The future of open vascular neurosurgery: perspectives on cavernous malformations, AVMs, and bypasses for complex aneurysms

Endovascular embolization of Spetzler-Martin Grade I brain arteriovenous malformations: A case report on patient-centered neurointervention

Brain arteriovenous malformations (AVM) present complex treatment decisions, particularly for low-grade AVM where surgical resection is often considered the standard. This case report emphasizes the importance of patient preferences and cultural considerations in selecting endovascular embolization over traditional surgical approaches for Spetzler-Martin Grade I AVM management, highlighting the evolving practice of patient-centered care in neurointervention. A 30-year-old male presented with recurrent seizures, characterized by a sudden onset of headache followed by speech arrest, without any preceding medical history of neurological deficits. Initial physical examination revealed no focal neurological deficits. Non-contrast computed tomography, magnetic resonance imaging, and magnetic resonance angiography suggested an AVM involving the cortical-subcortical regions of the left frontal lobe, measuring approximately 1.7 × 2.6 × 1.5 cm, fed by the left middle cerebral artery M3 segment, and draining into the superior sagittal sinus. Spetzler-Martin Grade I classification was confirmed via digital subtraction angiography. Given the patient's strong preference against invasive procedures, driven by personal and cultural beliefs, endovascular embolization was selected as the treatment strategy. Post-embolization, the patient showed marked symptomatic improvement with no evidence of residual AVM on follow-up imaging, and no postprocedure complications were reported. This case highlights the importance of considering patient preferences in AVM treatment planning, illustrating that endovascular embolization can be an effective and less invasive alternative to surgery in selected patients, reinforcing the need for personalized, patient-centered approaches in neurointerventional care.

Blood Flow Capacity Assessment of End-to-Side Arterial Anastomosis In Vivo in Rats

Introduction  The aim of this article was to assess the flow capacity of end-to-side arterial anastomosis depending on the method of its implementation. Materials and Methods  The study was conducted on 30 live Wistar rats in vivo, which were randomly divided into three groups. In each group of animals, an end-to-side microanastamosis was performed using three methods of donor artery preparation: 45 degrees (group A), 90 degrees (group B), and arteriotomy according to the "fish mouth" type (group C). The determination of flow capacity of anastomosis by measuring the blood volume flow with transonic flowmeter was performed. Results  The obtained average values after the anastomosis were, respectively, 7.335 mL/s (standard deviation [SD]: 2.0771; min: 4.05; max: 10.85), 7.36 mL/s (SD: 0.836 mi: 6.15; max: 8.75), and 6.37 mL/s (SD: 1.247; min: 5.05; max: 9.05). No statistically significant difference in the blood volume flow velocity between all types of anastomoses was obtained ( p  = 0.251). Conclusion  The flow capacity of end-to-side arterial anastomosis does not depend on the chosen method of anastomosis.

Microsurgical removal of supratentorial and cerebellar cavernous malformations: what has changed? A single institution experience

BACKGROUND

Features associated with a safe surgical resection of cerebral cavernous malformations (CMs) are still not clear and what is needed to achieve this target has not been defined yet.

METHODS

Clinical presentation, radiological features and anatomical locations were assessed for patients operated on from January 2008 to January 2018 for supratentorial and cerebellar cavernomas. Supratentorial CMs were divided into 3 subgroups (non-critical vs. superficial critical vs. deep critical). The clinical outcome was assessed through modified Rankin Scale (mRS) and was divided into favorable (mRS 0-1) and unfavorable (mRS ≥ 2). Post-operative epilepsy was classified according to the Maraire Scale.

RESULTS

A total of 144 were considered eligible for the current study. At 6 months follow-up the clinical outcome was excellent for patients with cerebellar or lobar CMs in non-critical areas (mRS ≤ 1: 91.1 %) and for patients with superficial CMs in critical areas (mRS ≤ 1: 92.3 %). Patients with deep-seated suprantentorial CMs showed a favorable outcome in 76.9 %. As for epilepsy 58.5 % of patients presenting with a history of epilepsy were free from seizures and without therapy (Maraire grade I) at last follow-up (mean 3.9 years) and an additional 41.5 % had complete control of seizures with therapy (Maraire grade II).

CONCLUSIONS

Surgery is safe in the management of CMs in non-critical but also in critical supratentorial locations, with a caveat for deep structures such as the insula, the basal ganglia and the thalamus/hypothalamus.

Three-Vessel Anastomosis for Direct Multiterritory Cerebral Revascularization: Case Series

BACKGROUND AND OBJECTIVE

Cerebral revascularization of multiple territories traditionally requires multiple constructs, serial anastomoses, or a combination of direct and indirect approaches. A novel 3-vessel anastomosis technique allows for direct, simultaneous multiterritory cerebral revascularization using a single interposition graft. We herein present our experience with this approach.

METHODS

Retrospective review of perioperative data and outcomes for patients undergoing multiterritory cerebral revascularization using a 3-vessel anastomosis from 2019 to 2023.

RESULTS

Five patients met inclusion criteria (median age 53 years [range 12-73]). Three patients with complex middle cerebral artery aneurysms (1 ruptured) were treated with proximal ligation or partial/complete clip trapping and multiterritory external carotid artery-M2-M2 revascularization using a saphenous vein interposition graft. Two patients with moyamoya disease, prior strokes, and predominately bilateral anterior cerebral artery hypoperfusion were treated with proximal superficial temporal artery-A3-A3 revascularization using a radial artery or radial artery fascial flow-through free flap graft. No patients experienced significant surgery-related ischemia. Bypass patency was 100%. One patient had new strokes from vasospasm after subarachnoid hemorrhage. One patient required a revision surgery for subdural hematoma evacuation and radial artery fascial flow-through free flap debridement, without affecting bypass patency or neurologic outcome. On hospital discharge, median Glasgow Outcome Scale and modified Rankin Scale scores were 4 (range 3-5) and 2 (range 0-5), respectively. On follow-up, 1 patient died from medical complications of their presenting stroke; Glasgow Outcome Scale and modified Rankin Scale scores were otherwise stable or improved.

CONCLUSION

The 3-vessel anastomosis technique can be considered for simultaneous revascularization of multiple intracranial territories.

Intraoperative Neurophysiologic Monitoring and Mapping in Children Undergoing Brainstem Surgery

SUMMARY

Intraoperative neurophysiologic monitoring during surgery for brainstem lesions is a challenge for intraoperative neurophysiologists and surgeons. The brainstem is a small structure packed with vital neuroanatomic networks of long and short pathways passing through the brainstem or originating from it. Many central pattern generators exist within the brainstem for breathing, swallowing, chewing, cardiovascular regulation, and eye movement. During surgery around the brainstem, these generators need to be preserved to maintain their function postoperatively. This short review presents neurophysiologic and neurosurgical experiences of brainstem surgery in children.

Deep learning-based video-analysis of instrument motion in microvascular anastomosis training

PURPOSE

Attaining sufficient microsurgical skills is paramount for neurosurgical trainees. Kinematic analysis of surgical instruments using video offers the potential for an objective assessment of microsurgical proficiency, thereby enhancing surgical training and patient safety. The purposes of this study were to develop a deep-learning-based automated instrument tip-detection algorithm, and to validate its performance in microvascular anastomosis training.

METHODS

An automated instrument tip-tracking algorithm was developed and trained using YOLOv2, based on clinical microsurgical videos and microvascular anastomosis practice videos. With this model, we measured motion economy (procedural time and path distance) and motion smoothness (normalized jerk index) during the task of suturing artificial blood vessels for end-to-side anastomosis. These parameters were validated using traditional criteria-based rating scales and were compared across surgeons with varying microsurgical experience (novice, intermediate, and expert). The suturing task was deconstructed into four distinct phases, and parameters within each phase were compared between novice and expert surgeons.

RESULTS

The high accuracy of the developed model was indicated by a mean Dice similarity coefficient of 0.87. Deep learning-based parameters (procedural time, path distance, and normalized jerk index) exhibited correlations with traditional criteria-based rating scales and surgeons' years of experience. Experts completed the suturing task faster than novices. The total path distance for the right (dominant) side instrument movement was shorter for experts compared to novices. However, for the left (non-dominant) side, differences between the two groups were observed only in specific phases. The normalized jerk index for both the right and left sides was significantly lower in the expert than in the novice groups, and receiver operating characteristic analysis showed strong discriminative ability.

CONCLUSION

The deep learning-based kinematic analytic approach for surgical instruments proves beneficial in assessing performance in microvascular anastomosis. Moreover, this methodology can be adapted for use in clinical settings.

The surgical strategy and technical nuances of in situ side-to-side bypass for the management of complex intracranial aneurysms

Background

Despite continuous advances in microsurgical and endovascular techniques, the treatment of complex aneurysms remains challenging. Aneurysms that are dilemmatic for conventional clipping or endovascular coiling often require bypass as part of a strategy to reduce the risk of ischemic complications. In anatomically favorable sites, the intracranial-intracranial in situ bypass may be an appealing choice. This article details the surgical strategies, operative nuances, and clinical outcomes of this technique with a consecutive series in our department.

Methods

A retrospective review of a prospectively maintained neurosurgical patient database was performed to identify all patients treated with side-to-side in situ bypass from January 2016 to June 2022. In total, 12 consecutive patients, including 12 aneurysms, were identified and included in the series. The medical records, surgical videos, neuroimaging studies, and follow-up clinic notes were reviewed for every patient.

Results

Of the 12 aneurysms, there were 5 middle cerebral artery aneurysms, 4 anterior cerebral artery aneurysms, and 3 posterior inferior cerebellar artery aneurysms. The morphology of the aneurysms was fusiform in 8 patients and saccular in the remaining 4 patients. There were 3 patients presented with subarachnoid hemorrhage. The treatment modality was simple in situ bypass in 8 cases and in situ bypass combined with other modalities in 4 cases. Bypass patency was confirmed in all cases by intraoperative micro-doppler probe and (or) infrared indocyanine green (ICG) video angiography intraoperatively and with digital subtraction angiography (DSA) or computed tomography angiography (CTA) postoperatively. None of the patients developed a clinically manifested stroke due to the procedure though a callosomarginal artery was intentionally removed in one patient. The median follow-up period was 16.2 months (6-36). All patients had achieved improved or unchanged modified Rankin scale scores at the final follow-ups.

Conclusion

Cerebral revascularization technique remains an essential skill for the treatment of complex aneurysms. The in situ bypass is one of the most effective techniques to revascularize efferent territory when vital artery sacrifice or occlusion is unavoidable. The configuration of in situ bypass should be carefully tailored to each case, with consideration of variations in anatomy and pathology of the complex aneurysms.

Endovascular trends in the treatment of intracranial aneurysms in a Peruvian reference center

Objectives

Endovascular treatment of intracranial aneurysms (IAs) has evolved in recent years and is currently the preferred treatment worldwide. We analyzed the trends in the number of patients, number of aneurysms, aneurysm characteristics, and techniques used in a pure endovascular cohort of patients treated in a reference center.

Materials and Methods

Between 2010 and 2020, a retrospective data collection of patients who underwent endovascular intervention of IAs was performed. We used the Mann-Kendal test to evaluate the trends. In addition, the moving-average technique was used to assess smoother curves.

Results

Eight hundred and forty-five aneurysms were treated in 765 patients, the mean age was 53.9 ± 14.6 years and 81% were women. The number of patients (P = 0.016) and aneurysms (P = 0.003) increased significantly. Unruptured (P = 0.029) and posterior communicating artery aneurysms increased their frequency of treatment (P = 0.042). Balloon remodeling (P = 0.01) and the use of flow diverters showed a positive trend (P = 0.016).

Conclusion

There have been an increased number of patients and aneurysms treated endovascularly at our institution, including unruptured and posterior communicating aneurysms. Advanced endovascular techniques also increased. Comparative studies including surgical cases must be done in our region to determine the best approach.

Hemodynamics of vascular shunts: trends, challenges, and prospects

Vascular bypass surgery takes a significant place in the treatment of vascular disease. According to various assessments, this type of surgery is associated with almost 20 % of all vascular surgery episodes (up to 23 % according to the Federal Neurosurgical Center of Novosibirsk). Even though the problem of using of vascular grafts is obvious and natural, many problems associated with them are not still elucidated. From the mechanics' point of view, a vascular bypass is a converging or diverging tee, and the functioning of such structures still does not have strict mathematical formulations and proofs in the general case, which forces many researchers to solve specific engineering problems associated with shunting. Mathematical modeling, which is the gold standard for virtual simulations of industrial and medical problems, faces great difficulties and limitations in solving problems for vascular bypasses. Complications in the treatment of the vascular disease may follow the difficulties in mathematical modeling, and the price can be a cardiac arrest or a stroke. This work is devoted to the main aspects of the medical application of vascular bypasses and their functioning as a mechanical system, as well the mathematical aspects of their possible setup.

Double-Interposition Bypass: Technical Case Report of a Novel Intraoperative Bypass Salvage Technique

BACKGROUND AND IMPORTANCE

Complex cerebrovascular bypass operations may confer an increased risk of intraoperative complications, such as graft thrombosis. Novel techniques are needed to optimize the management of these challenging cases.

CLINICAL PRESENTATION

A woman in her late 20s was incidentally diagnosed with a 1.5-cm basilar apex aneurysm, which grew to 3.5 cm over 2 years of active surveillance. Definitive treatment was then recommended with flow reversal and Hunterian ligation of the basilar trunk planned as a radial artery graft (RAG) bypass: M2 (S-Ec) RAG (E-Sc*) P2. Intraoperative graft thrombosis prompted multiple attempted salvage maneuvers; however, complete excision and repeat anastomosis were ultimately required. The procedure was completed using a novel double-interposition technique, with ligation of the index RAG approximately 1 cm proximal to the distal anastomosis (final bypass: M2 [S-Ec*] RAG [E-Ec*] RAG' [E-Sc] P2). These technical modifications yielded a less deep recipient site for the repeat bypass and an end-to-end anastomosis rather than an end-to-side anastomosis, collectively facilitating a more efficient and facile salvage. The patient recovered well from surgery, and flow reversal was successfully achieved within the aneurysm.

CONCLUSION

Despite the increased risk of intraoperative thrombosis with complex cerebrovascular bypass operations, facility with salvage techniques can lead to technically and clinically excellent outcomes. We report the successful use of a novel fourth-generation double-interposition bypass that shortens the working distance and uses a more favorable anastomosis technique. This bypass may facilitate safe and efficient microsurgery in patients who require complete revision of an intracranial-intracranial construct.

External carotid artery-radial artery graft-posterior cerebral artery bypass for complex vertebrobasilar aneurysms: efficacy and analysis of outcome in a single center

The purpose of this research was to demonstrate the effectiveness and clinical outcome of an external carotid artery-radial artery graft-posterior cerebral artery (ECA-RAG-PCA) bypass in the treatment of complex vertebrobasilar artery aneurysms (VBANs) in a single-center retrospective study. An ECA-RAG-PCA bypass may be a last and very important option in the treatment of complex VBANs when conventional surgical clipping or endovascular interventions fail to achieve the desired outcome. This study retrospectively analyzed the clinical presentation, case characteristics, aneurysm location, size and morphology, choice of surgical strategy, complications, clinical follow-up, and prognosis of the patients enrolled. The data involved were analyzed by the appropriate statistical methods. A total of 24 patients with complex VBANs who met the criteria were included in this study. Eighteen (75.0%) were male and the mean age was 54.1 ± 8.83 years. The aneurysms were located in the vertebral artery, the basilar artery, and in the vertebrobasilar artery with simultaneous involvement. All patients underwent ECA-RAG-PCA bypass surgery via an extended middle cranial fossa approach, with 8 (33.3%) undergoing ECA-RAG-PCA bypass only, 3 (12.5%) undergoing ECA-RAG-PCA bypass combined with aneurysm partial trapping, and 12 (50.0%) undergoing ECA-RAG-PCA bypass combined with proximal occlusion of the parent artery. The average clinical follow-up was 22.0 ± 13.35 months. The patency rate of the high-flow bypass was 100%. At the final follow-up, 15 (62.5%) patients had complete occlusion of the aneurysm, 7 (29.2%) patients had subtotal occlusion of the aneurysm, and 2 (8.3%) patients had stable aneurysms. The rate of complete and subtotal occlusion of the aneurysm at the final follow-up was 91.7%. The clinical prognosis was good in 21 (87.5%) patients and no procedure-related deaths occurred. Analysis of the good and poor prognosis groups revealed a statistically significant difference in aneurysm size (P = 0.034, t-test). Combining the results of this study and the clinical experience of our center, we propose a surgical algorithm and strategy for the treatment of complex VBANs.The technical approach of ECA-RAG-PCA bypass for complex VBANs remains important, even in an era of rapid advances in endovascular intervention. When conventional surgical clipping or endovascular intervention has failed, an ECA-RAG-PCA bypass plays a role that cannot be abandoned and is a very important treatment option of last resort.

Approach Selection Strategies for Repeat Resection of Brain Cavernous Malformations: Cohort Study

BACKGROUND

Neurosurgical management of cerebral cavernous malformations (CMs) often benefits from using skull base approaches. Although many CMs are cured by resection, residual or recurrent disease may require repeat resection.

OBJECTIVE

To review approach selection strategies for reoperation of CMs to aid decision-making for repeat procedures.

METHODS

In this retrospective cohort study, a prospectively maintained single-surgeon registry was queried for patients with CMs who underwent repeat resection from January 1, 1997, to April 30, 2021.

RESULTS

Of 854 consecutive patients, 68 (8%) underwent 2 operations; 40 had accessible data on both. In most reoperations (33/40 [83%]), the index approach was repeated. In most reoperations using the index approach (29/33 [88%]), that approach was deemed ideal (no equivalent or superior alternative), whereas in some (4/33 [12%]), the alternative approach was deemed unsafe because of conformation of the tract. Among patients with reoperations using an alternative approach (7/40 [18%]), 2 with index transsylvian approaches underwent bifrontal transcallosal approaches, 2 with index presigmoid approaches underwent extended retrosigmoid revisions, and 3 with index supracerebellar-infratentorial approaches underwent alternative supracerebellar-infratentorial trajectory revisions. Among patients with reoperations with an alternative approach considered or selected (11/40 [28%]), 8 of 11 patients had a different surgeon for the index resection than for the repeat resection. The extended retrosigmoid-based approaches were used most often for reoperations.

CONCLUSION

Repeat resection of recurrent or residual CMs is a challenging neurosurgical niche at the intersection of cerebrovascular and skull base disciplines. Suboptimal index approaches may limit surgical options for repeat resection.

Experience and Balance: Long-Term Trends in Preferred Skull Base Approach for a Case Series of Cavernous Malformation Resections

BACKGROUND

Skull base approaches are a foundation of modern cerebrovascular surgery; however, their application over time has varied.

OBJECTIVE

To assess trends in skull base approach selection for cavernous malformation (CM) resection.

METHODS

This is a retrospective case series of all first-time CM resections by a single surgeon from 1997 to 2021. Cases were classified by craniotomy and approach. Four sets of common comparator skull base approaches were identified by coauthor consensus: pterional and orbitozygomatic; retrosigmoid, extended retrosigmoid (xRS), and far-lateral; suboccipital and torcular; and trans-cerebellar peduncle (MCP) and transcerebellopontine angle. Counts were binned by 5-year or 10-year clusters for descriptive statistical assessment of temporal trends.

RESULTS

In total, 372 primary CM resections met the study criteria and were included. Orbitozygomatic approach use increased during the second 5-year period, after which the pterional approach rapidly became and remained the preferred approach. During the first two 5-year periods, the far-lateral approach was preferred to the retrosigmoid and xRS approaches, but the xRS approach grew in popularity and accounted for >50% of operations in this comparator group. Trans-MCP use compared with the transcerebellopontine angle approach closely mirrored the change in xRS use. The midline suboccipital approach accounted for a larger proportion (range, 62%-88%) of cases than the torcular approach (range, 12%-38%) across all periods.

CONCLUSION

The xRS and trans-MCP approaches have been increasingly used over time, while the orbitozygomatic and far-lateral approaches have become less common. These trends seem to reflect versatility, efficiency, and safety of these techniques.

Is STA really a low‐flow graft? A quantitative ultrasonographic study of the flow of STA for cerebral revascularization in MMD patients

OBJECTIVE

Direct revascularization remains an important tool in the treatment of patients with Moyamoya disease (MMD). The superficial temporal artery (STA) is the most commonly used donor vessel for direct bypass, and an STA graft has traditionally been considered a low-flow graft for flow augmentation. This study aimed to quantitatively evaluate the blood flow of the STA after direct revascularization.

METHODS

All direct revascularization procedures performed between 2018 and 2021 by one experienced neurosurgeon were screened. Quantitative ultrasound was used to measure the flow data of the patient's bilateral parietal branch of the STA(STA-PB), the bilateral frontal branch of the STA(STA-FB), and the left radial artery. Data on the patients' basic information, Suzuki grade, Matsushima type, anastomosis type, and blood biochemical parameters were collected and analyzed using univariate and multivariate models. An MBC Scale scoring system was proposed to evaluate the recipient artery network of the middle cerebral artery (MCA) tree. The relationship between MBC Scale score and STA graft flow was statistically analyzed.

RESULTS

In total, 81 patients (43 males and 38 females) successfully underwent STA-MCA bypass and were included in this study. The mean flow rates in the STA-PB graft on 1 day preoperatively, 1 day postoperatively, 7 days postoperatively, and >6 months postoperatively (long-term) were 10.81, 116.74, 118.44, and 56.20 mL/min respectively. Intraoperative graft patency was confirmed in all patients. Comparing the preoperative and all postoperative time points, the STA-PB flow rates were statistically significant (p < 0.001). The MCA-C score was significantly associated with postoperative flow rate on day 1 (p = 0.007).

CONCLUSION

The STA is a useful donor artery for direct revascularization inpatients with MMD and can provide sufficient blood supply to the ischemic cerebral territory.

Focused selection of open cerebrovascular cases for residents interested in cerebrovascular neurosurgery

INTRODUCTION

National and international trends continue to show greater emphasis on endovascular techniques for the treatment of cerebrovascular disease. The cerebrovascular neurosurgeon however must be adequately equipped to treat these patients via both open and endovascular techniques.

METHODS

The decline in open cerebrovascular cases for aneurysm clipping has forced many trainees to pursue open cerebrovascular fellowships to increase case volume. An alternative strategy has been employed at our institution, which is early identification of subspecialty focus with resident driven self-selection of open cerebrovascular cases.

RESULTS

This has allowed recent graduates to obtain enfolded endovascular training and a significant number of open cerebrovascular cases in order to obtain competence and exposure.

DISCUSSION

We advocate for further self-selection paradigms supplemented with simulation training in order to obviate the need for extended post-residency fellowships.

Association of Preoperative Vascular Wall Imaging Patterns and Surgical Outcomes in Patients With Unruptured Intracranial Saccular Aneurysms

BACKGROUND

MR vascular wall imaging (VWI) may have prognostic value in patients with unruptured intracranial aneurysms (UIAs).

OBJECTIVE

To evaluate the value of VWI as a predictor of surgical outcome in patients with UIAs.

METHODS

This prospective cohort study evaluated surgical outcomes in consecutive patients with UIAs who underwent surgical clipping at a single center. All participants underwent high-resolution VWI and were followed for at least 6 months. The primary clinical outcome was modified Rankin scale (mRS) score 6 months after surgery.

RESULTS

The number of patients in the no wall enhancement, uniform wall enhancement (UWE), and focal wall enhancement (FWE) groups was 37, 145, and 154, respectively. Incidence of postoperative complications was 15.5% in the FWE group, 12.4% in the UWE group, and 5.4% in the no wall enhancement group. The proportion of patients with mRS score >2 at the 6-month follow-up was significantly higher in the FWE group than in the UWE group (14.3% vs 6.9%; P = .0389). In the multivariate analysis, FWE (odds ratio, 2.573; 95% CI 1.001-6.612) and positive proximal artery remodeling (odds ratio, 10.56; 95% CI 2.237-49.83) were independent predictors of mRS score >2 at the 6-month follow-up.

CONCLUSION

Preoperative VWI can improve the surgeon's understanding of aneurysm pathological structure. Type of aneurysmal wall enhancement on VWI is associated with clinical outcome and incidence of salvage anastomosis and surgical complications.

Is it time to rethink microsurgical training for the treatment of intracranial aneurysms in Australia?

BACKGROUND

Case volume and complexity for microsurgical treatment of cerebral aneurysms have changed due to the growing use of endovascular therapy in clinical practice. The authors sought to quantify the clinical exposure of Australian neurosurgery trainees to cerebral aneurysm microsurgery.

METHODS

This observational, retrospective cross-sectional study examined the Australian National Hospital Morbidity database for all admissions related to microsurgical and endovascular treatment of aneurysmal subarachnoid haemorrhage (aSAH) and unruptured intracranial aneurysms (UIAs) for the years 2008 to 2018. Procedural volumes were compared with neurosurgical trainee figures to investigate the rate of procedural exposure relative to the neurosurgical workforce.

RESULTS

A total of 8,874 (41.6%) microsurgical procedures (3,662 for aSAH, 5,212 for UIAs), and 12,481 (58.4%) endovascular procedures (6,018 for aSAH, 6,463 for UIAs) were performed. Trainee exposure to microsurgery in aSAH declined from 9.1 to 7.3 cases per trainee per annum (mean 7.7), with case complexity confined mostly to simple anterior circulation aneurysms. There are significant state-by-state differences in the preferred treatment modality for aSAH. During the same study period, the number of microsurgical cases for UIAs increased (from 8.9 to 13.5 cases per trainee per annum, mean 11.0). Significantly more endovascular procedures are performed than microsurgery (10.7 to 17.0, mean 12.7 cases, for aSAH; 8.0 to 21.5, mean 13.7 cases, for UIAs).

CONCLUSIONS

Trainee exposure to open aneurysm surgery for aSAH have significantly declined in both case volume and complexity. There is an overall increase in the number of surgeries for elective aneurysms, but this varies widely from state-to-state.

Bibliometric and visual analysis of cerebral revascularization from 1999 to 2022

Background

Cerebral revascularization is a neurosurgical procedure used to restore the cerebral collateral circulation channel. This study examines the countries, institutions, authors, journals, keywords, and references related to the disease in the field of cerebral revascularization from 1999 to 2022 from a bibliometrics perspective, evaluates the changes of knowledge structure clustering and identifies the new hot spots and new research directions in this field.

Methods

The Web of Science Core Collection (WOSCC) database and the PICOS retrieval method were used to conduct a comprehensive search for articles and reviews pertaining to cerebral revascularization. The final filtered data were bibliometrically and visually drawn using Microsoft office 365, CiteSpace (v.6.1.R2), and VOSviewer (v.1.6.18).

Results

From 1999 to 2022, a total of 854 articles pertaining to cerebral revascularization, which originated from 46 nations, 482 institutions, and 686 researchers, were extracted from the WOSCC database, and the number of publications in this field of study was rising. The United States held the highest proportion in the ranking analysis of countries, institutions, authors, and journals. By analyzing co-citations, the scientific organization of this field and the development status of frontier fields were realized. Cerebral revascularization, moyamoya disease, extracranial intracranial bypass, and occlusion are the current research focal points in the field of cerebral revascularization. Hyperperfusion and vascular disorder may also become a new study focus in this discipline in the near future.

Conclusion

Using the method of bibliometrics, this study analyzed and reviewed the articles in the field of cerebral revascularization, which enabled scholars to better comprehend the dynamic process in this field and provided a foundation for future in-depth research.

A taxonomy for brainstem cavernous malformations: subtypes of medullary lesions

OBJECTIVE

Medullary cavernous malformations are the least common of the brainstem cavernous malformations (BSCMs), accounting for only 14% of lesions in the authors' surgical experience. In this article, a novel taxonomy for these lesions is proposed based on clinical presentation and anatomical location.

METHODS

The taxonomy system was applied to a large 2-surgeon experience over a 30-year period (1990-2019). Of 601 patients who underwent microsurgical resection of BSCMs, 551 were identified who had the clinical and radiological information needed for inclusion. These 551 patients were classified by lesion location: midbrain (151 [27%]), pons (323 [59%]), and medulla (77 [14%]). Medullary lesions were subtyped on the basis of their predominant surface presentation. Neurological outcomes were assessed according to the modified Rankin Scale (mRS), with an mRS score ≤ 2 defined as favorable.

RESULTS

Five distinct subtypes were defined for the 77 medullary BSCMs: pyramidal (3 [3.9%]), olivary (35 [46%]), cuneate (24 [31%]), gracile (5 [6.5%]), and trigonal (10 [13%]). Pyramidal lesions are located in the anterior medulla and were associated with hemiparesis and hypoglossal nerve palsy. Olivary lesions are found in the anterolateral medulla and were associated with ataxia. Cuneate lesions are located in the posterolateral medulla and were associated with ipsilateral upper-extremity sensory deficits. Gracile lesions are located outside the fourth ventricle in the posteroinferior medulla and were associated with ipsilateral lower-extremity sensory deficits. Trigonal lesions in the ventricular floor were associated with nausea, vomiting, and diplopia. A single surgical approach was preferred (> 90% of cases) for each medullary subtype: the far lateral approach for pyramidal and olivary lesions, the suboccipital-telovelar approach for cuneate lesions, the suboccipital-transcisterna magna approach for gracile lesions, and the suboccipital-transventricular approach for trigonal lesions. Of these 77 patients for whom follow-up data were available (n = 73), 63 (86%) had favorable outcomes and 67 (92%) had unchanged or improved functional status.

CONCLUSIONS

This study confirms that the constellation of neurological signs and symptoms associated with a hemorrhagic medullary BSCM subtype is useful for defining the BSCM clinically according to a neurologically recognizable syndrome at the bedside. The proposed taxonomical classifications may be used to guide the selection of surgical approaches, which may enhance the consistency of clinical communications and help improve patient outcomes.

Defining activities in neurovascular microsurgery training: entrustable professional activities for vascular neurosurgery

BACKGROUND

Entrustable professional activities (EPAs) represent an assessment framework with an increased focus on competency-based assessment. Originally developed and adopted for undergraduate medical education, concerns over resident ability to practice effectively after graduation have led to its implementation in residency training but yet not in vascular neurosurgery. Subjective assessment of resident or fellow performance can be problematic, and thus, we aim to define core EPAs for neurosurgical vascular training.

METHODS

We used a nominal group technique in a multistep interaction between a team of experienced neurovascular specialists and a medical educator to identify relevant EPAs. Panel members provided feedback on the EPAs until they reached consent.

RESULTS

The process produced seven core procedural EPAs for vascular residency and fellowship training, non-complex aneurysm surgery, complex aneurysm surgery, bypass surgery, arteriovenous malformation resection, spinal dural fistula surgery, perioperative management, and clinical decision-making.

CONCLUSION

These seven EPAs for vascular neurosurgical training may support and guide the neurosurgical society in the development and implementation of EPAs as an evaluation tool and incorporate entrustment decisions in their training programs.

The Learning Curve in Skull Base Surgery Part 1–From Historical-Philosophical Concepts to Microsurgical Lab Training

The learning curve reflects surgeons' experience in managing several patients with the same disease. In skull base surgery, the professional's place on the curve could be related to the number of times the same procedure was performed. Where does curve begin? What amount of training is necessary prior to its application in surgical settings? What were the results of the first few skull base tumor surgeries performed by a surgeon who goes on to produce excellent results, and how is reflected in the start of their learning curve? The only way for neurosurgeons to improve their results from the start is with prior training in the microsurgery laboratory. This learning technique is essential to maximize the chance of success of a neurosurgical procedures, minimizing the morbidity rate to which patients are subjected by less experienced neurosurgeons. This article is divided in two parts, and its purpose is to show how training in the microsurgical laboratory fits into the construction of knowledge about skull base surgery, based on authors' experience and reflections. This first part discusses the technical, psychological, and philosophical aspects of medical knowledge, primarily addressing those training in skull base surgery, the principles of some selected philosophical currents, and their influence on the development of current medical knowledge.

A taxonomy for brainstem cavernous malformations: subtypes of pontine lesions. Part 1: basilar, peritrigeminal, and middle peduncular

OBJECTIVE

Brainstem cavernous malformations (BSCMs) are complex, difficult to access, and highly variable in size, shape, and position. The authors have proposed a novel taxonomy for pontine cavernous malformations (CMs) based upon clinical presentation (syndromes) and anatomical location (findings on MRI).

METHODS

The proposed taxonomy was applied to a 30-year (1990-2019), 2-surgeon experience. Of 601 patients who underwent microsurgical resection of BSCMs, 551 with appropriate data were classified on the basis of BSCM location: midbrain (151 [27%]), pons (323 [59%]), and medulla (77 [14%]). Pontine lesions were then subtyped on the basis of their predominant surface presentation identified on preoperative MRI. Neurological outcomes were assessed according to the modified Rankin Scale, with a score ≤ 2 defined as favorable.

RESULTS

The 323 pontine BSCMs were classified into 6 distinct subtypes: basilar (6 [1.9%]), peritrigeminal (53 [16.4%]), middle peduncular (MP) (100 [31.0%]), inferior peduncular (47 [14.6%]), rhomboid (80 [24.8%]), and supraolivary (37 [11.5%]). Part 1 of this 2-part series describes the taxonomic basis for the first 3 of these 6 subtypes of pontine CM. Basilar lesions are located in the anteromedial pons and associated with contralateral hemiparesis. Peritrigeminal lesions are located in the anterolateral pons and are associated with hemiparesis and sensory changes. Patients with MP lesions presented with mild anterior inferior cerebellar artery syndrome with contralateral hemisensory loss, ipsilateral ataxia, and ipsilateral facial numbness without cranial neuropathies. A single surgical approach and strategy were preferred for each subtype: for basilar lesions, the pterional craniotomy and anterior transpetrous approach was preferred; for peritrigeminal lesions, extended retrosigmoid craniotomy and transcerebellopontine angle approach; and for MP lesions, extended retrosigmoid craniotomy and trans-middle cerebellar peduncle approach. Favorable outcomes were observed in 123 of 143 (86%) patients with follow-up data. There were no significant differences in outcomes between the 3 subtypes or any other subtypes.

CONCLUSIONS

The neurological symptoms and key localizing signs associated with a hemorrhagic pontine subtype can help to define that subtype clinically. The proposed taxonomy for pontine CMs meaningfully guides surgical strategy and may improve patient outcomes.

The trend of percutaneous and open surgical procedures for peripheral arteriovenous malformations in the National Health Service England

INTRODUCTION

This study aimed to assess the trend of percutaneous and open surgical procedures for peripheral arteriovenous malformations (AVMs) performed in NHS hospitals in England between 2012 and 2018.

METHODS

Hospital Episode Statistics (HES) is a freely available data warehouse that represents the whole population of England served by the NHS. Data from the HES database was obtained and analysed for all hospital episodes between 2012 and 2018 for the total number and trend of 'primary diagnosis', and 'primary procedures and interventions' identified for peripheral AVMs.

RESULTS

Over the period studied, there was an increase in the total number of admissions for peripheral AVMs; total primary diagnosis increased from 2242 to 2857 per year. Open surgery remained more commonly performed than percutaneous procedures throughout the studied period. However, the overall percentage of primary procedures and interventions being percutaneous in this period increased from 29.8% to 41.0% per year. The increase in the number of percutaneous procedures per year seemed to occur in both children (from 43 to 124) and adults (from 408 to 492) over the course of the study period.

CONCLUSIONS

This study concluded that open surgery remained the most commonly performed primary procedure for peripheral AVMs, although there was an increasing trend for percutaneous procedures in NHS hospitals in England. The increase in the number and percentage of percutaneous procedures for peripheral AVMs was likely to have significant resource implications for the provision of care for patients with peripheral AVMs in NHS hospitals.

Fourth-generation bypass and flow reversal to treat a symptomatic giant dolichoectatic basilar trunk aneurysm

BACKGROUND

Giant dolichoectatic basilar trunk aneurysms have an unfavorable natural history and are associated with high morbidity, but their neurosurgical treatment is complex and challenging.

METHODS

Flow reversal reconstruction with fourth-generation bypass and proximal vertebral artery clip occlusion is performed via orbitozygomatic craniotomy with the Kawase approach under rapid ventricular pacing.

CONCLUSION

Fourth-generation bypass is an innovative, technically challenging, and clinically effective tool in the treatment armamentarium for giant dolichoectatic basilar trunk aneurysms.

A taxonomy for brainstem cavernous malformations: subtypes of pontine lesions. Part 2: inferior peduncular, rhomboid, and supraolivary

OBJECTIVE

Part 2 of this 2-part series on pontine cavernomas presents the taxonomy for subtypes 4-6: inferior peduncular (IP) (subtype 4), rhomboid (5), and supraolivary (6). (Subtypes 1-3 are presented in Part 1.) The authors have proposed a novel taxonomy for pontine cavernous malformations based on clinical presentation (syndromes) and anatomical location (MRI findings).

METHODS

The details of taxonomy development are described fully in Part 1 of this series. In brief, pontine lesions (323 of 601 [53.7%] total lesions) were subtyped on the basis of predominant surface presentation identified on preoperative MRI. Neurological outcomes were assessed according to the modified Rankin Scale, with score ≤ 2 defined as favorable.

RESULTS

The 323 pontine brainstem cavernous malformations were classified into 6 distinct subtypes: basilar (6 [1.9%]), peritrigeminal (53 [16.4%]), middle peduncular (100 [31.0%]), IP (47 [14.6%]), rhomboid (80 [24.8%]), and supraolivary (37 [11.5%]). Subtypes 4-6 are the subject of the current report. IP lesions are located in the inferolateral pons and are associated with acute vestibular syndrome. Rhomboid lesions present to the fourth ventricle floor and are associated with disconjugate eye movements. Larger lesions may cause ipsilateral facial weakness. Supraolivary lesions present to the surface at the ventral pontine underbelly. Ipsilateral abducens palsy is a strong localizing sign for this subtype. A single surgical approach and strategy were preferred for subtypes 4-6: for IP cavernomas, the suboccipital craniotomy and telovelar approach predominated; for rhomboid lesions, the suboccipital craniotomy and transventricular approach were preferred; and for supraolivary malformations, the far lateral craniotomy and transpontomedullary sulcus approach were preferred. Favorable outcomes were observed in 132 of 150 (88%) patients with follow-up. There were no significant differences in outcomes between subtypes.

CONCLUSIONS

The neurological symptoms and signs associated with a hemorrhagic pontine subtype can help define that subtype clinically with key localizing signs. The proposed taxonomy for pontine cavernous malformation subtypes 4-6 meaningfully guides surgical strategy and may improve patient outcomes.

Surgical management outcomes of intracranial arteriovenous malformations after preoperative embolization: a systematic review and meta-analysis

OBJECTIVE

Preoperative embolization for brain arteriovenous malformations (AVMs) has been shown to mitigate morbidity for high-risk AVMs, chiefly by reducing lesional blood flow before resection. However, associated risks include postembolization AVM rupture, and the effect of preoperative embolization on outcome remains uncertain. We performed a meta-analysis of the literature on preoperative embolization for microsurgically treated AVMs.

METHODS

A systematic review and meta-analysis were conducted of all English-language publications reporting clinical outcomes after combined embolization and surgical resection for AVMs. Single- and 2-arm analyses were performed using random-effects modeling.

RESULTS

Thirty-six studies with 2108 patients were included in this analysis. Most patients (90.6%) who underwent embolization had at least a 50% obliteration of AVMs on posttreatment preoperative angiography, with a mean rate of obliteration of approximately 80% (range 28.8-100%). Among patients who had combined treatment, 3.4% (95% confidence interval [CI] 2.1-4.6%) experienced embolization-related hemorrhagic complications before surgery. Both treatment groups achieved excellent postsurgical complete resection rates (odds ratio [OR] 1.05; 95% CI 0.60-1.85). Neither the clinical outcome (OR 1.42; 95% CI 0.84-2.40) nor the total number of hemorrhagic complications (OR 1.84; 95% CI 0.88-3.85) was significantly different between the treatment groups.

CONCLUSIONS

In this meta-analysis, preoperative embolization appears to have substantially reduced the lesional volume with active AV shunting before AVM resection. Anecdotally, preoperative embolization facilitates safe and efficient resection; however, differences in outcomes were not significant. The decision to pursue preoperative embolization remains a nuanced decision based on individual lesion anatomy and treatment team experience.

The changing landscape of cerebral revascularization surgery: A United Kingdom experience

Objective

We describe the chronological trends in cerebral revascularization surgery through a single-surgeon experience; and we review whether in the context of giant and fusiform cerebral aneurysms, flow-diverting stents have impacted on the use of cerebral revascularization surgery.

Methods

We review our single institution prospectively collected database of cerebral revascularization procedures between 2006 and 2018. Comparing this to our database of flow-diverting endovascular stent procedures, we compare the treatment of fusiform and giant aneurysms. We describe patient demographics, procedural incidence, complications, and outcomes.

Results

Between 2006 and 2018, 50 cerebral revascularization procedures were performed. The incidence of cerebral revascularization surgery is declining. In the context of giant/fusiform aneurysm treatment, the decline in cerebral revascularization is accompanied by a rise in the use of flow-diverting endovascular stents. Thirty cerebral revascularizations were performed for moyamoya disease and 11 for giant/fusiform aneurysm. Four (14%) direct bypass grafts occluded without neurological sequela. Other morbidity included hydrocephalus (2%), transient ischemic attacks (2%), and ischemic stroke (2%). There was one procedure-related mortality (2%). Flow-diverting stents were inserted for seven fusiform and seven giant aneurysms. Comparing the treatment of giant/fusiform aneurysms, there was no significant difference in morbidity and mortality between cerebral revascularization and flow-diverting endovascular stents.

Conclusion

We conclude that with the decline in the incidence of cerebral revascularization surgery, there is a need for centralization of services to allow high standards and outcomes to be maintained.

Vertebrobasilar dissecting aneurysms: microsurgical management in 42 patients

OBJECTIVE

Vertebrobasilar dissecting (VBD) aneurysms are rare, and patients with these aneurysms often present with thromboembolic infarcts or subarachnoid hemorrhage (SAH). The morphological nature of VBD aneurysms often precludes conventional clip reconstruction or coil placement and encourages parent artery exclusion or endovascular stenting. Treatment considerations include aneurysm location along the vertebral artery (VA), the involvement of the posterior inferior cerebellar artery (PICA), and collateral blood flow. Outcomes after endovascular treatment have been well described in the neurosurgical literature, but microsurgical outcomes have not been detailed. Patient outcomes from a large, single-surgeon, consecutive series of microsurgically managed VBD aneurysms are presented, and 3 illustrative case examples are provided.

METHODS

The medical records of patients with dissecting aneurysms affecting the intracranial VA (V4), basilar artery, and PICA that were treated microsurgically over a 19-year period were reviewed. Patient demographics, aneurysm characteristics, surgical procedures, and clinical outcomes (according to modified Rankin Scale [mRS] scores at last follow-up) were analyzed.

RESULTS

Forty-two patients with 42 VBD aneurysms were identified. Twenty-six aneurysms (62%) involved the PICA, 14 (33%) were distinct from the PICA origin on the V4 segment of the VA, and 2 (5%) were located at the vertebrobasilar junction. Thirty-four patients (81%) presented with SAH with a mean Hunt and Hess grade of 3.2 at presentation. Six (14%) of the 42 patients had been previously treated using endovascular techniques. Nineteen aneurysms (45%) underwent clip wrapping, 17 (40%) were treated with bypass trapping, and 6 (14%) underwent parent artery sacrifice. The complete aneurysm obliteration rate was 95% (n = 40), and the surgical complication rate was 7% (n = 3). The 8 patients with unruptured VBD aneurysms were significantly more likely to be discharged home (n = 6, 75%) compared with 34 patients with ruptured aneurysms (n = 9, 27%; p = 0.01). Good outcomes (mRS score ≤ 2) were observed in 20 patients (48%). Eight patients (19%) died.

CONCLUSIONS

These data demonstrate that patients with VBD aneurysms often present after a rupture in poor neurological condition, but favorable results can be achieved with open microsurgical repair in almost half of such cases. Microsurgery remains a viable treatment option, with the choice between bypass trapping and clip wrapping largely dictated by the specific location of the aneurysm and its relationship to the PICA.

Using temporal and structural data to reconstruct 3D cerebral vasculature from a pair of 2D digital subtraction angiography sequences

PURPOSE

The purpose of this work is to present a new method for reconstructing patient-specific three-dimensional (3D) vasculature of the brain from a pair of digital subtraction angiography (DSA) image sequences from different viewpoints, e.g., from bi-plane angiography. Our long-term goal is to provide high resolution visualization of 3D vasculature with dynamic flow of contrast agent from limited data that is readily available during surgical procedures. The proposed method is the second of a three-stage process composed of 1) augmenting vessel segmentation with vessel radii and timing of the arrival of a bolus of contrast agent, 2) reconstructing a volumetric representation of the augmented vessel data from the augmented 2D segmentations, and 3) generating a 3D model of vessels and flow of contrast agent from the volumetric reconstruction. Unlike previous methods, which are either limited to relatively simple vessel structures or rely on multiple views and/or prior models of the vasculature, our method requires only a single pair of 2D DSA sequences taken from different view directions.

METHODS

We developed a new mathematical algorithm that augments vessel centerlines with vessel radii and bolus arrival times derived directly from the 2D DSA sequences to constrain the 3D reconstruction. We validated this method on digital phantoms derived from clinical data and from fractal models of branching tree structures.

RESULTS

In standard reconstruction methods, reconstruction by projection of two views into 3D space results in 'ghosting' artifacts, i.e., false 3D structure that occurs where vessels or vessel segments overlap in the 2D images. For the complex vascular of the brain, this ghosting is severe and is a major hurdle for methods that attempt to generate 3D structure from 2D images. We show that our approach reduces ghosting by up to 99% in digital phantoms derived from clinical data.

CONCLUSION

Our dramatic reduction in ghosting artifacts in 3D reconstructions from a pair of 2D image sequences is an important step towards generating high resolution 3D vasculature with dynamic flow information from a single DSA sequence acquired using bi-plane angiography.

Saccular aneurysms in the post-Barrow Ruptured Aneurysm Trial era

OBJECTIVE

The Barrow Ruptured Aneurysm Trial (BRAT) was a single-center trial that compared endovascular coiling to microsurgical clipping in patients treated for aneurysmal subarachnoid hemorrhage (aSAH). However, because patients in the BRAT were treated more than 15 years ago, and because there have been advances since then-particularly in endovascular techniques-the relevance of the BRAT today remains controversial. Some hypothesize that these technical advances may reduce retreatment rates for endovascular intervention. In this study, the authors analyzed data for the post-BRAT (PBRAT) era to compare microsurgical clipping with endovascular embolization (coiling and flow diverters) in the two time periods and to examine how the results of the original BRAT have influenced the practice of neurosurgeons at the study institution.

METHODS

In this retrospective cohort study, the authors evaluated patients with saccular aSAHs who were treated at a single quaternary center from August 1, 2007, to July 31, 2019. The saccular aSAH diagnoses were confirmed by cerebrovascular experts. Patients were separated into two cohorts for comparison on the basis of having undergone microsurgery or endovascular intervention. The primary outcome analyzed for comparison was poor neurological outcome, defined as a modified Rankin Scale (mRS) score > 2. The secondary outcomes that were compared included retreatment rates for both therapies.

RESULTS

Of the 1014 patients with aSAH during the study period, 798 (79%) were confirmed to have saccular aneurysms. Neurological outcomes at ≥ 1-year follow-up did not differ between patients treated with microsurgery (n = 451) and those who received endovascular (n = 347) treatment (p = 0.51). The number of retreatments was significantly higher among patients treated endovascularly (32/347, 9%) than among patients treated microsurgically (6/451, 1%) (p < 0.001). The retreatment rate after endovascular treatment was lower in the PBRAT era (9%) than in the BRAT (18%).

CONCLUSIONS

Similar to results from the BRAT, results from the PBRAT era showed equivalent neurological outcomes and increased rates of retreatment among patients undergoing endovascular embolization compared with those undergoing microsurgery. However, the rate of retreatment after endovascular intervention was much lower in the PBRAT era than in the BRAT.

Augmented reality–assisted microsurgical resection of brain arteriovenous malformations: illustrative case

BACKGROUND

Arteriovenous malformations (AVMs) of the brain are vessel conglomerates of feeding arteries and draining veins that carry a risk of spontaneous and intraoperative rupture. Augmented reality (AR)-assisted neuronavigation permits continuous, real-time, updated visualization of navigation information through a heads-up display, thereby potentially improving the safety of surgical resection of AVMs.

OBSERVATIONS

The authors report a case of a 37-year-old female presenting with a 2-year history of recurrent falls due to intermittent right-sided weakness and increasing clumsiness in the right upper extremity. Magnetic resonance imaging, magnetic resonance angiography, and cerebral angiography of the brain revealed a left parietal Spetzler-Martin grade III AVM. After endovascular embolization of the AVM, microsurgical resection using an AR-assisted neuronavigation system was performed. Postoperative angiography confirmed complete obliteration of arteriovenous shunting. The postsurgical course was unremarkable, and the patient remains in excellent health.

LESSONS

Our case describes the operative setup and intraoperative employment of AR-assisted neuronavigation for AVM resection. Application of this technology may improve workflow and enhance patient safety.

Untangling the Modern Treatment Paradigm for Unruptured Brain Arteriovenous Malformations

Brain arteriovenous malformations (AVMs) often present treatment challenges. Patients with unruptured AVMs must consider not only whether they want to be treated, but what treatment modality they would prefer. Vascular neurosurgeons, neurointerventional surgeons, and stereotactic radiosurgeons must in turn guide their patients through the most appropriate treatment course considering the risk of AVM rupture, an individual AVM’s characteristics, and patient preferences. In this review we will look at how the clinical trial “A Randomized Trial of Unruptured Brain Arteriovenous Malformations (ARUBA)” has influenced the approach to unruptured brain AVMs and the treatment modalities available to clinicians to deal with these formidable lesions.

A comparative propensity-adjusted analysis of microsurgical versus endovascular treatment of unruptured ophthalmic artery aneurysms

OBJECTIVE

Ophthalmic artery (OA) aneurysms are surgically challenging lesions that are now mostly treated using endovascular procedures. However, in specialized tertiary care centers with experienced neurosurgeons, controversy remains regarding the optimal treatment of these lesions. This study used propensity adjustment to compare microsurgical and endovascular treatment of unruptured OA aneurysms in experienced tertiary and quaternary settings.

METHODS

The authors retrospectively reviewed the medical records of all patients who underwent microsurgical treatment of an unruptured OA aneurysm at the University of California, San Francisco, from 1997 to 2017 and either microsurgical or endovascular treatment at Barrow Neurological Institute from 2011 to 2019. Patients were categorized into two cohorts for comparison: those who underwent open microsurgical clipping, and those who underwent endovascular flow diversion or coil embolization. Outcomes included neurological or visual outcomes, residual or recurrent aneurysms, retreatment, and severe complications.

RESULTS

A total of 345 procedures were analyzed: 247 open microsurgical clipping procedures (72%) and 98 endovascular procedures (28%). Of the 98 endovascular procedures, 16 (16%) were treated with primary coil embolization and 82 (84%) with flow diversion. After propensity adjustment, microsurgical treatment was associated with higher odds of a visual deficit (OR 8.5, 95% CI 1.1-64.9, p = 0.04) but lower odds of residual aneurysm (OR 0.06, 95% CI 0.01-0.28, p < 0.001) or retreatment (OR 0.12, 95% CI 0.02-0.58, p = 0.008) than endovascular therapy. No difference was found between the two cohorts with regard to worse modified Rankin Scale score, modified Rankin Scale score greater than 2, or severe complications.

CONCLUSIONS

Compared with endovascular therapy, microsurgical clipping of unruptured OA aneurysms is associated with a higher rate of visual deficits but a lower rate of residual and recurrent aneurysms. In centers experienced with both open microsurgical and endovascular treatment of these lesions, the treatment choice should be based on patient preference and aneurysm morphology.

Surgical Anatomy of the Middle Communicating Artery and Guidelines for Predicting the Feasibility of M2-M2 End-to-End Reimplantation

BACKGROUND

M2-M2 end-to-end reimplantation that creates a middle communicating artery has recently been proposed as a reconstruction technique to treat complex aneurysms of the middle cerebral artery that are not amenable to clipping.

OBJECTIVE

To examine the surgical anatomy, define anatomic variables, and explore the feasibility of this bypass.

METHODS

Sixteen cadaver heads were prepared for bypass simulation. After the middle cerebral artery bifurcation was approached, the proximal insular (M2) segments and perforators were explored. To define the maximal distance between the M2 segments that allows the bypass to be performed, the M2 segments were mobilized and reimplanted in an end-to-end fashion.

RESULTS

Successful reimplantation was performed in all specimens. The mean maximal distance between the M2 segments to create the proposed reimplantation was 9.1 ± 3.2 mm. The mean vessel displacement was significantly greater for the superior (6.0 ± 2.3 mm) M2 segment than for the inferior (3.2 ± 1.4 mm) M2 segment (P < .001).

CONCLUSION

In this cadaveric study, the stumps of the M2 segments located at a distance of ≤9.1 mm could be approximated to create a feasible M2-M2 end-to-end anastomosis. Intraoperative inspection of the M2 segments and their perforators could allow further assessment of the feasibility of the procedure before final revascularization decisions are made.

Efficacy and safety of embolization for arteriovenous malformations of the basal ganglia and thalamus via the transarterial approach

Background

To evaluate the effectiveness and safety profile of transarterial embolization in the treatment of brain arteriovenous malformations (bAVMs) within the basal ganglia and thalamus.

Methods

A retrospective clinical study was performed on 22 patients with bAVMs localized within the basal ganglia and thalamus who were treated with transarterial embolization (December 2012 and January 2019) in our center. The bAVMs were embolized via the transarterial approach with Onyx or Glubran according to the anatomical structure. A detachable or undetachable microcatheter was used in the procedure according to the length of the feeding artery. The data of these patients were retrospectively analyzed.

Results

Among the 22 patients, 9 bAVMs were located in the basal ganglia and 13 were located in the thalamus. Twenty patients presented with hemorrhage (90.9%), leaving 2 patients (9.1%) who had no symptoms. According to the Spetzler-Martin grading classification, 13 bAVMs (59.1%) were grade 3, 7 (31.8%) were grade 4, and 2 (9.1%) were grade 5. Procedure-related complications occurred in only 1 patient (4.5%). No deaths related to the operation occurred. All patients achieved anatomic stabilization and no bleeding was observed in the follow-up.

Conclusions

Selective embolization via the transarterial approach is safe and effective for bAVMs originating within the basal ganglia and thalamus. Our results demonstrate a low rate of complications and an elevated degree of anatomical disruption in the endovascular treatment of bAVMs stemming from the basal ganglia and thalamus.

The "Binder Ring" Bypass: Transection, Rerouting, and Reanastomosis as an Alternative to Macrovascular Decompression of a Dolichoectatic Vertebral Artery

BACKGROUND

In cases of extreme vertebrobasilar dolichoectasia, padding the cranial nerves (CNs) (microvascular decompression [MVD]) and clip-assisted sling transposition of the tortuous artery (macrovascular decompression [MaVD]) may be ineffective because the sling does not reduce the redundancy. Transposition may not decompress the nerves or may kink the artery. An alternative solution is needed.

OBJECTIVE

To introduce the "binder ring" bypass as a novel solution to this unusual macrovascular compression problem.

METHODS

The binder ring denotes the opening and closing of the offending vascular loop with standard bypass techniques with the artery transected, rerouted lateral to the CNs, and reanastomosed. An example case study is presented for a 72-year-old man whose severe vertebral artery tortuosity could not be relieved by MVD or MaVD. His pathology was exposed with an extended retrosigmoid craniotomy, the V4 segment was transected, the free ends were mobilized lateral to CN VII/VIII, and an end-to-end reanastomosis was performed with intraluminal suturing.

RESULTS

The example binder ring bypass was patent angiographically, and the patient experienced immediate and lasting symptom relief without complications.

CONCLUSION

The binder ring bypass applies standard bypass techniques to macrovascular compression but represents a significant escalation in technical challenges relative to traditional techniques. Patient tolerance to temporary arterial occlusion during reanastomosis depends on the location of the compressive arterial loop and the anatomy of collateral circulation. The binder ring bypass should be used as a last resort after medical therapy and MaVD techniques fail and performed only by neurosurgeons with advanced bypass skills.

Giant Aneurysm Management

The treatment of giant aneurysms has always been a challenge in the field of neurovascular disease. Giant aneurysms are larger in size and are associated with thrombosis development and the calcification of the aneurysmal wall and neck, which often interfere with direct clipping. Most giant aneurysms have a wide neck with an incomplete thrombus, making complete embolization almost impossible. Giant aneurysms of different sites have entirely different hemodynamic characteristics. Moreover, aneurysms at the same site may exhibit very different hemodynamics among different individuals. Therefore, careful assessment of each case is required before and during treatment to develop and carry out an individualized treatment plan.

Coding cerebral bypasses: a proposed nomenclature to better describe bypass constructs and revascularization techniques

OBJECTIVE

Bypass surgery has evolved into a complex surgical art with a variety of donor arteries, recipient arteries, interpositional grafts, anastomoses, and suturing techniques. Although innovation in contemporary bypasses has increased, the literal descriptions of these new bypasses have not kept pace. The existing nomenclature that joins donor and recipient arteries with a hyphen is simplistic, underinformative, and in need of improvement. This article proposes a nomenclature that systematically incorporates anatomical and technical details with alphanumeric abbreviations and is a clear, concise, and practical "code" for bypass surgery.

METHODS

Detailed descriptions and illustrations of the proposed nomenclature, which consists of abbreviations for donor and recipient arteries, arterial segments, arteriotomies, and sides (left or right), with hyphens and parentheses to denote the arteriotomies joined in the anastomosis and brackets and other symbols for combination bypasses, are presented. The literature was searched for articles describing bypasses, and descriptive nomenclature was categorized as donor and recipient arteries (donor-recipient), donor-recipient with additional details, less detail than donor-recipient, and complete, ambiguous, or descriptive text.

RESULTS

In 483 publications, most bypass descriptions were categorized as donor-recipient (335, 69%), with superficial temporal artery-middle cerebral artery bypass described most frequently (299, 62%). Ninety-seven articles (20%) used donor-recipient descriptions with additional details, 45 (9%) were categorized as ambiguous, and none contained a complete bypass description. The authors found the proposed nomenclature to be easily applicable to the more complex bypasses reported in the literature.

CONCLUSIONS

The authors propose a comprehensive nomenclature based on segmental anatomy and additional anastomotic details that allows bypasses to be coded simply, succinctly, and accurately. This alphanumeric shorthand allows greater precision in describing bypasses and clarifying technical details, which may improve reporting in the literature and thus help to advance the field of bypass surgery.

Double-barrel STA-MCA bypass and partial trapping of a ruptured mycotic MCA aneurysm with flash fluorescence technique

Mycotic brain aneurysms are rare and unusual cerebrovascular lesions arising from septic emboli that degrade the elastic lamina and vessel wall of intracranial arteries, which results in pathologic dilatation. Mycotic aneurysms are nonsaccular lesions that are not often suitable for clipping and instead require bypass, trapping, and flow reversal. This case demonstrates the use of indocyanine green “flash fluorescence” to identify the cortical distribution supplied by an aneurysm’s outflow, facilitating safe treatment with a double-barrel extracranial-intracranial bypass and partial trapping and conversion of a deep bypass to a superficial one.

The video can be found here: https://stream.cadmore.media/r10.3171/2021.10.FOCVID21163

A taxonomy for brainstem cavernous malformations: subtypes of midbrain lesions

OBJECTIVE

Anatomical taxonomy is a practical tool that has successfully guided clinical decision-making for patients with brain arteriovenous malformations. Brainstem cavernous malformations (BSCMs) are similarly complex lesions that are difficult to access and highly variable in size, shape, and position. The authors propose a novel taxonomy for midbrain cavernous malformations based on clinical presentation (syndromes) and anatomical location (identified with MRI).

METHODS

The taxonomy system was developed and applied to an extensive 2-surgeon experience over a 30-year period (1990-2019). Of 551 patients with appropriate data who underwent microsurgical resection of BSCMs, 151 (27.4%) had midbrain lesions. These lesions were further subtyped on the basis of predominant surface presentation identified on preoperative MRI. Five distinct subtypes of midbrain BSCMs were defined: interpeduncular (7 lesions [4.6%]), peduncular (37 [24.5%]), tegmental (73 [48.3%]), quadrigeminal (27 [17.9%]), and periaqueductal (7 [4.6%]). Neurological outcomes were assessed using modified Rankin Scale (mRS) scores. A postoperative score ≤ 2 was defined as a favorable outcome; a score > 2 was defined as a poor outcome. Clinical and surgical characteristics and neurological outcomes were compared among subtypes.

RESULTS

Each midbrain BSCM subtype was associated with a recognizable constellation of neurological symptoms. Patients with interpeduncular lesions commonly presented with ipsilateral oculomotor nerve palsy and contralateral cerebellar ataxia or dyscoordination. Peduncular lesions were associated with contralateral hemiparesis and ipsilateral oculomotor nerve palsy. Patients with tegmental lesions were the most likely to present with contralateral sensory deficits, whereas those with quadrigeminal lesions commonly presented with the features of Parinaud syndrome. Periaqueductal lesions were the most likely to cause obstructive hydrocephalus. A single surgical approach was preferred (> 90% of cases) for each midbrain subtype: interpeduncular (transsylvian-interpeduncular approach [7/7 lesions]), peduncular (transsylvian-transpeduncular [24/37]), tegmental (lateral supracerebellar-infratentorial [73/73]), quadrigeminal (midline or paramedian supracerebellar-infratentorial [27/27]), and periaqueductal (transcallosal-transchoroidal fissure [6/7]). Favorable outcomes (mRS score ≤ 2) were observed in most patients (110/136 [80.9%]) with follow-up data. No significant differences in outcomes were observed between subtypes (p = 0.92).

CONCLUSIONS

The study confirmed the authors' hypothesis that taxonomy for midbrain BSCMs can meaningfully guide the selection of surgical approach and resection strategy. The proposed taxonomy can increase diagnostic acumen at the patient bedside, help identify optimal surgical approaches, enhance the consistency of clinical communications and publications, and improve patient outcomes.

Microsurgical Clipping of Intracranial Aneurysms in the Endovascular Era

The treatment of intracranial aneurysms (IA) began in the late 19th century. Some degree of controversy has always surrounded the best treatment modality for IA. Cushing and Dandy debated about cervical carotid ligation as the only surgical alternative before the introduction of microsurgical clipping. In the early 21st century, the debate has centered on surgical versus^ endovascular techniques. With the advent of newer endovascular techniques and devices, there has been a dramatic shift in treatment paradigms toward endovascular intervention that is preferred by both physicians and patients. However, there will always be a need for microsurgical cerebrovascular expertise since some aneurysms cannot or should not be embolized. This creates a difficult conundrum as only the most complex of aneurysms will require open surgery, but the lack of volume and training will be a challenge in teaching and maintaining the surgical expertise required to safely treat them. The purpose of this review is to discuss the history of IA treatment and critically evaluate the current state of the art of IA treatment, with a specific focus on the necessary role microsurgical clipping continues to play in the current treatment landscape.

Novel System of Simulation Models for Aneurysm Clipping Training: Description of Models and Assessment of Face, Content, and Construct Validity

BACKGROUND

Aneurysm clipping simulation models are needed to provide tactile feedback of biological vessels in a nonhazardous but surgically relevant environment.

OBJECTIVE

To describe a novel system of simulation models for aneurysm clipping training and assess its validity.

METHODS

Craniotomy models were fabricated to mimic actual tissues and movement restrictions experienced during actual surgery. Turkey wing vessels were used to create aneurysm models with patient-specific geometry. Three simulation models (middle cerebral artery aneurysm clipping via a pterional approach, anterior cerebral artery aneurysm clipping via an interhemispheric approach, and basilar artery aneurysm clipping via an orbitozygomatic pretemporal approach) were subjected to face, content, and construct validity assessments by experienced neurosurgeons (n = 8) and neurosurgery trainees (n = 8).

RESULTS

Most participants scored the model as replicating actual aneurysm clipping well and scored the difficulty of clipping as being comparable to that of real surgery, confirming face validity. Most participants responded that the model could improve clip-applier-handling skills when working with patients, which confirms content validity. Experienced neurosurgeons performed significantly better than trainees on all 3 models based on subjective (P = .003) and objective (P < .01) ratings and on time to complete the task (P = .04), which confirms construct validity. Simulations were used to discuss clip application strategies and compare them to prototype clinical cases.

CONCLUSION

This novel aneurysm clipping model can be used safely outside the wet laboratory; it has high face, content, and construct validity; and it can be an effective training tool for microneurosurgery training during aneurysm surgery courses.

Trapping and P2-P3 Posterior Inferior Cerebellar Artery Reanastomosis for Treatment of a Ruptured Fusiform Aneurysm: Application of Fourth-Generation Technique: 2-Dimensional Operative Video

Aneurysms of the posterior inferior cerebellar artery (PICA) represent the second most common posterior circulation aneurysm and commonly have complex morphology. Various bypass options exist for PICA aneurysms,1-6 depending on their location relative to brainstem perforators and the vertebral artery, and the presence of nearby donor arteries. We present a case of a man in his late 40s who presented with 3 d of severe headache. He was found to have a fusiform right P2-segment PICA aneurysm. Preoperative angiogram demonstrated the aneurysm and a redundant P3 caudal loop that came in close proximity to the healthy P2 segment proximal to the aneurysm. The risks and benefits of the procedure were discussed with the patient, and they consented for a right far lateral approach craniotomy with partial condylectomy for trapping of the aneurysm with bypass. The aneurysm was trapped proximally and distally. The P3 was transected just distal to the aneurysm and brought toward the proximal P2 segment, facilitated by a lack of perforators on this redundant distal artery. An end-to-side anastomosis was performed. Postoperative angiogram demonstrated exclusion of the aneurysm and patent bypass. The patient recovered well and remained without any neurological deficit at 6-mo follow-up.  This case demonstrates the use of a "fourth-generation"5,7,8 bypass technique. These techniques represent the next innovation beyond third-generation intracranial-intracranial bypass. In this type 4B reanastomosis bypass, an unconventional orientation of the arteries was used. Whereas reanastomosis is typically performed end-to-end, the natural course of these arteries and the relatively less-mobile proximal P2 segment made end-to-side the preferred option in this case. Fourth-generation bypass techniques open up more configurations for reanastomosis, using the local anatomy to the surgeon's advantage.  The patient consented to the described procedure and consented to the publication of their image.