Abstract
The treatment of intracranial aneurysms, whether surgical or endovascular, is associated with various types of potentially catastrophic procedure-related complications. These complications include intraprocedural rupture, thromboembolic events, coil migration or prolapse into the parent artery, and aneurysm recurrence that requires further management. The highest complication rates are for treatment of ruptured aneurysms, with intraprocedural rupture more common in endovascular techniques using balloon-assisted and stent-assisted coiling. Using imaging studies to carefully study the anatomic characteristics of the aneurysm and its relationship to the parent vessel can inform preoperative and intraoperative decision-making and treatment. Complications are likely to be more manageable with appropriate selection of treatment, awareness of potential complications, immediate recognition of complications, and familiarity with salvage and adjuvant techniques.
Keywords
aneurysm, coiling, complications, endovascular treatment, intraprocedural rupture, recanalization, recurrence, thromboembolism
Highlights
- •
Endovascular techniques continue to evolve and are increasingly applied to more complex aneurysms.
- •
Potential devastating complications include intraprocedural rupture and rerupture, thromboembolic events, coil prolapse and migration, and aneurysm recurrence.
- •
Certain aneurysms are associated with higher rates of complications because of specific aneurysm characteristics and anatomy.
- •
Patient outcomes are improved by knowing how to help prevent complications, how to recognize them immediately when they occur, and how to utilize salvage techniques.
Background
The prevalence of intracranial aneurysms is about 3%, with the incidence of aneurysm subarachnoid hemorrhage (SAH) estimated to range from 10 to 15 cases per 100,000 people. Both surgical and endovascular techniques are available for aneurysm treatment. Factors that should be considered when selecting an intervention include patient presentation (e.g., ruptured vs unruptured aneurysm, patient age, comorbidities), anatomic considerations (e.g., aneurysm size, location, morphology), and surgeon expertise. Studies have demonstrated clinical equipoise regarding endovascular coiling and open surgery for treatment of intracranial aneurysms. However, as endovascular interventions continue to evolve, they are increasingly used for more complex aneurysms and have provided neurointerventionalists with an ever-expanding repertoire of technologies and techniques.
With the broader use of endovascular interventions has come an increased potential for devastating complications. We discuss the most common complications, their risk factors, and complication management strategies.
Potential Complications
The most common and clinically significant complications of coil embolization of intracranial aneurysms are hemorrhage from intraprocedural rupture and rerupture, ischemia from thromboembolic events, coil migration and prolapse of coils into the parent vessel, and aneurysm recanalization. A 2016 metaanalysis found a 12% overall complication rate for the coiling of intracranial aneurysms.
Intraprocedural Rupture and Rerupture
Intraprocedural rupture and rerupture are serious and potentially devastating complications that result in a substantial increase in overall morbidity and mortality. In the Analysis of Treatment by Endovascular Approach of Nonruptured Aneurysms (ATENA) study, the rate of intraprocedural rupture for unruptured aneurysms was 2.6% (18 of 700 procedures). The intraprocedural rate for ruptured aneurysms was somewhat higher in the Clinical and Anatomic Results in the Treatment of Ruptured Intracranial Aneurysms (CLARITY) study, which found the risk to be 3.7% (15 of 405 patients). Rates of intraprocedural rupture are likely higher in patients with ruptured aneurysms because of a preexisting decrease in aneurysm wall strength and because of aggressive coiling of ruptured aneurysms in an attempt to achieve tighter coil packing.
With the increasing use of newer endovascular techniques, including balloon-assisted coiling (BAC) and stent-assisted coiling (SAC), intraprocedural rupture remains a potentially catastrophic complication. Although Sluzewski et al. demonstrated a higher rate of intraprocedural rupture with BAC (4%; 3 of 71) than with coiling alone (0.8%; 6 of 756) in their 2006 study, Pierot et al. later demonstrated in 2011 that intraprocedural rupture rates are similar for BAC (4.4%; 7 of 160) and conventional coil embolization (4.6%; 28 of 608). Likewise, there appears to be no significant difference in intraprocedural rupture risk between SAC and traditional coil embolization. An important consideration is that SAC has been reserved primarily for patients who have not had a rupture because of the required use of antiplatelet therapy after stent deployment; the use of antiplatelet therapy can complicate the management of intracranial aneurysms when there is an intraprocedural rupture.
Thromboembolic Events
As with an intraprocedural rupture, ischemia from a thromboembolic event can be a potentially catastrophic event. The rates of ischemic events resulting from the endovascular treatment of unruptured and ruptured aneurysms were 7.3% (29 of 398) in the ATENA study and 13.3% (54 of 405) in the CLARITY study. The use of the SAC technique and the use of flow diverters are associated with a higher risk of ischemic events than the use of traditional coil embolization. This increased risk is likely a result of the permanent placement of a foreign object in the parent vessel. Although there is an obvious need for antiplatelet therapy upon the deployment of these devices, the optimal timing, regimen, and generalized standard of care have not been well established. Fortunately, many of the patients who experience thromboembolic events are generally asymptomatic or have only transient neurologic deficits; however, others have significant neurologic complications, and these ischemic events are associated with an overall increased morbidity and mortality.
Coil Migration and Prolapse Into Parent Vessel
One of the many advantages of modern coils and delivery systems is that they allow the delivery, repositioning, and evaluation of the placement of coils in the aneurysm before detachment. In most cases, a suboptimally placed coil can be removed or repositioned before final deployment. However, these coils can still protrude from the aneurysm sac into the parent vessel after deployment, and they can become intertwined with other coils or stents. The attempted removal of such coils can result in the coil stretching, unraveling, and breaking. The consequences of coil migration or prolapse range from asymptomatic flow alterations in the parent artery to devastating thromboembolic occlusion of major intracranial vessels and subsequent large territory infarcts. Depending on the site of coil breakage, pieces of coil may be carried into distal cerebral or even systemic blood vessels, creating a potentially dangerous thrombogenic mass. Data from a meta-analysis examining multiple series indicate that the incidence of cases with coil migration ranges from 2% to 6%. Another potential consequence of coil migration is the need for long-term systemic antiplatelet medication to reduce the risk of thromboembolism, which carries its own inherent risks, particularly in cases of ruptured aneurysms.
Aneurysm Recanalization
With the continued establishment of endovascular techniques as the first-line treatment for intracranial aneurysms, one of the greatest concerns is the observed rate of aneurysm recanalization after treatment. Recanalization may result in aneurysm rupture or rerupture. A recent meta-analysis reported a recanalization incidence of 8% to 33.6% after endovascular treatment, and another study reported a retreatment rate of 10.3% (572 of 5582) of all aneurysms because of recanalization. Although numerous small case series studies have attempted to elucidate factors associated with aneurysm recanalization, no definitive conclusions have emerged. A prospective trial designed to help determine predictive factors associated with aneurysm recanalization recently completed patient enrollment (ARETA; NCT01942512).
Anatomic Insights
A key component of preoperative and intraoperative decision-making and treatment execution for cerebral aneurysms is the careful study of the anatomic characteristics of the aneurysm and its relationship to the parent vessel. Certain characteristics (e.g., neck size, dome size, location, parent vessel angle, and rupture status) have been demonstrated to correlate with rates of complications after endovascular intervention ( Fig. 40.1 ).
Wide-Neck Aneurysms
Numerous studies have identified wide-neck aneurysms, which are typically defined as aneurysms with a neck diameter >4 mm, as having an increased risk of complications when treated by endovascular techniques. These complications include thromboembolic events and intraoperative rupture.
In addition to the absolute size of the aneurysm neck, the relative size of the neck is also an important anatomic characteristic of the aneurysm. A relatively wide neck, as calculated by the aneurysm dome-to-neck ratio (i.e., dome width to neck width) and by the aspect ratio (i.e., dome height to neck width), correlates with the need for adjunctive techniques during endovascular treatment.
Aneurysm Dome Size
The size of the aneurysm dome has also been associated with adverse effects of endovascular treatment; however, its relationship to complication rates is complex. Some studies have demonstrated that, unlike smaller lesions, large aneurysms (>10 mm) carry a higher risk of treatment-related thromboembolic events and overall greater rates of periprocedural morbidity and mortality. Aneurysms >10 mm have also been associated with an increased risk of revascularization and the need for retreatment. However, other studies have demonstrated that small aneurysms (<4 mm) carry a greater risk of procedural rupture or rerupture.
Aneurysm Location
Aneurysm location may be associated with the risk of complications after endovascular interventions; however, this relationship has not been fully elucidated. Some authors have reported higher rates of complications, including thromboembolic events and intraprocedural rupture, with middle cerebral artery aneurysms than with aneurysms in other locations. Other authors have demonstrated that posterior circulation aneurysms carry an increased risk of retreatment or that there is no correlation between location and risk.
Parent Vessel Angle
Fan et al. reported that a small parent vessel angle (<60 degrees) is associated with thromboembolic complications. They postulated that these complications may result from increased microcatheter instability and that repeat catheterization may cause endothelial injury and thrombi.
Ruptured Aneurysms
Aneurysms treated after rupture and SAH are associated with higher complication rates than those for unruptured lesions or aneurysms treated electively. Complications include intraprocedural rerupture, recanalization, thromboembolism, and procedural morbidity and mortality. Two possible reasons for higher rates of intraprocedural rerupture are decreased aneurysm wall strength and aggressive coiling of ruptured aneurysms to achieve tighter coil packing.
- •
Unfavorable aneurysm characteristics or anatomy (e.g., wide neck, very large or small dome, middle cerebral artery location, small parent vessel angle)
- •
Unfamiliarity with indicated technique
- •
Insufficient medical management of SAH sequelae
- •
Multiple medical comorbidities and challenging aneurysm anatomy for elective cases
Prevention
Prevention remains the most effective strategy for management of endovascular complications. It requires appropriate preoperative care, selection of the patient and technique, understanding and acknowledgment of device and personal capabilities and limitations, and meticulous study of anatomic information from both preprocedural and intraprocedural imaging studies.
Preoperative Care
For ruptured aneurysms, preprocedural stabilization with appropriate resuscitation, blood pressure and comorbidity management, neurologic monitoring, and possible external ventricular drain placement with intracranial pressure monitoring can improve both periprocedural and overall morbidity and mortality. Patients with aneurysmal SAH treated by experienced and multidisciplinary medical staff have improved overall outcomes.
Patient Selection
Nearly all patients with aneurysmal SAH should be considered for intervention, and patients with unruptured aneurysms who opt for elective intervention should be counseled on their risks based on patient-specific factors, such as family history and comorbidities. Certain comorbidities, such as smoking and hypertension, increase the likelihood of complications during endovascular surgery. Older age of patients undergoing endovascular treatment for cerebral aneurysms does not significantly increase the risk of complications ; however, some authors have reported a higher rate of complications in the elderly.
Intervention Selection
Like appropriate patient selection, optimal intervention selection based on the natural history of the disease and aneurysm anatomy must be considered. Doing so helps decrease complication rates and helps improve overall outcomes.
In elective treatment of wide-neck aneurysms or in other cases requiring the use of SAC or a flow diverter, initiation of antiplatelet therapy before the procedure may help reduce the likelihood of periprocedural thromboembolic events. Antiplatelet therapy regimens differ among institutions. We typically initiate dual antiplatelet therapy with clopidogrel and aspirin 10 to 15 days before the procedure and then assess the patient for platelet inhibition during preoperative testing. If patients were not pretreated but required dual antiplatelet coverage, we successfully used intraoperative intravenous and intra-arterial administration of abciximab, followed by postoperative aspirin and clopidogrel. Our group recently showed that this strategy was not associated with an increased risk of perioperative thromboembolic complications. Both SAC and BAC have been demonstrated to be safe and effective techniques for technically challenging wide-neck aneurysms, resulting in improved obliteration and decreased recurrence or progression. SAC has also been used for ruptured aneurysms with encouraging results. The optimal antiplatelet therapy strategy for these challenging cases and the implications for traditional SAH treatments (e.g., timing of external ventricular drain placement) remain to be fully elucidated.
Flushing catheters with heparinized saline to prevent formation of microthrombi that can subsequently embolize helps reduce the rates of thromboembolism. For unruptured lesions, we systemically heparinize all patients for the duration of the procedure, with no protamine sulfate reversal unless bleeding complications occur. Ruptured lesions are systemically heparinized just before intracranial microcatheterization, with protamine readily available in the angiography suite for rapid reversal in case of intraoperative rupture. This practice is not universal, and some surgeons prefer to hold systemic anticoagulation until partial dome protection is achieved.
Operator Ability
Microsurgical or endovascular treatment options are available for most intracranial aneurysms. Selecting the right treatment, for the right aneurysm, for the right patient is the first step in minimizing complications and improving outcomes. Complication rates have been associated with advanced endovascular techniques, and improved outcomes have been strongly correlated with experience, reflecting a learning-curve effect. As with all aspects of neurosurgery, understanding one’s own limitations and feeling comfortable with specific pathologies and techniques are crucial to providing appropriate patient care, especially for elective cases. For neurointerventionalists, this treatment selection process includes recognizing that open clipping will sometimes be the superior choice.
Related posts:
Medical Complications in Neurosurgery
Cerebral Vasospasm: Complications and Avoidance
Complications of Surgery for Pineal Region Tumors
Thalamic and Insular Tumors : Minimizing Deficits
Complications of Surgery for Peripheral Nerve Injuries and Tumors
Complications of Surgery for Intrinsic Spinal Cord Tumors
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
