Neuroform in-stent stenosis: Incidence, natural history, and treatment strategies

OBJECTIVE: Delayed in-stent stenosis is an important and well-characterized complication of angioplasty and stenting for the treatment of intra- and extracranial atheromatous disease. The current series describes the incidence and natural history of in-stent stenosis after the deployment of the Neuroform stent within the cerebrovasculature for the treatment of aneurysms. METHODS: The collaborative Cleveland Clinic Foundation-Barrow Neurological Institute endovascular database was reviewed to identify cases of delayed moderate or severe in-stent stenosis observed during the follow-up of cerebral aneurysms treated with the Neuroform stent. The hospital charts, clinic records, and operative reports for these patients were reviewed. RESULTS: Of a total of 156 patients with follow-up, nine (5.8%) cases of moderate or severe delayed (> 2 mo) in-stent stenosis were identified, including two parent vessel occlusions. In two cases, patients presented 3 months after stent-supported aneurysm embolization with focal neurological symptoms. Both of these patients were treated with angioplasty. One eventually required surgical bypass. Of the seven asymptomatic 3 patients, four demonstrated some degree of spontaneous resolution at follow-up, one progressed to complete occlusion, one is awaiting further follow-up, and one patient, died of unrelated causes. Of the nine patients in the series, five were treated with "bioactive" coils (Matrix, Hydrocoil, Cerecyte), three were treated with bare platinum coils, and one was treated with stenting alone. The earliest time interval to diagnosis was 2.5 months and 3 months for asymptomatic and symptomatic patients, respectively. The earliest interval documented for spontaneous resolution was 9 months. CONCLUSION: Delayed Neuroform in-stent stenosis, occurring in 5.8% of cases, is not a care phenomenon. The stenosis can be symptomatic and may require endovascular treatment or surgical bypass. In asymptomatic patients, a strategy of "watchful waiting" may be effective because many patients demonstrate partial or complete resolution at follow-up. The spontaneous resolution of delayed in-stent stenosis has not been previously described. This ay be a phenomenon unique to the application of low radial force, self-expanding stents within the nonatheromatous cerebrovasculature.