Procedure Planning

Review Imaging

• Computed tomography (CT) scan
  
  
  
  
  • Location and extension of SAH indicates the possible location of the aneurysm.
    
  • Presence of hydrocephalus indicates the need of an external ventricular drain (EVD). Presence of EVD requires special precautions during the procedure.
  
  
• CT angiogram
  
  
  
  
  • If available prior to diagnostic angiography portion of the procedure.
    
  • Analyze the size of the lesion particularly the size of the dome, neck, and its ratio. Sac/neck ratio < 2 indicates difficulty with coils placement and may indicate the need of stent or balloon assisted procedure.
    
  • Determine the dominance of the A1 vessel to select the preferred route for embolization.
    
  • Measure the diameters of the aneurysm to establish the size of the initial framing coil.
    
  • Establish the presence and measure the size of the vessels of the ACOM artery complex (A1, A2, and ACOM). These values are important if stenting is necessary and to evaluate the possible consequences of vessel sacrifice (i.e., high risk of stroke in ACOM artery embolization with hypoplastic contralateral A1).
    
  • Establish the direction of the dome and the neck of the aneurysm. ACOM aneurysms with necks directed purely perpendicular to the ACOM require special microcatheter shaping to improve stability.
  
  
• Angiogram
  
  
  
  
  • Cerebral angiogram should be performed prior to the coil embolization.
    
  • Observe the same characteristics described in the CT angiogram section.
    
  • Even if a CT angiogram has been obtained we recommend the confirmation of the aneurysms’ size, direction, and ACOM complex dimensions based on a transfemoral angiogram that is routinely performed at the beginning of the embolization procedure.

• There is no need for preprocedural intravenous (IV) antibiotics, dexamethasone, or mannitol.
  
• The patient’s maintenance anticonvulsants are continued.
  
• The authors recommend general anesthesia for the embolization of intracranial aneurysms to guarantee patient immobility during the aneurysm catheterization and embolization.
  
• Alert the anesthesia team of possible changes in the height of the angiographic bed, which affect the intracranial pressure (ICP) readings. We recommend, if the ICP is under control, not to drain cerebrospinal fluid (CSF) to avoid sudden reductions of ICP and risk of aneurysm re-rupture. If the ICP is elevated, careful drainage at a high pressure (15 to 20 cm H₂O) for short periods of time is advised.
  
• For unruptured aneurysms, heparin 5000 units IV should be initiated by the anesthesia team during the placement of the guide catheter in the internal carotid artery (ICA).
  
• For ruptured aneurysms, heparin 3000 to 5000 units IV should be initiated after the placement of the first (“framing”) coil.
  
• Heparin is repeated every hour at a dose of 1000 units IV during the procedure. The authors prefer to be notified by the anesthesia team before each dose.
  
• Blood pressure parameters
  
  
  
  
  • For unruptured aneurysms or patients with SAH with no vasospasm, keep systolic blood pressure (SBP) at baseline (120 to 140 mm Hg).
    
  • For patients with SAH with vasospasm, slightly higher SBP is tolerated (140 to 160 mm Hg).

Access

• Femoral puncture with Seldinger technique as for general angiography. Select the right common femoral artery if symmetric neurological exam. Select the artery of the side with neurological deficit if any. Before puncture confirm position with fluoroscopy (about the inferior border of femoral head) to avoid punctures above the inguinal ligament.
  
• Use a 6 French sheath. If tortuosity of the vessels (i.e., advanced age) is anticipated or stent assisted embolization is planned, the authors recommend use of a long 80 cm sheath that should be positioned under fluoroscopic guidance in the ICA selected for access, over a guide wire. (Do not pass the ICA origin if significant stenosis or atherosclerotic disease at this level.)
  
• Consider bifemoral approach if balloon assisted embolization is planned.

Cerebral Angiogram

• As described in the preoperative section.

Stent Deployment

• Please refer to the section with specific technical aspects in this regard.

• Advance an angled 6 French guide catheter to the selected ICA (dominant A1 side) if a long sheath has not been placed.
  
• Under roadmap guidance advance a microcatheter (10 or 14) to the dominant A1. The microcatheter size is selected in consideration of the size, shape, and directionality of the aneurysm. Large or giant aneurysms can be catheterized with microcatheters no. 14 or 18.
  
• Small aneurysms are challenging and require special considerations.
  
  
  
  
  • While a 10 microcatheter may be safer it can also be less stable and, therefore, inconvenient to obtain a complete embolization. In those cases the authors recommend to consider the orientation of the aneurysm neck. Aneurysms with necks directed toward the A1–A2 junction can be catheterized with microcatheters no. 10 or 14 with a simple angle tip shape. The authors recommend tailoring the tip shape for each case using steam instead of using preformed microcatheters. For aneurysms with the neck directed purely toward the ACOM the shape should have an S form that would improve the stability of the catheter in the a-com.
  
  
• In small aneurysms the authors recommend to enter the aneurismal sac very slowly. The removal of the micro–guide wire often produces rapid advancements of the microcatheter that should be avoided to prevent rupture. Alternatively, the microcatheter can be advanced over the micro–guide wire distal to the aneurysm neck, the micro-guide wire partially removed, and then slow traction of the microcatheter used to bring the microcatheter tip into the aneurysm lumen. In special cases of aneurysms smaller than 4 mm in diameter, it may be necessary to deliver the framing coil from the neck of the aneurysm.
  
• Be sure that an adequate position of the microcatheter is achieved before starting deployment of coils. It is preferable to change the shape of the microcatheter tip or the complete system if evidently unstable than to lose the position during the embolization. (It may be difficult to access the aneurysm again.)

Coil Embolization

• Select a first “framing coil” with a diameter that accommodate to the size of the aneurismal sac. The authors do not recommend to oversize the coil (increased risk of losing position and rupture) or undersize it (risk of embolization of parent artery in subsequent coils). For small aneurysm with necks directed toward the ACOM, standard or even soft coils may be necessary to avoid losing position in the aneurysm sac. For larger aneurysm or those oriented toward the A1–A2 junction, firmer coils can be used.
  
• Confirm patency of the parent arteries with an ICA angiogram before deployment.
  
• Continue embolizing the aneurysm with progressively smaller and softer coils until obtaining adequate packing.
  
• If the position is lost with partial embolization, attempts can be made to catheterize the aneurysm again. This often can be challenging specially for small aneurysms directed toward the ACOM—do not overdue it. If some protection of the aneurysm dome was obtained, this can be preferable to a procedural aneurismal ruptured.
  
• Reverse heparin at the completion of the procedure with protamine sulfate (1 mg IV per 100 units of heparin).

• Cerebral angiogram should be performed in different views and magnifications to confirm the embolization of the lesion and to evaluate for possible postoperative complications (i.e., embolic events, vessel dissection).
  
• The sheaths are removed and the puncture site closed with percutaneous closure devices (i.e., Perclose, Angio-Seal) or manual compression.