This research study is being done to test the effectiveness of a new generation FDA approved device for treating aneurysms compared to the current standard device for endovascular aneurysm treatment which is bare platinum coils. Endovascular procedures are a form of minimally invasive surgery, which is performed on blood vessels. The technique involves the introduction of a catheter which is a long, thin, flexible, hollow plastic tube through the skin into a large blood vessel. Typically the chosen blood vessel is the femoral artery found near the groin. The catheter is then maneuvered through the body to the location of the aneurysm in the brain using image guidance. Coils are delivered into the aneurysm through the catheters. Once the coils are delivered in the aneurysm, they are detached from the catheter. This is repeated until enough coils fill the aneurysm, blocking the blood flow to the aneurysm. The body responds by forming blood clots around the coil(s), which helps block the flow of blood into the aneurysm and keeps the vessel from rupturing or leaking. This study will compare the study device to the standard bare platinum coil to see which is better at preventing future rupturing or leaking. The study device is called the HydroCoil Embolization System and this study is a post-market clinical trial.

About 600 subjects from multiple institutions will take part in this study.

Your part in this study will last up to 24 months and will involve 6 visits (1 baseline visit before your surgery, the surgical procedure and 4 follow-up visits). These visits will occur at the same time as the visits you would receive as standard of care after your surgery.

If you are in this study, you will be placed in one of two study groups by chance using a process similar to the flip of a coin. This process is called randomization. Neither you nor the study staff will select the group you will be in. One group, the control group, will have their aneurysm treated by the bare platinum coils during their endovascular procedure. The other group, the study group will receive coils from the HydroCoil Embolization System. Both groups will receive the same standard of care and follow-up, but during the surgery different types of coils will be used.

Inclusion Criteria:

Candidates for this study must meet the following criteria to be enrolled in the study:

1. Patient is between 18 and 75 years of age (inclusive).
2. Patient has a documented untreated intracranial saccular aneurysm 3-14 mm diameter angiographic lumen, ruptured or unruptured, suitable for embolization with coils.
3. Patients presenting with a HUNT and HESS Grade 0-3 or improving to such a grade before treatment
4. Any type of bare platinum coils and HydroCoil ® Coils are treatment options (all shapes allowed).
5. Patient or next of kin or person with appropriate power of attorney has provided written informed consent.
6. Patient is willing and available for study follow-up visits
7. Patient has not been previously entered into this Study

Exclusion Criteria:

Candidates will be ineligible for enrollment in the study if any of the following conditions apply:

1. Inability to obtain informed consent

2. Patient is < 18 or > 75 years old

3. Target aneurysm is not saccular in nature (mycotic, fusiform, dissecting).

4. Target aneurysm is > 14 mm maximum luminal dimension, < 3 mm maximum luminal dimension

5. Target aneurysm has been previously clipped or coiled

6. Target aneurysm is in the physician's estimate unlikely to be successfully treated by endovascular techniques.

7. Patient has known hypersensitivity to platinum, nickel, stainless steel or structurally related compounds found in HydroCoil®, HydroSoft®, HydroFrame® Coils and/or bare platinum coils.

8. Baseline Hunt and Hess scale 4 or 5 for ruptured aneurysms

9. Intended use of a flow diverting stent (e.g. pipeline)

10. Subject has concurrent intracranial pathology, e.g.

    • Moyamoya
    • Vasculitis documented by biopsy results
    • AVMs
    • AV fistulas
    • Significant atherosclerotic disease (i.e. symptomatic and or >50% narrowing of the parent arteries necessary to traverse in order to coil the target aneurysm)
    • Intracranial Hematoma (unrelated to the target aneurysm)
    • Brain tumors
    • Vascular tortuosity and other conditions preventing access to target aneurysm

11. Subject has serious co-morbidities that could confound the study results:

    • Uncontrolled hypertension
    • Uncorrectable coagulation abnormality
    • Contraindications for heparin, aspirin or clopidogrel
    • Uncontrolled Diabetes Mellitus
    • Organ failure of kidney, liver, heart, or lung
    • Myocardial infarction within the past 6 months
    • Cancer likely to cause death within 2 years or less.

12. Subject history indicates high risk of non-compliance (e.g., substance abuse, psychosocial issues, etc.)

13. Subject has a known history contraindicating contrast dye or iodine that cannot be pre-medicated prior to coiling procedure (vs. sensitivity which can be safely controlled by antihistamine, steroid, etc.). Medical clearance will be needed for this issue.

14. Patients who are unable to complete scheduled follow up assessments at the enrolling center due to limited life expectancy (<2 years), co-morbidities or geographical considerations

15. Subject is currently breast feeding, pregnant or plans to become pregnant in the next 2 years.

16. Major surgical procedure or trauma within 30 days prior to randomization

17. The patient is currently enrolled in another clinical study (device or drug).

18. More than one aneurysm needing treatment at the same time.