On waffle cones and in vitro analysis of endovascular aneurysm treatment

摘要

Wide-necked bifurcation aneurysms frequently present a difficult anatomic challenge for endovascular treatment. This scenario frequently requires placement of one or more intraluminal stent devices to reconstruct the aneurysm neck. When the aneurysm efferent vessel cannot be easily navigated, we have favored deployment of a stent device with the distal stent end deployed within the aneurysm fundus at its neck, with subsequent placement of detachable coils in the aneurysm perched at the distal end of the deployed stent. We have applied this technique with use of both Neuroform and Enterprise stents (Codman, Raynham, Massachusetts, USA) (6, 8) and use of the Solitaire stent (Covidien Neurovascular, Irvine, California, USA) for this technique (12) has been described as well. This device configuration has come to be known as a "waffle cone" due to its appearance (8).In this issue of WORLD NEUROSURGERY, Hsu et al. describe an in vitro study of this stent-coil configuration. The theoretic risks of this technique are well outlined by the investigators (i.e., the stent may act as a flow-diversion device, thereby increasing flow into the aneurysm dome and increasing the risk of rupture or recurrence). The strength of this study is its offering a better understanding of the Neuroform stent and its stability in this configuration. The Neuroform stent when deployed end-on within an aneurysm was not displayed to have a flared-out distal end, as previously noted in vivo (8). Mechanical compression tests of the Neuroform stent suggest higher supporting force from en face compression (as in the waffle cone configuration), rather than eccentric compression (as in standard aneurysm stent remodeling), which Hsu et al. suggest may allow for more dense packing of detachable coils within the aneurysm with the waffle cone configuration. Ideal positioning of the distal stent end is between the aneurysm neck and center of the aneurysm. At this positioning, the distal free-cell segments are able to interact with the coil mass within the aneurysm and the next free-cell segments in an extra-aneurysmal position, open and preserving flow into the efferent vessels. Placement of the stent in optimal position may be somewhat difficult, as the 4-mm "safety range" for Neuroform stent deployment is limited by the two distal free-cells measuring 2 mm each. With subsequent placement of detachable coils, a stable waffle cone construct was able to be formed in all six described models.