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Residual aneurysm from incomplete clipping or slowly recurrent aneurysm is associated with high risk of subarachnoid hemorrhage. We describe complete treatment of the lesions by surgical clipping or endovascular treatment.
We analyzed 11 patients of residual or recurrent aneurysms who had undergone surgical clipping from 1998 to 2009. Among them, 5 cases were initially clipped at our hospital. The others were referred from other hospitals after clipping. The radiologic and medical records were retrospectively analyzed.
All patients presented with subarachnoid hemorrhage at first time, and the most frequent location of the ruptured residual or recurrent aneurysm was in the anterior communicating artery to posterior-superior direction. Distal anterior cerebral artery, posterior communicating artery, and middle cerebral artery was followed. Repositioning of clipping in eleven cases, and one endovascular treatment were performed. No residual aneurysm was found in postoperative angiography, and no complication was noted in related to the operations.
These results indicate the importance of postoperative or follow up angiography and that reoperation of residual or slowly recurrent aneurysm should be tried if such lesions being found. Precise evaluation and appropriate planning including endovascular treatment should be performed for complete obliteration of the residual or recurrent aneurysm.
For many years surgical clipping has been used in treatment of intracranial aneurysms. Development of three dimensional angiography and endovascular technique has contributed to gain better results of aneurysm treatment. Nevertheless, good surgical results are not always achieved and occasionally further evaluation and retreatment might be needed11). Some authors report very small size of residual aneurysm such as dog ear seen in postoperative angiography has less risk of hemorrhage, but subarachnoid hemorrhage (SAH) from a narrow residual neck have reported in many cases. According to Feurberg et al.10), incomplete clipping rate vary from 1.6 to 14%16,24). Recurrent aneurysm developed by arterial wall damage from earlier manipulation and clip edge is different from residual aneurysm in that the former is possible even if complete clipping has performed. But, the prevention and management of hemorrhage is a difficult problem to neurosurgeon.
The purpose of this study was to present the usefulness of postoperative or follow up angiography and management of residual or recurrent intracranial aneurysms based on the authors' experience over the past eleven years.
Between 1998 and 2009, 857 surgical clipping of intracranial aneurysms were performed at our hospital. This study includes eleven patients with residual or recurrent aneurysms. The patients' age at first surgery ranged from 44 to 70 years (mean 53.90). There were 4 men and 7 women. The mean latent period from initial treatment to rupture was about 15.2 days. Whereas recurrent aneurysms were detected with a mean latency of 8.12 years from the initial treatment. The first clinical presentation in all cases was SAH. All 11 cases underwent microsurgical clip as the primary therapy. Among these, six patients who suffered recurrent SAH were referred to our clinic for regrowth of the aneurysmal sac. Three were detected by routine postoperative angiography; the other was found as a consequence of evaluation of other aneurysms (Table 1).
The residual or recurrent aneurysms were diagnosed based on the completeness of initial treatment by angiography and intraoperative findings. We reviewed retrospectively, the patients' intraoperative videos and images to find all cases with the incomplete clipping. Recurrent aneurysms were detected either after several years by angiography when presented SAH or follow up due to another untreated aneurysms.
Residual aneurysms were found in 6 out of 11 patients, recurrent aneurysms were found in 3 patients, and the distinct etiologies could not found in remaining cases.
The most common location of residual aneurysms was in anterior communicating artery (ACOA). Four aneurysms were located in ACOA, and the others were located in middle cerebral artery, and distal anterior cerebral artery (DACA). All patients presented with SAH due to rupture of residual aneurysm, which were identified on conventional angiography. The mean latent period from initial treatment to rupture was about 15.2 days. The confirmation of residual aneurysm was relatively easy because incomplete clipping with residual neck distal to the clip was verified in both preoperative angiography and intraoperative findings. In one patient (case 4), progressive clip slippage was noted in ACOA aneurysm (Fig. 1). Five patients underwent reoperation with application of a new clip after removal of the former clips. One patient (case 1) was treated by endovascular embolization and good result was achieved (Fig. 2). The outcomes were good for all patients without any complications.
The two recurrent aneurysms after initial complete clipping were mostly in posterior communicating arteries. The other two aneurysms were located in ACOA and DACA. The mean latent period from initial treatment to rupture was about 8.12 years. Surgical clipping was performed in the all patients using new clips. The previous clip was kept in one patient (case 7) with the recurrent part being clipped with new clips (Fig. 3). The outcomes were good for all patients without any complication like residual aneurysm.
Delayed detected intracranial aneurysms after initial treatment are classified into two types. One is residual aneurysm arising from initial incomplete treatment, and the other is slowly developed eccentrically in relation to the clip, or existed from a dome between the previous clips22).
Despite small sized residual aneurysms have been thought to pose relatively little risk, incomplete clipping of intracranial aneurysm may result in progressive enlargement of residual portion and rupture of weak point. The rates of residual aneurysm after initial clipping have been reported about 3.8 to 18%3,7,8,10,14-16,23). It can also present with neurologic symptoms from local mass effect8,14) The rebleeding rate of aneurysms with residual necks has been reported to be about 3.5 to 28%7,8,10), and aneurysm regrowth has been reported to occur in 3.5-15% patients8,10). Fuerberg et al.10), found that residual aneurysms rebled at a rate of about 0.5% per year. Consequently, treatment of the residual aneurysm is mandatory especially in young age14).
According to Ebina et al.9), recurrent aneurysm can be developed by arterial wall damage from earlier manipulation and applied clip edge. In a completely clipped aneurysm, recurrent hemorrhage and recurrent aneurysm formation are very rare events2), and the risk of annual regrowth rate of a completely clipped aneurysm (0.26%) is much lower than the annual risk of de novo aneurysm formation (0.89%)25). However, a 2.7% rate of aneurysm rerupture was reported even after complete surgical clipping of the aneurysm4). In this regard, a new multidisciplinary decision-making process has been performed6).
Incomplete clipping occurs as results of inadequate exposure, incomplete dissection, or poor visualization of the aneurysm. Also, other factors such as inappropriate clips or insufficient surgeon's experience can be considered as barrier to the complete clipping. Fragility of the parent artery adjacent to the aneursym9), vessel injury due to repeated temporary clipping24), and lack of detection also cause incomplete clipping, because postoperative angiography was not routinely performed16). On the other hand, recurrent aneurysm will slowly progressive, even with complete clipping in the initial treatment due to hemodynamic stress, clip slippage7).
Residual aneurysm due to incomplete clipping is not detected until a postoperative angiography is performed, except in cases where it is left remain by intention such as risk of obliateration of perforator, or severe atherosclerotic change on aneurysm neck. Postoperative angiography gives some risk and financial burden to the majority of patients whose aneurysms proven to be adequately treated20). Although postoperative angiography is not routinely performed, it should be done whenever incomplete clipping is doubted in operation or in difficult cases. Recently, three dimensional angiography has made diagnosis more accurate1,13).
In diagnosis of recurrent aneurysm, considering that SAH is a catastrophic event, adequate length of follow up ensure the future safety of the patient. In one study, the majority of new aneurysm were found in patients who had undergone angiography more than 9 years after initial treatment. And majority of the these patients developed SAH after 9 years25). Another study reported that average time was 9.75 years for symptoms due to mass effect and 10.5 years for bleeding11). These statistical studies tell us that, considering of the fatality rate of SAH, follow-up investigation may be needed about 10 years after surgery even for patients with completely clipped aneurysms11,25,26). Moreover, in patients who had risk factors more frequent follow-up angiography may be indicated (e.g., 3-5years)17,21,25,26).
Feuerberg et al.10) reported reoperation is not necessary because the risk of residual aneurysm in some cases is very low. Sato et al.23) even reported spontaneous obliteration of recurrent aneurysms. In contrast, Drake and Allcock insisted on reoperation to eliminate the risk. Lin et al.14) suggested that the risk of 1 to 2 mm sized small aneurysm is the same as that for a large residual aneurysm.
Reoperation can be a difficult procedure because of arachnoid adhesion and scar formation. And, because the previous clip is situated in compromising position, removal and repositioning of newly applying clip can be more difficult. Intraoperative rupture or tearing of the parent artery should be managed properly. Some reported that intracerebral hemorrhage can occur more often with a poor outcome8,14). Giannotta and Litofsky11) reported that the removal of the previously applied clip is always required to completely secure the aneurysm.
A wide exposure and complete dissection of the aneurysm are required. After pertinent bony exposure and slacking down the brain, proximal control for preparing the premature rupture and complete neck dissection should be done. Preparation of adequate clip preparation is also mandatory. The previous applied clip can be a barrier to new clipping. Therefore, if it is possible after securing the parent artery, it may be removed. When it is difficult to secure the parent artery due to severe adhesion, only residual portion can be clipped. Intraoperative angiography can useful help for complete clipping of residual aneurysm3). Because of these difficulties in surgical treatment, endovascular treatment can be a good option. However, it can't be used in a very small residual aneurysms or when a parent vessel cannot be selected or a parent vessel cannot be distinguishable or incorporated from the neck of aneurysms5,12,19).
Aggressive treatment must be considered from the fact that residual or recurrent aneurysm may cause fatal SAH. In particular, residual aneurysm from incomplete clipping has quite different characteristics. Postoperative aneurysm neck after incomplete clipping is known to result in recurrent hemorrhage with serious consequences. Most presentations of recurrence reported in the literature were SAH18). If an aneurysm is detected on postoperative angiography, careful consideration should be given for treatment strategies and follow-up. If an aneurysm has a static dog ear neck, repeated angiography and close observation are necessary. Aggressive treatment is necessary if the aneurysm shape has changed or enlarged (Fig. 4).
Reoperation for residual aneurysm is a difficult approach and requires more meticulous surgical technique than the initial operation. The direct reoperation is often challenging due to scar adhesions to the surrounding tissue as a result of the previous operation. Especially, adhesion is more severe in recurrent aneurysm because time interval from initial treatment to rebleeding is long. Therefore, the surgical anatomy may be obscure and confusing; caution should be exercised during the dissection, and it is preferable to check the initial operation by video or operative records before conducting the second surgery18). A wide exposure and fine dissection of the aneurysm are also essential. Proximal control for preparing the premature rupture and complete neck dissection should be types of clip should be prepared for proper selection. When clipping, a previous compromisingly positioned clip can interfere with the new clipping. Therefore, if it is possible after securing the parent artery, the old clip should be removed first and reclipping is favorable for a successful occlusion. But, due to possible severe adhesion and difficulty in securing the parent artery, clipping the residual sac should be very careful. In our series, ten patients (except case 2) were occluded with new clips after removal of previous clip. Therefore, when intraoperative angiogram can be used, the completeness of the clipping of the neck needs to be confirmed during operation3).
If the possibility of recurrence is suspected, additional reinforcement following neck clipping and early postoperative angiography should be performed to prevent early rebleeding27). The endovascular procedure should be considered as an alternative to microsurgical treatment in all patients with residual or recurrent aneurysm, but it can't be used when the aneurysm is tiny.
Residual or recurrent aneurysm has high risk of rupture and aggressive treatment is necessary. Postoperative or follow up angiography at least 10 years should be performed in even after complete clipping. When the residual or recurrent aneurysm is found, careful evaluation and appropriate planning are required. Endovascular treatment can be a good alternative treatment.
This study was supported by a faculty research grand of Yonsei University College of Medicine for 6-2007-0039.