Matthew Edwardson, MD

Chalouhi N, Starke RM, Yang S, Bovenzi CD, Tjoumakaris S, Hasan, D, et al. Extending the Indications of Flow Diversion to Small, Unruptured, Saccular Aneurysms of the Anterior Circulation. Stroke. 2013

The Pipeline Embolization Device (PED) is a stent designed for insertion across the mouth of an aneurysm. It diverts cerebral blood flow and promotes aneurysm occlusion often without any adjunctive coiling. PEDs offer benefits in terms of reduced procedure times and possibly higher rates aneurysm obliteration when compared to coiling. The FDA, however, has approved the PED only to treat large and giant wide-necked aneurysms in the cavernous or superior hypophyseal ICA. Interventionalists remain leery of clinical PED use in other types of aneurysms due to lingering safety concerns. In this article, Chalouhi and colleagues seek to allay some of these fears.

The authors performed a case-control study in patients with small (<10mm), unruptured, saccular aneurysms in the anterior circulation. 40 patients treated with one or more PEDs were matched in a 1:4 ratio with 160 patients treated with stent-assisted coiling based on age, aneurysm size, aneurysm location, and gender. The authors found similar procedural complications rates (5% with PED, 3% with stent-assisted coiling, p = 0.7) and clinical outcomes (mRS ≤ 2 in 100% with PED, 98% with stent-assisted coiling at follow-up). Those receiving PEDs had a trend toward higher rates of aneurysm obliteration at follow-up (80% with PED, 70% with stent-assisted coiling, p = 0.2).

This is the first study directly comparing flow-diverting stents with stent-assisted coiling to treat small, unruptured aneurysms. The results are encouraging and provide preliminary evidence that PEDs may have a similar safety profile to stent-assisted coiling in this patient population. A few caveats to opening the pipeline to widespread PED use in this population remain. The average follow-up in the PED group in this study was only 7 months and PEDs are known to have a higher risk of delayed aneurysm rupture and stent migration. This study was performed at one site with a great deal of clinical experience; whether these low complication rates generalize to other treatment centers remains uncertain. It should be stressed that the risk of subarachnoid hemorrhage with unruptured aneurysms < 10mm is fairly low, with most studies estimating a rate < 1% per yr. Therefore even low complication rates may negate the benefit of intervening on these patients. Calouhi and colleagues provide encouraging results on the safety of PED use in this patient population. They lay the groundwork for future trials involving multiple centers and longer follow-up to determine whether more widespread use of PEDs is appropriate for treating small unruptured aneurysms.