Lawton, Michael T.

OBJECTIVE Cognard type V dural arteriovenous fistulas (dAVFs), defined by spinal perimedullary venous drainage, represent a rare and aggressive neurovascular pathology. Comprehensive multicenter data remain scarce. The authors present the largest multicenter analysis to date, characterizing presentation, radiology, treatment, complications, and functional outcomes of Cognard type V dAVFs. METHODS The authors retrospectively analyzed patients with angiographically confirmed Cognard type V dAVFs from the Consortium for Dural Arteriovenous Fistula Outcomes Research (CONDOR), spanning 16 academic centers. Patient demographics, imaging features, treatment strategies, procedural complications, and modified Rankin Scale (mRS) scores were recorded. RESULTS Among 1077 patients with dAVFs, 37 (3%) had Cognard type V lesions. The mean patient age was 57 years, and 59.5% of patients were male. Most presented with nonhemorrhagic neurological deficits (68%), while 14% had hemorrhage. The most common location was the foramen magnum (32%). Embolization was the primary treatment in 67% of cases, complete obliteration was achieved in 71% of cases. Upfront microsurgery was performed in 22% of patients (obliteration rate 88%), and radiosurgery in 14% (success rate 40%). Salvage treatment further improved obliteration outcomes. Temporary complications occurred in 8% of patients (3/37): 2 with transient neurological deficits postembolization and 1 with transient hydrocephalus after surgery. Permanent complications were observed in 3% (1/37) due to treatment-related hemorrhage. At the last follow-up (mean 2.4 years), 69% (24/35) of patients maintained or improved to an mRS score ≤ 2. No deaths occurred. Functional improvement was seen in 29% (10/35), while mRS decline was in 40% of patients (14/35), all unrelated to the dAVF itself. CONCLUSIONS Cognard type V dAVFs carry a high risk of neurological morbidity. However, favorable functional outcomes are achievable with timely, multimodal intervention. Complication rates remain low, with most being transient. These data support aggressive but tailored management to prevent permanent disability in this high-risk population.

OBJECTIVE Dural arteriovenous fistulas (dAVFs) are rare cerebrovascular anomalies. Tentorial dAVFs (TDAVFs) have more aggressive features, making them prone to symptomatic presentations and hemorrhage. TDAVFs are heterogenous and require tailored surgical approaches. Presented is a multicenter analysis of TDAVF surgical outcomes. METHODS The Consortium for Dural Arteriovenous Fistula Outcomes Research (CONDOR) consortium compiled data on dAVFs from 16 international centers from 1990 to 2021 retrospectively. Microsurgical treatment success was defined as angiographically confirmed complete obliteration of the fistula or discontinuation of cortical venous drainage (CVD) in high-grade TDAVFs. TDAVF subtypes and tailored surgical approaches were reviewed. RESULTS Of 1360 patients in CONDOR, 161 had TDAVFs and 27% (44/161) of these patients underwent surgical management, with the majority (52% [23/44]) receiving surgery as a salvage treatment following failed embolization. The mean age (SD) of this cohort was 56 (15) years, and 68% (30/44) were male. In total, 91% (40/44) of surgically treated patients presented with aggressive symptoms: 64% (28/44) presented with hemorrhage and 27% (12/44) with nonhemorrhagic neurological deficit (NHND). The median (IQR) duration from symptom onset to diagnosis was 1 (1–4) day. The median time (IQR) between diagnosis and surgery was 15 (3–80) days. Surgical approaches varied across the cohort, with the retrosigmoid being the most common (44% [18/41]), followed by the midline suboccipital (24% [10/41]) and occipital (15% [6/41]) approaches. Perioperative complications occurred in 11% (5/44) of cases, as well as permanent neurological deficits in 2% (1/44). Surgical success was achieved in 90% of patients (38/42). During the mean 3-year follow-up, 2 patients experienced a recurrence of their fistula including representation of CVD (2/38 [5%]) and 1 patient had a new NHND (1/43 [2%]). Shorter symptom duration was significantly associated with success (15.6 vs 181.5 days, p = 0.001). Primary versus salvage microsurgery showed no difference in outcomes. Both patients with recurrent fistula were effectively treated with Gamma Knife radiosurgery. CONCLUSIONS Resection is safe and durable for the treatment of TDAVF not otherwise amenable to embolization. It can achieve a high degree of success with a low rate of perioperative complications and permanent neurological deficits, benefits far exceeding the risks associated with TDAVF natural history or management with less effective modalities.

BACKGROUND AND OBJECTIVES: Stereotactic radiosurgery is a popular intervention for small vestibular schwannomas in patients with preserved hearing. Gamma Knife radiosurgery (GKRS) and CyberKnife radiosurgery (CKRS) represent 2 alternative modalities, with CKRS potentially allowing for the delivery of higher doses over multiple sessions. However, the optimal dosing and hearing outcomes of CKRS remain unclear. This study systematically reviewed all literature describing outcomes following treatment of vestibular schwannomas with CKRS, with a focus on tumor control, hearing preservation, and dosing schema. METHODS: The PubMed, Scopus, and Embase databases were queried to identify primary retrospective studies reporting local tumor control and hearing preservation rates following CKRS for vestibular schwannoma. Studies were reviewed, and the systematic review and meta-analysis were performed according to PRISMA and meta-analysis guidelines. RESULTS: Fifteen studies with study periods ranging from 1998 to 2018 were included. These studies comprised 2018 patients (mean age, 60.2 years; range, 11-91 years; 52% female), of whom 64 had neurofibromatosis type 2. The mean follow-up was 40 (range, 6-120) months, and 309 patients had undergone prior treatment (surgery and/or stereotactic radiosurgery). In aggregate, local control at the last follow-up was 96% (95% CI, 95%-98%), and 73% (95% CI, 66%-81%) of patients had preserved hearing. The most common major complications after CKRS were facial neuropathy (1.4%), trigeminal neuralgia (1.3%), and hydrocephalus (0.5%). CKRS provides a high rate of short-term and mid-term tumor control with hearing preservation comparable with GKRS, but long-term outcomes remain under investigated. CONCLUSION: This systematic review and meta-analysis found that CKRS offers high rates of tumor control and hearing preservation in patients undergoing stereotactic radiosurgery for vestibular schwannomas. Current data suggest that CKRS is a reasonable, safe therapeutic option for patients with small tumors and preserved hearing. Further exploration in larger cohorts and direct comparison with GKRS is merited.

BACKGROUND AND OBJECTIVES: Preventive treatment of unruptured intracranial aneurysms (UIAs) requires assessment of treatment risks vs expected benefit. Although established scores exist to estimate rupture and growth risk, currently, no externally validated tools exist to estimate the risks of microsurgical treatment of UIAs. Clinical prediction models based on machine learning enable generation of personalized risk estimates for each individual patient based on their specific patient and aneurysm characteristics. METHODS: Using data from 20 international centers from the prediction of adverse events after microsurgery for intracranial unruptured aneurysms study on patients treated microsurgically for UIAs, we developed and externally validated clinical prediction models for 3 outcomes measured at hospital discharge: poor neurological outcome (modified Rankin Score ≥3), new sensorimotor neurological deficits, and all-cause adverse events (Clavien-Dindo Grade ≥1). RESULTS: A total of 3705 patients were included. Data from 13 centers (2881, 78%) were used for model development. Fully trained models were evaluated on 824 patients (22%) from 7 additional centers. Average age was 56 ± 12 years, and 1049 (28%) were male. At discharge, poor neurological outcome was seen in 514 patients (14%). New sensorimotor deficits were observed in 534 patients (14%), and 894 patients (24%) experienced adverse events until discharge. At external validation, prediction of poor neurological outcome was achieved with good calibration and an area under the curve (AUC) = 0.70 (95% CI: 0.63-0.75). Similarly, new neurological deficits were predicted with good calibration and with an AUC = 0.69 (95% CI: 0.63-0.74). Prediction of all-cause adverse events only achieved an AUC = 0.59 (95% CI: 0.55-0.64) with fair calibration. The prediction model was integrated into a web application accessible at https://neurosurgery.shinyapps.io/PRAEMIUM/. CONCLUSION: The developed models for prediction of poor neurological outcome and new sensorimotor neurological deficits at discharge exhibit good calibration and fair discrimination based on a multinational external validation, indicating that the predicted probabilities correspond well to real-world risks and may thus be clinically useful in more objectively estimating the risk of microsurgical treatment.

OBJECTIVE Objective values on procedural risk are essential to facilitate informed consent and optimize clinical decision-making in patients with unruptured intracranial aneurysms (UIAs). While robust heuristics, such as the PHASES (population, hypertension, age, size of aneurysm, earlier subarachnoid hemorrhage, and site of aneurysm) score, are established for predicting rupture risk, contemporary and granular benchmarks for procedural safety remain scarce. The multinational Prediction of Adverse Events After Microsurgery for Intracranial Unruptured Aneurysms (PRAEMIUM) study aims to comprehensively characterize contemporary adverse event rates following microsurgical treatment at high-volume expert centers, stratified by aneurysm location, morphology, and complexity factors to better inform individual risk/benefit analyses. METHODS A cohort study among 20 participating expert centers from 9 countries was established. Patients treated microsurgically for UIAs were included. The authors describe the epidemiology of treated patients and UIAs and a comprehensive adverse event profile using 3 outcomes measured at hospital discharge: 1) poor neurological outcome (modified Rankin Scale score ≥ 3), 2) new sensorimotor neurological deficits, and 3) all-cause adverse events (Clavien-Dindo grade ≥ 1). Subgroup reports were given for aneurysm location, morphology, and complexity factors (prior aneurysm treatment, calcifications, complex angioanatomy involving critical branch vessels or perforators, and thrombosis). The authors purposely chose discharge as the time point to capture early postoperative risks and complications in patients with asymptomatic UIAs, for whom preserving neurological function is paramount. RESULTS The cohort included 3705 patients (mean age 56 [SD 12] years, 28% male). Overall, at discharge 13.9% of patients (95% CI 12.8%–15.0%) had poor neurological functional outcomes, 14.4% (95% CI 13.3%–15.5%) had new sensorimotor deficits, and 24.1% (95% CI 22.8%–25.5%) experienced all-cause adverse events. Poor neurological outcomes ranged from 8.5% (M1 aneurysms) to 37.4% (posterior circulation aneurysms), neurological deficits from 9.3% (distal anterior cerebral artery [ACA] aneurysms) to 34.2% (posterior circulation aneurysms), and all-cause adverse events from 21.2% (distal ACA aneurysms) to 31.3% (posterior circulation aneurysms). Dissecting and fusiform aneurysms showed notably high rates of poor neurological outcomes (22.0%–33.3%), new deficits (25.4%–26.7%), and adverse events (26.7%–37.0%). Complexity factors significantly influenced outcomes, with prior treatment (22.9%, 19.7%, and 30.1%), calcification (16.3%, 18.1%, and 30.5%), complex angioanatomy (13.1%, 15.9%, and 26.9%), and thrombosis (19.6%, 23.9%, and 39.6%) notably increasing the risks for poor neurological outcomes, deficits, and adverse events, respectively. CONCLUSIONS This large international cohort provides contemporary benchmarks for microsurgical treatment of UIAs, emphasizing variability in outcomes based on aneurysm location, morphology, and complexity. The presented granular and quotable adverse event rates support informed patient counseling and individualized risk/benefit assessments in comparable high-volume centers.

Importance Annual rates of first intracranial hemorrhage (ICH) from unruptured brain arteriovenous malformations (AVMs) are often quoted as 2% to 4% in clinical practice. Precise estimates and risk factors are unavailable to inform treatment decisions. Objective To provide estimates of rates and risk factors for first ICH in a large cohort study of unruptured brain AVMs. Design, Setting, and Participants The Multicenter Arteriovenous Malformation Research Study (MARS) included data from 9 cohorts, each contributing 100 or more unruptured brain AVMs. The study was conducted from 2017 to 2023 with retrospective and prospective data collection for existing cohorts and/or new recruitment. This was an international study (2 population-based and 7 referral-based cohorts) that included participants diagnosed with an unruptured brain AVM. Exposures Demographic, clinical, and angiographic characteristics. Main Outcome and Measure The primary outcome was time to first ICH after diagnosis of unruptured brain AVM. Data were collected using standardized definitions; missing data were imputed. Cox regression analysis was performed, censoring at first brain AVM treatment, death, or last visit, and allowing baseline hazards to vary by cohort. Results A total of 3225 individuals were eligible for participation in this study. After 195 exclusions, 3030 participants (median [IQR] age, 38 [25-50] years; 1524 female [50.3%]) were included. Among 2989 participants with unruptured brain AVMs, 1333 (45%) presented with seizure. The median (IQR) maximal brain AVM diameter was 3.1 (2.2-4.4) cm, 248 of 2466 AVMs (10%) had exclusively deep venous drainage, 297 of 2690 (11%) were in supratentorial deep or cerebellar locations, and 457 of 2440 (19%) had associated arterial aneurysms. First ICH occurred in 159 participants over 11 339 person-years of follow-up for an ICH rate of 1.40 (95% CI, 1.20-1.64) per 100 person-years. Significant independent risk factors included (1) increasing age category at diagnosis (hazard ratio [HR], 0.87; 95% CI, 0.53-1.41 for those aged 20 to 39 years; HR, 1.23; 95% CI, 0.74-2.04 for those aged 40 to 59 years; and HR, 2.01; 95% CI, 1.14-3.57 for those aged 60 years vs younger than 20 years; P = .008), (2) presence of associated aneurysms (HR, 1.66; 95% CI, 1.06-2.59; P = .03), and (3) cerebellar or supratentorial deep location (HR, 1.87; 95% CI, 1.16-3.00; P = .01). Conclusions and Relevance The annual ICH rate from unruptured brain AVM was lower than that commonly cited in clinical practice. Increasing age, associated arterial aneurysms, and cerebellar or supratentorial deep brain AVM location were associated with risk of first ICH. These results may be used to counsel patients about the natural history of unruptured brain AVMs.

Artificial intelligence (AI) is reshaping neurosurgery, offering unprecedented opportunities to enhance diagnostics, personalize treatment, and predict outcomes. At the heart of this transformation is the ability to effectively harness big data (BD) within the electronic medical record. Understanding these data structures is essential for making sense of the vast volumes of information generated in modern neurosurgical practice. Equally important are the machine learning (ML) models driving these advancements. From supervised learning and convolutional neural networks to generative AI, these tools are already making a mark in areas such as brain tumor segmentation and spine surgery outcome predictions. Their versatility highlights the potential of ML to complement clinical expertise and streamline decision-making in neurosurgery. However, adopting BD and ML also brings ethical challenges that cannot be ignored. Bias in algorithms threatens to reinforce health disparities, whereas concerns about data privacy demand vigilance in handling sensitive patient information. In addition, the question of liability looms large as ML increasingly influences clinical decisions. The aim of the study was to provide a roadmap for neurosurgeons navigating the evolving intersection of BD, ML, and ethical responsibility in the AI era.

Background and objectives Arteriovenous malformations (AVMs) with perinidal aneurysms and single draining vein are associated with an elevated risk of rupture and increased procedural complexity. The role of preoperative embolization in this high-risk anatomical subset remains unclear. This study aimed to evaluate the safety and efficacy of microsurgery with preoperative embolization, compared with microsurgery alone in patients with such AVMs. Methods We conducted a multicenter retrospective analysis of an AVM registry from the MISTA (Multicenter International Study for Treatment of Brain AVMs) consortium and included AVMs with perinidal aneurysms and a single draining vein. Baseline characteristics, angiographic outcomes, functional outcomes, and complication rates were compared. Propensity score weighting (PSW) using the covariate balancing method was applied to adjust for baseline differences. Results Out of a total of 1919 patients, 65 met the inclusion criteria; 45 patients underwent preoperative embolization followed by microsurgery, and 20 underwent microsurgery alone. After adjustment, complete obliteration rates were similar between groups (OR 0.87, 95% CI 0.04 to 16.33, P=0.92), as were rates of functional independence at discharge and follow-up. Overall complication, symptomatic complication, and mortality rates did not differ significantly between groups. However, permanent complications were significantly lower in patients with preoperative embolization (OR 0.06, 95% CI 0.004 to 0.84, P=0.03). Discussion In patients with AVMs featuring perinidal aneurysms and single draining vein, preoperative embolization followed by microsurgery was associated with fewer permanent complications and no increase in adverse outcomes compared with microsurgery alone. However, given the small number of events, this finding should be interpreted cautiously.

Background Given the low haemorrhagic risk of intracranial low-grade dural arteriovenous fistulas (dAVFs), the benefits of routine intervention remain controversial. This study compares patient outcomes treated with stereotactic radiosurgery (SRS) versus conservative management. Method Multicentre retrospective analysis of the Consortium for Dural Arteriovenous Fistula Outcomes Research and the International Radiosurgery Research Foundation data. Inclusion criteria were (1) intracranial low-grade dAVF diagnosed by catheter-based angiography, (2) no prior dAVF-related haemorrhage and (3) management with upfront SRS (intervention group) or conservative management (observation group). The primary outcome was symptomatic improvement. Secondary outcomes included dAVF obliteration, up-conversion, haemorrhage, improvement and favourable modified Rankin Scale (mRS) at follow-up. Results 304 patients with a mean age of 56 years (SD 13.5) and a follow-up of 46.7 months (SD 45.5) were included. 135 (44.4%) were managed conservatively and 169 (55.6%) had upfront SRS. Compared with the observation group, symptomatic and mRS Score improvement (≥1-point decrease in baseline score) was more likely in the intervention group (95.1% vs 58.5%; OR=13.75 (5.61–33.69) and 37.0% vs 24.0%; OR=1.85 (1.09–3.15), respectively). These findings remained significant after multiple imputation and propensity score matching. Remaining outcomes were similar between groups. The all-cause mortality rate was 5.4% (n=16), unrelated to the dAVF or treatment. Five (3.0%) SRS-related complications were reported and resolved during the follow-up period. Conclusions SRS was associated with increased symptomatic and mRS Score improvement for low-grade dAVFs compared with conservative management. SRS had a low complication risk and did not appear to alter dAVF obliteration or haemorrhage. Future prospective trials on SRS as a first-line intervention for symptomatic low-grade dAVFs should be considered.

OBJECTIVE Blister aneurysms of the internal carotid artery (ICA) have high associated mortality rates and are challenging due to their friable wall and poorly defined neck. Microsurgical and endovascular treatment options have been suggested, including bypass of the parent vessel to exclude the aneurysm. The goal of this study was to evaluate the safety and efficacy of microsurgical versus endovascular interventions. Additionally, for patients treated with open surgery, the outcomes of bypass were compared to nonbypass techniques. METHODS Three databases were systematically queried for primary studies comparing microsurgery to endovascular therapy and assessing bypass versus nonbypass treatment modalities for blister aneurysms of the ICA. All relevant studies published between 2000 and 2023 were eligible for inclusion. All articles were screened against title and abstract by 2 authors, as were those eligible for full-text assessment. Ultimately, relevant data from all included studies were pooled for meta-analysis in which the Mantel-Haenszel method with random-effects modeling was used. RESULTS Among the 504 cases reported across 24 studies, 182 (35.1%) blister aneurysms of the ICA were surgically treated, whereas 337 (64.9%) involved endovascular treatment. There were 235 (46.6%) female patients in the cohort. Functional outcomes were comparable between groups, with 83% of surgically treated patients and 85% of endovascularly treated patients achieving a favorable outcome (p > 0.05). Among the 7 studies (178 patients) comparing bypass to nonbypass microsurgery, rates of postoperative bleeding, ischemic infarct, vasospasm, recurrence, favorable outcomes, and mortality were comparable for bypass (n = 54, 30.3%) and nonbypass groups (n = 124, 69.7%). CONCLUSIONS Blister aneurysms of the ICA are rare intracranial aneurysms that are difficult to treat with microsurgical and endovascular techniques. Considering only patients treated with open surgery, there appears to be no significant difference in complication profile or functional outcomes between patients undergoing bypass or alternative microsurgical techniques. However, it must be noted that the complex nature of bypass procedures means that much of the data granularity is lost on meta-analysis, suggesting that additional investigations comparing bypass to other open microsurgical techniques may be merited. Similarly, future studies should determine the limitations of dual antiplatelet therapy in endovascular treatment and the efficacy of different numbers and types of overlapping, flow-diverting devices.