Special Issue Article

Patient selection for endovascular treatment of intracranial aneurysms Ali Alaraj, Joanna Ti, Reza Dashti, Victor Aletich Department of Neurosurgery, College of Medicine, University of Illinois at Chicago, IL, USA With recent advancement in medical imaging, techniques, and endovascular tools more patients are diagnosed with unruptured intracranial aneurysms. The main aim of offering aneurysm treatment is to ameliorate the risk of future aneurysm bleeding, while not posing additional risks on the patient from the treatment itself. We discuss in this paper our approach of selecting patients for treatment (simple coiling, balloon-assisted, stent-assisted, vessel sacrifice, or flow-divertion stents). Our decision-making is based on the published data and our center experience. Risks of all option are compared to each other and weighed against natural history of intracranial aneurysms. In this paper, literature is cited and case illustrations are presented to support this approach. Factors that affect our decision-making are aneurysm location, presentation, size, aneurysm geometry, parent vessel anatomy, and relevant co-morbidities. Keywords: Aneurysms, Balloon remodeling, Stent-assisted coiling, Flow diverters, Patient selection, Subarachnoid hemorrhage

Introduction The treatment of neurovascular disorders has rapidly evolved in the last few decades. More importantly, the range of treatment options has increased dramatically, with more treatment options available today than ever before. In this exciting and evolving field, we as physicians now face the challenge of making the correct treatment choice for each patient. Most aneurysms are discovered incidentally, others are discovered after they rupture resulting in acute subarachnoid hemorrhage (SAH). Subarachnoid hemorrhage result in 32–67% mortality with more than 20% long-term dependency in survivors.1 There are a number of randomized controlled trials (RCTs) and observational cohort trials that guide our decisionmaking process like the International Subarachnoid Aneurysm Trial (ISAT), International Study of Unruptured Intracranial Aneurysms (ISUIA), and the Barrow Ruptured Aneurysm Trial (BRAT).2–5 Treatment has been recommended for most unruptured intracranial aneurysms,6 although there is uncertainty concerning treatment of small aneurysms due to their low rate of bleeding.5,7 Nevertheless, in the real world, patient selection is often more complicated than is presented in the RCTs. The primary objective of aneurysm treatment is to eliminate the future risk of SAH and reduce the symptoms related to mass effect once present. Currently, the most independent

Correspondence to: Ali Alaraj, Neuropsychiatric Institute (MC 799), Department of Neurosurgery, University of Illinois at Chicago, 912 South Wood Street, Chicago, IL 60612-5970, USA. Email: [email protected]

ß W. S. Maney & Son Ltd 2014 DOI 10.1179/1743132814Y.0000000328

indicator of future aneurysm bleeding risk is the extent of aneurysm occlusion.8,9 All treatment options should take this in account, as partial treatment does not offer safety of future aneurysm rupture10 and adds to the inherent risk of aneurysm recanalization post treatment.11,12 Taking the above into account it is essential to establish a rigorous surveillance protocol for follow-up. The expansion of endovascular techniques require decision making based on comparative analysis of outcomes and complications among the various endovascular techniques including surgical clipping and extracranial–intracranial bypass techniques. As the technology evolves and practitioners develop more clinical experience, embolization has been used with increasing frequency to include patients who were considered in the past as purely surgical candidates.13,14 More centers are treating patients with surgical clipping only if they cannot be treated with endovascular means.13 Therefore, we aim to review the various factors that play a role in patient selection in neuroendovascular treatment and will illustrate some of these points by showing examples of cases.

Selection by Aneurysm Location Anterior circulation Aneurysms in the anterior circulation such as anterior communicating artery (Acomm), pericallosal artery, and carotid bifurcation aneurysms can be treated with equanimity with both surgical clipping and endovascular coiling (Figs. 1–3). Middle cerebral artery (MCA) aneurysms are preferentially surgically treated, not necessarily for the location of the

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Figure 1 A 64-year-old patient with a ruptured anterior communicating artery (Acomm) aneurysm. Aneurysm measured 2.5 6 3 mm. The aneurysm has a relatively favorable neck anatomy to maintain the coils inside the aneurysm thus were treated with simple coiling. (A) Aneurysm is treated with detachable coils, sequential filling of the aneurysm is seen (B, C) as coils are deployed. This resulted in complete obliteration of the aneurysm (D).

aneurysm but usually due to aneurysm geometry, to be discussed further in the next section. There are recent data suggesting good results with endovascular coiling of MCA aneurysms15,16 with good occlusion rate (.95%) in 90% of the patients, and low morbidity and mortality in one series.17 Internal carotid artery (ICA) aneurysms such as superior hypophyseal artery aneurysms, paraophthalmic artery aneurysms, ophthalmic artery aneurysms, and cavernous ICA aneurysms present a challenge surgically because they often have wide neck morphology, fusiform nature of the parent vessel and close to the base of skull, which may require extensive skull base dissection with resection of the anterior or posterior clinoid process to gain surgical access. These aneurysms therefore are preferentially treated with endovascular coiling.18,19 Endovascular treatment with adjuvant therapy (balloon- or stentassisted coiling) has been shown to achieve good occlusion rate in about 62–93.9% with mortality ranging between 0 and 6%.20–22

Posterior circulation Surgical treatment of aneurysms in the posterior circulation are challenging due to the proximity of the

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brain stem and cranial nerves and difficult surgical access. In addition aneurysms in the posterior circulation have higher incidence of rupture.5 As surgical treatment carries a significant risks of morbidity and a mortality ranging from 3 to 10%,23,24 endovascular results of basilar tip aneurysms have been consistently better than those of surgical clipping. Thus it is our preferred approach to treat these aneurysms with endovascular techniques24–26 (Figs. 4–6). In ruptured posterior circulation aneurysms where the anatomy does not favor simple coiling, then balloon remodeling techniques are often utilized to provide maximum immediate protection against rupture. If a remnant remains, then the aneurysm is treated with stentassisted techniques on an elective base when the use of anti-platelets therapy is safe.27 This approach will provide immediate protection against further aneurysm rupture in the acute setting, without increasing the morbidity of the procedure by dual anti-platelet therapy, which is required in stent-assisted coiling. Compared to surgical access, endovascular access to posterior circulation aneurysms is almost equivalent to anterior circulation aneurysms, unlike the risk of surgical clipping. Aneurysms located in the basilar

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Figure 2 A ruptured right posterior communicating (Pcomm) internal carotid artery (ICA) aneurysm in a 32-year-old female patient, grade I subarachnoid hemorrhage (SAH). (A) Large right fetal Pcomm is originating from the neck of the aneurysm. The aneurysm is treated with balloon remodeling technique with the intention to preserve the origin of the Pcomm artery with the compliant balloon. (B, C) First framing coil herniated into the origin of the Pcomm. (D, E) Framing coil retrieved and deployed to save the Pcomm origin. (F, G) Further coiling with balloon remodeling, hyperform balloon appear herniating into the Pcomm origin to protect it. (H) Final angiogram showing well secured aneurysm with preservation of fetal Pcomm origin.

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Figure 3 A ruptured left posterior communicating (Pcomm) internal carotid artery (ICA) aneurysm (4 6 5.5 mm) with 4 mm neck in a grade I subarachnoid hemorrhage (SAH) in a 64-year-old patient. (A) Non-fetal Pcomm is originating from the neck of the aneurysm. (B, C) Deployment of framing coil is seen within the aneurysm using balloon remodeling technique. The balloon provides stability of the coils to stay within the aneurysm. (D) Balloon is over inflated to invaginate into the origin of the right Pcomm. This ensures patency of the side branch during coiling. (E) Final angiogram showing well secured aneurysm, with preservation of the Pcomm origin.

trunk, proximal anterior-inferior cerebellar artery (AICA), P2 segment of the posterior cerebral artery (PCA), vertebral artery (VA), and vertebrobasilar junction should be treated primarily with endovascular means.28 Posterior-inferior cerebellar artery (PICA) aneurysms in the posterior circulation have a more straightforward surgical access than the other posterior circulation aneurysms and surgical treatment can be considered an alternative option.

Selection by Aneurysm Geometry Neck dimensions In several studies, aneurysm neck size has been a predictor of the likelihood of complete occlusion by coil embolization.29–31 The definition of wide neck aneurysm is aneurysms with an absolute neck more than 4 mm, neck diameter more than half parent vessel diameter, and the aneurysm width over neck ratio of less than two.31 Traditionally, wide-necked aneurysms were treated with surgical clipping, as standard endovascular coiling would result in coil herniation and occlusion of parent artery.32 However,

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with the ongoing advances in endovascular techniques, now almost all aneurysms, whether wide-, or narrow-necked, can be coiled with balloon assistance, stent remodeling techniques, or flow-diverting stents. These techniques will continue to evolve and provide more and more endovascular options to the patient and the physician. It is important to keep in mind, however, that the placement of one or more stents ideally also requires dual anti-platelet inhibition and any contraindication to the latter may make surgery more appealing.33 Narrow neck aneurysms are more straightforward to treat, both via the endovascular approach and with surgery. With endovascular coiling, narrow neck aneurysms often can be treated with standard coiling, as the dome/neck ratio is favorable to maintain coil stability inside the aneurysm without requiring balloon- or stent-assisted technique (Fig. 1). A large proportion of patients with wide neck aneurysms can be considered candidates for coiling using balloon remodeling techniques29–31 (Figs. 5, 7, 8). The utilization of balloons in such conditions

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Figure 4 An irregular-shaped basilar tip aneurysm in a 45-year-old patient who presented with grade III subarachnoid hemorrhage (SAH). Owing to the hemorrhagic presentation, the aneurysm was treated with balloon remodeling technique, no stenting. (A) AP (anteroposterior) and (B) lateral angiogram showing the irregular shaped aneurysm. (C, D) Road map and angiogram post deployment of the first coil in the anterior secular chamber of the aneurysm. (E, F) Roadmap with balloon inflated and later deflated to check the stability of added coils into the elongated segment of the aneurysm. (G, H) Final lateral 3D rotational angiography demonstrating stability of the coils within the aneurysm, both posterior cerebral arteries remain patent and no coils are herniating into the basilar top.

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Figure 5 A basilar tip aneurysm in a 70-year-old male patient presented with subarachnoid hemorrhage (SAH). (A) The aneurysm appears to be bilobed, with a 5.5-mm wide neck; this involves both posterior cerebral arteries. Endovascular treatment is offered because of relatively increased risk associated with surgical clipping in this location. (B) The aneurysm is treated with balloon remodeling technique to avoid deployment of stents in the acute rupture period. The balloon appears to be inflated within the right posterior cerebral artery (PCA), across the aneurysm neck before the first coil is detached. (C) The balloon is deflated to check for the coil stability, no coil displacement was seen. (D) Further coils are deployed in the second compartment of the aneurysm with the intermittent balloon inflation and deflation. (E) Post balloon deflation no coils appear to be herniating into the basilar tip. (F) Final angiogram showing adequate aneurysm embolization and preservation of patency of both posterior cerebral arteries.

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Figure 6 A 6-mm basilar tip aneurysm in a 45-year-old male patient, the aneurysm was discovered incidentally during work up for headache. (A) The aneurysm appears to be originating from the anterior wall of the basilar tip and partially incorporate both posterior cerebral artery (PCA) origins. Y-stent-assisted-coiling was performed in this patient in an effort to maintain patency of both posterior cerebral arteries. (B) Vertebral artery (VA) injection post Y-stent deployment into both posterior cerebral arteries. (C) Unsubtracted and (D) subtracted VA angiogram showing complete occlusion of the aneurysms – post coiling – with preservation of patency of both posterior cerebral arteries.

provides microcatheter and coil stability during placement of the coils. An exclusion of this category includes aneurysms with funnel-shaped neck or fusiform aneurysm where the aneurysm neck involves more than 180u of the circumference of the parent vessel wall. Aneurysms located in the anterior or posterior circulation; ruptured or unruptured aneurysms are equally selected for coiling based on this approach. The use of anti-platelets therapy is not routine unless there is a large surface area of coils exposed to the lumen of the parent vessel, or a small arterial branch arises from the base of neck of the aneurysm, such as the ophthalmic artery, posterior communicating (Pcomm) artery, or the anterior choroidal artery. The use of stents as an adjunct therapy during coiling can provide the advantage of preventing coil migration into the parent vessel, possible increased packing density within the aneurysm, and provide some flow diversion away from the aneurysm neck.34,35 This is attributed to dynamic angular vascular modeling with alteration of the wall shear stress around the aneurysm.35 The long-term

occlusion rate of large aneurysms with stent-assisted coiling is at best 69%.36 These facts lead to the increasing use of flow diversion devices in this category of patients.37

Aneurysm morphology Aneurysms may have a single lobule, or be multilobulated. These lobules may be of similar sizes or of widely varying sizes. Multilobulated aneurysms with different-sized lobules may present a challenge for endovascular coiling as the technique of coiling depends on forming a coil ‘basket’ with larger coils first and then filling in the ‘basket’ with smaller-sized diameter coils in a Russian-doll technique. If the different-sized lobules form almost separate compartments of the aneurysm, it may be possible to coil the compartments of the aneurysm separately, with different-sized coils but this is not common practice. The utilization of balloon remodeling technique allows the microcatheter to move between the two lobules while coiling is performed, thus securing the aneurysm (Fig. 5). Therefore, multilobulated aneurysms are often labeled as complex and surgery is

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Figure 7 A ruptured recurrent posterior communicating (Pcomm) aneurysm, in a 69-year-old female patient, the same aneurysm has been coiled 9 years ago, with evidence of coil compaction and recanalization. (A) Angiogram showing a widenecked cone-shaped aneurysm, previous coils appears to be displaced inferiorly within the aneurysm. Owing to the recent hemorrhage, we avoided using stent and treated this aneurysm with balloon remodeling technique. (B) Aneurysm is treated with balloon remodeling technique. Framing coil is deployed, balloon deflated to check for coil stability. (C) This is followed by balloon re-inflation and deployment of more coils. (D) Angiogram during the coiling to check for the location of the coils within the aneurysm and the relationship to the parent vessel. (E–G) Sequential balloon inflation, deflation, and re-inflation while deploying more coils at the neck of the aneurysm. (H) Final angiogram demonstrating tight coiling at the neck of the aneurysm. The parent vessel if preserved, with no coil migration into the parent vessel.

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Figure 8 A ruptured right fusiform right posterior communicating (Pcomm) aneurysm in a 67-year-old male patient with grade IV subarachnoid hemorrhage (SAH), severe heart failure, and acute pulmonary edema. As the patient presented with SAH, the fusiform aneurysm was treated with balloon remodeling technique, no stent was deployed. Owing to the poor medical condition, no surgical intervention was offered to this patient. (A) Fusiform right Pcomm with a large Pcomm originating from the aneurysm neck. The adjacent parent internal carotid artery (ICA) is fusiformly dilated. The aneurysm involves the ICA from the Pcomm origin to the carotid terminus. (B) Angiogram before detaching the first coil, using balloon remodeling technique. The coils are checked for stability, and the Pcomm origin is checked for patency. (C) Balloon is re-inflated across the aneurysm neck; balloon is positioned distally into the M1 segment of the middle cerebral artery (MCA) to ensure carotid terminus patency. (D) Final angiogram post coiling showing adequate coiling of the Pcomm aneurysm. The adjacent ICA remains patent, and the Pcomm origin is preserved.

preferred, provided all other deciding factors are similar. Occasionally, in cases of ruptured aneurysms, the pseudo-aneurysmal component of the aneurysm can appear as an irregular ‘nipple’ suggestive of the rupture site or appear as a ‘baby aneurysm’ attached to the main aneurysm. This pseudo-aneurysmal component is very unstable and prone to re-rupture, especially as there is no true wall surrounding it. During endovascular coiling, the tip of the microcatheter is maneuvered to avoid the pseudo-aneurysm, and the size of the coils is chosen based on the size of the main aneurysm, and not directly placed in the pseudo-aneurysm. Once the aneurysm is fully packed with coils, thrombosis occurs in the aneurysm and also in the pseudo-aneurysm.

Aneurysm size It has been our approach preferably to select aneurysms with narrow necks for endovascular treatment with coiling. This reflects the approach followed by most major endovascular centers,14 where patients with ruptured or unruptured, anterior or posterior circulation aneurysms are selected for coiling treatment. These patients do not require antiplatelets therapy, since the risk of thrombo-embolic complications is relatively very low.38 The indication for treatment of very small (less than 3 mm), unruptured intracranial aneurysms is controversial. Data from the ISUIA trial have shown that the risk of SAH is small.5 Thus, the risk of treatment of such aneurysms should be weighed against the natural history. Very small ruptured

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Figure 9 (A) A 10 mm left supraclinoid internal carotid artery (ICA) aneurysm with fusiform dilatation at the base of the aneurysm. Owing to the fusiform nature of the parent ICA, the aneurysm was treated with a Pipeline flow diverter embolization device (PED). (B) Cross-section of the PED (DYNA CT scan) at the end of the PED deployment. (C) X-ray lateral projection showing the PED in place across the aneurysm neck into the cavernous ICA segment. (D) Follow-up angiogram at 6 months demonstrating complete aneurysm thrombosis and vascular remodeling.

aneurysms measuring ,3 mm should be approached endovascularly with great caution, due to its small size, precise placement of the microcatheter is essential, to avoid perforating the aneurysm wall with the tip of the microcatheter (Fig. 1). In addition, as microcatheters distal outer lumen diameter measure 1.9 French (0.63 mm), this represents a significant volume within a small aneurysm, and during coiling; this will allow less ‘free movement’ of coils in the aneurysms during coiling. This increases the risk of procedural rupture with a combined mortality and morbidity up to 7.3% in published literature.39–41 The balloon remodeling technique in the case of very small aneurysms is associated with an increased risk of perforations as the inflated balloon pushes the coil against the fragile aneurysm wall.41 It is important to assess the risk of surgical clipping and coiling in this subset of patients along with other co-morbid condition. If the risk of coiling is judged to be technically more than the expected surgical risk, we would prefer surgical clipping. The use of stents as an adjunct therapy in patients with wide neck aneurysms have improved the

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long-term occlusion rates as compared to simple coiling alone.22,42 This is attributed to increase packing density and because the stent have a potential role in diverting flow away from the aneurysms.43,44 Despite this, the long-term occlusion rate was in the 60–70%22,42 with favorable clinical outcome and protection against future risk of aneurysm rupture. The use of a stent as an adjunct in aneurysm coiling requires the use of dual anti-platelets therapy (Fig. 6). Aspirin and clopidrogel are initiated before for a minimum of a week. Goal PRU of 120–180 for clopidrogel and ,550 ARU for aspirin45 are aimed for before the procedure. If a stent is deployed without adequate anti-platelet response then the patient is maintained on heparin until a therapeutic response of PRU is attained postoperatively. This is reached with a second loading of clopidrogel or switching to Prasugrel if the second loading failed to reach a therapeutic window.46 At that stage genetic testing for CYP12C2 is performed. Several series have demonstrated that larger ruptured aneurysms are more likely to recur if treated with coiling. In aneurysms larger than 2 cm there is a corresponding annual re-rupture rate of 2.7%,13 recurrence

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Figure 10 (A) Unruptured large left fusiform supraclinoid internal carotid artery (ICA) aneurysm. The aneurysm has a separate inflow and outflow zone. (B) The aneurysm was treated with Pipeline flow diverter embolization device (PED). Contrast stagnation is seen after the PED deployment. (C) The aneurysm is coiled through a separate microcatheter (jailed) to decrease the risk of future bleeding. (D) Bulls eye view demonstrating patency of the PED after aneurysm coiling.

rates for large aneurysms are reported up to 62.5%.47–49 The use of stents in patients with ruptured aneurysms is associated with a higher rate of hemorrhagic complications because of the use of the dual anti-platelets therapy.50,51 Giant aneurysm remains a challenging entity to treat. Approaches like stent-assisted coiling have shown inferiority to other surgical options (bypass and parent vessel occlusion) in terms of long-term occlusion and recanalization, while simple coiling approaches are not viable options at all in this condition due to inherent neck nature of these aneurysms. Endovascular parent artery sacrifice is an established and effective method for treatment of proximal ICA large and giant aneurysms.52,53 Owing to this fact, in the past, it has been our approach to perform parent vessel occlusion with or without extracranial–intracranial bypass for such cases.54,55 For patients with symptoms due to mass effect, this treatment result in improvement of cranial nerve dysfunction.53 Recently, with the introduction of the flow diversion stents to the market (pipeline, and before that Silk under FDA compassionate use) more

of these patients are treated with flow diversion stents.56 Typical giant aneurysms that are considered for flow diverters include those located within the cavernous sinus and the para-ophthalmic region.57 Flow diverter stents have shown higher rates of aneurysm occlusion as compared to stent/coiling58 (Fig. 9). Owing to the hemorrhagic risk associated with the use of flow diverters,59,60 we prefer to also place coils when possible in the aneurysm at the same time when the flow diverters are deployed using dual microcatheter techniques. Patients treated with flow diverters are routinely maintained on dual antiplatelets therapy, thus their use is limited in patients with contraindications for such therapy.

Parent vessel anatomy The decision of whether to perform neuroendovascular treatment of an aneurysm also depends on the anatomy of the parent artery or of the adjacent arteries. Aneurysms which are fusiform rather than saccular require concurrent treatment of the associated abnormal parent artery. Recently, flow-diverting stent therapy in the treatment of fusiform

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Figure 11 A 74-year-old female patient presented with acute subarachnoid hemorrhage (SAH) localized at the right cerebellopontine angle. (A) Diagnostic cerebral angiogram demonstrated the presence of a dissecting aneurysm of the intracranial portion of the right vertebral artery (VA) distal to the origin of the posterior-inferior cerebellar artery (PICA). (B) The intracranial VA was considered to be primarily dissected and was treated with short segment coil sacrifice of the aneurysm/VA distal to the PICA origin. Small diameter coils were tightly compacted within the dissected segment to obtain complete occlusion with the shortest segment of VA occlusion in an attempt to preserve the origin of the PICA and associated perforators coming from the VA. (C) Post coil sacrifice of the right VA, left VA angiogram showing retrograde flow into the distal right VA distal to the aneurysm with no opacification of the treated aneurysm. (D) Baseline CT scan on presentation showing the SAH within the right cerebellopontine angle. (E) CT scan post coil sacrifice showing the coil mass within the region of the SAH confirming that the dissecting aneurysm is the source of the hemorrhage.

aneurysms, or of extremely wide-necked aneurysms has emerged as a valuable method to treat such aneurysms (Figs. 9 and 10). As most saccular aneurysms occur at bifurcations of arteries, the neck of the aneurysm often incorporates an important artery, such as the Pcomm artery, ophthalmic artery, or the Acomm. This would then make endovascular coiling with balloon-assistance an attractive option, as the balloon is compliant it can be inflated to bulge

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into the neck of the aneurysm and to protect the origin of the branch artery (Fig. 2). Occasionally, in cases of a dissecting aneurysm, for example of the V3/V4 segment of the VA, treatment requires vessel sacrifice, as the artery itself is diseased. This can be achieved via endovascular means by sacrificing and occluding the diseased artery with a combination of coils and embolic material such as nbutyl cyanoacrylate (n-BCA) and/or Onyx embolic

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Figure 12 A 64-year-old lady presented with progressive severe headache and cavernous sinus syndrome, with III, IV, and VI cranial nerve ophthalmoplegia. (A) CT scan showing a large partially thrombosed right cavernous internal carotid artery (ICA) aneurysm. (B) Quantitative magnetic resonance angiography flow maps showing no measurable flow in the right ICA, with reversal of the flow in the posterior communicating (Pcomm) artery and anterior communicating (Acomm) artery contributing to the flow in the right middle cerebral artery (MCA). (C) Angiogram of the right ICA demonstrating the partially thrombosed cavernous ICA aneurysm, associated with severe stenosis of the supraclinoid segment. (D) Baseline left ICA angiogram demonstrating perfusion of the right MCA through a patent Acomm artery segment. Options like stent-assisted coiling or Pipeline flow diverter embolization device (PED) were not considered because of the poor long-term occlusion rate in the stent-assisted group for such aneurysms, and because PED are contraindicated in vessels with severe stenosis. (E) Post coil sacrifice of the right ICA, coiling is augmented with n-butyl cyanoacrylate (n-BCA) (glue) injection at the end of the coiling to ensure long-term durability of the sacrifice. Patient’s symptoms and ophthalmoplegia completely resolved at 3 weeks post treatment.

material61 (Fig. 11). More discussion regarding parent artery occlusion for fusiform aneurysms will be discussed in the section of aneurysms with mass effect.

Selection by Clinical Presentation Ruptured versus incidental The randomized ISAT randomized patients to coiling versus surgical clipping in a sample of 2143 patients. Results suggested that endovascular coiling have better outcome as compared to surgical clipping (23.7 vs 30.9%) determined by dependency or death

at 1 year.62 Based on this trial, endovascular coiling is offered as a first option for ruptured aneurysms. Ruptured aneurysms are treated emergently, as there is a high risk of re-rupture. These aneurysms also present a higher treatment risk, whether that treatment is surgical clipping or endovascular coiling. A significant advantage with endovascular techniques is the use of balloon-assistance. Although primary use of a balloon is for the treatment of wide-necked aneurysms, the presence of a balloon allows temporary

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Figure 13 (A, B) A 2.5 cm giant partially thrombosed distal posterior cerebral artery aneurysm (PCA) in a 32-year-old male patient. The patient presented with progressive headaches. (C) The aneurysm was treated with coil sacrifice of the aneurysm along with the adjacent parent PCA. The distal PCA territory was supplied by collateral circulation from the middle cerebral artery (MCA) branches; no PCA territory strokes were encountered. (D) T1-weighted MRI before treatment and (E) 3 months post treatment of the aneurysm. The aneurysm had become smaller in size, with the resolution of the surrounding edema.

occlusion of the parent artery in the unexpected event of an intra-procedural rupture, resulting in cessation of blood flow while steps such as protamine sulfate to reverse the heparin and further packing of the aneurysm with coils can occur (Fig. 4).

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Patients with large hematomas secondary to a ruptured aneurysm represent a separate subset of patients, because of associated mass effect/midline shift and impending brain herniation. These cases require surgical evacuation of the hematoma and

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Figure 14 (A) A fusiform partially thrombosed proximal basilar artery aneurysm in a 78-year-old male patient. The patient presented with progressive gait disturbances and secondary significant edema within the pons. (B) A Pipeline flow diverter embolization device (PED) was deployed across the proximal segment of the basilar artery. Post PED angiogram showing the flow alteration within the basilar artery. (C) Preoperative MRI of the brain stem demonstrating the partially thrombosed aneurysm projecting into the pons with extensive brain stem edema. (D) CT scan immediately post PED deployment showing contrast stasis within the partially thrombosed aneurysm. (E) Follow-up CT angiography 3 months post treatment showing vascular remodeling with patency of the vertebra-basilar vessels.

decompression. Most surgeons would surgically clip the offending aneurysm at the same craniotomy.63 Large hematomas are a relative contraindication to endovascular treatment; as endovascular treatment requires the administration of therapeutic doses of heparin increasing the risk of hematoma expansion. The use of stents in acute SAH, doubles the

procedural related morbidity and mortality64 and mortality can approach 12% in one series51 and should be avoided at all costs in the acute setting. In cases of unruptured intracranial aneurysms, additional endovascular treatment options are available. These include stent-assisted wide-necked aneurysm not amenable for balloon remodeling technique

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Figure 15 A 47-year-old female patient presented with 1-month history of complete right third nerve palsy. (A) CT angiography and a diagnostic cerebral angiogram (B) showed a right posterior communicating (Pcomm) artery aneurysm, with two components of the aneurysm, the inferior part is partially thrombosed. As the cranial nerve symptoms were chronic, (C) the aneurysm was treated with endovascular coiling using balloon remodeling technique. (D) Efforts were made to obtain tight packing of the aneurysm at the neck to avoid aneurysm re-canalization. The patient’s third nerve palsy started to improve the second day post procedure, with partial recovery at 2 weeks.

(Fig. 6), or most recently, flow-diverting stents for the treatment of extremely wide-necked or fusiform aneurysms. Stent deployment requires anti-platelet medication, ideally dual agents with adequate platelet inhibition. Dual platelet inhibition, on the other hand, is not highly recommended in ruptured aneurysm cases, although has been used as a last resort in challenging aneurysms.65

Mass effect Partially thrombosed aneurysms represent a unique category among intracranial aneurysms, since the lumen of the aneurysm is partially filled with thrombus leaving a smaller component of the aneurysm for coiling and traditionally have poor results after endovascular coiling.66 Thrombus formation in giant aneurysms can be quite dynamic, resulting in high rates of coil compaction and recanalization.67 It is our preference not to coil these aneurysms with coils (with or without assisted techniques stents/balloons) since the recurrence rate is high with displacement of the coil into the thrombus and at times growth of the aneurysm lumen. These patients are considered for flow diverters, if the location of the aneurysm is appropriate for stent placement, or vessel sacrifice

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following passing a balloon test occlusion53,66,68 (Fig. 12). Parent vessel occlusion with endovascular means remain one of the most effective way to treat patients with proximal giant ICA aneurysms four decades after its introduction by Serbaninko.69 Patients with cranial nerve dysfunction secondary to aneurysmal mass effect have resolution of their symptoms following proximal parent artery sacrifice53 (Fig. 13). Recent data suggest significant improvement in compressive neurological symptoms post deployment of flow diverters68 (Fig. 14). Large aneurysms may present as a mass effect on adjacent structures. The classic example is complete third nerve palsy with a Pcomm artery aneurysm (Figs. 15 and 16). Another example is a large midbasilar artery aneurysm causing mass effect on the brain stem. Endovascular treatment of the aneurysms is twofold; as there is a long-term risk of rupture, but more importantly, the mass effect from the aneurysm. Post endovascular treatment of these aneurysms, the pulsating untreated aneurysm significantly decreases immediately and over a period of weeks to months, thus leading to improvement of such mass effect symptoms. Results for recovery from cranial palsy are non-consistent in terms of long-term

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Figure 16 A 37-year-old female patient with acute left eye third nerve palsy, the patient was diagnosed to be legally blind in that eye secondary to long standing history of optic neuritis. (A) Angiogram showing a posterior communicating (Pcomm) artery aneurysm, projecting inferiorly. (B, C) Since the recovery of the third nerve was not an important factor in the decision making since she was blind in that eye, plan was for endovascular coiling. This was performed using balloon remodeling technique with (D) complete occlusion of the aneurysm and preservation of patency of the adjacent parent vessel.

results ranging from 32 to 74% improvement in compressive symptoms.70–75 This is presumably related to reducing the pulsatile pressure within the aneurysm, allowing the aneurysm to shrink with time. Aneurysm-related visual dysfunction from direct compression improve poorly in one published series.76–78 Long-term results fusiform and dolichoectatic aneurysms and posterior circulation aneurysms treated with flow diverters have a relatively higher complication rates (9.4%),79 with long-term mortality rate of 4/7 patients in one series, and high morbidity rate.80

Recurrent aneurysms As more aneurysms are treated with endovascular techniques, there has been an increase in number of cases requiring retreatment. Over time, a subset of treated aneurysms will demonstrate recurrence, either by coil compaction or growth of the residual lumen following compaction.81–83 Factors associated with increased risk of recurrence include larger aneurysms, ruptured aneurysms, and terminus and incomplete aneurysm occlusion.84–86 The reported rate of aneurysm re-treatment ranges from 9 to 13%.3,4,86 The Cerebral Aneurysm Re-ruptured After Treatment (CARAT) established 1.1% risk of re-bleeding with incomplete aneurysm occlusion, which increases to 17.6% with less than 70% occlusion.9 The use of

stents in patients with previously ruptured aneurysm is not associated with an increased morbidity and mortality,50 and is a preferred choice in aneurysms with incomplete initial treatment because of poor aneurysm geometry (Fig. 17). Patients with recurrent basilar tip aneurysms are often treated with Y-stentassisted coiling based on prior literature supporting very low aneurysm recurrence in patients treated with this technique87 (Fig. 18). The uses of stents in patients with recanalized aneurysms have been associated with lower rate of aneurysm recurrence88 and might be attributable to increase packing density and potential role of the stent in flow remodeling.89,90 Recently flow diverters have been used in recurrent aneurysms (coiling, stent-coiling, and clipping), though the presence of prior stenting reduced the efficiency of flow diverters.91 In the posterior circulation, the use of flow diverters was associated with significant perforator stroke and should be considered with care.79 Another patient factor in recurrent aneurysms, include previous craniotomies for related or unrelated conditions. Previous craniotomy favors endovascular treatment as surgical clipping entails re-exploration, which may be potentially complicated by scar tissue or anatomical distortions.92 For these reasons we prefer to treat recurrent aneurysms with endovascular means.

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Figure 17 A 3.5-mm ruptured right superior cerebellar artery (SCA) aneurysm in a 75-year-old male patient. (A) The aneurysm origin was close to the SCA. This was treated with balloon remodeling technique in order to preserve the SCA origin. (B) Coil embolization with balloon inflated across the origin of the aneurysm. (C) Angiogram at the end of the coiling showing complete occlusion of the aneurysm and SCA origin preservation. (D) Follow-up angiogram performed at 6 months. This shows aneurysm re-growth with coils migrating away from the neck of the aneurysm. (E) As there was no contraindication for anti-platelets therapy at the time of the follow-up, the aneurysm was retreated with stent-assisted coiling, with no recanalization at follow-up.

Co-morbid Conditions Aside from the aneurysm characteristics discussed in the first three sections, patient co-morbidities play a major role in the decision process to treat an aneurysm with endovascular techniques. A subset of patients will present with concurrent cardiac and pulmonary failure93 due to pre-existing medical conditions or in the setting of acute SAH. Neurogenic pulmonary edema may be an additional complication. These patients may better tolerate an endovascular approach, due to its less invasive nature (Fig. 8). Patients who present with poor grade SAHs (Hunt and Hess Grades 4 and 5) or those with significant brain swelling are also usual candidates for endovascular coiling, as it is less invasive and better tolerated by the ill patient94,95 (Fig. 19). A subset of patients will present days after the SAH with symptomatic vasospasm. The outcome of these patients did not differ between patients treated with endovascular coiling vs surgical clipping,96 yet the endovascular option might provide an added benefit since angioplasty and infusion of vasodilators would be offered at the same setting of coiling, and possibly delayed in the surgical clipped patients (Fig. 20). Other factors include religious beliefs such as Jehovah’s witnesses, where blood transfusion is contraindication, and favors endovascular approach

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due to minimal/negligible blood loss during the procedure. Other factors affecting our decision include severe allergies (radiographic contrast, Nickel with respect to stents)97 or renal failure.

Flow Related and Mycotic Aneurysms Aneurysms can develop in locations with relatively higher blood flow, such as Acomm or Pcomm artery segments in patients with ipsilateral ICA occlusions98 or perinidal feeding arteries in patients with arteriovenous malformations (AVMs). Risks of treating of Acomm or Pcomm artery aneurysms, where the communicating segment is the sole perfusion to the contralateral hemisphere, would place both hemispheres at risk to potential complications. If the anatomy of the aneurysm is favorable, endovascular options should be considered, since temporary occlusion during surgical clipping may place substantial risk on the contralateral hemisphere (Fig. 21). In the setting of a ruptured arteriovenous malformation (AVM), the acute management includes identifying any potential causes of the rupture, such as intranidal aneurysms. These are believed to have a higher risk of future re-rupture and treatment is recommended in the acute setting. If there are intranidal aneurysms in a ruptured AVM, endovascular treatment

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Figure 18 An 8-mm ruptured basilar tip wide neck aneurysm in a 49-year-old male patient. (A) Although the aneurysm was incorporating the origin of both posterior cerebral arteries (PCA), stents were avoided in this patient because of the hemorrhagic presentation. (B) Angiogram at the end of the balloon remodeling technique showing a small neck remnant. The balloon needed to be inflated partially into the aneurysm in order to keep the coils from occluding the PCAs. (C) Follow-up angiogram at 6 months showing coil compaction and neck re-growth. (D) Owing to the wide neck nature of the aneurysm, and the fact that the aneurysm does incorporate the origin of both PCA, since there was no contraindication for anti-platelets therapy at this time; we treated this aneurysm with Y-stent-assisted coiling with complete aneurysm occlusion.

with n-BCA (glue) or Onyx is our current practice. Once the high-risk components of intranidal aneurysms are treated, surgical resection of the AVM typically is reserved until the complete work-up of the AVM has been performed (Fig. 22). Occasionally, patients may develop cerebral mycotic aneurysms secondary infective endocarditis and present with SAH or parenchymal hemorrhage. These aneurysms have an extremely high risk of rerupturing and endovascular treatment is becoming the treatment of choice in the acute setting.99,100 Cerebral mycotic aneurysm treated showed resolution with antibiotics alone in about 30–50%,101–103 and the majority are fed by distal branches of the MCA.100,102 As most of these patients will require acute cardiac valve replacement with prolonged anticoagulation therapy, endovascular options for treatment appears to be the preferred option, since anticoagulation limits any surgical treatment. Allen et al. found a overall mortality rate of 13% in patients who received intervention versus 40% who received antibiotics alone.100 Vessel sacrifice remains a preferred option for proximal vessel aneurysms, while vessel sacrifice with embolic agents is a better option for distal cortical mycotic aneurysms (Fig. 23).

Conclusion The field of endovascular neurosurgery has evolved significantly in the last two decades with more available endovascular options. In addition to simple coiling, balloon remodeling and stent-assisted coiling have expanded the indications to include wide neck aneurysms. The introduction of flow divertion stents has for the first time, provided good occlusion rates for aneurysms that historically had poor long-term occlusion rates such as fusiform and giant aneurysms. Whatever treatment option (surgical or endovascular) is selected, one always needs to consider the aneurysms natural history against short-term complication rates and long-term recanalization rate. Any treatment offered to patients should maximize the long-term outcomes (aneurysm bleeding risk) and minimize complications related to the procedure.

Disclaimer Statements Contributors Drs Alaraj, Ti, Dashti and Aletich: literature review, manuscript drafting and editing. Dr Alaraj: image selection, manuscript finalizing. Funding None.

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Figure 19 (A) Ruptured right posterior-inferior cerebellar artery aneurysm (PICA) in a 78-year-old female patient. The patient presented with cardiac failure and severe pulmonary edema, thus this patient was considered too sick to undergo surgical clipping. The PICA appears to be originating from the aneurysm itself. Complete coiling of the aneurysm will involve sacrifice of the PICA. (B) The aneurysm was treated with coiling, with the (C) intentional plan to leave a small remnant at the origin of the PICA.

Conflicts of interest Dr Alaraj and Dr Aletich are consultants to Cordis–Codman. No financial interests are related to this article. Ethics approval Local University of Illinois IRB approval is obtained before reviewing the patients’ charts.

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Figure 20 A 47-year-old female patient presented 5 days after the onset of severe headaches. On presentation the patient was hemiplegic in the left upper extremity. (A) Diagnostic cerebral angiogram on initial presentation showing severe vasospasm in the right middle cerebral artery (MCA), M1, M2, and distal MCA branches. There is a 5-mm irregular-shaped MCA bifurcation aneurysm incorporating the origin of both MCA branches. Owing to the severity of the symptoms secondary to vasospasm, the vasospasm was treated pre and post aneurysm coiling, with planned sub-total coiling of the aneurysm using the balloon remodeling technique. (B) Angiogram performed post infusion of 10 mg of verapamil. Mild treatment of the vasospasm was planned before securing the aneurysm so that the microcatheter and the balloon can be navigated safely through the MCA. (C, D) Coiling of the wide neck MCA aneurysm using balloon remodeling technique, balloon is partially inflated in the M2 segment to prevent the coils from herniating into the MCA bifurcation. (E) Roadmap post aneurysm coiling, the balloon is pulled into the MCA where balloon angioplasty was performed to treated the symptomatic vasospasm. (F) Complete angiogram post aneurysm coiling, and angioplasty of the MCA, a small aneurysm remnant is seen at the neck, MCA is fully dilated. Patient had resolution of the hemiplegia at the end of the procedure. and clinical outcomes in 115 consecutive patients. Neurosurgery. 2009;64(5):876–88; discussion 888–9. 18 Javalkar V, Banerjee AD, Nanda A. Paraclinoid carotid aneurysms. J Clin Neurosci. 2011;18(1):13–22. 19 Fox JL. Microsurgical treatment of ventral (paraclinoid) internal carotid artery aneurysms. Neurosurgery. 1988;22(1 Pt 1):32–9. 20 Park HK, Horowitz M, Jungreis C, Kassam A, Koebbe C, Genevro J, et al. Endovascular treatment of paraclinoid aneurysms: experience with 73 patients. Neurosurgery. 2003;53(1):14–23; discussion 24.

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Figure 21 Angiogram of a 75-year-old male patient who presented with subarachnoid hemorrhage (SAH) from a 3-mm ruptured anterior communicating artery (Acomm) aneurysm. (A) The left internal carotid artery (ICA) is chronically occluded. (B) The right ICA angiogram demonstrating the Acomm aneurysm, with cross flow across the aneurysm, with the left middle cerebral artery (MCA) exclusively supplied from the right ICA. (C) The aneurysm was coiled primarily, with preservation of the cross from the right ICA to the left MCA territory.

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Figure 22 A 55-year-old female patient presented with recent headaches. Work up performed in outside institution included cerebral angiogram. (A) Angiogram showing a left frontal arteriovenous malformation (AVM). This is associated with two proximal perinidal aneurysms (arrow) on a distal anterior choroidal branch. No treatment was offered for AVM/aneurysm. (B) Patient presented 2 weeks later to our facility with new onset frontal hemorrhage. Repeat angiogram demonstrating increase in the size of the perinidal aneurysm (arrow). (C) The aneurysm was treated with selective catheterization of the anterior choroidal artery and n-butyl cyanoacrylate (n-BCA) (glue) injection into the feeding vessel and the aneurysm. (D) CT scan on admission showing the left frontal hemorrhage adjacent to the frontal AVM. (E) Post embolization CT scan showing the glue cast within the hemorrhage region confirming that the expanding aneurysm was the source of the hemorrhage.

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Figure 23 A 29-year-old female patient known to have sickle cell, post mitral valve replacement, on Coumadin and recent diagnosis of endocarditis presented with right-sided parieto-occipital hemorrhage. She underwent surgical evacuation of the hematoma, significant bleeding was encountered intra-operatively suggestive of a mycotic aneurysm. (A) Post craniotomy angiogram showing the presence of a contralateral distal posterior cerebral artery (PCA) mycotic aneurysm (arrow). This was treated with n-butyl cyanoacrylate (n-BCA) (glue) embolization. (B) Selective angiography through a microcatheter positioned distally in the PCA proximal to the mycotic aneurysm (arrow). (C) Glue cast post embolization; the glue cast appears to fill the pseudo-aneurysm (arrow) with occlusion of the patent vessel. (D) Post embolization angiogram confirming the occlusion of the mycotic aneurysm along with the adjacent parent vessel (arrow).

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