The Operation for Intracranial Aneurysms in Children

Patient Positioning

• Position according to location of aneurysm: Positioning depends on the location of the aneurysm. However, a frontotemporal craniotomy or a lateral supraorbital craniotomy are the most common approaches and may involve supine positioning with slight head rotation and extension. General principles include elevating the head to maximize venous drainage, avoiding a bending occlusion 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 younger than 2 years, a pediatric head holder with four short pins or a padded headrest may avoid pin site fracture.

Surgical Approach

• Scalp incision and superficial approach: Large superficial vessels (e.g., temporal artery) should be preserved for possible extracranial-intracranial bypass. Note that blood loss-sparing surgical techniques are 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. In children, brain aneurysms may be associated with syndromes such as moyamoya or microcephalic osteodysplastic primordial dwarfism type II, or with tumors. In such cases, prior surgeries may introduce complications such as extradural-intradural collateral vessels limiting the availability of safe surgical corridors. The resulting modification of the craniotomy and approach to the aneurysm may risk damage to the cerebrovascular blood supply or previously injured tissues.
• Dural opening: When dealing with a ruptured aneurysm, dural opening must be performed only when preparations for clipping are complete, 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, consider intraoperative drainage of CSF from cisterns to allow better access. However, if the aneurysm has ruptured, caution is recommended in draining too much CSF as changes in transmural pressure can lead to re-rupture.

Intervention

• 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 based on the size and shape of the aneurysm neck and the presence of nearby structures (cranial nerves, other blood vessels, etc.) in the brain.
• 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 dissection around the neck or permanent clip application. In infants, or children with congenital dwarfism, the surgical corridor may be more limited; low-profile clips, single-shaft clip appliers, and modified craniotomy approaches may be required to successfully clip the aneurysm through narrower corridors.
• Bypass techniques or combined approaches: In selected cases (mainly involving complex aneurysms), aneurysm trapping with blood flow restoration might be indicated. The use of radial artery conduits (which can be harvested and used as high-flow bypass grafts) and extracranial-intracranial bypass techniques is possible (11,116).
• 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.
• Microsurgical treatment of infectious aneurysms: Occasionally, infectious aneurysms may be treated with open microsurgery. As direct clipping of these aneurysms is associated with considerable morbidity, the most common microsurgical approach is trapping and resection of the involved vessel segment with possible bypass (86,117).
• Microsurgical treatment of nontraumatic dissecting, giant, and traumatic aneurysms: It may be possible to treat nontraumatic dissecting and giant aneurysms with direct clipping or with trapping and bypassing (118). Traumatic aneurysms have been treated with clipping, trapping, wrapping, and extracranial-intracranial bypass (119). Parent vessel occlusion may be tolerated with lower risk of significant stroke and greater likelihood of long-term recovery from stroke in children than in adults.

Exposure and surgical clipping of a right MCA bifurcation aneurysm in a 14-year-old child with microcephalic osteodysplastic primordial dwarfism type II: (A) To assist with surgical planning, a 3D reconstruction of the cerebral vasculature was generated for this 14-year-old patient with microcephalic osteodysplastic primordial dwarfism type II, prior bilateral pial synangiosis for moyamoya arteriopathy, and growing right MCA bifurcation aneurysm (yellow arrow), right anterior choroidal aneurysm, and P2 aneurysm. (B) Exposure of the MCA bifurcation aneurysm (yellow arrow) was performed via supraorbital craniotomy due to the limitation of prior moyamoya revascularization pedicle from the lateral approach. (C) This image shows a temporary clip (yellow arrow) on the M1, the aneurysm, and an M2 branch below the aneurysm. After clip placement, the M2 branch was preserved.

Closure

• 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 increased.