Intraoperative Rupture and Parent Artery Injury During Aneurysm Surgery

Abstract

Intraoperative rupture during surgery to clip intracranial aneurysms is an inevitable, but manageable occurrence. Myriad patient and anatomic factors, as well as surgical missteps, increase the risk of intraoperative rupture or parent artery injury. Strict patient selection for surgery over endovascular treatment mitigates the risk of rupture. Once intraoperative rupture of an aneurysm occurs, calmness under pressure and the decisive application of corrective techniques allow the surgeon to limit bleeding, and then visualize and definitively clip the aneurysm to maximize the likelihood of favorable outcome.

Keywords

intracranial aneurysm, aneurysm clipping, complication, intraoperative rupture

Highlights

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Intraoperative rupture during intracranial aneurysm surgery is a stressful but manageable event.
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Successful management of intraoperative rupture requires the operator to stay calm and employ steps to clear the field of blood, limit continued bleeding, and clip the aneurysm.
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The neurologic outcome after aneurysm surgery complicated by intraoperative rupture is related to the reaction of the surgeon. If the surgeon rushes to blindly place clips on the aneurysm before the aneurysm is sufficiently dissected in an attempt to stop heavy bleeding, the tear may be made worse or the parent vessel may be irreparably damaged.

Background

As the proportion of intracranial aneurysms (IAs) treated by endovascular therapies rises, surgically treated patients will harbor more complex aneurysms. Although the role of open microsurgical treatment of IAs remains, trainees and younger vascular neurosurgeons will be less experienced than their mentors. Experience is the ultimate tool in the surgeon’s armamentarium to avoid complications and mitigate their potentially deleterious effects. Vascular neurosurgeons must develop strategies to hone microsurgical skills to keep the surgical treatment of IAs minimally disruptive in the combined microsurgical and endovascular era.

Intraoperative rupture (IOR) and/or parent vessel injury (PVI) are among the most nerve-wracking and potentially devastating complications in the treatment of IAs. IOR occurs in as many as one-third of cases of microsurgically treated IAs and is more common when operating on ruptured aneurysms. Aneurysm size, location, and morphology and the adherence of the fundus to surrounding structures are associated with IOR. Patient outcomes after IOR are varied. Rupture before opening the dura or arachnoid dissection is predictive of unfavorable outcomes. Surgeon experience has been shown to have no effect on the rate of IOR, but it is positively associated with improved outcomes, indicating “mental anticipation and technical repetition over time transform into efficiency, confidence and insight in the management of [IOR].” IOR is inevitable; however, with adequate preparation and calm and decisive action, the surgeon can limit the possibility of IOR but also effectively manage the rupture while mitigating complications.

Anatomic Insights

Comprehensive understanding of the anatomy of IAs is imperative for prevention and management of IOR/PVI. The location of the aneurysm within the intracranial circulation determines the safest and most easily accessed sites of proximal control. The size and geometry of the aneurysm drive clipping strategy may increase the risk of IOR or PVI, and can dramatically influence the surgeon’s ability to safely apply clips without injuring or occluding the parent artery, nearby perforators, or en passage vessels. Specific anatomic insights are noted throughout the ensuing text where appropriate.

Prevention

Prevention of IOR begins with patient selection. Surgical treatment of IAs is higher risk in many patient populations, including the elderly, those with multiple medical comorbidities, and those with subarachnoid haemorrhage and poor neurologic status or vasospasm. Atherosclerotic neck calcification makes IA surgery more difficult. Certain aneurysms are better treated endovascularly. With the advent of flow diversion, many surgically challenging IAs are successfully treated in this manner with less risk. Ultimately, patient selection is the first line of defense against any surgical complication, including IOR.

Adequate bony exposure and a craniotomy that provides the most direct route to the aneurysm limit the need for brain retraction and provide adequate proximal control and maximal degrees of freedom to maximize clip application angle ( Fig. 9.1 ). The pterional craniotomy is the workhorse of cerebrovascular surgery. When completed appropriately, the pterional approach provides a direct working corridor to most anterior circulation aneurysms as well as aneurysms that arise from the basilar artery apex (BAA) and superior cerebellar artery (SCA) origin. The entire anterior sylvian fissure is exposed, and the need for brain retraction is limited if the lesser wing of sphenoid is drilled completely flat. The modified orbito-zygomatic approach is sometimes necessary to visualize the BAA and distal basilar artery when the BAA is above the level of the posterior clinoid. A “half-and-half” approach provides the most versatile combination of angles of attack for many BAA and SCA aneurysms. In addition to performing a standard pterional craniotomy, the squamosal temporal bone is drilled flush with the floor of the middle fossa in the half-and-half approach, thereby granting access to the BAA through the optico-carotid cistern or oculomotor triangle, a subtemporal approach, or a combination. Liberal drilling of the occipital condyle provides wide exposure to visualize posterior inferior cerebellar artery (PICA) aneurysms.

Meticulous arachnoid dissection is vital in the prevention of IOR/PVI. Adequate dissection of the arachnoid releases cerebrospinal fluid (CSF) from the cisterns. Egress of CSF in addition to administration of osmotic diuretics provides brain relaxation sufficient to limit the need for fixed retractors, which not only cause white matter injury, but also may lead to a tear in the dome of an aneurysm that is adherent to surrounding brain if retraction is overly aggressive. Microdissection should be completed sharply whenever possible, particularly when dissecting the neck of an IA. Forceful or blind blunt dissection of the neck of the aneurysm, the parent artery, and surrounding structures increases the risk of IOR/PVI.

Temporary clipping of the parent artery proximal to the inlet of an IA softens the aneurysm and can make final dissection and clip application safer. Temporary clipping is particularly useful in the setting of large or turgid aneurysms or for aneurysms where the orientation of the aneurysm neck and the origin of branch vessels, small perforating arteries, or surrounding cranial nerves is complicated and extensive dissection is required to define the anatomy. The surgeon must be mindful of the duration of parent vessel temporary occlusion to limit the possibility of irreversible ischemic injury. Several strategies can be employed, typically in concert, to protect the brain during temporary clipping, including hypothermia and pharmacologic burst suppression to limit metabolic demand from ischemic brain, and induced hypertension to maximize pial collateralization to the ischemic territory.

Modern aneurysm clips are available in a wide range of sizes and configurations, which makes clipping of IAs a versatile and durable treatment. Selection of the permanent clip(s) can have a profound effect on the likelihood of IOR/PVI. The risk of IOR increases each time an aneurysm clip is removed and reapplied. The most parsimonious combination of clips to completely occlude the IA should be used. The long axes of clip application and the parent vessel should be aligned as well as possible. Application of an aneurysm clip(s) parallel to the long axis of the parent artery limits stress on the arterial wall at the neck and increases the likelihood that the entire neck is obliterated, which limits the need for additional clip application. Additionally, angled, bayonetted, and right-angle clips all have lower closing force than straight clips and may lead to incomplete occlusion. A well-thought-out, simple clipping strategy, executed deftly, maximizes the potential for complete occlusion and limits manipulation of the aneurysm, IOR, and PVI. Overall, IOR is better prevented than managed. Although IOR is inevitable, keeping to the principles of cerebrovascular surgery will limit the risk.

Red Flags

Patient-related:
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  Atherosclerotic vessels
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  Large and giant aneurysms
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  Blister aneurysms
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  Adherent en passage vessels
Surgeon-related:
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  Inadequate exposure
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  Failure to gain proximal control
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  Clipping perpendicular to the long axis of the parent vessel
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  Blind clipping
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  Blunt arachnoid dissection
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  Aggressive brain retraction