Due to results shown by the Cerecyte Clinical Trial, HCAT stopped enrolling.

The study will compare clinical and angiographic outcomes in patients receiving Hydrocoil aneurysm treatment versus patients receiving non-HydroCoil aneurysm treatment.

With prospective, randomized trials in progress evaluating the effectiveness of Hydrocoils and Cerecyte coils in comparison to bare platinum coils, the next step is a direct comparison of Hydrocoils and non-HydroCoils (Cerecyte or Platinum). Considering the increased costs to society of treatment with these new coils, it is essential that the benefits of the new technology are properly evaluated against the existing platinum coil technology in a scientifically valid manner.

Inclusion Criteria:

1. Patient presenting with a ruptured or un-ruptured cerebral aneurysm appropriate for endovascular treatment as determined by the neurovascular team (neurosurgeon/neurointerventionalist)
2. The neurointerventionalist believes that the aneurysm can be safely treated with either Cerecyte or Hydrogel.
3. Patients between (and including) 21 and 90 years of age.
4. Patient HUNT AND HESS Grade 0-3.
5. Patient has given fully informed consent to endovascular coiling procedure. If patient cannot consent for themselves, appropriate written consent has been sought from their next of kin, or from appropriate power of attorney.
6. Aneurysm 5-20mm in maximum diameter.
7. Patient is willing and able to return for clinical evaluation and follow-up imaging evaluation (angiography or MRA) at both 6-months and 12-18 months after endovascular treatment.
8. The patient has not been previously randomized into this or another related ongoing trial.
9. The aneurysm has not previously been treated (by coiling or clipping).

Exclusion Criteria:

1. Patient has more than one aneurysm requiring treatment in the current treatment session If a patient has multiple aneurysms, but only one will be treated at the time of enrollment, they are eligible for the trial. (Additional aneurysms may be treated at a later date, and may be treated with any coil type that the operator chooses).

2. Target aneurysm has had previous coil treatment or surgically clipped.

3. Patient has an H&H score of 4 or 5 after subarachnoid hemorrhage (SAH).

4. Inability to obtain informed consent.

5. Medical or surgical co-morbidity such that the patient's life expectancy is less than 1 year.

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