General Description

Since the introduction of detachable coils by Guglielmi in 1991, the standard endovascular therapy for cerebral aneurysms has been coil embolization. The benefit of coil embolization in the treatment of ruptured aneurysms was proven in the randomized, controlled International Subarachnoid Aneurysm Trial (ISAT), the results of which were published in 2002. The basic therapy has since evolved with new techniques, including balloon and coil assistance and is considered part of the standard of care. Once the decision is made to approach an aneurysm through an endovascular approach, the endovascular surgeon plans his or her technical approach on the basis of the angiographic anatomy of the aneurysm and its location, including lesion shape, size, neck, and relation to the parent vessel.

Evidence for Coil Embolization

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  The ISAT investigators randomized 2,143 patients with ruptured aneurysms to either microsurgical clipping or endovascular coiling on the basis of intention to treat. This study demonstrated 23.7% of patients in the endovascular group to be dependent or dead versus 30.6% of those in the surgical group, showing a risk reduction of 6.6%. Overall, ISAT demonstrated equivocal results when comparing endovascular versus microsurgical intervention.

  
  
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  Anatomical results of endovascular therapy have improved over the years with progressively good outcomes from initial studies done by Vinuela et al. in 1997 ¹ showing 100% occlusion in only 25% of coil-treated aneurysms to studies done by Raymond et al. in 2003 ² and Mejdoubi et al. in 2006, ³ showing > 95% occlusion in > 90% of coil-treated aneurysms. Coil embolization treatment of cerebral aneurysms with endovascular therapy has grown in popularity in U.S. and European centers.

  
  
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  Aneurysm recurrence rates after coiling of unruptured aneurysms vary from 15% to 26.5% in the analysis of studies such as the Analysis of Treatment by Endovascular Approach of Nonruptured Aneurysms (ATENA). Factors leading to increased risk of recurrence include neck width > 4 mm, overall sac size (< 3 mm vs. > 3 mm), and presence of intrasaccular thrombus.

  
  
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  In addition, data from the International Study of Unruptured Intracranial Aneurysms (ISUIA) indicate that the rate of cumulative adverse outcomes including stroke and death for endovascular coiling was 9.3%, compared to 13.7% for surgical clipping.

Indications

After ISAT demonstrated equivalent results with coiling for ruptured cerebral aneurysms, the indications for aneurysm coiling increased. Ruptured and unruptured aneurysms may be amenable to endovascular therapy. Indications to treat cerebral aneurysms include risk assessments based on patient history, life expectancy, and location and size of the aneurysm. This has been supported by ISUIA and the 2016 Japanese Small Unruptured Intracranial Aneurysm Verification (SUAVe) study, which evaluated the treatment of small (≤ 5 mm) unruptured aneurysms. In addition, changes to aneurysm size and shape may indicate the need to treat. Typically, aneurysms amenable to primary coiling include a favorable neck-to-dome ratio, such as aneurysms with narrow necks of < 4 mm, saccular domes, and more proximal locations. Patients with posterior circulation aneurysms have demonstrated favorable outcomes with endovascular therapy, and these aneurysms may be more approachable via endovascular therapies.

Neuroendovascular Anatomy

The internal carotid artery (ICA) is divided into seven segments. The last three are intradural and can give rise to cerebral aneurysms. The cavernous and carotid cave typically form aneurysms that remain within the cavernous segment, but understanding the relation of the aneurysm to the distal dural ring becomes important when making a risk assessment for subarachnoid hemorrhage risk over a patient’s lifetime. (If the aneurysm is proximal, it has a low rate of subarachnoid hemorrhage because it is outside the dura.) The ophthalmic segment and communicating segments provide the two most common sources of intracranial aneurysms arising from the ICA. The ICA bifurcation leads to the anterior cerebral artery and middle cerebral artery (MCA) branches. According to Yasargil and Rhoton’s understanding of aneurysm formation, aneurysms tend to arise from bifurcations and thus typical locations include the anterior communicating artery, the MCA bifurcation, pericallosal artery, and posterior communicating artery. In the posterior circulation, the basilar terminus and posterior inferior cerebellar artery origin are the two most common sites that require angiographic evaluation.

Periprocedural Medications

No overt periprocedural medication regimen is required for aneurysm coil embolization. Typically, patients are placed on aspirin, 325 mg daily postoperatively, as an adjunct therapy to prevent platelet aggregation and thrombus formation. If there are concerns for coil extrusion, dual antiplatelet therapy with clopidogrel, 75 mg daily for 3–6 months, can be considered. Dual antiplatelet therapy is typically not indicated for primary aneurysm coiling. If stent-assisted coiling is suggested, this therapy may become a consideration.

Systemic heparinization is administered during the procedure because of the inherent risk of intraprocedural thrombus formation. A weight-based intravenous bolus of heparin aimed at an activated clotting time (ACT) of 250–300 s may limit thromboembolic complications. For acute thrombus formation during the procedure, a glycoprotein IIb/IIIa inhibitor (e.g., eptifibatide) is utilized. Administration of half of a dose of heparin is typically instituted in settings of acute subarachnoid hemorrhage after the first coil deployment.

Specific Technique and Key Steps

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   A 6 or 8 French (F) sheath is inserted in the femoral artery.

   
   
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   After a femoral angiogram has been performed to confirm the absence of any irregularity or dissection, a guide catheter is advanced over a curved microwire (0.035-inch angled Glidewire, Terumo) into the aorta. This maneuver is completed under fluoroscopic guidance.

   
   
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   Depending on the arch anatomy, the guide catheter can be advanced directly over a 0.035-inch angled Glidewire or advanced over a 4–5F intermediate diagnostic catheter, such as a Vitek (Cook Medical) or Berenstein (Cook Medical) catheter. Utmost care should be taken to prevent the microwire, diagnostic catheter, or guide catheter from crossing the stenotic lesion.

   
   
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   Cerebral angiography is performed to obtain a baseline set of images of the intracranial vasculature. Three-dimensional digital subtraction angiography with rotational spins can be performed and evaluated to determine the best working angles prior to microcatheter access ( Fig. 23.1–23.11, Video 23.1–23.11 ).

   
   
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   Under roadmap guidance, the microcatheter is advanced over the microwire and advanced to the aneurysmal neck ( Video 23.1–23.11 ).

   
   
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   The wire is used to cross the aneurysm, and the microcatheter is advanced past the aneurysm. The wire is brought back into the catheter tip, and the catheter is slowly pulled back until it clicks into the aneurysmal dome, as with posterior communicating artery aneurysms ( Fig. 23.6, 23.7, Video 23.6, 23.7 ) or anterior communicating artery aneurysms ( Fig. 23.4, 23.5, Video 23.4, 23.5 ). Another option is to use the microwire to navigate directly into the aneurysmal dome.

   
   
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   Using a push–pull technique, the microwire is stabilized as the microcatheter is advanced into the dome of the aneurysm.

   
   
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   Optimal microcatheter position is obtained when the tip of the catheter is two-thirds of the way into the aneurysm dome.

   
   
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   Framing coils are selected based on aneurysm size and gently advanced into the dome. After the first break (i.e., the first turn of the coil, part of the natural point at which the coil will turn), coil location is verified. Angiographic runs are obtained after coil deployment to confirm position and prior to softer packing coils ( Video 23.1–23.11 ).

   
   
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    In unruptured settings, patients are fully heparinized with a goal-ACT of 250–300 s. In ruptured settings, half-dose heparin is administered after the deployment of the first framing coil.

    
    
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    After the final coil is detached, the coil pusher wire is slowly withdrawn under fluoroscopic guidance to confirm detachment.

    
    
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    If the coil pulls back, detachment is attempted again.

    
    
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    The pusher wire is then exchanged out over the microcatheter to advance the last coil remnant further into the dome and prevent coil extrusion.

    
    
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    A final (i.e., control) cerebral angiogram is always recommended to assess for smooth synchronized perfusion, looking specifically for delayed capillary filling or other larger occlusion (vessel dropout).

Device Selection

In the authors’ and editors’ practice, the following are common set-ups and devices used for aneurysm coil embolization:

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  6 or 8F sheath.

  
  
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  6F guide catheter (i.e., Envoy DA XB, Codman Neuro or Benchmark, Penumbra).

  
  
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  0.035-inch angled Glidewire.

  
  
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  Intermediate 5F-diagnostic catheter (Vitek).

  
  
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  Microcatheter:

  
  
  
  
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    Ruptured: typically choose softer tip catheters to be able to visualize and feel coil kickback (SL-10, Stryker Neurovascular; Prowler 4, Codman Neuro) ( Fig. 23.3, Video 23.3 ).

    
    
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    Unruptured: may warrant a stiffer catheter to be able to push into the dome of aneurysm and coil more effectively (Prowler Select Plus, Codman Neuro; XT 17, Stryker Neurovascular; Headway DUO, MicroVention).

  
  
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  Microwire (Synchro 2, Stryker Neurovascular; Synchro 10, Stryker Neurovascular; Transcend, Stryker Neurovascular).

Pearls

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  Catheter selection is paramount. Selecting a softer catheter, such as an SL-10, in ruptured settings may give the surgeon enough tactile and visual feedback to know that a coil is offering significant resistance and should be redeployed. This may prevent intraoperative rupture.

  
  
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  When guide catheter runs are being performed between coil deployments, tighten the rotating hemostatic valve around the microcatheter to prevent it from moving.

  
  
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  A balloon contingency or coiling contingency should be planned in case of intraprocedural rupture.

  
  
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  During coiling, the proximal marker on the coil becomes crucial, especially in relation to skull base landmarks. The proximal marker will serve as a primary marker for the surgeon to visualize pressure while coiling as well as how well the microcatheter tip is painting (i.e., moving back and forth) the coil inside the aneurysmal dome. Maintaining a slow but steady cadence is important when filling the aneurysm dome, and appropriate sizing of framing coils can play an important role in this cadence ( Video 23.1–23.11 ).

  
  
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  When navigating the microcatheter into the aneurysm dome, make sure to prevent the microcatheter from buckling proximally as this may indicate that potentially hazardous force is developing proximally in the microcatheter. Reducing this redundancy prior to selective catheterization the aneurysm is important.

References

Case Overview: CASE 23.1 Cavernous Internal Carotid Artery Aneurysm: Primary Coiling

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  A 43-year-old male presented to the emergency department with acute onset of transient diplopia. On physical examination, he was found to have a left sixth nerve palsy; the rest of his neurological exam was normal. His past medical significant history was relevant for ulcerative colitis. His father died of a ruptured intracranial aneurysm. He is currently taking no medications.

  
  
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  Computed tomography was normal. CT angiography demonstrated a left cavernous internal carotid artery (ICA) aneurysm.

Tips, Tricks & Complication Avoidance

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  Microcatheterization of cavernous or paraclinoid ICA aneurysms, especially on the dorsal wall of the ICA, can be challenging because of the curvature of the carotid syphon. Shape the tip of the microwire as needed (e.g., “tight J,” “pig-tail” shape) to obtain the proper angulation to access the aneurysm.

  
  
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  A 45° or 90° angle microcatheter is an alternative for easier aneurysm access.

  
  
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  Because of the proximal location of these aneurysms, there is rarely the need for an intermediate catheter, as long as the guide catheter is at or near the petrous ICA segment.

Case Overview: CASE 23.2 Internal Carotid Artery Terminus Aneurysm: Primary Coiling

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  A 57-year-old male presented to the emergency department with possible transient ischemic attack. Neurological examination was normal. He had a past medical history significant for hypertension and coronary artery disease and recent coronary stenting. Patient has been on dual antiplatelet therapy (aspirin and clopidogrel).

  
  
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  Computed tomography was normal with no evidence of subarachnoid hemorrhage. CT angiography demonstrated a right internal carotid artery (ICA) terminus aneurysm.

Tips, Tricks & Complication Avoidance

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  The majority of the bifurcation aneurysms are not centered at the bifurcation, they are rather off to one side of the bifurcation arteries.

  
  
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  The use of an intermediate catheter helps by stabilizing the endovascular construct, reducing “snaking” of the microcatheter and facilitating aneurysm catheterization. We do not advocate the use of an intermediate catheter for all bifurcations cases, only when necessary.

  
  
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  For ICA bifurcation aneurysms, usually a straight microcatheter with no angulation is adequate and sufficient.

Case Overview: CASE 23.3 Very Small Ruptured Anterior Cerebral Artery Aneurysm: Primary Coiling

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  A 35-year-old male presented to the emergency department complaining of the “worst headache of his life.” Neurological examination was normal, no focal deficits. He had no significant past medical history. Patient was not taking any medications.

  
  
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  Computed tomography (CT) demonstrated diffuse subarachnoid hemorrhage. CT angiography demonstrated a very small (2 mm) aneurysm on the dorsal wall at the junction of the internal carotid artery (ICA) and anterior cerebral artery (ACA).

Related posts:

30 Endovascular Vasospasm Treatment 24 Balloon-Assisted Coiling 27 Intrasaccular Flow Diverter for Intracranial Aneurysms (WEB) 29 Aneurysm Embolization with Liquid Embolic Agents 28 Novel Aneurysm Neck Reconstruction Devices Part V Intracranial Aneurysms

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