Coiling was accomplished in 75 aneurysms, but failed in 1. The aneurysms were treated by using single catheter , multi-catheter, balloon-assisted, stentassisted, and combination of multi-catheter and balloon-assisted technique (n=3). One patient died from consequence of subarachnoid hemorrhage (SAH) occurring 9 hours after coiling. One intra-procedural aneurysm rupture occurred, which was controlled by insertion of further coils and left no sequelae. There was 1 cortical and 1 basal ganglia infarction, but both recovered completely. Treatment-related permanent morbidity and mortality rates were 0% and 1.4%, respectively. Postembolization control angiography revealed 40 complete, 30 near-complete, and 5 incomplete aneurysm occlusions. Clinical follow-up was available in all surviving patients (mean, 23 months; range, 4 - 105 months) except for one who was lost to follow-up. There was no SAH, but 1 death from acute myocardial infarction. None of the remaining patients had neurological deterioration. Follow-up angiographies were available in 63 aneurysms at least once at 4 - 24 months (mean, 11 months). Three major and 6 minor recurrences were detected. All 3 major recurrent aneurysms could be re-treated by coiling without complication.
Conclusions: Using appropriate techniques and devices, most unruptured MCA aneurysms could be safely treated by coiling with acceptable outcomes.
INTRODUCTION
Since intracranial subarachnoid aneurysm trial (ISAT),[1] endovascular coiling has been increasingly used as first treatment option for ruptured or unruptured aneurysms that are feasible for coiling. However, for the middle cerebral artery (MCA) aneurysms, endovascular coiling is less likely to be applied in most institutions. Most case series reported that coiling of MCA aneurysms was limited and showed unfavorable results compared with microsurgical clipping. [2 - 5] On the contrary, in a few literature, the results of coiling for MCA aneurysms were favorably comparable to clipping.[6, 7] In this study, we report our experience of treating 76 unruptured MCA aneurysms by endovascular coiling as first treatment option in 70 consecutive patients.
PATIENTS AND METHODS
The institutional review board approved this retrospective study and patient informed consent was not required. Seventy patients with 76 unruptured MCA aneurysms, treated by coiling in a tertiary referral hospital between May 2000 and February 2009, were retrospectively reviewed and evaluated. The patients with preexisting significant neurological deficit (modified Rankin Scale score, mRS 3), either due to previous subarachnoid hemorrhage (SAH, n=23) from the aneurysm at other site or due to infarction (n=1), were excluded. But the patients with mild neurological deficit (mRS, 0 - 2) were included. The patients included 30 men and 40 women with ages ranging from 27 to 77 years (mean, 59 years). Medical records and radiological studies were reviewed to obtain relevant information. Endovascular coiling
Antiplatelet premedication was not routinely prescribed in the early study period. Single regimen antiplatelet premedication (aspirin or clopidogrel) was given to most patients since 2006. Anticoagulation was initiated by injection of a bolus of 3000 - 5000 IU of heparin
intravenously at the beginning of the procedure, followed by continuous infusion of heparin by rate of 1000 IU/h. Activated coagulation time was maintained between 2 - 3 times the baseline value during and next 24 - 48 hours after the procedure. The techniques used for coil embolization were similar to those described in previously reported case series.[8] In most cases, coiling was initiated using the conventional single catheter technique with various types of coils. When single catheter technique failed, multi-catheter (two or three catheters,
catheter-assisted single catheter, or catheter-assisted two-catheter technique), balloon-assisted, stent-assisted, or combination of these techniques (multi-catheter plus balloon or stent) were used according to the aneurysm geometry. Two- or three-catheter technique is that 2 or 3 coils are sequentially or alternatively deployed through 2 or 3 prepositioned microcatheters
without detachment, for making the coil basket appropriate for saving the parent artery and/or incorporated branch. [9, 10] For catheter-supported single- or two-catheter technique, 1 microcatheter is inserted into the branch for protection, and the other 1 or 2 catheter(s) tip is positioned into the aneurysm dome to be used for coil deployment (Fig 1)[11]. Balloon- or
stent-assisted technique was used as indicated and described in the literature. (Fig 2) [12
16] Combination of these techniques means combined use of two-catheter technique and a stent- or a balloon-assisted technique. The parent artery is protected by using a balloon or a stent, and two catheters inserted into the aneurysm sac are used for making the coil basket appropriate for saving both the parent artery and its branches (Fig 3). The technique of gradually increased complexity was chosen to obtain a satisfactory result. When the single catheter technique was not effective, multi-catheter, balloon-assisted, or stent-assisted technique was used. At once, multi-catheter, balloon-assisted, or stent-assisted technique was primarily tried when aneurysm geometry was unfavorable for conventional single catheter technique on 3-dimensional reconstruction of rotational angiography. When these techniques
also failed, combination of these techniques was finally tried.
Immediate angiographic results were classified into 3 categories; complete was defined as when entire sac of the aneurysm was occluded, near complete as when contrast media filled in the minimal portion of the neck region, or incomplete as when contrast media filled in the aneurysm dome.
Clinical and Angiographic Follow-up
The patients were clinically assessed at admission, before and after the treatment, at discharge, and at clinical follow-up by the neurosurgeons and/or the interventional neuroradiologists. Each patient's outcome was evaluated according to the modified Rankin Scale score (mRS), and the patient's clinical status at the last follow-up was defined as the final functional outcome.
Follow-up angiographic results were classified into 3 categories; stable or improved occlusion, minor recurrence which does not require retreatment, or major recurrence which requires retreatment.
RESULTS
Table 1 summarizes demographic data and clinical and angiographic outcomes after coiling of unruptured MCA aneurysms. Coiling could be accomplished in 75 aneurysms but failed in 1 due to both unfavorable aneurysm geometry and small size. The patient had no complication and refused further treatment. Thirty aneurysms were treated by using single catheter, 18 by multi-catheter, 11 by balloon-assisted, 13 by stent-assisted, and 3 by combination of multi-catheter and balloon-assisted technique. One patient died from consequence of subarachnoid hemorrhage (SAH) occurring 9 hours after coiling. Intraprocedural aneurysm rupture occurred in 1, which was controlled by insertion of further coils and left no sequelae. One cortical and 1 basal ganglia infarction occurred in relevant MCA
territory in 2 patients, but both of them completely recovered at discharge. Therefore, treatment-related permanent morbidity and mortality rates were 0% and 1.4%, respectively. Immediate postembolization control angiography revealed complete in 40, near complete in 30, and incomplete in 5 aneurysms. Clinical follow-up was available in all surviving patients (mean, 23 months; range, 4 - 105 months) except for one who was lost to follow-up. There was no SAH but 1 death from acute myocardial infarction during clinical follow-up. One patient developed lymphoma but still survives. None of the patients had deterioration of functional neurological outcomes (mRS, 0 - 2). Follow-up angiographies were available in 63 (84%) of 75 treated aneurysms at least once at 6 - 24 months (mean, 11 months). Three major and 6 minor recurrences were detected. All 3 major recurrent aneurysms could be retreated by coiling without any complication.
DISCUSSION
Endovascular coil embolization has been widely accepted not only as an alternative to microsurgical clipping but also as a primary modality for treatment of most ruptured or unruptured intracranial aneurysms. Intracranial subarachnoid aneurysmal trial (ISAT) proved the superiority of endovascular coiling for the treatment of ruptured intracranial aneurysms over microsurgical clipping. Also, in the treatment of unruptured intracranial aneurysms, endovascular coiling has shown equal or superior results to clipping.[17 - 19] However, application of endovascular coiling to MCA aneurysms has shown higher procedural failure rate and unfavorable results compared to the application to the aneurysms at other sites.[2 - 5] In ruptured MCA aneurysms, subgroup analysis of ISAT in older patients more than 65 years revealed inferiority of coiling to clipping. [20] There are several factors presumed to be responsible for the unfavorable outcome of coiling in ruptured MCA aneurysms. First, hematoma frequently associated with ruptured MCA aneurysm may be a cause of unfavorable
outcome of coiling, because coiling itself cannot remove the hematoma. Second, the aneurysm geometry unfavorable for coiling, which is frequently met in MCA aneurysms, can be another factor. Also, for unruptured MCA aneurysms, primary application of coiling has been limited, mainly due to the unfavorable aneurysm geometry (relatively wide neck and/or frequent incorporation of a branch into the sac or neck).[3, 5] However, owing to the rapid advances of devices and techniques in endovascular treatment, such drawbacks of coiling have been overcome more and more. In our case series, endovascular coiling failed in only 1 (1.3%) of 76 unruptured MCA aneurysms, which is a very low failure rate compared with those of previously reported case series.[2, 3, 5] Newly developed endovascular techniques and devices, such as multi-catheter, balloon-assisted, stent-assisted, or combination of these, permit coiling of the aneurysm having a branch incorporated into the sac as well as the wide- necked aneurysms.[8, 21]
One concern about coiling the MCA aneurysms is possible increased risk of treatment- related complications due to the aneurysm geometry unfavorable for coiling. From the point of view of treatment-related complications, however, the results of our case series were favorably comparable to those of surgical series of unruptured MCA aneurysms. The treatment-related permanent morbidity and mortality rate of our series was 1.4%, while the reported treatment-related permanent morbidity and mortality rate for clipping of unruptured MCA aneurysms ranged from 3% to 15%. [5, 22 - 26] Another major concern is the probable higher recurrence rate after coiling of MCA aneurysms. However, recurrence rate of our case series was favorably comparable to those after endovascular coiling in the literature.[27] It seemed to be partly because all cases were unruptured aneurysms and partly because most of our cases were small aneurysms (less than 10mm in maximum diameter). As reported in the literature, the small and/or unruptured aneurysms are less likely to recur after coiling than the large or ruptured ones.[28] In addition, though there were considerable numbers of
recurrences (n=9, 14.3%), all 3 major recurrent MCA aneurysms could be re-treated by coiling without any complication. As reported in the literature,[29 - 31] re-coiling of recurred aneurysms after initial treatment is less likely to increase the risk of treatment-related complications. Nevertheless, we agree that large unruptured aneurysms in younger patients should be treated by surgery or by combination of endovascular and surgical method because of the anticipated higher probability of recurrence during the one's life. In our opinion, MCA aneurysms should not be allocated solely to clipping but only the large MCA aneurysms in young patients, which are likely to recur.
Some limitations are present in this series. It can be criticized that small, unruptured MCA aneurysms were treated. It is beyond the scope of this study whether or not the small, unruptured aneurysms should be treated. This issue of critical importance requires well- designed randomized prospective study. And therefore, we cannot address that issue in this retrospective case series. Because of the retrospective nature of this study, another major limitation is selection bias, which may have affected the results. However, all the unruptured MCA aneurysms were initially tried to be treated by coiling without exception in the hospital (Kangbuk Samsung Hospital) where treatments were performed, and all the data of the unruptured MCA aneurysms treated endovascularly were recorded prospectively into a database. And therefore, selection bias might be minimized. Limited number of angiographic follow-up is also a limitation of this study, which may have lowered the recurrence rate. To address that issue and to elucidate the role of coil embolization in unruptured MCA aneurysms, further study with longer follow-up angiography in a larger population is warranted.
Conclusion
Using appropriate techniques and devices, most unruptured MCA aneurysms could be
safely treated by coiling with acceptable angiographic and clinical outcomes.
