- Position according to location of aneurysm: Positioning is dependent on the location of the aneurysm. However, the most common situation will be supine positioning with the head rotated 30-45° and reclined 10° for a pterional approach. General principles include elevating the head to maximize venous drainage, avoiding kinking of cervical vessels, and allowing optimal access to the operative site for both the primary surgeon and the assistant.
- Rigid head fixation: Rigid head fixation is generally required for aneurysm surgery. In children under 2 years of age a pediatric head holder with 4 short pins or a padded headrest is recommended.
- Scalp incision and superficial approach: Large superficial vessels (e.g., temporal artery) should be preserved for possible extracranial-intracranial bypass. Moreover, blood loss sparing surgical technique is required in young children even at this early stage of the operation.
- Craniotomy: Craniotomy should provide easy access to the aneurysm and allow for proximal control of the vasculature. Usually refixation of the bone flap is planned. If a mass lesion is present and brain swelling is anticipated, a decompressive craniectomy might be indicated.
- Dural opening: When dealing with a ruptured aneurysm, dural opening must be performed only when everything is prepared for clipping, as intraoperative re-rupture might be encountered from this stage onward.
- Brain relaxation: In addition to the administration of mannitol and draining of CSF via an EVD or lumbar drain, intraoperative drainage of CSF from cisterns allows better access. If the aneurysm has ruptured, caution is recommended in draining off too much CSF as changes in transmural pressure can lead to re-rupture.
- Expose surrounding vessels: The neighboring vessels, parent vessel, and the aneurysm itself must be exposed to ensure accurate clip positioning and preservation of normal vasculature.
- Select clip: A suitable aneurysm clip is determined.
- Application of clip: The aneurysm clip is applied to the aneurysm’s neck. A temporary clipping might be used to reduce the blood flow to the aneurysm to assist in the permanent clip application.
- Bypass techniques or combined approaches: In selected cases (mainly in complex aneurysms), aneurysm trapping with blood flow restoration might be indicated. The use of radial artery conduits and extracranial-intracranial bypass techniques is possible (6).
- Assess patency of normal vessels: The patency of the parent and neighboring vessels as well as the complete occlusion of the aneurysm are verified by inspection, micro-Doppler sonography, and/or intraoperative ICG video angiography.
- Routine: Routine dural closure is performed. Since intraoperative opening of the cisterns is routinely performed in aneurysm surgery, the risk of CSF leak might be higher.