Endovascular treatment of an inaccessible aneurysm in moyamoya‑like vessels using the floating‑coil technique

In moyamoya disease (MMD), moyamoya‑like vessels develop at the base of the brain. A ruptured aneurysm originating from these vessels is challenging to manage with endovascular treatment (EVT). When direct catheterization is infeasible, parent artery occlusion (PAO) may be the last resort. However, if liquid embolic agents are unsafe due to a short reflux distance, deploying floating coils into the parent artery to occlude or trap the aneurysm offers a viable alternative. This maneuver, termed the "floating‑coil technique," has not been previously described. A 60‑year‑old man with subarachnoid hemorrhage (Hunt-Hess grade II) had MMD and an aneurysm in moyamoya-like vessels arising from the posterior cerebral artery. During EVT, neither the Marathon nor the Echelon‑10 microcatheter could be navigated into the parent artery because of an acute angulation. The floating-coil technique was used: first, an Axium Prime 1 mm × 2 cm coil was pushed out, detached, and floated into the parent artery. Then, 3 Axium Prime 1 mm × 1 cm coils were similarly deployed to occlude the parent artery of the aneurysm. Post‑EVT angiography showed disappearance of the aneurysm and occlusion of moyamoya‑like vessels. The patient had no new deficits and recovered well, with a modified Rankin Scale score of 0 at the 2‑month follow‑up. Thus, the "floating‑coil technique" is a valid choice for inaccessible aneurysms in moyamoya‑like vessels.