**9. Complications**

308 Aneurysm

**8. Results** 

The morphological results on immediate and late post-operative angiograms are categorized according to the revised Raymond classification into 1 of the following groups: complete occlusion, neck remnant, and residual aneurysm. Follow-up examinations with Digital Substraction Angriography or Magnetic Resonance Angiograms are then scheduled at minimum intervals of 6, 18 and 36 months. In cases of early recanalization, a DSA would be

The rates of complete occlusion differ significantly from the results observed on the immediate postoperative angiogram after stent-assisted coiling. In a recent study on the Neuroform Stent in our institution, we observed that the percentage of complete occlusion tends to stabilize after six months. However, progressive thrombosis and subsequent increase of the degree of aneurysm occlusion between the immediate postoperative and sixmonth angiograms are observed in roughly 50% of the aneurysms treated with stentassisted techniques (Maldonado et al., 2010). Of 76 aneurysms studied, 31.6% were completely occluded in the initial embolization, 63.8 at six months and 64.7% at 18 months. However, in three years of follow-up, six aneurysms with an initial complete occlusion and five with a neck remnant recanalized. The analysis by type of coil did not demonstrate any

**Figure 8.** Endovascular treatment of a repermeabilized aneurysm of the right middle cerebral artery using the Neuroform Stent System. *A*, after initial embolization; *B*, repermeabilization seven months later; *C*, after re-treatment using a Neuroform stent and a 'jailing' technique; *D*, angiographic control 14 months after retreatment, showing adequate reconstruction and re-endothelization of the bifurcation zone.

preferred in order to properly assess the need for retreatment.

association between complete occlusion and coil type.

Recent case series report incidences of adverse events ranging from 8.4 to 18.9%. Risk factors for complications are age, presence of significant atherosclerotic disease, subarachnoid hemorrhage, small aneurysm and large/giant aneurysm. The most common of those adverse events in the peri-operative phase are navigation problems, stent misplacement, stent migration, vessel dissection or perforation, and thromboembolic events.

Delayed stroke due to intrastent thrombosis or intrastent stenosis are less frequent but may be observed, especially in patients with irregular use of antiplatelets. In a recent study published by the authors on 76 aneurysms treated with a Neuroform Stent-assisted technique, a five-month delayed symptomatic stroke and three clinically silent in-stent stenosis were observed.

There is currently significant concern about the risk of delayed rupture after flow-diversion treatment. The exact mechanism of this adverse event is not completely understood. There are two main hypotheses for this phenomenon. First, the mural thrombus may act as a source of inflammatory substances such as proteases leading to chemical degradation and weakening of the aneurysm wall. Second, flow diversion may induce changes in intraaneurysmal flow pattern with a consequent increase in stress to areas that were not previously exposed. In a series of recent international cases of rupture after flow diversion, the following risk factors seemed to be important (Kulcsar et al., 2010):


#### **10. Post-operative management**

During the procedure, patients are anticoagulated with a bolus of standard heparin (70–100 IU/kg) followed by an intravenous drip through an automated syringe (40–60 IU/kg/h) to maintain an activated clotting time of 250 seconds, which may be continued for 12-24 hours. At the end of the procedure, they receive an IV dose of 250–500 mg of ASA unless they are

already using oral Aspirine. A daily dose of clopidogrel (75 mg) and ASA (75 mg) is then administered for two or three months. After that period, only one of those antiplatelet agents is continued, for a period of time that has varied in literature from three months to indefinitely.

### **Author details**

Igor Lima Maldonado *Universidade Federal da Bahia, Brazil* 

Alain Bonafé *Université Montpellier 1, France* 

### **11. Acknowledgement**

We would like to express our thanks to Mr José Alberto Maldonado Via for his assistance with the illustrations.

#### **12. References**


Lavine S., Larsen D., Giannotta S.& Teitelbaum G. (2000). Parent vessel Guglielmi detachable coil herniation during wide-necked aneurysm embolization: Treatment with intracranial stent placement: Two technical case reports. *Neurosurgery*, Vol. 46, No., pp. 1013-1017.

310 Aneurysm

indefinitely.

Alain Bonafé

**Author details** 

Igor Lima Maldonado

*Universidade Federal da Bahia, Brazil* 

*Université Montpellier 1, France* 

**11. Acknowledgement** 

with the illustrations.

**12. References** 

already using oral Aspirine. A daily dose of clopidogrel (75 mg) and ASA (75 mg) is then administered for two or three months. After that period, only one of those antiplatelet agents is continued, for a period of time that has varied in literature from three months to

We would like to express our thanks to Mr José Alberto Maldonado Via for his assistance

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