Neurosurgical Endovascular Credentialing in Europe and the United Kingdom for the “Complete” Neurovascular Surgeon: The Time has Come

Since the birth of cerebral angiography in 1927,1,2 the field of endovascular neurosurgery has seen an exponential expansion for the treatment of neurovascular pathologies. Several technical landmark developments paved the way for endovascular practice as we know it today, including the introduction of intravascular balloon devices in 1964,3 particles for embolization in 1960,4 detachable coils in 1991,5 and flow diverters in 2011.6 The results of the International Subarachnoid Aneurysm Trial supported endovascular techniques over open surgery for the treatment of ruptured aneurysms.7 By extrapolation, unruptured aneurysms are also often managed with endovascular techniques. Today's neuroendovascular landscape includes a variety of techniques for the treatment of cerebrovascular diseases. Mechanical thrombectomy (MT) is increasingly replacing pharmacological thrombolysis for the treatment of acute large vessel occlusion (LVO) strokes and is considered a gold standard treatment that should be accessible to all stroke patients. The irrefutable future of neurological treatment will be dominated by neuroendovascular techniques. There is wide variation internationally of how clinicians obtain neuroendovascular training. In many European countries and the United Kingdom, endovascular training is accessible only through a radiology training route. Training of neurosurgeons and the retainment of endovascular skills in a “hybrid” practice situation is subject to limitations, which are variable by country. In North America, neuroendovascular training is easily accessible to neurosurgeons, and “hybrid” practice is common. This difference in workforce composition has resulted in differing patterns of practice among many other countries. In North America, several pathways were developed simultaneously that allowed for endovascular training of specialists from multiple disciplines. Endovascular program directors, as well as practicing endovascular neurosurgeons, first accepted neurosurgeons into fellowship training. The Committee on Advanced Subspecialty Training was created as a mechanism of maintaining training standards; these are applicable to trainees from different specialties and are reviewed regularly at multiple institutions. Fellowship accreditation for endovascular training for all specialties was initially provided through the NeuroEndovascular Surgery Advisory Committee, organized under the auspices of The Society of Neurological Surgeons.8 Later, the Credentialing Endovascular Surgery Advisory Committee was established with multispecialty representation on the board, which allowed for fellow credentialing with recognition of focused practice.9 In the nationalized health care systems of Europe and the UK, neuroendovascular services were largely developed by an expanding interventional neuroradiology (INR) workforce. Although inherent differences in health care structures exist, there are also numerous examples in Europe/UK of “dual”-trained neurosurgeons maintaining a hybrid practice. The European Board of Neuroradiology credentials endovascular training through the European Diploma in INR (EDiINR).10 Where candidates are not radiologists by background, alternative pathways to certification11 can be achieved through attendance at training courses and experience in diagnostic neuroradiology, as attested by local radiology departments. Despite this existing scaffold, many still encounter barriers to training and practice in Europe, where much of the resistance is encountered at national and regional levels. The issue of accessible training in endovascular neurosurgery and the barriers faced by many for credentialing and maintaining a practice are yet to be resolved. Recent progress was made in the UK to introduce neurosurgeons formally into endovascular practice. The General Medical Council approved a credential for MT that was published by the Royal College of Radiologists in June 2023.12 The intent of this credential is to train a workforce that can learn and deliver 24/7 MT services across England, through the recruitment of neurosurgeons and other specialists. The interest among neurosurgeons worldwide to train in neuroendovascular techniques is longstanding; in many places, this has been met with systemic hurdles and lack of collaboration with radiologists.13,14 A recently published, comprehensive summary of the landscape and obstacles to practice in Europe/UK is illustrated in Peschillo and Meling.14 The divergence in endovascular and open surgery training has created a knowledge gap for aspiring neurovascular surgeons through a lack of familiarity with endovascular imaging and techniques and a reduction in open surgical volume. Moreover, there is a need for the workforce to meet the increasing demand for “essential services” in neuroendovascular procedures, the definition of which is rapidly expanding. This is particularly pressing for acute LVO ischemic stroke. We acknowledge that endovascular licensing, legislature, and practice in Europe is heterogeneous and ever-shifting. We do not presume to describe all practices accurately nor do we wish to make generalizations when referring to “Europe and the UK.” The intent of this article is to highlight existing discrepancies and benefits of systems whereby “dual” training of neurosurgeons is accessible and “dual” practice is permitted. Referral to the “UK and wider Europe” will be used to describe practices of countries, or parts of countries, whereby hurdles exist in the training and practice of endovascular techniques by neurosurgeons. The field must evolve through expansion and further inclusion of neurosurgeons in Europe and the UK. This can only be achieved through multispecialty collaboration. We must break down the barriers to credentialing and make high-quality training accessible to those wishing to pursue a career in endovascular surgery. The time to act is now. CURRENT PRACTICE Currently, in much of wider Europe and the UK, coverage of endovascular services is provided by INR. The training for INR consists of core years of diagnostic training and further years of neurointervention training—across Europe, the median time is 5 years.15 In many countries, a dedicated fellowship program is necessary for neurosurgeons to obtain credentialing, whereas in others, a neurosurgeon must go through radiology training in addition to their own training. In a few countries, legislation does not permit neurosurgeons to practice endovascular treatments. In addition, in many countries, institutional barriers exist to neurosurgeons establishing a “hybrid” practice, despite successful completion of “dual” training.12 In recent years, the volume of endovascularly treated aneurysms has escalated, with a commensurate decrease in the volume of open microvascular procedures. Consequently, the number of trained “open” vascular neurosurgeons has decreased over time. This has had implications for the availability of neurovascular surgical expertise, particularly in the delivery of emergency on-call services. There exists variability in hospital admission privileges and follow-up patient care by radiologists. In addition, many institutions do not provide 24/7 endovascular service, and out-of-hours management of neurovascular emergencies does not include a full spectrum of treatment options. For wider Europe and the UK, neuroendovascular experience is not mandated in the neurosurgical curriculum; many trainees will have observation experience only in the angiography suite. Currently, 8 countries in Europe (Bulgaria, Denmark, Finland, France, Germany, Greece, Hungary, and Ukraine) provide training fellowships for neurosurgeons11 in comparison with 116 established endovascular fellowship programs in the United States.16 A lack of familiarity with vascular imaging among trainees is in contrast to the ethos for which neuroangiography was initially developed as an adjunct for the evaluation of surgical anatomy to aid the performance of open surgery. The diminishing requirement for “open” vascular surgery further compounds a reduced neurovascular experience for neurosurgical trainees; among whom there are likely to be immeasurable deficiencies in the “complete” assessment and management of neurovascular patients. It is the widely accepted view that “dual” training results in a neurovascular surgeon with a comprehensive toolkit to enable balanced decision making: this can provide holistic care and generate unique insights.17 In wider Europe and the UK where “hybrid” practice does not exist, the acute treatment of patients with aneurysmal subarachnoid hemorrhage must involve two specialties (neurosurgery and neuroradiology). There is potential for miscommunication, mismanagement of postprocedural complications, and vulnerabilities in “ownership” of cases. A further example is illustrated through embolization treatment of arteriovenous malformations. The use of embolization alone with curative intent can be dangerous, as well as suboptimal. By contrast, there is evidence to suggest efficacy and safety of multimodal treatment of arteriovenous malformations18 when no delays occur between modalities.19 In Europe and the UK, multidisciplinary meetings are used to generate consensus in treatment plans involving neuroradiologists and neurosurgeons. Although a team-based approach to treatment planning should be seen as the gold standard of care, optimal multidisciplinary teamwork is reliant on consistent and excellent communication. A “hybrid” neurosurgeon can add value by providing a bridge between the 2 services. Multifaceted evaluations and unbiased counseling should be cornerstones of modern-day neurovascular practice. Flexible, tailored plans are replacing “either-or” approaches to treatment—a “hybrid” neurosurgeon will be perfectly suited to care for the modern day neurovascular patient. FUTURE PRACTICE MT is used in the treatment of <2% of acute ischemic stroke cases in Europe,20 with 1 in 3 patients having access to a specialized stroke unit.12 In the UK, there is a concerted effort to increase utilization of MT from 1% to 10%.12 By comparison, access to MT centers in the United States is 48.7%.21 An international shortage currently exists for a workforce capable of delivering MT. Evidence is growing to extend time-window criteria to offer MT beyond 6 hours22,23 and to augment the role of MT beyond LVO.24,25 This phenomenon implicates expansion of MT services not only in major stroke centers but also in stroke “hubs” outreaching further geographical areas. Although this can be met with increased training of clinicians across specialties in North America, the barriers Europe and the UK face will remain high if neurosurgeons are not recruited. New additions to the armamentarium of wide-necked aneurysms include flow diverters,6 intrasaccular devices,26 and neck-remodeling devices.27 Many products are delayed from entering the US market because of wait times for Food and Drug Administration approval. However, despite late adoption, comparatively short times are seen from the technique approval to utilization and amass of clinical data. The advancement of research in neurovascular disorders will be aided by “dual”-trained neurosurgeons through faster availability in a neurosurgical community. The lack of neurosurgeons within an endovascular workforce may impede future uptake of neuroendovascular techniques. Examples include middle meningeal artery embolization in the treatment of chronic subdural hematomas, venous stenting for idiopathic intracranial hypertension, and future techniques, such as eShunting (CereVasc) for communicating hydrocephalus and intra-arterial chemotherapy for brain tumors. BREAKING BARRIERS TO CREDENTIALING The adoption of endovascular techniques and the workforce structure of neuroendovascular procedures is dependent on individual health systems, which govern demand and supply to patients. In the absence of financially driven incentives, a nationalized health care system must justify division of resources through patient outcomes and the use of “quality-adjusted life years” or similar metrics. We have highlighted the benefits and inevitability of increased need for neuroendovascular work in wider Europe/UK, for which the fast solution is recruitment of neurosurgeons. Here, we discuss major barriers and potential solutions to neurosurgical credentialing. Although a curriculum and standards are being developed, there is lack of clarity for how a high-volume experience can be achieved in practice. Institutions capable of training neurosurgeons need to have high-volume, 24/7 coverage of service, as well as experience in novel techniques. Expansion of the training capacity necessitates a need to formally identify high-volume institutions capable of delivering credentialing. Detailed curriculum requirements may vary at the national or local level; however, the framework for licensing, particularly within Europe, can already be achieved through EDiINR. For those who do not wish to follow EDiINR eligibility criteria and terms and conditions,10 numerous other examples for accreditation standards exist8,9,28,29 and may be consulted. We may wish to consult the journey of establishing the NeuroEndovascular Surgery Advisory Committee and Credentialing Endovascular Surgery Advisory Committee in North America; the inclusion of a multispecialty committee for accreditation and credentialing is vital. We should recognize this as a goal from the outset and draw on their existing experience in a standard setting that is assessable and achievable through all backgrounds. The basis of credentialing will most likely consist of three assessable parts: knowledge, practical experience, and radiation safety. We propose that practicing endovascular neurosurgeons be consulted to set standards, whereby transferrable skills in neurosurgery can be acknowledged and used. This will prevent unnecessary prolongation of training and inflexible access to practice, such as the requirement to complete a radiology residency. Scarcity of high-volume endovascular units may mean endovascular training is reserved for formal fellowships and cannot start at the residency level. For those wishing to pursue international fellowships, wider Europe and the UK may wish to define checklists by which such training can be mapped onto local credentialing standards. Importantly, we urge the removal of legislative barriers for neurosurgeons in endovascular practice where this currently exists—precise standards for competency may be variable, although recognition of suitability should be universal. Concerns exist regarding dilution of experience for current neuroradiologists accruing independent operating experience. However, the current gap in service delivery is undeniable, and the volume of work will continue to rise. Gap analyses in MT access and future work force predictions exist, although we could not find examples of gap analyses in other domains of endovascular treatment. Regulation of credentialing and protection of neuroradiology experience through assessment of future need will be facilitated through open and frank exchange between all parties involved. We advocate for neurosurgical representation in all national INR groups. Inversely, concern also exists regarding dilution of “open” neurovascular experience for a neurosurgical trainee, as well as inability to contribute to on-call services. The volume of neuroendovascular work required to reach competency, combined with infrequent exposure to “open” vascular procedures, suggest that fellowships may require two years of training, akin to many existing fellowship programs. Simultaneous availability of two neurosurgical endovascular fellows at an institution can help cover neurosurgical on calls, as well as increase exposure to both open and endovascular cases. Once trained, “dual” neurosurgeons will require job planning across both departments, the division of which can be tailored to the needs for their institutions. We can all draw on and benefit from the existing experience of hybrid neurosurgeons in Europe and the UK. Multidisciplinary teamwork has and will continue to set a high standard of care for neurovascular treatment. The addition of neurosurgeons with endovascular training does not diminish this need; rather, we endorse a future, whereby teams can be “multidisciplinary” through an individual's expertise in multiple fields and not simply defined by individuals belonging to a single specialty. It is our hope that hybrid neurosurgeons will be a driving force for neurovascular expertise, develop a multidisciplinary model that is robust, and assume a leading role in the future development of neurovascular care. Finally, we do not impose an idea of dual-trained neurosurgeons carrying out a perfect balance of endovascular vs open practice nor do we presume to predict how this balance will manifest itself. Neuroendovascular techniques are a unique skill set; it is commonly observed that “hybrid” neurosurgeons will adopt a majority open or endovascular practice. However, what is clear is the need to maintain endovascular expertise among neurosurgeons, both as a reservoir for future service provision, as well as to maintain channels by which future developments in the field will have access. CONCLUSION The potential of neuroendovascular practice has not been fully realized in Europe and the UK. There is both a desire and a pressing need to train future generations of “hybrid” neurosurgeons to integrate them into the neurovascular workforce of Europe/UK. This will be for the benefit of our existing systems, our patients, and future advancement of the field. Progress is underway, slowly but surely, across Europe/UK to break down barriers for neuroendovascular credentialing. However, there remain many systemic hurdles before we see a full integration of “hybrid” neurosurgeons into practice. Perhaps what is an “elephant in the room” and challenging to address is the hesitancy of neuroradiologists to allow neurosurgeons into the field. The international Union Européenne des Médecins Spécialistes (European Union of Medical Specialists) 2009 Charter30 concluded that neuroendovascular training is nondefinable by traditional specialties; rather, there is tremendous experience from multiple specialties that will benefit the field in practice. We do not wish to dwell on “turf wars;” rather, this inceptional philosophy is what we wish to draw on, the founding principle on which we implore all specialties to consider. Although the field has been divided since its origins, we all have much to gain through a future of multidisciplinary neurointervention. For British and European neurosurgeons wanting to gain neuroendovascular skills and practice: our time has come!