Coil embolization of intracranial aneurysms, the LSUHSC-S experience.
The overall frequency of intracranial aneurysms in the general population ranges from 0.2% to 9.9% with the incidence of aneurysmal subarachnoid hemorrhage (SAH) varying from 6 to 21 cases per 100,000 per year. Once an intracranial aneurysm ruptures and causes SAH, it carries a 30-day mortality rate of 45%, with approximately 50% of survivors sustaining permanent, irreversible brain damage. (1) In the past, open surgical clipping was the only option for the management of these eventualities. However, the emergence of endovascular coiling as a safe and durable modality of treatment for ruptured intracranial aneurysms has provided physicians and patients an alternative to open brain surgery.
MATERIAL AND METHODS
We retrospectively reviewed our experience with endovascular management of aneurysms over a period of 18 months from July 2006 to December 2007. A total of 67 patients underwent 70 coil embolization procedures for 68 intracranial aneurysms. During the same time period 51 patients underwent surgical clipping. Of these 67 patients, only one patient underwent coil embolization for two different aneurysms and another underwent repeat coil embolization following recanalization. One patient underwent repeat embolization for a residual aneurysm. All patients included were consecutive. No patients were excluded from the study.
We reviewed the medical records and angiograms before and after treatment and analyzed demographic information, location of aneurysm, total occlusion rate, and complications following coil embolization of intracranial aneurysms. Patient charts were reviewed for complications including vasospasm, coil protrusion into parent vessel, intraprocedure rupture, catheter protrusion through dome, occlusion and thrombosis of parent vessel, stent occlusion, and recanalization. All procedures were performed by a single neurointerventional radiologist (MW) with patients under general anesthesia utilizing live simultaneous roadmapping. Continuous intravenous anticoagulation was maintained throughout procedures utilizing a 5000 unit intravenous bolus and 1000 units per hour for the duration of the procedure. Antiplatelet agents were begun three days prior to stent-assisted coiling procedures and continued for a minimum of three months post-procedure, preferably for life. Dosing included clopidogrel 75 mg and aspirin 325 mg daily for three days prior to or alternatively clopidogrel 300 mg and aspirin 325 mg on the morning of the procedure. Patients were continued on daily dosing of both agents for a period of three months post-procedure with discontinuation of clopidogrel and continuation of aspirin at three-month follow-up.
The presence of residual aneurysmal filling was determined at the end of each procedure. When the percentage of occlusion was 100% it was defined as complete occlusion and when the occlusion rate was >90% it was defined as near complete occlusion. The feasibility of coiling versus clipping was assessed by the senior author (AN) in conjunction with the endovascular team. Statistical analysis was performed with commercially available software (SPSS version 13). Chi square test was used to indentify any association among variables. A p value <0.05 was considered significant.
Mean patient age was 51 years (range 15-89 years). There was a slight female preponderance (58.2% vs 41.8%). The majority of the aneurysms that underwent coil embolization had ruptured (83.8%). Most of the aneurysms were located in the anterior circulation (77.9%). Posterior circulation aneurysms constituted only 22%. Aneurysm location in decreasing order of frequency was as follows: anterior communicating (ACOM) (36.8%) followed by posterior communicating (PCOM) (17.6%) and basilar artery (14.7%). Location of the aneurysms is summarized in Table 1.
Mean aneurysmal dome size was 5.9 mm (range 2-20 mm). The majority of the aneurysms that underwent coiling were small (<10 mm) in size (91.2%). Large aneurysms 11-25 mm) constituted only 8.8%. There were no aneurysms larger than 25 mm in this series.
Balloon and Stent-Assisted Embolization
Endovascular remodeling techniques were attempted in 21 procedures (30%). Of these, balloon remodeling was attempted in 10 (14%) and stent-assisted coiling was attempted in nine cases (13%). The remaining two procedures (2.8%), utilized both stent and balloon remodeling. Of these, one resulted in failed embolization, while the other resulted in successful occlusion.
Overall, complications were observed following endovascular embolization in 20 cases (28.6%). Minor complications included local vasospasm, occurring following five (7.1%) procedures. Of the cases involving coil protrusion into the parent vessel, there was evidence of non-occlusive thrombus in two (2.8%) with the remainder showing no evidence of thrombus. The lone case of aneurysmal puncture showed no evidence of extravasation of contrast post-embolization. Major complications included intra procedure rupture occurring during four procedures (5.7%) ,occlusion and thrombosis of parent vessel resulting in transient hemiparesis in one case, coil protrusion into the parent vessel, seen in six (8.5%) procedures and catheter protrusion through the aneurysm dome occurring in one (1.4%) case. The hemiparesis was resolved by Reopro bolus and subsequent infusion. All complications are summarized in Table 2.
Complications occurred following procedures involving embolization of anterior circulation aneurysms in 24% of cases, whereas complications were noted in 44% of posterior circulation aneurysms (Table 3). This trend for greater frequency of complications with posterior circulation aneurysms failed to reach statistical significance (p=0.126, Chi-Square).
Complete post-procedure aneurysm occlusion was achieved following endovascular embolization of 33 aneurysms (47%). Near-complete occlusion (>90%) was seen in 65 cases (91.4%). Residual small neck remnants were present in 23 cases (34.2%). The proportion of aneurysms with near-complete post-procedure occlusion was similar between anterior and posterior circulation aneurysms (54% and 50% respectively) (Table 4). There was no statistical association between location of the aneurysm and near-complete post-procedure occlusion (p=0.794, Chi-square). Binary logistic regression analysis was performed to look for predictors of complete occlusion. The variables that were included were location of aneurysms (anterior vs posterior circulation), size in mm and presence or absence of subarachnoid hemorrhage. Size in mm showed a trend toward being an independent predictor of complete occlusion (P=0.073, HR 0.809 CI 0.642-1.02).
In 1991, Guglielmi first published the use of detachable coils for the management of intracranial aneurysms in fifteen high risk intracranial aneurysms. (2,3) The FDA first approved detachable coils for inoperable or high risk intracranial aneurysms in 1994. (4) Biocompatible coils are composed of inert materials that allow for effective treatment without systemic host response. (5) Nitinol, platinum, nickel, iridium, and tungsten are the primary metals used in fabrication and are usually combined as alloys to ensure optimal strength. (5) A platinum (92%)/tungsten (8%) alloy has become the mainstay material for most current coil designs. In recent years there has been a significant change in the endovascular management of aneurysms including matrix detachable, hydrogel-coated and cercyte coils. In addition, development of techniques for balloon-and stent-assisted coiling of aneurysms have broadened the scope to include irregular and wide necked intracranial aneurysms. Generally, aneurysms with a dome-to-neck ratio of at least two and with an absolute neck diameter of less than 5 mm are the preferred aneurysms that can be treated by endovascular coiling. (6) Aneurysms located in posterior circulation are selected for endovascular approach as well. (7) Patients with poor neurological grade regardless of age undergo endovascular procedure. (7) Those with large intraparenchymal hematoma undergo evacuation of hematoma and surgical clipping at the same time. (7)
To Clip or Not to Clip?
With the establishment of reliable, reproducible endovascular occlusion techniques for increasingly more difficult aneurysm configurations, the conundrum for physicians becomes how best to treat aneurysms that are suitable for both modalities of treatment. The International Subarachnoid Aneurysm Trial (ISAT) was undertaken to compare the safety and efficacy of endovascular coiling compared with standard neurosurgical clipping techniques. (8) Published results showed significantly better outcome in terms of survival free of disability at one year with endovascular coiling. (8) These findings have led to a paradigm shift towards increasing focus on endovascular therapies. Subsequent reports published by the ISAT group in 2005 supported initial findings that patients harboring ruptured intracranial aneurysms suitable for either treatment showed greater likelihood of independent survival at one year with endovascular coiling than with the neurosurgical clipping. The survival benefit was shown to continue for a period of seven years. (9) ISAT has faced several criticisms based on site and patient selection bias, lack of extended follow-up and the comparative expertise of the surgeons and interventionalists. (10)
Unruptured Intracranial Aneurysms
Patients suffering aneurysmal SAH and those harboring incidental or symptomatic unruptured aneurysms represent two distinct patient populations, each with its own spectrum of comorbidities. Appropriate management of the later does not necessarily mirror that of the former. In a recent international study of unruptured aneurysms performed by Wiebers et al, the 5-year cumulative rupture rate for patients without a history of SAH with aneurysms located in the anterior circulation were 0% for aneurysms less than 7 mm, 2.6% for aneurysms 7-12 mm, 14.5% for aneurysms 13-24 mm and 40% for aneurysms 25 mm or greater. (11) As a comparison, aneurysms involving the posterior circulation including the PCOM showed rupture rates of 2.5%, 14.5%, 18.4%, and 50% respectively. Patients with unruptured aneurysms of less than 7 mm had the lowest rate of rupture. According to the authors, aneurysm site, size and natural history should be balanced on an individual basis with age-specific risks of the choice of repair. (11)
Komtor et al, in their recent literature review have recommended conservative management for unruptured aneurysms less than 5 mm. (12) Aneurysms larger than 5 mm in patients less than 60 years of age should be considered seriously for treatment, and aneurysms larger than 10 mm should be treated in all patients. Endovascular versus open surgical approach remains a decision to be made on a case by case basis.
Balloon Remodeling and Stent-Assisted Coil Embolization
The two important adjunctive techniques currently used to treat wide-necked aneurysm are balloon remodeling (13) and stent-assisted coiling. (14) The balloon remodeling technique involves a temporary inflation of non-detachable balloon over the ostium of the aneurysm neck during coil placement. Moret et al showed a 77% total occlusion rate in a series of 52 wide-neck aneurysms not amenable to standard coiling techniques. (13) Limitations of this technique include risk of thromboembolism and compromise of distal arterial flow. (15) However, a recent meta-analysis by Shapiro et al did not demonstrate a statistically higher incidence of thromboembolic events or iatrogenic complications when compared with unassisted coiling. (16)
For complex, wide-necked aneurysms, a stent may aid in packing of the aneurysm with Guglielmi detachable coils by acting as a rigid scaffold that prevents coil herniation into the parent vessel. (14) Limitations of this procedure include difficult stent placement in tortuous vessels and migration of the stent during the procedure. (15)
Intraoperative rupture during endovascular coil embolization is widely considered the most dreaded complication with a mortality approaching 100%. Brisman et al reported a 1% incidence of intraprocedure rupture in their series of 600 patients. (17) This would seem to compare favorably to the established rate in the literature of 2%-5%. (17) In our series, the incidence of intraprocedure aneurysm rupture was 5.7% and that of aneurysm perforation without contrast extravasation was 1.4%.
The literature reports the incidence of thromboembolic events following endovascular coiling to be from 4.4%-13.1%. (1) In our series, these complications were observed following four procedures (5.7%). Of these, two experienced coil protrusion into the parent vessel with non occlusive thrombus, one showed occlusion and thrombosis of the parent vessel with resulting transient hemiparesis, and one developed a thrombus following aneurysm rupture. The case of hemiparesis was resolved by Reopro bolus and subsequent infusion.
Kurre et al, in their review of 100 endovascular coiling procedures reported a procedure related mortality of 0.9%-3.5%. There was no mortality in our series.
Occlusion Rates-GDC Coiling
In a recent review by Raja et al, the endovascular groups reported total or near total occlusion in 25%-100% of patients with a mean of 77.6%. (18) In our series, complete post-procedure aneurysm occlusion were achieved following endovascular embolization in 33 cases (47%). Near-complete occlusion (>90%) was seen in 65 (91.4%). Our results appear to compare favorably with those published in the literature.
Our study at LSUHSC-S shows encouraging results with coil embolization for intracranial aneurysms and mirrors immediate post procedure near complete occlusion rates of approximately 90%.
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(9.) Molyneux AJ, Kerr RS, Yu LM, et al. International subarachnoid aneurysm trial (ISAT) of neurosurgical clipping versus endovascular coiling in 2143 patients with ruptured intracranial aneurysms: a randomised comparison of effects on survival, dependency, seizures, rebleeding, subgroups, and aneurysm occlusion. Lancet 2005;366:809-817.
(10.) Diringer MN. To clip or to coil acutely ruptured intracranial aneurysms: update on the debate. Curr Opin Crit Care Apr 2005;11:121-125.
(11.) Wiebers DO, Whisnant JP, Huston J, 3rd, et al. Unruptured intracranial aneurysms: natural history, clinical outcome, and risks of surgical and endovascular treatment. Lancet 2003;362:103-110.
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(13.) Moret J, Cognard C, Weill A, et al. Reconstruction technic in the treatment of wide-neck intracranial aneurysms. Long-term angiographic and clinical results. Apropos of 56 cases. J Neuroradiol 1997;24:30-44.
(14.) Lanzino G, Wakhloo AK, Fessler RD, et al. Efficacy and current limitations of intravascular stents for intracranial internal carotid, vertebral, and basilar artery aneurysms. J Neurosurg 1999;91:538-546.
(15.) Bendok BR, Hanel RA, Hopkins LN. Coil embolization of intracranial aneurysms. Neurosurgery 2003;52:1125-1130.
(16.) Shapiro M, Babb J, Becske T, et al. Safety and efficacy of adjunctive balloon remodeling during endovascular treatment of intracranial aneurysms: a literature review. AJNR Am J Neuroradiol 2008;29:1777-1781.
(17.) Brisman JL, Niimi Y, Song JK, et al. Aneurysmal rupture during coiling: low incidence and good outcomes at a single large volume center. Neurosurgery 2008;62:1538-1551.
(18.) Raja PV, Huang J, Germanwala AV, et al. Microsurgical clipping and endovascular coiling of intracranial aneurysms: a critical review of the literature. Neurosurgery 2008;62:1187-1202.
Raul Cardenas, MD; David Connor, DO; Vijayakumar Javalkar, MD; Michael Williams, MD; and Anil Nanda, MD, FACS
Drs. Cardenas, Connor, Javalkar, Williams, and Nanda are with the Louisiana State Health Sciences Center in Shreveport.
Table 1. Location of aneurysm. n % Supraclinoid ICA 7 10.3 ACA 1 1.5 ACOM 25 36.8 MCA 4 5.9 Paraclinoid ICA 2 2.9 PICA 2 2.9 PCOM 12 17.6 PCA 2 2.9 Vertebral 2 2.9 Basilar 10 14.7 Superior cerebellar 1 1.5 Total 68 100.0 ICA = internal carotid artery; ACA=anterior cerebral artery; ACOM = anterior communicating artery; MCA = middle cerebral artery; PICA=posterior inferior cerebellar artery; PCOM = posterior communicating artery; PCA = posterior communicating artery Table 2. Complications following 70 endovascular procedures. Anterior Posterior Complication n % circulation circulation Spasm 6 8.50% 3 3 Coil protrusion into 6 8.50% 3 3 parent vessel Intra procedure rupture 4 5.70% 3 1 Catheter protrusion 1 1.40% 1 0 through dome Occlusion and thrombosis 1 1.40% 1 0 of parent vessel Stent occlusion 1 1.40% 1 0 Recanalization 1 1.40% 1 0 Table 3. Comparison of complications following 70 endovascular procedures across anterior vs posterior circulation aneurysms. Complication yes no Total Anterior circulation N 13 41 54 % 24.1 75.9 Posterior circulation N 7 9 16 % 43.8 56.3 Total N 20 50 70 % 28.6 71.4 Table 4. Comparison of incomplete occlusion following 70 endovascular procedures across anterior vs posterior circulation aneurysm. Incomplete occlusion yes no Total Anterior N 29 25 54 circulation % 53.7 46.3 Posterior N 8 8 16 circulation % 50.0 50.0 Total N 37 33 70 % 52.9 47.1
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|Author:||Cardenas, Raul; Connor, David; Javalkar, Vijayakumar; Williams, Michael; Nanda, Anil|
|Publication:||The Journal of the Louisiana State Medical Society|
|Date:||Sep 1, 2010|
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