A prospective single-center analysis of the safety and efficacy of the HydroCoil embolization system for the treatment of intracranial aneurysms

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The HydroCoil embolization system is a helical platinum coil coated with a polymeric hydrogel that expands when it contacts aqueous solutions to increase filling volumes, improve mesh stability, and possibly elicit a healing response within the aneurysm. In this paper, the authors report the 1-year recurrence and complication rates of 67 aneurysms embolized with the HydroCoil system.


Sixty-four consecutive patients (67 total aneurysms) with small (≤ 7 mm), large (8–15 mm), very large (16–24 mm), and giant (≥ 25 mm) aneurysms in the anterior and posterior intracranial circulations were treated with HydroCoils between March 2003 and September 2004. All aneurysms were embolized by the senior author (A.S.B) with HydroCoils alone or in combination with bare platinum coils, until either there was no further angiographic contrast filling of the aneurysm or the microcatheter was pushed out of the dome by the coil mass. Balloon assistance was used in three cases and combined Neuroform stent–coil embolization in eight other cases. To evaluate the safety and 1-year efficacy of the HydroCoil system, periprocedural complications were recorded, and angiographic recurrences were categorized using the Raymond–Roy Occlusion Classification (RROC) system.

The 1-year aneurysm recurrence rate independent of size was 15% in patients treated with HydroCoils. Seventy percent of the patients had stable occlusions. The recurrence rate for small aneurysms was 3.7%, and the combined recurrence rate for small and large aneurysms was 6%. Fifteen percent of the aneurysms initially categorized as RROC Type 2 or 3 with stasis of contrast material at the time of initial embolization improved in RROC type, allowing the authors to develop the aneurysm embolization grade to predict recurrence. The neurological complication rate was 14.9%, of which 4.5% represented permanent neurological deficits.


The HydroCoil embolization system is safe and provides excellent 1-year occlusion of small and large aneurysms with initial RROC Type 1, as well as those with RROC Types 2 and 3 with stasis of contrast material at the time of embolization. Very large and giant aneurysms were not as successfully occluded with this system. Treatment of large and giant internal carotid artery aneurysms was more likely to result in cranial nerve palsies and postembolization headaches than treatment in other locations. The aneurysm embolization grade the authors developed using the results of this study accurately predicted 1-year recurrence rates based on the immediate postembolization angiographic characteristics of the treated aneurysm.

Abbreviations used in this paper:BA = basilar artery; ICA = internal carotid artery; NPH = normal-pressure hydrocephalus; OphA = ophthalmic artery; RROC = Raymond–Roy Occlusion Classification; SAH = subarachnoid hemorrhage; VBJ = vertebro-basilar junction; VP = ventriculoperitoneal.

Article Information

Address reprint requests to: Alan S. Boulos, M.D., Department of Surgery, Division of Neurosurgery, Albany Medical Center, 47 New Scotland Avenue, Albany, New York 12208. email: BoulosA@mail.amc.edu.

© AANS, except where prohibited by US copyright law.



  • View in gallery

    Pie chart showing the distribution of aneurysm location. Acom = anterior communicating artery; MCA = middle cerebral artery; Pcom = posterior communicating artery; SCA = superior cerebellar artery.

  • View in gallery

    Pie charts showing the frequency of initial RROC Types 1 to 3 for small (A), large (B), very large (C), and giant (D) aneurysms treated with HydroCoils.

  • View in gallery

    Pie charts showing the 1-year recurrence rates for small (A), large (B), very large (C), and giant (D) aneurysms treated with HydroCoils.



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