Rarity of disease and current practice in the field made enrollment challenging.

In this study, patients with large anterior circulation IAs with neck and fundus morphologies amenable to either traditional endovascular treatments using coils or reconstruction with the flow diversion will be randomly assigned to either treatment technique.

This is a prospective, randomized trial comparing the endovascular coiling (endovascular coiling) versus the flow diversion for large and giant aneurysm treatment. The endovascular coiling used in this study are FDA-approved and in common use at institutions in this country and across the world. The flow diversion devices are FDA-approved for anterior circulation aneurysms >10 mm and are in common use at institutions in this country and across the world. Patients will be enrolled who meet the inclusion criteria and consent to participate. Patients will be randomly assigned by a central web-based system in a 1:1 manner to treatment with either endovascular coiling or flow diversion. Data on each patient will be collected at the time of enrollment and treatment, and at subsequent follow-up visits.

Inclusion criteria

1. Age 21 to 75 years, inclusive

2. Patient has a single target IA that: is located in the following regions of the internal carotid artery:

   1. Paraophthalmic (including paraclinoid, ophthalmic and hypophyseal segments)
   2. Cavernous
   3. Petrous

3. has a parent vessel with diameter 2.5-5.0 mm

4. Wide neck aneurysm ≥4 mm.

5. Target IA has size (maximum fundus diameter) 10 mm

6. The operator feels that the aneurysm can be appropriately treated with traditional endovascular techniques (endovascular coil embolization with or without adjunctive devices or parent artery deconstruction) using endovascular coiling or flow diversion devices.

7. Modified Rankin Scale 0-3

8. Signed and dated informed consent

4.2 Exclusion criteria

1. More than one IA requiring treatment in the next 6 months
2. Subarachnoid hemorrhage in the past 60 days
3. Any intracranial hemorrhage in the last 42 days
4. Major surgery (requiring general anesthesia) in the last 42 days
5. Coils in place in the target IA
6. Unstable neurologic deficit (i.e., any rapidly worsening clinical condition in the last 30 days (defined by a change in mRS of 2 or more))
7. Known irreversible bleeding disorder
8. Platelet count < 100 x 103 cells/mm3 or known platelet dysfunction
9. Clinically documented evidence in medical history of adverse reaction or contraindication to medications used in treatment of the aneurysm (i.e. Plavix, heparin, aspirin)
10. Prior stent placement at target site
11. Documented history of dementia
12. Contraindication to CT scan and MRI (ie. contrast allergy, or other condition that prohibits imaging from either CT or MRI)
13. Known allergy to contrast used in angiography that cannot be medically controlled
14. Known severe allergy to platinum or cobalt/chromium alloys
15. Relative contraindication to angiography (e.g., serum creatinine > 2.5 mg/dL)
16. Pregnancy, breast-feeding, or positive pregnancy test [either serum or urine] (Woman of child-bearing potential must have a negative pregnancy test prior to the study procedure.)
17. Evidence of active infection (indicated by fever [at or over 99.9 °F] and/or open draining wound) at the time of randomization
18. Other known conditions of the heart, blood, brain or intracranial vessels that carry a high risk of neurologic events (e.g., severe heart failure, atrial fibrillation, known carotid stenosis)
19. Current use of cocaine or other illicit substance
20. Any comorbid disease or condition expected to compromise survival or ability to complete Follow-up assessments through 180 days
21. Extracranial stenosis greater than 50% in the carotid artery
22. Intracranial stenosis greater than 50% in the treated vessel
23. Based on investigator's judgment, patient does not have the necessary mental capacity to participate or is unwilling or unable to comply with protocol follow up appointment schedule.
24. "Previously randomized into this trial or currently participating in another trial where the data is intended to be used to obtain marketing approval or to broaden an indication, without the approval of the study principal investigator, that may confound the results of this study.

A screen failure log of all cases referred or presented for possible inclusion, but who were not randomized, and the reason(s) for exclusion will be maintained.