aSAH) survivors and identify clinical variables linked to poor cognitive outcomes.

Design/assessments Retrospective cohort (2009–2024) with cognitive testing ≥6 months post-aSAH using MoCA-22, Digit Span Forward/Backward, and Verbal Fluency; poor outcome defined as MoCA-22 <25th percentile (norm-adjusted).

Prevalence 34% (53/156) had MoCA-22 <25th percentile despite most having good functional recovery at discharge (mRS ≤2 in 79% of those with poor MoCA-22).

Cognitive profile Moderate/severe deficits (z-score >1 SD below norms) occurred in 11% on DST-F, 27% on DST-B, and 9% on VFT, highlighting prominent working-memory/executive-function vulnerability.

Key risk factors Modified Fisher grade 4 on admission and new radiological infarction during hospitalization were independently associated with poor MoCA-22 outcomes (aOR 2.43 and 2.71, respectively).

Quality of life impact Radiological infarction was associated with worse work productivity (OR 0.69) and social relationships (OR 0.72).

Behavioral sequelae Among those assessed, 27% reported at least mild depressive symptoms and 64% showed acquired personality disturbance.

Bottom line Cognitive/behavioral deficits can persist long after aSAH even with favorable mRS; higher hemorrhage burden (modified Fisher 4) and in-hospital infarction signal higher risk.

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Perimesencephalic hemorrhage: a proposed explanation of its cause and clinical manifestations

J Neurosurg 144:740–746, 2026

This neurosurgical forum article analyzes perimesencephalic hemorrhage (PMH), proposing that small dural arterial variants—particularly the artery of Wollschlaeger and Wollschlaeger (AWW) arising from the superior cerebellar artery—can undergo distraction-avulsion and explain PMH’s characteristic cisternal distribution and benign clinical course. The authors present a surgical case with intraoperative identification of an SCA-derived dural branch and perform detailed anatomical correlation.

The paper contrasts venous and arterial hypotheses, reviews perimesencephalic cisternal anatomy and tentorial blood supply, and argues that spontaneous tearing of a tethered intradural dural branch best accounts for imaging, pathophysiology, and low recurrence of PMH, while acknowledging limits of confirmatory testing.

PMH profile Nonaneurysmal perimesencephalic hemorrhage (PMH) is ~10%–15% of spontaneous cisternal SAH, with CT blood confined around the midbrain and typically a benign course with complete recovery and rare recurrence.

Unknown etiology Despite decades of imaging/anatomical work, the cause often remains unidentified on initial and follow-up angiography, leading to the concept of “SAH of unknown cause,” especially when bleeding is perimesencephalic-only.

Index case A 54-year-old woman with SAH had angiography showing a dural arteriovenous fistula (DAVF) fed by the meningohypophyseal trunk and draining via the superior petrosal vein; surgery disconnected the fistula with good outcome.

Unexpected anatomy Intraoperatively, a dural branch from the superior cerebellar artery (SCA) was found bridging the ambient cistern to the undersurface of the tentorium (the artery of Wollschlaeger and Wollschlaeger, AWW) and was sacrificed; it had not been seen on preop angiography and was not the hemorrhage source in that case.

Key anatomical concept The perimesencephalic cistern system (interpeduncular, ambient, quadrigeminal) surrounds the midbrain at the tentorial incisura; vessels can traverse cisternal spaces and arachnoid septations, influencing where blood can collect.

Tentorial dural supply variants The medial tentorium can be supplied by the marginal tentorial artery from the meningohypophyseal trunk, plus intradural-origin dural branches from the PCA (artery of Davidoff and Schechter, ADS) and from the SCA (AWW) that course within the ambient cistern before entering tentorium.

Competing sources considered Two structures fit many PMH constraints: the basal vein of Rosenthal (BVR) (venous, tethered to vein of Galen) and the ADS/AWW (arterial dural branches tethered to the medial tentorial edge).

Proposed mechanism for PMH Spontaneous distraction-avulsion of the AWW from its fragile tentorial attachment during everyday Valsalva/exertion could cause focal cisternal bleeding that self-limits as pressure equalizes in the confined cistern; this is proposed to explain PMH distribution, negative angiography, generally mild course, low hydrocephalus/vasospasm, and rare rebleed.

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The Helsinki Unruptured Intracranial Aneurysm Quality of Care study: a prospective observational study

J Neurosurg 144:507–516, 2026

This prospective single-center study evaluates the safety of unruptured intracranial aneurysm (UIA) treatments by prospectively measuring postprocedural diffusion-weighted MRI (DWI) lesions and correlating them with clinical outcomes at 3 months. Among 169 consecutive patients, 63% developed new DWI lesions, with endovascular cases showing more multiple lesions and surgical cases showing larger lesions.

Despite excellent functional outcomes by modified Rankin Scale (98% mRS 0–1) and high return-to-work rates, DWI lesions were associated with increased neurological symptoms, longer hospital stays, and worse outcomes when ≥10 mm. The authors argue that routine DWI should complement mRS to better capture ischemic burden and guide quality assessment and follow-up.

Objective Evaluate safety of unruptured intracranial aneurysm (UIA) treatment by measuring postprocedural ischemic lesions on MRI diffusion-weighted imaging (DWI) and correlating them with clinical outcomes.

Design Prospective, investigator-initiated, single-center observational cohort of consecutive UIA patients treated at Helsinki University Hospital (Dec 2022–Aug 2024) with brain MRI within 3 days and 3-month follow-up (mRS, neurological symptoms, return to work).

Cohort 169 patients: 120 (71%) endovascular and 49 (29%) surgical; aneurysm location distribution differed (most surgical cases were MCA aneurysms).

DWI incidence New DWI lesions occurred in 63% overall, with no difference between endovascular and surgical treatment (63% vs 63%).

Lesion patterns by modality Endovascular treatment more often produced high lesion counts (≥6 lesions: 14% vs 0%), while surgery more often produced larger lesions (≥10 mm: 20% vs 8%).

Symptoms association Most DWI lesions were asymptomatic (85%), but having any DWI lesion increased risk of new neurological symptoms (15% vs 2%), with 59% of symptoms transient.

mRS association Any DWI lesion was not associated with mRS outcomes, but lesions ≥10 mm were linked to poorer mRS status (mRS 0–1: 84% vs 99%) and higher risk of mRS worsening (21% vs 1%).

Return to work & conclusion 97% of previously working patients returned to work within 3 months; DWI lesions are common despite excellent mRS outcomes, and DWI may add information that mRS alone misses when assessing quality of care.

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Intraoperative Evaluation of Dural Arteriovenous Fistula Obliteration Using FLOW 800 Hemodynamic Analysis

Operative Neurosurgery 30:250–259, 2026

This clinical study evaluates intraoperative indocyanine green videoangiography with FLOW 800 software to quantify hemodynamic changes during cranial and spinal dural arteriovenous fistula (dAVF) microsurgical obliteration. Using four FLOW 800 metrics across venous regions of interest, the authors compare pre- and post-obliteration measurements confirmed by intraoperative digital subtraction angiography.

Key findings identify increased Delay Time and decreased Speed as consistent, significant markers of successful dAVF obliteration, supported by nonparametric tests, logistic and Bayesian regression, and PCA visualization. The study suggests FLOW 800 as a practical adjunct to intraoperative imaging, while acknowledging limitations from small sample size and ROI selection variability.

Key Hemodynamic Parameters: Intraoperative FLOW 800 analysis of indocyanine green videoangiography quantifies four hemodynamic parameters—Delay Time, Speed, Time to Peak, and Rise Time—across venous drainage regions before and after dAVF (dural arteriovenous fistula) obliteration.

Most Sensitive Indicators: Delay Time (time for dye to reach ROI) and Speed (rate of dye flow) are the most sensitive and consistent hemodynamic indicators of successful dAVF obliteration, with Delay Time increasing and Speed decreasing significantly post-obliteration.

Statistical Significance: Delay Time increased from a median of 2.07s to 7.86s (P = .020), and Speed decreased from 13.5 s⁻¹ to 5.5 s⁻¹ (P = .029), both changes being statistically significant; Time to Peak and Rise Time showed no significant association.

Predictive Value: A 50% increase in Delay Time is associated with 2.16 times higher odds of achieving obliteration (OR = 4.59), while a 50% decrease in Speed is associated with 1.28 times higher odds; Delay Time and Speed are the strongest predictors in regression analyses.

Clinical Utility: FLOW 800 provides real-time, semiquantitative intraoperative feedback, supporting its use as a noninvasive adjunct to traditional imaging (like intraoperative DSA) for confirming dAVF obliteration, especially where DSA is unavailable.

Study Limitations: The study is limited by small sample size (8 patients, 14 ROIs), single-center design, and possible variability in ROI selection; findings require validation in larger, multicenter studies.

Practical Considerations: Complete visualization of venous outflow is necessary for FLOW 800 utility; current evidence supports its use as a complementary tool rather than a replacement for DSA.

Clinical Outcome: All patients in the study had successful dAVF obliteration confirmed by intraoperative DSA, no complications or recurrences at median 19.4 months follow-up, and FLOW 800 changes were consistent with successful surgical outcomes.

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Predicting chronic subdural hematoma risk in elderly patients with mild traumatic brain injury

Acta Neurochirurgica (2026) 168:40

This study develops and validates a concise bedside risk score to predict chronic subdural hematoma (CSDH) within 2–12 weeks after mild traumatic brain injury in patients aged 65+. Using a large retrospective cohort (7,246 events) and multivariable modeling, pathological CT at presentation, male sex, older age, and renal failure emerged as key predictors.

The score-based model (including anticoagulant use by expert choice) achieved AUROC 0.76 and 86% sensitivity at the chosen threshold, classifying ~61% as high-risk. Authors propose this tool to guide targeted surveillance and earlier intervention, while noting limitations from retrospective data and need for external validation.

Pathological CT Findings: Pathological findings on initial head CT after mild traumatic brain injury (TBI) are the strongest predictor for developing chronic subdural hematoma (CSDH) within 2–12 weeks in elderly patients.

Key Risk Factors: Older age, male sex, and renal failure are also significant independent predictors for CSDH following mild TBI.

Anticoagulant Use: Chronic use of anticoagulant medications showed a trend toward increased risk but was not statistically significant in this cohort; antiplatelet use was not associated with increased risk.

Prediction Model: A simple score-based risk model was developed, incorporating pathological CT (14 points), male sex (4), renal failure (4), anticoagulant use (4), and age (1 point per 5 years over 65), with a threshold of 5 points or higher identifying high-risk patients.

Model Performance: The risk model achieved an area under the ROC curve (AUROC) of 0.76 and a sensitivity of 86% for detecting CSDH, but the positive predictive value was low (1.6%) due to the rare occurrence of the outcome.

Clinical Implications: Early identification of high-risk patients may enable targeted surveillance, timely CT scanning, and consideration of non-surgical management options such as corticosteroids or middle meningeal artery embolization.

Population Impact: The incidence of CSDH is rising globally due to population aging and increased use of antithrombotic agents, with elderly adults being particularly at risk.

Study Scope: The findings support the use of bedside risk stratification in the emergency department for elderly patients with mild TBI, but further research is needed before widespread clinical implementation.

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