Use of Self-Expanding Stents in Distal Small Cerebral Vessels

Materials and Methods

A retrospective review of all aneurysms treated with the Neuroform stent from January 2004 to October 2005 in our center was conducted. Of the 70 stents placed, 8 were in small distal vessels measuring <2 mm. Patient demographic and clinical data, indication for stent use, radiographic images, aneurysm or stenotic characteristics, procedural notes, and postprocedure hospital course were reviewed. Particular attention was given to technical- and management-related complications. CT angiography with 3D reconstruction was performed before all interventional procedures.

All procedures were performed with the patient under general anesthesia. Heparin was titrated during the procedure to achieve an activated clotting time of 2–2.5 times that of baseline. Patients were treated with 75 mg of clopidogrel and 325 mg of aspirin at least 5 days before the endovascular procedure and were maintained on the same dosage of each, daily, for at least 12 weeks. Aspirin was continued indefinitely. The Neuroform stent was either deployed before aneurysm coiling or at the termination of aneurysm coiling to treat coil herniation. The smallest and shortest Neuroform stent available at the time was chosen for all procedures.

Postprocedural MR imaging and MR angiography (MRA) were performed within 2 weeks of treatment and again at 6-month intervals up to 2 years. Clinical modified Rankin Scale (mRS) scores were obtained 24 hours posttreatment and 2 weeks, 6 months, and 1 year posttreatment. Efficacy of aneurysm coiling was assessed by using the Raymond scale. Evidence of stroke in the treated territory via MR imaging or CT, perfusion status, and stent patency was documented.

Results

Outcomes

In the 8 aneurysms, the Neuroform stent was deployed before aneurysm coiling in 6 patients (6/8) and at the termination of aneurysm coiling (2/8) to treat coil herniation. Half of the patients (4/8) demonstrated complete aneurysm occlusion (Raymond scale, 0), whereas in the other half, near-complete aneurysm occlusion (Raymond scale, 1) was achieved. Intraprocedural thrombus occurred in 2 (25%) of the 8 patients and resolved with abciximab (ReoPro) bolus administration. No diffusion abnormalities in the treated vascular territory were found on the postoperative MR imaging in either patient.

Example case 1.

Patient 2 (Fig 1) was a 51-year-old man who presented with a large (10 × 10 × 12 mm) right pericallosal aneurysm with a wide neck. Because of the broad neck, initial placement of a 2.5 × 15 mm Neuroform stent was required in a 1.5-mm pericallosal artery to restrain the coils within the aneurysm. This allowed successful aneurysm treatment in an otherwise difficult case. Thrombus did occur along the stent interstices despite adequate intraprocedural anticoagulation. This resolved quickly with 10 mg of abciximab. At the conclusion of the case, thrombus was noted in 1 of the middle cerebral artery (MCA) branches, presumably related to thrombus from the guide catheter. The aneurysm appeared well treated without stroke in the anterior cerebral artery (ACA) territory on the postoperative MR imaging. The patient did experience mild left-handed weakness related to a small stroke from the MCA thrombus. Eight months postprocedure, the hand weakness had resolved.

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Fig 1.

Large pericallosal aneurysm treated with Neuroform stent and coils. Frontal (A) and lateral (B) angiograms showing large wide-necked pericallosal aneurysm. Native lateral projection (C) image showing placement of Neuroform stent across the aneurysm neck. D, Subsequent placement of coils within the aneurysm is well constrained by the stent. Final frontal (E) and lateral (F) angiograms showing the coiled pericallosal aneurysm. At the conclusion of the case, thrombus was noted in 1 of the MCA branches, presumably related to thrombus from the guide catheter.

Example case 2.

Patient 4 (Fig 2) was a 77-year-old woman with an enlarging anterior communicating artery (AcomA) aneurysm. Because of the large neck, initial placement of a 3 × 20 mm Neuroform stent was required. The aneurysm was then treated with multiple coils. A small residual dog ear remained at the conclusion. At follow-up 18 months later, the thrombosed portion of the aneurysm had markedly diminished, and the small dog ear remained. The stent was widely patent.

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Fig 2.

(A) Noncontrast CT, contrast-enhanced CT, and axial CTA images showing a large partially thrombosed AcomA aneurysm. Frontal oblique angiograms showing the aneurysm before (B) and after (C, D) treatment. Eighteen-month follow-up MRA sequential source images (E-H) and maximum intensity projection (I) show stent widely patent and resolution of the aneurysm thrombus. The area of signal intensity dropout in the A1 segment was stable in the immediate postoperative and other follow-up MRAs and was related to artifact from the end markers on the stent.

Discussion

Previously, endovascular therapy was reserved for patients harboring aneurysms/lesions considered high risk for surgical treatment due to location and/or morphology.^8,9 The results of the International Subarachnoid Aneurysm Trial (ISAT) trial¹⁰ demonstrated positive outcomes in patients undergoing endovascular therapy for ruptured cerebral aneurysms and have helped validate the role of aneurysm coiling. The confirmation of endovascular therapy has stimulated an increase in research in this field, allowing rapid development of new tools such as the Neuroform stent. The Neuroform stent is a US Food and Drug Administration–approved device indicated for use in wide-necked aneurysms.

The release of newer sophisticated devices enables treatment of lesions that were previously deemed untreatable. However, beyond the scope of the indications for use in the device manual, little is known about the limits of the device. To this end, there are no reports in the literature detailing the feasibility, use, or safety of stents in small (<2 mm) cerebral vessels. This article describes 8 patients who have safely and successfully undergone stent treatment in vessel diameters <2 mm with positive short- and intermediate-term results.

All aneurysms and stenoses were safely and effectively treated (Table 1). No untoward outcomes related to the device were observed in the short term (6 months) or intermediate term (18 months). There was increased incidence of intraprocedural thrombus formation (25%), which was successfully treated with an abciximab bolus. Although this finding suggests that there is an increased risk of thrombus formation despite adequate prophylaxis, it did not result in any untoward clinical or imaging outcomes. This outcome does reinforce the use of the Neuroform stent for electively treated aneurysms, in which additional thrombolytics can be used if required for intraprocedural thrombus formation. The 2 stents placed for aneurysm treatment related to coil herniation adequately displaced the coil loops back into the aneurysm neck. The development of sophisticated small adjunctive devices such as the Neuroform stent increases the type and number of aneurysms that can be treated by endovascular means and with improved safety.

Conclusions

The use of self-expanding stents in vessel diameters <2 mm can be performed safely and efficaciously. The development of lower profile endovascular devices allows accessibility and treatment of lesions in distal cerebral vessels. Intraprocedural thrombus formation was seen in a relatively high (25%) number of patients but resolved quickly with abciximab administration. No untoward clinical outcomes were seen. Further follow-up and experience are necessary to determine the durability of these promising results.