Learning Objectives: After participating in this CME activity, the neurosurgeon should be better able to:
- Describe clinical scenarios in which cerebral aneurysms are best treated with endovascular techniques or open microsurgical techniques.
- Compare the advantages/disadvantages of hybrid and dual cerebrovascular subspecialty training.
The management strategies of intracranial aneurysms continue to evolve rapidly. The neurosurgeon's armamentarium has grown tremendously with a vast array of microsurgical and endovascular techniques. Advancements in knowledge and technology have helped to reduce the high morbidity and mortality historically associated with this disease. To take full advantage of our modern technology, technical skill, and clinical knowledge, the training of neurosurgeons who treat aneurysms has also become more complex. In our opinion, the modern-day neurosurgeon best equipped to treat cerebrovascular disease is going to be one who has obtained hybrid or dual training in both endovascular and microsurgical techniques. Neurosurgeons comfortable with both open microsurgical and endovascular techniques can use these skills interchangeably and safely to treat a broad spectrum of disease and hopefully reduce complications by not leaning too far toward to one particular treatment strategy.
Historically, the term “aneurysm” has been attributed to Galen in ad 2, who combined the 2 Greek words, ana (across) and eurys (broad). It was Buimi of Milan in 1765 who gave the first documented clinical account and autopsy report of the disease. After clinical medicine became more sophisticated, Hutchinson in 1875 accurately diagnosed an aneurysm in a live patient followed by Quincke in 1891, who demonstrated blood in cerebrospinal fluid after subarachnoid hemorrhage.
As neurosurgical techniques improved, the ligation of ruptured aneurysms became feasible but remained technically challenging with very high morbidity and mortality rates. The field continued to advance as Harvey Cushing first described a metal clip for aneurysms not amenable to suture ligation in 1921, and Walter Dandy operated on a 43-year-old woman with a right third nerve palsy and an unruptured aneurysm in 1937.
As clip ligation techniques were refined, the field of angiography began to blossom with Moniz, who performed the first angiogram in 1927 and then later, in 1933, reported angiographic localization of a ruptured aneurysm.
By 1954, angiograms began to be described as routine procedures for diagnosis and localization of aneurysms. A decade later interventional techniques were already being used to treat aneurysms, such as balloon occlusion of aneurysms in 1964 by Luessenhop and Velasquez, and in 1965 J. F. Alksne reported using a magnetic field to guide iron microspheres into aneurysms. The precursor to today's coil embolization was first reported in 1991 in Gugliemi's publication on detachable coils.
At the present time, both endovascular and open microsurgical techniques are frequently used safely and effectively to treat a wide variety of aneurysms. There are now many centers that offer postresidency subspecialty training in endovascular, open microsurgical, or both techniques. However, it remains frequently debated in which clinical scenarios what specific technique would produce a superior outcome. In our opinion, the 21st-century neurosurgeon best equipped to navigate these scenarios and provide unbiased comprehensive treatment of aneurysms will have undergone dual or hybrid training in both endovascular and open microsurgical techniques.
Pathways to Hybrid and Dual Training
Historically, there have been several different pathways to obtaining dual or hybrid cerebrovascular subspecialty training in neurosurgery: (1) A postresidency endovascular fellowship followed by a separate open cerebrovascular fellowship; (2) An open cerebrovascular fellowship followed by an endovascular fellowship; (3) A postresidency hybrid fellowship, which provides experience in both endovascular and open cerebrovascular cases; (4) An in-folded endovascular fellowship during residency followed by a postresidency open cerebrovascular fellowship; (5) An in-folded open cerebrovascular fellowship during residency followed by a postresidency endovascular fellowship; (6) A postresidency endovascular fellowship followed by an open cerebrovascular fellowship as an attending; (7) A postresidency open cerebrovascular fellowship followed by an endovascular fellowship as an attending. A discussion of the merits of each path is beyond the scope of this article.
Dual Versus Hybrid Fellowships
Hybrid cerebrovascular fellowships are postresidency fellowship programs, in which mentors provide subspecialty training simultaneously in endovascular and open cerebrovascular cases. Potential advantages may include more integrated training, more “real life” scenarios, and potentially a shorter fellowship length. Disadvantages of hybrid training may include limited experience in one component from a bias toward either open or endovascular techniques.
Dual cerebrovascular fellowship training, on the other hand, is obtained through 2 separate fellowships, either at a single institution or at different institutions. An advantage of the dual fellowship pathway is that the trainee might potentially gain a more extensive and intensive training in each respective area. A second advantage is the benefit of gaining different perspectives from separate institutions.
Advantages of Hybrid/Dual Training
The choice of technique in the treatment of complex vascular cases is informed by the individual practitioner's training and specific expertise. The ability to seamlessly switch from an open vascular plan to an endovascular or vice versa with minimal bias is one advantage of dual or hybrid training. The main purpose of this article is to provide case examples of a variety of complex vascular cases treated by the senior author, with an emphasis on cases that required a change in initial plan or those planned with a combined approach. Examples will be given of cases attempted endovascularly but then treated surgically, surgical attempts followed by endovascular treatment, combined treatments, cases when a surgical approach is superior (in the author's estimation), cases when an endovascular approach is superior (again in the author's opinion), and cases with no good treatment option.
Endovascular Attempt Followed by Surgical Treatment
Case 1. A 59-year-old woman presented with Hunt and Hess (HH) grade 3, Fisher grade 4 subarachnoid hemorrhage. A diagnostic cerebral angiogram identified a 5.4-mm basilar tip aneurysm with very narrow and tortuous anatomy (Figure 1). Coil embolization was attempted but was not possible due to a tortuous origin of the left vertebral artery precluding safe passage of the guide catheter. The endovascular procedure was aborted, and a right fronto-orbitozygomatic craniotomy was performed and the aneurysm was successfully treated with clip ligation (Figure 2). A follow-up angiogram showed no residual aneurysm.
Relative contraindications to endovascular approaches are severe vessel tortuosity, distal anterior cerebral artery aneurysms (ie, pericallosal), difficulties with access, and very small aneurysms (<2 mm).
Surgical Attempt Followed by Endovascular Treatment
Case 2. A 65-year-old woman presented after a transient ischemic attack. A diagnostic cerebral angiogram identified 2 left internal carotid artery (ICA) aneurysms (ophthalmic and ventral wall), a basilar tip aneurysm, and 2 right ICA aneurysms (Figures 3–5). A left craniotomy was performed for clip ligation of the largest lesion and the ophthalmic aneurysm. The small ophthalmic lesion was clipped, but heavy wall calcification precluded safe clipping of the ICA aneurysm. Therefore, clipping of this aneurysm was not performed. The aneurysm was successfully coiled, as were the other 3 aneurysms (Figure 6).
Benefits of Combined Modality Treatment
Case 3. A 66-year-old woman presented with transient dizziness. CT angiography (CTA) identified both an unruptured large right M1 aneurysm and a smaller right M2 aneurysm (Figure 7). She was evaluated with a diagnostic cerebral angiogram and taken to the operating room (OR) for clip ligation of both aneurysms. The smaller M2 aneurysm was completely clipped. The heavily calcified M1 trifurcation aneurysm resisted complete clip closure but narrowed the neck of the aneurysm sufficiently to facilitate coil embolization. A follow-up angiogram showed complete obliteration of the smaller aneurysm and constriction of the larger aneurysm. This more proximal aneurysm was then treated successfully with coil embolization (Figure 8).
Case 4. A 54-year-old woman presented with an HH grade 3, Fisher grade 3 subarachnoid hemorrhage. CTA identified a wide-neck (defined as dome-to-neck ratio <2.0 and/or neck length of 4 mm or more), complex middle cerebral artery (MCA) aneurysm with multiple lobes (Figure 9). A cerebral angiogram was performed, and the aneurysm was initially treated with coil embolization, with coils placed in each distinct lobe to provide early protection. The respective domes were well protected with densely packed coils and elimination of blood flow, but residual aneurysm was seen in the neck. She was treated aggressively for severe vasospasm and discharged home in good condition at the end of her hospitalization. A follow-up angiogram several weeks later continued to show residual filling at the neck of the aneurysm (Figure 10). The patient underwent successful elective clip ligation of the residual aneurysm (Figure 11).
Case 5. A 55-year-old woman presented with a 4-month history of diplopia and vertigo and a long-standing history of cardiac arrhythmias. Imaging was performed, which identified a large wide-neck, right superior cerebellar artery (SCA) aneurysm. The decision was made to treat the aneurysm with stent-assisted coil embolization, which requires dual antiplatelet therapy. Multiple attempts to place the stent microcatheter and wire past the aneurysm into the right posterior cerebral artery failed because the high turbulent flow into the aneurysm resulted in the microcatheter being deflected into the aneurysm with each attempt and the procedure was aborted. Given the large girth of the aneurysm, a surgical approach with hypothermic circulatory arrest was contemplated. After consultation with cardiology, it was determined that her history of arrhythmias made the proposed procedure too dangerous. After extensive discussion with the patient, she was then taken to the OR for a right fronto-orbitozygomatic approach craniotomy for clip ligation. The neck of the aneurysm could not be visualized around the large dome and thus multiple clips were placed in parallel at the dome. An intraoperative angiogram showed a sizable crescent-shaped residual. A few months later a second attempt at endovascular treatment was attempted. On this occasion, the reduced flow into the dome of the aneurysm made navigation of the microcatheter across the neck possible, and the stent was deployed without difficulty. The aneurysm was then successfully coiled (Figure 12).
Endovascular Approach Alone Is Superior
Case 6. A 33-year-old woman presented with an HH grade 3, Fischer 4 subarachnoid hemorrhage. A CTA showed a complex, wide-neck, bilobed aneurysm at the vertebrobasilar junction. Given the location and complexity of the lesion, the decision was made to treat endovascularly. A stent-assisted coil embolization of the distinct domes of the aneurysm was accomplished. Complete obliteration of the aneurysm was seen on follow-up imaging (Figure 13).
Case 7. A 75-year-old woman presented with progressive diplopia. A CTA and diagnostic cerebral angiogram identified an unruptured, large, wide-neck, 17 × 15 × 8-mm right cavernous carotid aneurysm (Figure 14). This aneurysm was successfully treated with deployment of a flow-diverting Pipeline stent. Immediate follow-up showed a slight stagnation of flow within the aneurysm, with normal perfusion of the ICA without any in-stent stenosis. On delayed follow-up imaging, the aneurysm was found to be completely obliterated, without any stenosis of the parent ICA (Figure 15).
Open Surgical Approach Is Superior
Relative indications for craniotomy over endovascular treatment often include aneurysms with branch vessels from the neck, large or giant aneurysms with wide necks, aneurysms causing compression of critical structures, aneurysms associated with a large compressive hematoma, or aneurysms with partial or complete thrombosis (Figure 16).
Case 8. A 52-year-old woman presented with dizziness and a CT scan suspicious for an unruptured ICA aneurysm. Follow-up CTA and diagnostic angiogrphy revealed a small ophthalmic segment aneurysm with the ophthalmic artery arising from the aneurysm neck. To attempt to reduce the risk of ophthalmic artery thrombosis, the patient was taken to the OR for craniotomy for clip ligation. Intraoperative angiography showed complete obliteration of the aneurysm (Figure 17).
Case 9. A 36-year-old woman presented with a recent history of seizures and headaches. MRI of her brain demonstrated a nearly completely thrombosed giant left MCA aneurysm. On further evaluation with a diagnostic cerebral angiogram, the aneurysm was confirmed to be completely thrombosed. Because of the mass effect, this patient was taken to the OR for craniotomy for surgical resection and clip ligation of the aneurysm. Follow-up imaging showed compete obliteration of the aneurysm (Figure 18).
Case 10. This patient presented with a large ruptured left ICA terminus aneurysm (Figures 19A and 19B). Given the poorly defined neck, the decision was made to take the patient to the OR for clip ligation. The bulbous nature of the neck prevented an initial optimal placement of the clip because it slid down on the neck to partially occlude the parent vessel. Advantage was taken of this initial placement, and the dome was aspirated with a 23-gauge needle (Figure 19C). The collapse of the dome then facilitated placement of a second clip in tandem followed by removal of the first. The angiogram showed complete obliteration (Figure 20).
Cerebral Aneurysms Without Good Treatment Options
Case 11. A 29-year-old patient presented to the neurosurgery clinic with report of a neck bruit. A diagnostic angiogram was performed, which showed diffuse atherosclerotic disease with an absent right vertebral artery and high-grade stenosis of the left vertebral artery (Figure 21). Both of the ICAs were found to have very irregular, complex fusiform dilations and multiple irregular aneurysms involving the posterior communicating vessels, the basilar artery tip, the basilar trunk, and the A1 segment (Figures 22–24). The left ICA was occluded above the posterior communicating artery. We elected not to intervene on any of her multiple lesions.
Modern advances in medical knowledge, technology, and surgical/endovascular technique have greatly increased our ability to effectively treat cerebral aneurysms. As the subspecialty of cerebrovascular neurosurgery continues to be refined, so must the training of the 21st-century neurosurgeons who treat aneurysms. The complex nature of the techniques and clinical care needed to treat aneurysms requires extensive subspecialty training. As mentioned in this article, there are clinical scenarios in which endovascular techniques are more favorable; others where open approaches are more favorable; others where combined approaches are needed; and finally, some situations in which any intervention will be more likely to cause harm. If neurosurgeons have completed fellowship training in only endovascular or only open surgical approaches, there is a risk they may make overly biased decisions and have limited options to offer their patients. Although training in each subspecialty is standardized, there are still several options for the sequence of training. Neurosurgeons with dual or hybrid subspecialty training will be in a position to offer their patients a fully comprehensive approach with possibly less biased approaches to manage aneurysms and may lead to potentially more favorable outcomes.
Bracard S, Abdel-Kerim A, Thuillier L, et al Endovascular coil occlusion of 152 middle cerebral artery aneurysms: initial and midterm angiographic and clinical results. J Neurosurg. 2010;112(4):703–708.
Meckel S, McAuliffe W, Fiorella D, et al Endovascular treatment of complex aneurysms at the vertebrobasilar junction with flow-diverting stents: initial experience. Neurosurgery. 2013;73(3):386–394.
Keywords:Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved
Cerebral aneurysm; Dual training; Endovascular technique; Microsurgical technique