Emerging Subspecialties in Neurology: Endovascular surgical neuroradiology
Michael Chen, MD and
Thanh Nguyen, MD
From the Department of Radiology (M.C.), New York Presbyterian Hospitals of Columbia and Cornell, New York; and Department of Radiology (T.N.), Centre Hospitalier de l'Université de Montréal, Quebec, Canada.
Address correspondence and reprint requests to Dr. Michael Chen, Department of Neurological Sciences, Rush University Medical Center, 1725 West Harrison Street, Suite 1118, Chicago, IL 60612-3824 Michael_Chen{at}rush.edu.
In 1998, the World Federation of Interventional and TherapeuticNeuroradiology published fellowship guidelines for interventionalneuroradiology (INR), specifying requirements for trainees withbackgrounds in either neuroradiology or neurosurgery.1 In 2006,the Accreditation Council for Graduate Medical Education (ACGME)announced the revised program requirements in the United Statesfor fellowship education in endovascular surgical neuroradiology(ESN). ESN was not only to be the new name in the United Statesfor what was previously called interventional neuroradiology,but trainees with a neurology background were also included.2
ESN is defined by the ACGME as a clinical subspecialty for thediagnosis and treatment of neurovascular diseases using x-rayfluoroscopy and angiography. Devices designed for the treatmentof intracranial cerebral aneurysms, cerebral arteriovenous malformations,head and neck tumors, acute stroke, and intracranial stenosishave all gained Food and Drug Administration approval at varyinglevels, each with specific indications for therapy in the brain,head, neck, and spinal cord. Devices designed for extracranialand intracranial use include microcatheters, microguidewires,detachable coils, particulate and liquid embolic materials,clot retriever devices, stents, and balloons. Treatment optionsin interventional neuroradiology familiar to neurologists includeextracranial and intracranial carotid revascularization andacute intraarterial thrombolysis (chemical or mechanical) forstroke. In recent years, there has been a greater awareness,development, and understanding of these treatment options, leadingmore neurologists to adopt an aggressive approach in consultingtheir neurointerventional colleagues. In addition, the evolutionof the field has led some neurologists to pursue the necessaryadditional training to perform these procedures.
ACGME REQUIREMENTS FOR ESN FELLOWS WITH NEUROLOGY TRAINING
The major ACGME requirements for neurology-trained fellows includethe following2:
1) Completion of an ACGME-accredited residency in neurology
2) Completion of an ACGME-accredited 1-year vascular/strokefellowship or a neurocritical care fellowship
3) Completionof 3 months of clinical experience within an ACGME-accreditedneurologic surgery program
4) Completion of a preliminaryyear within neuroradiology duringwhich the program will provideeducation and clinical experienceto ensure that the fellowwill receive the following training
A course in basic radiographicskills, including radiation physics;radiation protection; andthe pharmacology of radiographic contrastmaterials acceptableto the program director where the neuroradiologytraining willoccur
Performance and interpretation of a minimumof 50 diagnosticneuroangiograms under the supervision of aqualified physician(board-certified neuroradiologist, interventionalneuroradiologist,or endovascular neurosurgeon with appropriatetraining)
Instructionin the use of needles, catheters, guidewires,andangiographicdevices and materials
Recognition and managementof complicationsof angiographicprocedures
Understandingthe fundamental noninvasiveneurovascular imagingstudies pertinentto the practice of endovascularsurgery includingCT/CTA, MR/MRA,and sonography of neurovasculardiseases
Egas Moniz, a Portuguese neurologist in the 1920s, is regardedas the pioneer who performed the first cerebral angiogram.3At the time, the only intracranial anatomy that could be visualizedwas the ventricles with the introduction of air into the ventricularsystem. Imaging the living human brain was not considered possibleat the time. Moniz began by giving large doses of bromides topatients orally, thinking that this sedating agent of atomicweight 80 would accumulate in the brain, and help opacify thebrain parenchyma under fluoroscopy. The brain could not be visualizedwith this agent, even with injections directly into the carotidarteries. Further studies with different doses and techniquesusing decapitated heads eventually led to the use of iodine,which has an atomic weight of 127. In 1927, Moniz was able todistinctly visualize portions of the internal carotid arteryin the Sylvian fissure, and he presented his work for the firsttime at the meeting of the Society of Neurology in Paris.3 Hepublished his first book on cerebral angiography 4 years later,entitled Diagnostic des tumeurs cerebrals et epreuve de l'encephalographiearterielle.4
Neurointerventional therapies were not a natural extension fromdiagnostic cerebral angiography. These therapies were developedby physicians who were first and foremost clinicians, who daredto pioneer the riskier work with the goal of developing effectiveneuroendovascular therapies (Jean Raymond, MD, personal communication).Although neurologists in the United States have recently beguntraining in this field, it was neurologists outside of the UnitedStates who are regarded as among the original pioneers in interventionalneuroradiology. Professor Luc Picard, who trained in both neuroradiologyand neurology, performed his first set of cerebral embolizationsin 1968. In 1982, he organized the annual meeting of the WorkingGroup in Interventional Neuroradiology at Val d'Isère,France. He is a founding member of the World Federation of Interventionaland Therapeutic Neuroradiology, of which he was the Presidentfrom 1993 until 1995. Professor Georges Salamon, who trainedin neurology in Marseille, was the first to create a nationalteaching program of neuroradiology, called "the course of Marseille."This course is considered to be the origin of clinical neuroradiologyin France. In 1966, he created the INSERM Research Unit, theequivalent of NIH, under Professor Gastaut. This was a laboratorydevoted to the anatomic basis of neuroimaging.5 Professor AugusteWackenheim trained in neurology and radiology at Strasbourg,and he eventually became Chairman of Diagnostic Radiology in1979. He saw himself not so much as a film reader but more ofa thinker and initiator. He was one of the first on the continentto embrace and develop computers in radiology as well as CT.6Professor Rene Djindjian, a neuropsychiatrist, worked with theneurosurgical service and Professor Houdart at the LariboisiereHospital, and he led the French contingent of the "American/English/Frenchconnection" in pursuit of unraveling the enigma of spinal vascularmalformations (Luc Picard, MD, personal communication).
A unique and complicating feature of ESN is the overlappinginterest in performing neurovascular interventions from severalmedical subspecialties, including neurology, neurosurgery, radiology,vascular surgery, and cardiology. Multiple editorials have highlightedthe controversies over which type of physician is most appropriateto perform interventions such as carotid stenting and acutestroke thrombolysis.7,8 Some radiologists have expressed a concernthat "INR is practiced today by an ever increasing number ofpractitioners not always optimally trained, as various specialiststry to highjack INR resulting in its fragmentation."9 Intrahospitalpolitics are sometimes exacerbated as new practitioners areviewed suspiciously by those who are more established.
However, as clinical research and practice in this field advance,it may become less relevant which specialist is performing theprocedure. Philosophically, Picard believes that a fundamentalinterest in the human nervous system supersedes a physician'straining background. With a group of highly trained physiciansinterested in the nervous system with an open spirit, with thegoal being the best care of the patient, the specialty shouldcontinue to evolve in a positive direction.
Some neurologists may have experienced the awkward situationof trying to make a clinical decision in the angiography suitewhile balancing this with the technical ability and judgmentof the neurointerventionalist. Selection of patients eligibleor ineligible for neurovascular interventions is not easy, evenfor physicians with neuroscience training.10 Difficult casescan strain this collaborative effort between neurologists andinterventionalists and may magnify the differences in trainingbetween the two. Neurologists with ESN training have the abilityto streamline care for patients with cerebrovascular diseaseand participate in clinical decision-making both inside andoutside of the angiography suite. In addition, their broaderexposure to cerebrovascular natural history and medical treatmentsduring neurology training allows them to manage the patientalong the continuum from admission, to intervention (if indicated),to discharge. This unique skill set for the endovascular neurologisthas positive implications never before seen in advancing thecare of patients with cerebrovascular disease.
The motivations driving neurologists to endovascular neuroradiologyare both practical and personal. Picard was motivated by a fieldin medicine that was both logical and effective. Although hefelt neurology to be logical, he did not find it very effectivein the 1960s, whereas he felt neurosurgery to be too aggressive.Neuroradiology appeared to him poised to undergo immense developmentwith a potential for what he describes as having "grand efficacy."Another endovascular neurologist states that his motivationto pursue additional training was to acquire the ability toprovide a range of treatment options for his patients with cerebrovasculardisease (Adnan I. Qureshi, MD, personal communication). Stillothers were motivated more by a sense of frustration with thelack of research in the area of endovascular therapies for acuteischemic stroke. They sensed that ESN-trained neurologists couldcontribute to the advancement of acute stroke therapies viaa consortium of neurointerventionalists similar to the Thrombolysisin Myocardial Infarction study group, which has made great stridesin cardiology research (Rishi Gupta, MD, personal communication).
The highest training standard should be applied to physiciansinterested in performing any neurovascular intervention becauseprocedural complications can be disabling or fatal.11 Expertisein neurovascular anatomy, stroke pathophysiology, and neurodiagnosticand angiographic interpretation, combined with proficiency incatheter/device manipulation, is essential to developing thesuccessful neurointerventionalist. Ideally, the year of vascularneurology training should be at an institution that treats alarge volume of ischemic stroke with IV tissue plasminogen activatorand intraarterial recanalization therapies (Rishi Gupta, MD,personal communication). While vascular neurology may be anacceptable route in preparation for ESN, some find neurocriticalcare training an important prerequisite for ESN training, particularlyas it pertains to the periprocedural clinical care of the patientwith subarachnoid hemorrhage or an acute stroke (Adnan I. Qureshi,MD, personal communication). These patients are often criticallyill, and the ability to manage the airway, blood pressure, andraised intracranial pressure among other issues can only improvepatient management. For the neurologist in ESN training, particularattention should be dedicated to interpretation of as many cerebralangiograms, brain CT scans, and brain MRI scans related to patientcare as possible, since prior neurologic training may not haveprovided as much imaging exposure compared to a radiologisttrainee. Three-dimensional visualization of cerebral blood vesselsas they relate to the brain parenchyma and skull is anotherimportant skill that allows choosing the best views for catheternavigation and safe intervention.
Neurologists need to prepare themselves during training suchthat they can contribute clinical acumen in patient managementas well as provide a clinically oriented perspective in neuroendovascularresearch. Active involvement in clinical research and writingpapers to better understand the scientific process in anticipationof using one's endovascular training to design properly conceivedclinical trials is recommended (Rishi Gupta, MD, personal communication).Compared to other interventional specialties such as cardiology,there is a relative paucity of trials in endovascular neuroradiology.Obstacles to high quality neuroendovascular research may relateto the lower volume of cases and the discomfort associated withrandomizing patients. Residency training in neurologic programstends to embrace research and clinical trial work, which shouldbe cultivated as the neurologist develops a career in endovascularneuroradiology.
The decision by a young neurologist to pursue the additionalyears of ESN training must include some sense of what realisticpractice options exist after finishing training. Recent federalpolicy changes in Medicare reimbursement have led hospitalsto prioritize acute stroke care. Tertiary hospitals have moreincentive now to acquire a JCAHO comprehensive stroke centerdesignation, and neurointerventionalists play a critical rolein helping centers achieve this certification. As a result ofthis momentum, opportunities currently are increasingly availablefor ESN-trained neurologists. A crucial issue for the endovascularneurologist in the initial job search remains being able tostrike an acceptable balance between providing clinical careas a vascular neurologist, a neurointensivist, a neurointerventionalist,or some combination of the three. Of course, in any role, thelocal community and hospital further defines the role basedon its needs, resources, and strengths.
Two career paths are often described that recently trained ESNneurologists have taken (Adnan I. Qureshi, MD, personal communication).The first, called a dual practice model, involves clinical managementof patients with cerebrovascular diseases regardless of theneed for interventional procedures. A practice, for example,may have one third of the patients requiring interventionalprocedures. The second model is more along the lines of a radiologist-consultantwhereby the focus is exclusively interventional procedures andperiprocedural management.
A Society of Vascular and Interventional Neurology (SVIN) hasrecently formed, comprised largely of neurologists trained inESN from around North America. It currently has about 150 memberswhose mission is to operate and represent a society interestedin the innovative treatment of cerebrovascular and other neurologicdiseases. Their aim is to promote cooperation, foster scientificresearch, raise awareness, and conduct teaching conferencesfor physicians and scientists interested in vascular and interventionalneurology. This organization is not limited to interventionalistsor neurologists and the society is actively recruiting new members.Interested persons can refer to the SVIN website at www.svineuro.org,where fellowship and job opportunities are listed. At this time,most training programs in the United States, even those ledby neurosurgeons and neuroradiologists, seriously consider qualifiedneurologists for fellowship positions.
At the first annual SVIN meeting in Boston, Walter Koroshetz,deputy director of National Institute of Neurological Disordersand Stroke, addressed the question, "Why the neurologist?" Heemphasized that a vascular or neurocritical care backgroundis an essential aspect of training, as this is the expertisethe neurologist contributes to a field with neuroradiologistsand neurosurgeons. Other advice he offered:
1) Be wary of burnout.
2) Be generous and collaborate withothers.
3) Get over the feeling that you are always right.C. MillerFisher said he was wrong 90% of the time when he cameto braincutting.
4) Evidence is necessary because you needto know you are helpingthe patient. The NIH is interested inresearch that definesoutcomes.
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ACGME REQUIREMENTS FOR ESN...
HISTORY
