Single centre experience of flow diverter treatment of complex intracranial aneurysms from South India: Intermediate and long-term outcomes
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.263195
Source of Support: None, Conflict of Interest: None
Background and Purpose: To report the intermediate and long-term clinical and angiographic outcomes of the treatment of complex intracranial aneurysms with flow diverter (FD) stents. Setting: A tertiary care centre from south India.
Keywords: Complications, flow diverter stents, intracranial aneurysms, outcome
Flow diverter (FD) stents have revolutionized the treatment of complex cerebral aneurysms, and several studies and meta-analysis have demonstrated the efficacy and safety of these new devices in the management of aneurysms that are not amenable to conventional endovascular or surgical therapy.,,, The concept of flow diversion includes decoupling of inflow jet and centralized diversion of flow vectors resulting in stagnation of blood flow within the aneurysm and eventual thrombosis and exclusion of the aneurysm from the circulation. These stents also act as a scaffold for the neoendothelialization, leading to durable and sustained occlusion. The experience of FD stent in our country is limited with only one study of small series reported in the literature. In this study, we aim to report a single institutional experience on the treatment of complex aneurysms with flow diverters with emphasis on the immediate and long-term clinical and angiographic outcomes.
All patients who had undergone FD stent placement as treatment for complex intracranial aneurysms at this institute were included in this retrospective study. Clinical documents of the patients, imaging records, preprocedural management regime, periprocedural notes, and subsequent outpatient follow-up details were analyzed. FD treatment was generally considered for aneurysms that are giant, fusiform, or recurrent and not amenable to conventional endovascular therapy.
Preprocedural antiplatelet protocol
After obtaining baseline platelet function tests using light aggregometry test (LTA), the patients were started on dual antiplatelets such as aspirin 150 mg and clopidogrel 75 mg, and the platelet function tests were repeated after 7 days to assess the degree of suppression. If the suppression was found to be unsatisfactory, prasugrel was initiated at 10 mg and embolization was planned after 5 days. Six patients required prasugrel following the observation of clopidogrel resistance (46%). Aspirin resistance was not observed in our cohort.
All the procedures were performed under general anesthesia and systemic heparinization was achieved to maintain the activating clotting time (ACT) between 250 and 300 s. The target vessel was accessed using a 6F guide catheter and coaxial systems were considered when the arteries were tortuous. The artery distal to the aneurysm was accessed by Marksman catheter (for pipeline embolization device, PED, Covidien, US) or Headway 27 (for flow restoration embolization device, FRED, Microvention, Tustin, US). The device diameter was matched to the largest arterial diameter which was usually the proximal artery. Multiple overlapping devices were considered if the neck could not be covered adequately with a single stent. Three-dimensional (3D) computed tomography (CT) was routinely obtained to assess the wall apposition and opening of the FD stent. If the stent mal-apposition was found, the segment was angioplastied using compliant balloons such as Scepter C (Microvention, Tustin, US). The arterial access sites were later closed using Perclose vascular closure device (Abbot vascular, Redwood City, California, USA). The patients were routinely discharged after 3–4 days of observation.
The follow-up protocol included regular clinic visits at 1, 3, 6, and 12 months and yearly thereafter. A CT angiogram was routinely obtained at a 1-month follow-up visit and digital subtraction angiography was performed after 6 months. Further imaging studies were decided based on the angiographic findings. All the patients were continued on dual antiplatelet therapy for at least a year, and on lifelong aspirin thereafter, if the stent remained patent and features of in-stent stenosis were absent.
A total of 13 patients with complex intracranial aneurysms have been considered for FD stents at our institute thus far. The demographic characteristics, clinical features, and aneurysm characteristics are presented in [Table 1]. Of the 13 patients, 3 patients underwent prior treatment of the aneurysm; 2 for treatment failure following balloon-assisted coiling and 1 patient after regrowth of aneurysm following surgical wrapping. One patient had bilateral cavernous aneurysms and had undergone surgery and parent vessel trapping for the contralateral side; and, another patient had been treated for direct carticocavernous fistula of the ipsilateral side 16 years ago. The rest of the patients had no previous history of surgical or endovascular treatment.
The procedure was successfully completed in 11 patients (84.6%), and in 2 patients, embolization was abandoned due to the inaccessibility of delivery microcatheter beyond the aneurysm into the distal parent artery. PED was deployed in 8 patients and FRED in 3 patients. A total of 12 PEDs were deployed, 1 each in 6 patients and 3 in two patients. No significant technical issues were noted in the patients treated with a single PED. In patients treated with multiple PEDs, the loss of distal arterial access after deployment of the first or second device resulted in prolongation of treatment duration. Among the FRED cohort, inadequate opening of the device and inability to introduce the device through the recommended catheter resulted in the use of additional FRED in two patients.
Major morbidity was noted in 1 patient (9%) who developed a large hematoma in the basal ganglia immediately after the procedure. This patient underwent emergent craniectomy and evacuation of hematoma. He had significant weakness of left upper and lower limb and his modified Rankin score at the time of discharge was 4. Transient worsening of the 3rd cranial nerve palsy was noted in 2 patients, which regressed gradually with conservative management. Two patients had postprocedural retroperitoneal hematoma that was managed conservatively. One patient developed self-limiting hematuria. The overall incidence of minor complications was 45% (5 patients). No thromboembolic complications were noted.
Early clinical and imaging outcomes
One-month CT imaging study was available for 90% of the patients that revealed complete exclusion of the aneurysm in 54% of patients and near complete occlusion (<10%) in 28% of patients. Significant residual filling of aneurysm (>20%) was noted in 1 patient.
Intermediate and long-term clinical outcomes
The clinical follow-up ranged from 3 to 30 months. Glasgow outcome score remained 0 in 90% of the patients during the follow-up period. One patient had residual 3rd nerve and V1 nerve palsy on a long-term follow up. This patient along with another patient developed trigeminal neuralgia at 6 months that was alleviated with medical treatment. Preprocedural cranial nerve deficits and visual field defects noted in patients showed improvement on follow up visits. Periprocedural events and long-term outcomes of FD treatment are shown in [Table 2].
An angiographic follow-up (>6 months) was available for 9 patients. Complete or near-complete obliteration of the aneurysm was noted in 89% of the patients, and in 1 patient, mild residual filling of the aneurysm (~10%) was observed. There was no in-stent stenosis or recanalization of the aneurysm. Progressive aneurysmal obliteration was noted in 25% of patients in the follow-up period. Asymptomatic occlusion of covered branch artery was observed only in 1 patient. Representative cases of FD treatment of cerebral aneurysms are demonstrated in [Figure 1] and [Figure 2].
FD stents represent a new treatment paradigm where the arterial segment harbouring the aneurysm is reconstructed using a tightly-woven mesh stent with a high metal and pore density. The metal density varies between 35–50% among the various stents and porosity varies between 45 and 70%. There are currently four flow diverters available in our country; PED, SILK (Balt Extrusion Technology, Montmorency, France), FRED, and Surpass (Stryker Neurovascular, Fremont, CA, USA). The stents are delivered through a large lumen microcatheter (0.021–0.027 inch) placed beyond the aneurysm in the distal parent artery, and the stent is deployed by a combination of unsheathing and forward push of the microcatheter to ensure a good opening of the stent as well as wall apposition. SILK, FRED, newer generation PED, Pipeline Flex, and Surpass allow partial-to-complete resheathability after deployment. Though the FD was initially considered for complex, difficult-to-treat aneurysms, recently it is being increasingly considered for simple uncomplicated aneurysms, blister aneurysms, or dissecting aneurysms.,,
Several reports demonstrate the technical feasibility and safety of FDs in the treatment of complex intracranial aneurysms. Technical problems or failures were noted in 5% of PED procedures in a pooled analysis. Though most of the studies report an overall technical success of more than 95–99% across the various FDs, device malfunction or migration is an important concern for most of the FDs. While incomplete expansion necessitating additional balloon apposition was observed in 12% of PEDs, device misdeployment leading to additional interventions such as stenting or balloon dilatation or consequent parent artery occlusions were observed in 12% of SILK stents., Similarly, an imprecise deployment, guide wire perforation, or intrastent clot formation were reported with Surpass stent; malapposition was an important concern leading to additional manoeuvres in 19.4% of the study population. Significant technical issues were not reported for FRED., The immediate angiographic changes observed within the aneurysm following FD include intrasaccular stagnation of contrast; however, the aneurysm progressively thromboses in the follow-up period, achieving occlusion rates similar to that obtained following conventional endovascular therapy. The aneurysm obliteration rate achieved was high among the different FDs, which varied between 73 and 83% at 6-month of follow up.,,,,, The aneurysms also demonstrated higher occlusion rates on long-term follow-up with significant reduction in the mass effect. The treatment with FD is not without complications; the mortality rates vary between 0 and 4.9% and the morbidity rates were reported to be between 4 and 12% for different FDs.,,, The periprocedural complications and mortality rates were observed to be higher with SILK stents. The long-term impact of a FD on parent vessel is not clearly delineated and there are conflicting reports of high as well low incidence of in-stent stenosis after FD treatment. These lesions are often asymptomatic; however, they may warrant a long-term clinical and angiographic surveillance to characterize the progression and plan therapeutic modulation or further intervention.,
The present study is the largest study from our country reporting the feasibility, immediate, and long-term outcomes of FD treatment for complex intracranial aneurysms. One important disadvantage of our study is that the number of subjects included in the analysis was low compared to other reports. This observation was primarily due to the fact that the number of subjects ultimately willing for FD treatment among the referred patients was very less due to the huge treatment costs involved, especially when multiple FDs were contemplated. In our study, the inclusion criteria were homogeneous and all the patients underwent antiplatelet function tests to document the degree of platelet activity suppression, and the aggressive usage of a potent antiplatelet drug such as prasugrel was considered only when the response was inadequate. As point of care assays, such as multiplate assay or verifynow assay, are not widely available in our country, we relied on the gold standard conventional light aggregometry tests to assess the degree of suppression of platelet function.
In our series, procedural failure was noted in 2 patients, in whom the microcatheter could not be negotiated beyond the aneurysm into the distal parent artery. The authors noted a few important observations regarding the 2 FD stents used in this study. PED was found to be more sturdy while deployment with minimal proximal or distal migration, which helped in accurate placement of the stent across the aneurysm. Although the distal end of the FRED is flared to improve wall apposition, significant distal migration was noted during the deployment and while manoeuvring the stent to improve stent expansion. The longer available lengths of the FRED and retrievability become important when longer coverages are needed or catheter instability is contemplated. However, these observations stem from the authors' modest experience and might reflect the steep learning curve associated with these procedures. The permanent morbidity and mortality rates of the present series and other previously published larger studies are compared in [Table 3].,,,,,,,,,,,,,,,,,, Thromboembolic complications are reported in 6.8% patients undergoing PED placement; however, we did not observe any such events in our cohort. This may be related to the rigorous adherence to the protocol of performing platelet function tests in all the patients considered for FD. The periprocedural self-limiting non-neurological hemorrhagic complications and vascular injuries were relatively high in this series (36%). Six minor periprocedural events were observed in the present study, of which, 4 were directly related to the embolization and two were related to the clinical consequence of the FD therapy. Aggravation or new onset oculomotor nerve palsy or trigeminal nerve involvement in the postoperative period is an expected complication of giant cavernous internal carotid artery aneurysms due to progressive thrombosis of the aneurysmal sac. Minor complications have rarely been a focus in many series; however, Park et al., reported 28.6% of temporary complications with PED, of which 12.6% were related to the procedure alone. Retroperitoneal hematoma is a dreaded complication with disastrous consequences, and its early recognition is important to avoid a potential catastrophe. We routinely perform hemoglobin estimation 4 and 12 h after the procedure for its early recognition and to initiate further investigations such as ultrasound or CT scanning, and blood transfusion. We believe that the probable cause of a retroperitoneal hematoma in uneventful arterial access is slow extravasation from the puncture site or posterior wall of the artery, and hence, the artery is regularly compressed for a while after securing the sheath to minimize the ongoing extravasation.
Significant obliteration of the aneurysm >90% was noted in 82% patients at a 1-month follow-up and progression to complete occlusion at an intermediate follow-up was seen in 25% of patients. Asymptomatic branch vessel occlusion was seen in 20% patients in our cohort, which is consistent with the reported literature. Our results show that the FD treatment of giant aneurysms is technically feasible with minimal mortality and acceptable morbidity. The majority of morbidities were transient and did not have any clinical impact when expeditiously managed. Although the procedural complexity compared to the conventional endovascular technique is less, the deployment of FD is technically challenging and has a steep learning curve, which will ultimately determine the outcome of the treatment., Long-term angiographic data showed that the aneurysm obliteration was durable and there were no delayed stent-related complications.
FD treatment of complex cerebral aneurysms was associated with favorable clinical and angiographic outcomes in the intermediate and long-term follow up. Minor complications were common which needed to be effectively managed to prevent major catastrophic events. The steep learning curve influenced the technical success of the procedure.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3]