Objective The stent-assisted coiling technique has expanded the applicability of endovascular treatment for wide-neck intracranial aneurysms. However, the stability of the deployed stent has been questioned. We present this case to demonstrate intraprocedural migration of the deployed stent and subsequent management.
Clinical presentation A 59-year-old female patient presented with dizziness and fatigue. Imaging, including CT and MR angiography, revealed a 7×6.5 mm wide-neck basilar tip aneurysm.
Intervention Stent-assisted coiling was attempted. After deployment of the stent, the distal portion of the stent migrated into the aneurysm sac, and then stabilized. Since attempted coiling without an assistance device was unsuccessful, the balloon-assisted coiling technique was applied. Near-total obliteration of the basilar tip aneurysm was accomplished.
Conclusion The stability of a deployed stent should be confirmed to exclude the possibility of intraprocedural stent migration. If stent migration into the target aneurysm occurs, the balloon-assisted coiling technique through the deployed stent is a feasible and valuable tool for successful coil embolization.
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The use of self-expandable intracranial stents has significantly widened the applicability of endovascular therapy for the treatment of wide-neck intracranial aneurysms. The employment of this technique allows for denser coil packing and more effective aneurysm neck coverage.1–5 Recently, reports regarding delayed stent migrations on mid-term follow-up angiography have been published. These reports raise an important question regarding the stability of the deployed stent.2–4
In this report, we describe a case of intraprocedural spontaneous proximal migration of a deployed stent into a target aneurysm. The procedure was successfully completed with embolization of the aneurysm using the balloon-assisted coiling technique. To the best of our knowledge, there have been no reports regarding spontaneous intraprocedural stent migration and management.
A 59-year-old female patient presented with dizziness and fatigue. Magnetic resonance angiography (MRA) and subsequent CT angiography (CTA) demonstrated a cranial and slightly posterior projecting relatively wide-neck 7×6.5 mm basilar tip aneurysm. Considering the location and size of the aneurysm, as well as the patient's age, endovascular treatment with stent-assisted coiling was recommended. Plavix 75 mg/day and aspirin 325 mg/day were given from 5 days prior to the intervention.
The procedure was performed under general anesthesia. Heparin was administered at the beginning of the procedure and intermittently during the procedure to maintain the activated clotting time at between 250 and 290 s.
A 4.5×22 mm sized Enterprise® stent (Cordis, Miami, Florida, USA) was chosen since the mid-basilar artery diameter measured 3.0 (short diameter)×3.6 mm (long diameter) on 3D rotational angiography and the diameter of the proximal P1 segment of the left posterior cerebral artery (PCA) measured 2.0 mm. Through the right vertebral artery, the stent was deployed across the neck of the aneurysm, from the mid-portion of the left P1 segment of the left PCA to the mid-basilar artery. Although the initial location of the deployed stent was slightly more proximal than planned, the stent adequately covered the target aneurysm neck (figure 1A–C). The authors' routine intracranial arterial stenting protocol allows for 15 min of intermission after stent deployment to establish stability of the deployed stent and to rule out possible acute in-stent platelet aggregation. A subsequent angiogram performed 15 min after the stent deployment showed subtle proximal migration of the stent.
Approximately 30 min after deployment, the stent appeared to stabilize, but the distal end of the stent had migrated into the aneurysm sac. Radiographic imaging revealed that two of the four distal stent markers were in the aneurysm sac, with the remaining two distal markers present at the junction of the aneurysm neck and the left PCA P1 segment (figure 2A,B).
Since the stent did not show additional migration during an additional 20 min of observation, coil embolization of the aneurysm was performed. Initial attempts without an assistance device were unsuccessful due to inadequate coverage of the aneurysm neck. This was especially evident on the left side of the migrated stent (figure 3). Thus, a 4×7 mm Hyperform balloon (eV3 Neurovascular, Irvine, California, USA) was placed across the junction of the aneurysm neck and the left proximal P1 segment of the left PCA and distal basilar artery through the stent (figure 4A,B). With balloon assistance, uneventful coil embolization of the aneurysm was performed. Near complete obliteration of the aneurysm sac was achieved (figure 5). The patient tolerated the procedure well and was neurologically intact on discharge 48 h post procedure.
Delayed spontaneous migration of intracranial self-expandable stents is a known complication that is seen 3–5 months post procedure.2–4
Our case report demonstrates that spontaneous intraprocedural migration of a self-expandable intracranial stent after uneventful initial deployment is also possible. Successful subsequent management of this circumstance can be achieved by applying the balloon-assisted coiling technique.
The cause of the intraprocedural stent migration may be related to the ‘watermelon seed effect’.3 In our case, due to the luminal size discrepancy of the PCA and the basilar artery, the PCA (distal) portion of the stent might have been constrained to a greater degree than the basilar (proximal) portion. This difference in the degree of constraint may have generated a constant retrograde force through the stent struts, resulting in the migration of the deployed stent.
Since the Enterprise stent is currently available in only one diameter (4.5 mm), which is much larger than our PCA P1 segment diameter (2.0 mm), it may have contributed to the downward force on the stent.2
Placement of the stent more distally in the left PCA may have helped offset this retrograde migrational force. However, regardless of how far distally the stent is placed, a certain degree of stent constraint may be unavoidable. This hypothesis may also be a possible explanation for the delayed migration of intracranial stents. One may consider the use of a longer stent, which covers enough length of both the distal and proximal segments of the parent artery. However, this strategy may unnecessarily increase the potential risk of in-stent stenosis.6–8
Stent migration during or after coil detachment into the aneurysm may increase the risk of the coil loops being pulled into the parent artery by the migrating stent, resulting in an increased risk of thromboembolic or occlusive events, and increasing the possibility of aneurysm rupture if the migrating stent pushes the deployed coil mass towards the aneurysm dome. Therefore, even with satisfactory stent deployment, we recommend observing the stability of the stent position for at least 15 min after intracranial stent deployment and before pursuing coil embolization of the intracranial aneurysm.
Our case report also demonstrates the feasibility of the balloon remodeling technique through the deployed stent struts. Applying the balloon-assisted coiling technique through the stent may disrupt the stent struts, especially in a closed cell designed stent, which could disrupt the entire stent and potentially create a stent-related thromboembolic complication. However, using a compliable balloon catheter system and under-inflation of the balloon during the procedure, may prevent these potential complications.
The stent-assisted coiling technique is promising and has expanded the applicability of endovascular treatment for wide-neck intracranial aneurysms. However, the possibility of intraprocedural spontaneous stent migration after stent deployment must be considered. As a matter of routine, we recommend observing the stability of the deployed stent position for at least 15 min after each stent deployment. If stent migration into the target aneurysm occurs, the balloon-assisted coiling technique through the deployed stent is a feasible and valuable tool for accomplishing successful coil embolization.
About 15 min of observation time after stent deployment is recommended since intraprocedural stent migration can occur.
Balloon-assisted coiling technique through stent struts is feasible.
We appreciate the help of Mr Vinald Francis in the creation of the medical illustrations.
Competing interests None declared.
Patient consent Obtained.
Provenance and peer review Not commissioned; not externally peer reviewed.