The future of cerebrovascular neurosurgery: the European perspective

Introduction

In the dawn of the current millennium Heros & Morcos published an editorial on Neurosurgery regarding the past, the present, and the future of cerebrovascular neurosurgery (1). They concluded in their article that “Where we go from here is entirely dependent on the open-mindedness of the old and the determination of the young. As long as we continue to be inspired by innovation and tolerate creativity, free-spirited innovators can submit their genius to the rigors of evidence-based medicine, and conviction is not prejudice, enthusiasm is not greed, and aggressiveness is not foolishness, the welfare of our discipline and its practitioners in the 21st century seems assured. After 25 years, the landscape of cerebrovascular neurosurgery has dramatically changed. However, a large proportion of the challenges that cerebrovascular neurosurgeons face today have remained essentially unchanged.

We are still struggling as a community to develop evidence-based practices for managing common pathological entities such as intracranial aneurysms and cavernous malformations (CMs). Despite all the undoubtful advances in the management of brain aneurysms, there are complex aneurysm cases that their safe management remains highly questionable. Giant aneurysms, middle cerebral artery aneurysms with vessels originating from the aneurysmal dome, remnants of a partially clipped aneurysm, or recanalized coiled aneurysms represent characteristic examples of such challenging cases. Likewise, we still face difficulties in managing patients with complex grade B according to the Spetzler-Ponce classification of arteriovenous malformations (AVMs) despite all technological advances and the evolution of not only cerebrovascular microsurgery but also of endovascular neurosurgery and stereotactic radiosurgery (SRS) (2). Moreover, the management of patients with grade C AVMs has remained quite problematic, with no sound treatment options available for these patients, at least in the majority of centers around the world. Similarly, many dilemmas still exist regarding the most efficacious management of patients with deep-seated or eloquent cortical CMs.

Additionally, the obstacles faced in daily practice and the current challenges differ greatly not only between continents but also within different regions of the same continent. The current landscape of cerebrovascular surgery differs significantly between high- and middle- or low-income countries. The health systems are quite different, the available resources are incomparable, and even the neurosurgeons’ training is quite variable. A characteristic example of this heterogeneity represents the European continent, where the same cerebrovascular pathological entity has different therapeutic approaches based on where a patient lives. The health system varies significantly between the developed north and the developing south of the European continent, while frequently these differences are quite prominent even within the same country, depending on the geographical area (urban vs. rural areas) (3).

Undoubtedly, cerebrovascular neurosurgery is not the only neurosurgical subspecialty taking advantage of the recent technological advances. The clinical practice of surgical neuro-oncology has been modified by the application of fluorescent- and/or spectroscopic-guided resection, the wide application of frameless neuro-navigation, and the employment of laser interstitial thermal therapy (LITT) in the management of deep-seated tumors. Likewise, functional and epilepsy surgery has taken advantage of the recent technological advances in the field of robotics, the wide application of open- or closed-loop stimulation for neuromodulation, as well as the employment of magnetic resonance (MR)-guided focused ultrasound or LITT in the management of movement disorders or epilepsy cases. Similarly, spinal surgery demonstrates significant advances in the field of neuro-navigation, the clinical application of robotics, and the development of a plethora of minimally invasive techniques, mostly based on the technological evolution of endoscopy. However, the impact of technology in the field of cerebrovascular neurosurgery was greater and faster, mostly due to the development of all endovascular devices [different types of coils, stents, embolic materials, as well as flow diverters (FDs) and endosaccular devices]. The impact of this technological explosion resulted in the dramatic change in the daily neurovascular practice with a decrease of the volume of the performed microsurgical procedures, and the respective increase of that of endovascular cases (4).

In our current article, we attempt to outline the current challenges of cerebrovascular surgery within the European continent and the potential solutions that may be seen in the near future. We try to identify the most controversial topics in cerebrovascular surgery, and to map those developing strategies and technological advances, which will assist neurosurgeons in tackling daily vascular problems and improving the safety and the efficacy of patients’ management.

Future of microsurgical technique

Advances in microsurgical instruments and devices, improvement of surgeons’ training and performance, as well as development of hospitals’ infrastructure and facilities, may shape a brighter future for neurovascular microsurgery.

Micro-instruments future developments

Microsurgical treatment of cerebral aneurysms and AVMs shares common principles, relying on precision, visualization, and advanced intraoperative tools to optimize outcomes while minimizing procedural risks. Indocyanine green (ICG) angiography has become the gold standard for managing both pathologies, offering real-time visualization of arterial feeders, draining veins, and aneurysm flow dynamics, as well as detecting residual malformations (5,6). The use of ultrahigh-definition 3D exoscopes in aneurysm surgery provides excellent magnification and lighting, comparable to traditional operating microscopes (7). Microsurgical clipping remains the definitive treatment for cerebral aneurysms, refined by the usage of ICG angiography and high definition exoscopes, which enhance depth perception and surgical visualization.

Non-stick bipolar forceps and microclips facilitate precise vessel occlusion and bleeding control, particularly in AVM nidus dissection and aneurysm neck clipping. Intraoperative ultrasound and neuronavigation enhance surgical accuracy by providing detailed imaging, enabling precise localization and resection of complex AVMs and aneurysms, especially in eloquent brain regions. Intraoperative micro-Dopplers and flow measurement devices are vital for ensuring proper blood flow dynamics during AVM nidus dissection and confirming successful aneurysm occlusion (5).

Endoscope-assisted microneurosurgery (EAM) enhances visualization and precision in aneurysm surgery, showing 77% better outcomes compared to standard techniques, and a quite low complication rate of 6% and 0% mortality. It improves clip placement, resulting in clip repositioning in 13% of cases in this series, ensuring optimal results (8). Further refinement of the currently available endoscopes may further enhance intraoperative visualization and thus improve the surgeon’s dexterity and precision.

Surgeon’s factors

The constantly increasing application of tailored craniotomies and retractor-less surgery has been adopted in both aneurysm and AVM procedures, minimizing brain retraction and reducing surgical trauma. Finally, novel bypass constructs are employed for complex aneurysms and challenging AVM cases, ensuring optimal blood flow management and reducing rupture risks (6).

While traditional open microsurgical approaches for treating cerebral aneurysms and AVMs have long been the gold standard, their invasive nature, the required extended recovery periods, and the higher risk of complications make them less appealing in the era of modern neurosurgery. Minimally invasive microsurgical techniques, such as the supraorbital keyhole (SOKC) and the mini pterional keyhole craniotomy (PKC), represent a middle ground, combining thus the precision and control of open surgery with the reduced morbidity and faster recovery associated with endovascular approaches.

Indeed, minimally invasive techniques, such as the SOKC and the PKC, offer effective approaches for microsurgical clipping of cerebral aneurysms while minimizing surgical trauma and brain retraction. A meta-analysis comparing these techniques found no significant differences in clipping success, final occlusion rates, operative duration, or complication profiles, including intraoperative rupture, postoperative hemorrhage, vasospasm, and infection (9). Both approaches demonstrated favorable neurological outcomes for patients with ruptured and unruptured aneurysms. These findings highlight the versatility and reliability of SOKC and PKC, allowing surgeons to tailor their approach based on patient-specific factors while achieving excellent clinical results.

Endoscopic endonasal clipping (EEC) is a feasible alternative for midline intracranial aneurysms, with an overall treatment success rate of 86%. However, it is associated with a higher complication rate, particularly in posterior circulation aneurysms, where ischemic complications are more frequent when compared with traditional approaches (10).

Despite their clear advantages, minimally invasive approaches come with a steep learning curve that cannot be overlooked. Mastery of these techniques demands exceptional microsurgical skills, refined hand-eye coordination, and a deep understanding of neurovascular anatomy within restricted operative corridors. The successful adoption of minimally invasive approaches hinges on structured training programs, dedicated simulation platforms, and hands-on workshops.

Hospital’s factors

It has been adequately demonstrated that the integration of hybrid operating rooms (ORs) allows real-time intraoperative angiography, enabling neurosurgeons and neurointerventional radiologists to collaborate seamlessly, improving precision and reducing the need for reoperation (5). The availability of intraoperative post-clipping angiography has been demonstrated to decrease the possibility of partially aneurysm clipping significantly and subsequently the risk of aneurysm future growth or rupture (11). It has also been postulated that the performance of intraoperative angiography in a hybrid OR may increase the detection rate and the proper management of early post-clipping vasospasm (12). Moreover, the crucial role of a hybrid OR in an integrated training program for the next generation of residents has been adequately identified in the pertinent literature (12). It has to be mentioned, however, that despite all the previously mentioned advantages of a hybrid OR, the increased radiation exposure for the patient and the staff needs to be seriously taken into consideration (13). The development of virtual reality and augmented reality (VR & AR) platforms and their integration in tomorrow’s OR may not only minimize the radiation exposure but also diminish procedural times, while enhancing precision and safety (14).

Use of artificial intelligence (AI) and machine learning (ML)

AI and ML have significantly advanced the diagnosis, data management, and imaging analysis of cerebrovascular diseases, including brain aneurysms, AVMs, and stroke. These technologies improve diagnostic accuracy, streamline workflows, and enable predictive analytics for better patient outcomes (15).

Platforms like Viz.ai and RapidAI leverage AI algorithms for real-time image interpretation and centralized communication, expediting critical decision-making in stroke care. Figurelle et al. (2023) reported a 39% reduction in door-to-groin time for off-hours large-vessel occlusion (LVO) cases and a 30% improvement in communication efficiency following Viz.ai implementation. Similarly, AI-driven predictive models can assess hematoma expansion, aneurysm rupture risk, and AVM bleeding potential, enhancing treatment strategies and resource allocation (15,16).

In imaging, AI segmentation tools provide quantitative data on aneurysm attributes, improving monitoring and rupture risk assessment. Zhou et al. (2024) demonstrated the effectiveness of AI in classification, detection, and segmentation of intracranial aneurysms, thus reducing diagnostic variability while enhancing imaging precision (17).

Despite all these advances, important limitations remain. Most studies on AI applications in cerebrovascular disease are retrospective and reported on single-center experience, limiting the generalized applicability of their findings across institutions with different imaging protocols and systems (15,17). Furthermore, many reported models rely on manual input and exhibit high false-positive rates, which can reduce both automation benefits and clinician trust (17). Integration into clinical workflows is further challenged by technical demands, infrastructure variability, and the need for specialized, time-requiring training (16). Ethical concerns, such as data privacy, algorithmic bias, and the potential erosion of clinical judgment, also require careful consideration (15). Moreover, current algorithms often struggle with complex cases like intraventricular hemorrhages or coexisting cerebrovascular conditions, underscoring the need for robust, multicenter prospective validation and the development of more transparent, adaptable systems (15,17). It also has to be taken into consideration that the possibility of surgeons gradually losing their communication and other soft skills by the wide application of AI models in their daily clinical practice.

Despite these challenges, AI continues to show immense promise in transforming cerebrovascular care. By accelerating workflows, enhancing diagnostic precision, and enabling earlier, data-driven interventions, AI is not only improving patient outcomes but also shaping a more efficient and personalized future in neurovascular medicine (15-17).

Present & future of endovascular techniques

Coiling

The development of detachable coils by Guido Guglielmi in the early 1990s marked a significant change in the treatment of cerebral aneurysms (18). The safety profile of coil embolization has proven to be comparable to standard microsurgical treatment for ruptured and unruptured intracranial aneurysms (19). Endovascular treatment (EVT) has increasingly replaced the microsurgical approach. With the use of adjunctive devices such as intracranial stents, balloons, and pre-shaped and shapeable microcatheters, endovascular therapy is now considered a viable option for treating both ruptured and unruptured intracranial aneurysms (20).

Despite the rapid advances in the field of EVT, large, giant, wide-neck, and bifurcation aneurysms, as well as fusiform, or blister aneurysms, still pose a challenge for conventional endovascular coiling because of the significant risk of coil protrusion into the parent artery. Additionally, recanalization remains a challenge in 20% to 80% of cases because of coil compaction, migration of coils into the aneurysm thrombus, or dome re-growth (21,22). Endovascular devices have been developed to treat aneurysms that are not amenable to primary coil embolization. Balloon and stent-assisted techniques have been developed to expand indications for EVT of cerebral aneurysms (Figure 1A-1D). Traditional stents were designed to facilitate coil embolization. These stents have low metal surface-area coverage and high porosity for maintaining both parent and branch vessel patency (23). Despite the development of such endovascular devices, the observed recurrence rates were unacceptably high, especially for large and giant, wide-neck cerebral aneurysms. Thus, the idea of vessel reconstruction using endoluminal implants resulted in the development of FD devices.

Figure 1 Digital subtraction angiography during endosaccular procedures. (A,D) Saccular aneurysm of the anterior communicating artery (black arrow) treated with stent-assisted coiling (red & white arrows). (B,E) Saccular aneurysm of the basilar tip (black arrow) treated with the Woven EndoBridge device (red arrow). (C,F) Saccular aneurysm of the internal carotid artery (black arrow) treated with the Contour device (red arrow).

FD

Three critical parameters were identified as vital for optimizing flow reduction within the aneurysm through the FD, while also preserving side branch patency: (I) porosity (ratio of metal-free to metal area); (II) pore or mesh density (pores per mm²); and (III) metal coverage ratio (MCR; the fraction of the stent that is metal-covered compared to the metal-free area) (24).

The mechanism of action of FDs can be divided into three components: hemodynamic, thrombus formation, and endothelialization (25). The hemodynamic stage occurs immediately after FD deployment, reducing blood flow within the aneurysmal sac and promoting smooth laminar flow through the stent toward the parent artery, known as central diversion. This is followed by stasis within the aneurysm and progressive formation of a stable thrombus over a period of days to weeks. The endothelialization stage represents the progressive neo-intima formation, initially occurring at the device contact interface and eventually advancing to the aneurysm neck. This allows for the exclusion of the aneurysm from circulation and the remodeling of the parent artery. Proper stent wall apposition is crucial for an effective endothelialization process.

Pre- and post-procedure dual antiplatelet treatment (DAPT) is considered the standard of care for FD procedures. This is necessary for minimizing the risk of thromboembolism, and thus, their clinical usage in acutely ruptured aneurysms may be limited. While the use of DAPT is widely accepted, various dosing regimens exist. The most common DAPT regimen includes aspirin (81–325 mg) in association with clopidogrel (75 mg) (26). The post-procedural duration of DAPT is also not standardized. Generally, DAPT is usually continued for 3–6 months. Aspirin monotherapy continues for a minimum of 6 months. It has been reported that clopidogrel resistance is associated with increased incidence of thromboembolic complications. Platelet function testing (PFT) has been used to assess the DAPT response and mitigate the risk of thrombotic/hemorrhagic complications. Ticagrelor or prasugrel are sometimes added to replace clopidogrel in platelet hypo-responders or even used directly as first-line antithrombotic agents (24). Additional research is needed in the future to establish an evidence-based “best” protocol for pre- and post-procedure DAPT in procedures involving FDs.

The Pipeline Embolization Device (PED) (Medtronic, Irvine, CA, USA) was the first device to gain widespread use in North America (24). Since then, we have observed substantial growth in technological advancements and the applications of various FDs. Beyond their inherent characteristics, the design of FDs mainly relies on cobalt chromium (Pipeline and Surpass) or nitinol (the rest of the commercially available devices). Cobalt/chromium provides stiffness and radial force, whereas nitinol offers flexibility and ease of navigation and deployment. Cobalt/chromium implants respond more effectively to ballooning during instances of incomplete wall apposition observed. The Pipeline of Uncoilable or Failed Aneurysms (PUFS) study was initiated in 2008 and concluded in 2014 (27). It included 109 large and giant wide-necked aneurysms of the internal carotid artery proximal to the posterior communicating artery. The PUFS trial demonstrated high efficacy (complete occlusion rate 95.2% at 5 years), and low thromboembolic serious complications. Additionally, several systematic reviews and meta-analyses have evaluated the safety and efficacy of FDs. In 2013, Brinjikji et al. reported a meta-analysis of 29 studies representing 1,451 patients treated with FDS and found complete occlusion, morbidity, and mortality rates of 76%, 5%, and 4%, respectively (28). Arrese et al. analyzed 15 studies including 897 patients and found a 76.2% complete occlusion rate: 7.3% early vs. 2.6% late morbidity; and 2.8% early vs. 1.3% late mortality (29). In 2015, Briganti et al. reviewed 18 studies of FDS and identified a complete occlusion rate of 81.5%, a morbidity rate of 3.5%, and a mortality rate of 3.4% (30). In 2022, Li et al. assessed 18 studies with 1,001 patients with FDs and 1,133 patients with conventional endovascular techniques (coiling alone, stent alone, stent-assisted coiling, balloon-assisted coiling) and found that the placement of a FD may lead to more procedure-related complications, but there is a higher rate of complete occlusion, and lower rates of recurrence and re-treatment (31).

Several other studies have reported complications related to FDs. Periprocedural complications include thromboembolic events, intracranial hemorrhage, and FD malposition. The IntrePED study retrospectively analyzed 906 IAs (ICA >10 mm, ICA <10 mm, other anterior, and posterior circulation aneurysms) treated with PED. The study reported a neurologic morbidity and mortality rate of 8.4% (highest in the posterior circulation group and lowest in the ICA <10 mm group). The intracranial hemorrhage rate was 2.4%, while the observed ischemic stroke rate was 4.7%, highest in patients with posterior circulation aneurysms (32). In their meta-analysis published in 2017, Zhou et al. included 60 studies that involved 3,125 patients. The use of FDs was associated with an overall complication rate of 17% and a mortality rate of 2.8%. A significantly higher complication rate was found in ruptured cases than in unruptured aneurysms (33).

Delivering an FD into distal and small vessels may be technically challenging, as these systems have a higher profile than conventional stents. However, several FDs have recently been developed to enhance the deliverability of FD devices to distal aneurysms. These systems enable smaller ID microcatheters (0.017–0.021 inches) to deliver micro-FD devices into parent vessels ranging from 1.5 to 3.0 mm. Overall, the small size of parent vessels, the coverage of essential bifurcation branches, and perforators increase the risk of ischemic complications. According to the pertinent literature, adequate occlusion and treatment-related complication rates range from 60% to 90% and 4% to 17%, respectively (34,35).

Likewise, EVT of wide-necked, bifurcation aneurysms (WNBAs) by placement of FDs may be technically easier, with a higher complete occlusion rate than assisted coiling. Therefore, there is a growing interest in FDs in managing bifurcation aneurysms. However, FDs may be associated with severe clinical complications in a vessel bifurcation, since they cover both the aneurysm neck and the side branch. Abbasi et al. in their meta-analysis showed that sidewall and bifurcation aneurysms treated with FDs demonstrated no significant differences in complications or occlusion rates (36).

However, the employment of DAPT is necessary for preventing any thromboembolic complications. Therefore, placement of FDs in the acute setting of aneurysmal SAH imposes additional risks for hemorrhagic complications. Cagnazzo et al., in their meta-analysis of 20 studies including 223 patients with acutely ruptured IAs treated with FDs, identified that the treatment-related complication rate was 17.8%, with an aneurysm rebleeding rate of 4%, highest within the first 72 hours (37). The aneurysm rebleeding rate is higher than that demonstrated in the ISAT study (2.7%), while the reported treatment-related complications are more common than those reported from the unruptured aneurysms PED studies (5.6–8.4%). Therefore, FD treatment for ruptured IAs has been limited to lesions, in which traditional surgical and endovascular techniques are unlikely to be successful. Recent surface modification coating technology advances, which reduce stent thrombogenicity, may become efficient in managing these ruptured cases. In theory, these coated devices are expected to lessen the necessity for and the duration of DAPT. Additional research is required to evaluate the safety and effectiveness of the various surface modifications and their possible uses for single antiplatelet therapy (SAPT). It appears that as new and innovative features for FDs are developed, a more significant number of aneurysms will become treatable.

Intra-saccular device implantation

Intrasaccular devices have recently become available for treating more complex aneurysms, especially WNBAs, which comprise a significant proportion, accounting for approximately 26% to 36% of all cerebral aneurysms. Intrasaccular devices offer a less technically challenging treatment solution, reducing procedural times and safely securing the aneurysm. These devices are deployed entirely within the aneurysm, with no extension into the parent vessel, and cover the entire aneurysm wall and neck. Upon positioning the device, this unfolds, covering the aneurysm neck and disrupting blood flow into the sac, thus promoting thrombosis and aneurysm exclusion. Furthermore, intrasaccular devices provide an environment for progressive endothelial tissue growth, resulting in long-term stability and reduced aneurysm recurrence rates. It has to be emphasized that the intra-aneurysmal position of these devices does not require dual antiplatelet therapy (38).

The first intrasaccular device to be widely used was the Woven EndoBridge (WEB) device, followed by the Artisse Embolization System. Both devices were introduced in 2010. First reports of the use of Contour neurovascular system and Saccular Endovascular Aneurysm Embolization System (SEAL) were in 2020 and 2021, respectively.

The WEB device is a self-expanding mesh when deployed. It adapts to the aneurysm wall, using lateral compression to retain its shape and prevent device failure compression, thus providing full aneurysm neck coverage (Figure 1B-1E). It is therefore recommended to oversize the device by adding 1–2 mm to the average width of the aneurysm in two dimensions, to ensure adequate wall apposition. Three European studies, the “French Observatory study”, and the following WEBCAST and WEBCAST 2, were the first multicenter, prospective studies demonstrating the safety and efficacy of the WEB device (39-41). At the 1-year follow-up, aneurysm occlusion was achieved in 52.9% of cases, with neck remnants in 26.1%, and dome remnants occurring in 20.9%. Overall, 6.9% of the treated aneurysms required re-treatment. The CLARYS study, which stands for Clinical Assessment of WEB device in Ruptured Aneurysms, was a European prospective study involving 60 patients with ruptured aneurysms. Results indicated that the rebleeding rate associated with the WEB device was 0% at both the 1-month and the 1-year follow-ups (42). WEB is the only current device with Food and Drug Administration (FDA) approval for utilization in both ruptured and unruptured intracranial aneurysms.

Artisse embolization device is a self-expanding, double-layered, braided, mesh device that is electrolytically detached and delivered through a 0.021-inch microcatheter. Its sizes range from 4.5 to 8.0 mm in diameter. Its specially designed, atraumatic distal end diminishes the risk of rupturing the aneurysm during the device’s deployment.

The Contour Neurovascular System features a dual-layered mesh design, deployed within the aneurysm where it fits snugly against the neck (Figure 1C-1F). It operates by creating a complete seal at the neck and ensuring proper apposition, which is essential for effective flow diversion and aneurysm treatment occlusion. The sizes range from 2 to 10.5 mm. Griessenauer et al. published a multicenter study, from 10 European centers, evaluating the safety and efficacy of Contour embolization in 279 aneurysms. In their series, the majority of treated aneurysms were from the anterior circulation, with 11.1% being acutely ruptured. The authors reported an overall adequate aneurysm occlusion rate of 91.5% at a median follow-up of 12 months, along with a thromboembolic complication rate of 6.8% (43).

The SEAL device is a dual-layered mesh device with the largest diameters compared with the other intravascular devices. Its larger dimensions make it suitable for managing large aneurysms.

The Trenza embolization device is an intrasaccular, braided-frame, coil implant designed to disrupt the blood flow. It functions as a stable omega-shaped basket within the aneurysm, which is subsequently filled with coils. This device is suitable for treating WNBAs or sidewall aneurysms measuring 6 to 12 mm. Theoretically, Trenza’s dual action of intrasaccular flow disruption and standard coiling could result in higher occlusion rates compared to coiling alone, while it could also reduce the risk of thromboembolic complications when compared to stent-assisted coiling.

The preliminary results of all these devices have been encouraging, and indeed, their technological evolution is remarkable. A comparative summary of the strengths and limitations of these intrasaccular and other endovascular devices is presented in Table 1. The hope is that its evolution will continue, eventually providing long-lasting, satisfactory clinical outcomes comparable to those obtained with microsurgery, while maintaining the minimally invasive nature of endovascular procedures. Moreover, the adoption of surface-modified stents and FDs has facilitated the use of SAPT, particularly in ruptured aneurysms, reducing the need for prolonged DAPT. Similarly, intrasaccular devices have expanded the treatment options for WNBAs, offering a minimally invasive, shorter in duration alternative to clipping. These trends are increasingly reflected in contemporary clinical practice and illustrate the gradual integration of novel technologies into standard cerebrovascular workflows—a direction also endorsed through current treatment strategies at our institution.

Consensi

The existence of several controversial issues in the management of patients with cerebrovascular lesions is highlighted by the publication of several consensi attempting to present the current practicing trends. The management of unruptured intracranial aneurysms represents one of the most controversial topics in cerebrovascular surgery. A recent attempt was made by the European Stroke Organization in 2022 to present the current trends on the subject (44). Despite this systematic effort, there are still many unanswered questions regarding the best treatment option for patients harboring unruptured aneurysms. More solid data will allow the drawing of more robust conclusions in the near future. In regard to the management of ruptured intracranial aneurysms and the future perspectives, these have been concisely outlined in the ARISE I review consensus (45). The development of national and international registries, as well as the employment of AI in the management of all macro-data will provide the opportunity for extracting more robust conclusions and developing precise and efficacious management protocols for patients with intracranial aneurysms.

The management of AVMs remains challenging despite the development of specialized centers providing multidisciplinary treatment combining microsurgical, endovascular, and radiosurgical modalities. The recently published international consensi with European participation underscores the complexity of these lesions and the necessity of careful combined therapeutic approach (46,47). The ARISE I consensus emphasized the paramount importance of developing highly specialized neurovascular centers with great experience in the management of these perplexing vascular lesions, as well as the necessity of prospectively collecting data on the genetic and phenotypic profile of brain AVM patients (47). On the other hand, the other international consensus with participants practicing in developing countries identified the importance of providing proper training to neurosurgeons for managing such complex lesions, and also the necessity of performing a thorough cost analysis on each case (46). The importance of individualized treatment as well as the collection of prospective data was pointed out by both consensi and needs to be further established in the near future.

Likewise, there were several attempts to address the issues associated with the management of central nervous system CMs within the last few years (48,49). Although all of them were international consensi, the current European practice was strongly expressed in them. The collection of more robust data in the future may address the plethora of the still-existing controversial issues associated with the natural history, the prompt imaging follow-up, and the safest management of these lesions. The necessity of a multidisciplinary approach has to be emphasized not only for defining the exact role of each treatment modality, microsurgical resection or SRS, but also for clarifying the role of SRS in the development of pseudocavernomas (50-52).

Training

Proper training of residents and fellows in neurovascular surgery constitutes a timeless challenge in neurosurgery. This has become more and more perplexing during the last years, mainly due to the constantly decreasing number of the performed microsurgical cases, at least in Europe, and the increasing demand of society, and also of the legal system, for achieving excellent outcomes in all cases. Although the current situation guarantees no bright future for neurovascular training, there are developments in this field that allow some optimism. These developments follow two axes: interdisciplinary training of young neurosurgeons and simulation-based training for residents and fellows.

Despite the rise of EVTs, microsurgery remains indispensable for managing certain complex aneurysms that are not amenable to minimally invasive methods. Additionally, previously treated aneurysms that present with revascularization further highlight the ongoing need for experienced neurosurgeons. New generations of bypass techniques are being developed to address complex aneurysms requiring revascularization. These advancements include intracranial interpositional bypasses and innovative combinations of anastomoses, which are crucial in cases where traditional approaches fall short. These techniques play a significant role in managing challenging cases that cannot be endovascularly addressed. Despite these advancements, the field faces a significant challenge: a constantly declining volume of open aneurysm surgeries due to the widespread adoption of EVTs. However, complex cases continue to necessitate the expertise of skilled microsurgeons. This underscores the critical need for specialized training and collaborative efforts in academic centers, ensuring that future neurosurgeons are properly trained to handle such demanding procedures (53).

The importance of continued longitudinal exposure to both endovascular and open cerebrovascular surgical fields has been emphasized in a recently published systematic review (54). The authors recommended the application of multidisciplinary exposure of neurosurgery residents to all available treatment modalities, and close collaboration between them with specialists from the fields of neuroradiology, neurology, and radiosurgery. The importance of such multidisciplinary training has been outlined in the description of standards of training neurovascular centers (55). The necessary entrustable professional activities (EPAs) for neurovascular surgeons in Europe have been identified and described in a recent publication (56). The authors summarized these in a concise frame of seven EPAs, which may be used not only as a compass for young neurosurgeons pursuing a career in neurovascular surgery, but also as a tool for the evaluation of European neurovascular training centers.

Multidisciplinary engagement for neurosurgery residents is of paramount importance, necessitating an extensive educational experience encompassing all accessible therapeutic approaches, and fostering intimate collaboration with experts from neuroradiology, neurology, and radiosurgery. This holistic methodology guarantees a comprehensive repertoire of competencies and is congruent with the training criteria established for neurovascular centers, which underscore the importance of program accreditation and practitioner certification (55). Additionally, high-volume centers play a pivotal role by providing the necessary case load to develop proficiency in complex microsurgical techniques. Despite the growing dominance of EVTs, these techniques remain crucial for managing specific aneurysms, Furthermore, these centers foster a collaborative environment, enabling specialists to address challenging cases that cannot be managed through less invasive methods. Together, multidisciplinary collaboration and high-volume exposure form a comprehensive foundation for advanced training in neurovascular surgery (53).

The recent, swift technological advances, mainly in the field of 3D-printing and the VR and AR promise the development of realistic and educational neurovascular simulation-based models. Their crucial role in training has been outlined in a series of recent publications (57-61). The integration of 3D modeling, VR, hybrid simulators, and robotic assistance is revolutionizing training in microsurgery for intracranial aneurysms. Additive manufacturing enables the creation of realistic 3D-printed models that replicate intricate anatomical details, including blood flow dynamics. These cost-effective and reusable models provide a hands-on platform for improving surgical precision and pre-operative planning (61). Similarly, VR simulators simulate the entire microsurgical workflow, offering bimanual haptic feedback and tracking surgical gestures to create an immersive learning experience (62). Hybrid simulators, which combine physical models with VR environments, enhance training by integrating tactile feedback and visual realism, allowing neurosurgeons to refine their techniques in a dynamic, risk-free setting (62). In parallel, robotic assistance is being explored for precise surgical clipping, with robotic manipulators and guidance systems offering increased stability and reducing human error during microsurgical interventions (61). These advancements collectively improve surgical planning, refine technical skills, and shorten the learning curve for complex aneurysm cases (63). Despite these innovations, challenges remain. Validation and standardization of simulation technologies are crucial to ensure their efficacy in improving surgical outcomes. Systematic assessments and benchmarking tools are needed to evaluate their impact on skill development and patient safety (57). Furthermore, limitations persist, such as the lack of precise haptic feedback in VR simulators and the inability of 3D models to fully replicate microanatomical details. Addressing these gaps through ongoing research and technological refinement will be essential for advancing the future of neurosurgical training (57).

Many European centers and research teams have already developed are working toward this direction, and a few of them already provide training courses. The validity, the realism, and the affordability of the developed simulation-based neurovascular models need to be carefully evaluated in the near future. Moreover, stressful situations as intraoperative brain edema development and/or troublesome venous bleeding, need to be taken into consideration and incorporated in any future training models.

The establishment of official, large-volume, training centers, providing multidisciplinary neurovascular fellowships across Europe, seems to be mandatory for continuing and improving the provided neurovascular education. There are several centers across Europe, including Austria, the Czech Republic, Finland, France, Germany, Greece, the Netherlands, Switzerland, and the UK, currently provide structured fellowships in neurovascular surgery. The efforts of the European Association of Neurosurgical Societies (EANS) focus on the development of many more training centers and the development of a common core curriculum for neurovascular surgery. This will help not only in the continuation and further development of the craft of cerebrovascular surgery but also in the widespread distribution of this dexterity across the European continent.

Current study’s strengths and limitations

This review offers a comprehensive overview of current advances in cerebrovascular neurosurgery, combining microsurgical, endovascular, and training future perspectives, with a focus on the European landscape. Its strengths include its multidisciplinary character, the discussion of emerging technologies like AI and VR and AR simulation, and the outlining of regional disparities and specific training needs. However, as a narrative review, it may be subject to selection bias. It has to be emphasized that our current review does not provide a systematic or quantitative synthesis. While major developments are highlighted, some recent data may be omitted due to the fast-evolving nature of the neurovascular surgery field. Despite these limitations, the review serves as a relevant and practical resource for clinicians and trainees.

Conclusions

Although the current management of complex cerebrovascular clinical entities remains challenging, both microsurgical and endovascular approaches have rapidly evolved and present great potential in the near future. The development of therapeutic guidelines, either in the form of scientific society recommendations and/or international organization consensi will further provide neurosurgeons around the globe with confidence and scientific support for managing perplexing neurovascular pathological entities. The importance of individualization of treatment needs to be emphasized in the future. The issue of training young neurovascular surgeons remains a challenge, particularly for Europe. Simulation-based training, exposure of residents and fellows to microsurgery, endovascular neuroradiology, and radiosurgery, as well as development of high-volume specialized training centers appear to be the only way for the European neurosurgical community to face the future of neurovascular surgery.

Acknowledgments

None.

Footnote

Provenance and Peer Review: This article was commissioned by the Guest Editor (Christos Tolias) for the series “State of Neurovascular Surgery. The Way Forward” published in AME Surgical Journal. The article has undergone external peer review.

Peer Review File: Available at https://asj.amegroups.com/article/view/10.21037/asj-25-8/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://asj.amegroups.com/article/view/10.21037/asj-25-8/coif). The series “State of Neurovascular Surgery. The Way Forward” was commissioned by the editorial office without any funding or sponsorship. The authors have no other conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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