Incomplete stent apposition in Enterprise stent–mediated coiling of aneurysms: persistence over time and risk of delayed ischemic events

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Incomplete stent apposition of the closed cell–design Enterprise stent following stent-mediated coil embolization of intracranial aneurysms has been associated with increased risk of periprocedural thromboembolic events. In this study, the authors seek to determine the natural history of incomplete stent apposition and evaluate the clinical implications of the phenomenon.


Since January 2009, all patients receiving Enterprise stents in the treatment of intracranial aneurysms at the authors' institution have undergone serial 3-T MRI with incomplete stent apposition identified by the crescent sign on multiplanar reconstructions of MR angiograms. Magnetic resonance images and MR angiograms obtained at 3, 9, and 18 months after stent-assisted coil embolization were analyzed along with admission and follow-up clinical medical records. These records were evaluated for any radiographic and clinical, transient or permanent ischemic neurological events.


Fifty patients receiving Enterprise stents were eligible for inclusion and analysis in the study. Incomplete stent apposition was identified in postoperative imaging studies in 22 (44%) of 50 patients, with 19 (86%) of 22 crescent signs persisting and 3 (14%) of 22 crescent signs resolving on subsequent serial imaging. Delayed ischemic events occurred in 8 (16%) of 50 cases, and all cases involved patients with incomplete stent apposition. The events were transient ischemic attacks (TIAs) in 5 cases, asymptomatic radiographic strokes in 2 cases, and symptomatic strokes and TIAs in the final case. There were no delayed ischemic events in patients who did not have incomplete stent apposition. Only 1 of the delayed ischemic events (2%) was permanent and symptomatic. The postoperative presence of a crescent sign and persistence of the crescent sign were both significantly associated with delayed ischemic events (p < 0.001 and p = 0.002, respectively).


Incomplete stent apposition is a temporally persistent phenomenon, which resolves spontaneously in only a small minority of cases and appears to be a risk factor for delayed ischemic events. Although further follow-up is needed, these results suggest that longer duration of antiplatelet therapy and clinical follow-up may be warranted in cases of recognized incomplete stent apposition.

Abbreviations used in this paper:DWI = diffusion-weighted imaging; ICES = Interstate Collaboration of Enterprise Stent/Coiling; ISA = incomplete stent apposition; MRA = MR angiography; mRS = modified Rankin Scale; SAH = subarachnoid hemorrhage; TIA = transient ischemic attack.

Article Information

Address correspondence to: Adel M. Malek, M.D., Ph.D., Department of Neurosurgery, Tufts Medical Center, 800 Washington Street, Box 187, Proger 7, Boston, Massachusetts 02111. email:

Please include this information when citing this paper: published online March 15, 2013; DOI: 10.3171/2013.2.JNS121427.

© AANS, except where prohibited by US copyright law.



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    A and B: Preembolization (A) and postembolization (B) lateral-view digital subtraction angiograms obtained in a 56-year-old woman harboring a left-sided posterior communicating artery aneurysm (black arrows). C: 3D MRA reconstructions of the cerebrovascular circulation performed on (from left to right) postoperative Day 1 and at the 3-, 7-, and 25-month follow-up examinations. The crescent sign (white arrows) is clearly evident on the image from postoperative Day 1, nearly resolved on the 3-month follow-up image, and undetectable on the 7- and 25-month follow-up images.

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    A and B: Preembolization lateral-view digital subtraction angiogram (A) and lateral-view 3D reconstruction (B) of the left internal carotid artery in a 71-year-old woman harboring a left-sided supraclinoid aneurysm. C: Lateral-view digital subtraction angiogram showing postembolization result. D–F: Postoperative 3-T MR angiograms obtained on postoperative Day 1 (D) and at the 3-month (E) and 10-month (F) follow-up visits revealing the presence and persistence of incomplete stent apposition as shown by the crescent sign (arrows). G–I: Day 1 postoperative diffusion-weighted MR imaging (G) revealed an acute area of restricted diffusion in the white matter of the left frontal lobe, which was confirmed by corresponding hypointense signal on the ADC (apparent diffusion coefficient) map (H). This area was identified on T1-weighted MR imaging (I) at the 3-month follow-up to be permanently infarcted, as indicated by the confined area of volume loss (arrow) corresponding to the previous area of restricted diffusion.

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    A and B: Preembolization (A) and postembolization (B) lateral-view digital subtraction angiograms obtained in a 25-year-old man demonstrating a left paraclinoid carotid aneurysm (black arrows). C: T2-FLAIR MR image obtained at the 7-month follow-up demonstrating a gyriform area of ischemia representing an evolving chronic infarct in the left frontal cortex (white arrow). D: 3D MRA reconstructions of the cerebrovascular circulation showing persistence of the crescent sign on the outer curve of the vessel with imaging performed (from left to right) on postoperative Day 1 and at the 7-, 13-, 19-, and 31-month follow-up examinations.



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