The purpose of this study is to assess the safety and effectiveness of the Artisse™ Intrasaccular Device in the treatment of unruptured and ruptured wide-neck bifurcating intracranial aneurysms.

The Artisse™ IDE study is a prospective, multi-center, single-arm Investigational Device Exemption (IDE) study of the Artisse™ Intrasaccular Device for the treatment of IAs. The primary objective of the Artisse™ IDE study is to assess the safety and effectiveness of the Artisse™ Intrasaccular Device in the treatment of unruptured and ruptured wide-neck bifurcating intracranial aneurysms. The effectiveness of the Artisse™ Intrasaccular Device is measured by its ability to completely occlude the treated aneurysm without retreatment of the target aneurysm, recurrent subarachnoid hemorrhage from the target aneurysm, or significant parent artery stenosis (> 50% stenosis) at 1 year post-procedure.

Inclusion Criteria:

1. Subject or subject's Legally Authorized Representative (LAR) has provided written informed consent using the Institutional Review Board/Ethics Committee (IRB/EC) approved Informed Consent Form (ICF). Health Insurance Portability and Accountability Act (HIPAA)/data protection authorization has been provided and signed by the subject or subject's LAR.

2. Subject is 18-75 years of age at the time of consent.

3. Subject has a single unruptured or ruptured IA requiring treatment. If the patient has an additional IA, the additional IA must not be deemed to require treatment within 1-year of the index procedure.

4. The target aneurysm must have the following characteristics:

   1. Saccular morphology
   2. Located at a bifurcation in the anterior or posterior circulation
   3. Aneurysm Width appropriate for treatment with the Artisse™ Intrasaccular Device for device sizingper the Instructions for Use.
   4. Wide-necked, defined as neck size ≥ 4 mm and/or a dome-to-neck ratio of ≥ 1 and < 2.

5. If the target aneurysm was acutely ruptured, subject must be neurologically stable with Hunt and Hess Grade of I or II.

   Ruptured IA is defined as showing evidence of SAH attributed to the target aneurysm within the last 30-days (using computed tomography (CT), magnetic resonance imaging (MRI), or lumbar puncture (LP).)

6. Subject is able to comply with all aspects of the Clinical Investigation Plan (CIP) requirements (e.g., screening, evaluation, treatment, and the post-procedure follow-up schedule).

7. Subject meets one or more risk factors for IA rupture, such as age, hypertension, cigarette smoking, use of sympathomimetic drugs, Japanese or Finnish ancestry, history of prior aneurysmal subarachnoid hemorrhage (aSAH), familial intracranial aneurysms or SAH, clinical or radiological mass effect, reduced quality of life due to fear of rupture, IA size, location, and morphology, documented growth of IA on serial imaging (or enhanced aneurysm walls on contrast), presence of multiple IAs, and presence of concurrent pathology.

8. Treating physician has already selected the subject for endovascular treatment of the target aneurysm after considering risk-benefit of clipping vs endovascular treatment

9. If the subject has an additional IA that was treated previously, the additional IA must have been clinically stable in the past 90 days (i.e. without ongoing adverse events related to the previous treatment).

Exclusion Criteria:

1. During treatment planning, it is determined that subject may need an adjunctive implant device in addition to the Artisse™ Intrasaccular Device. (Subjects who need unplanned adjunctive implant devices are not excluded.)
2. Subject's target aneurysm was previously treated with other devices/implants (e.g., coils) or parent artery has a stent or other obstruction that could interfere with the correct placement of the Artisse™ Intrasaccular Device.
3. Subject has a known active systemic bacterial infection.
4. Subject has anatomy or physiology considered unsuitable (e.g., vessel anomaly or disease) for endovascular treatment with the Artisse™ Intrasaccular Device by the treating physician.
5. Subject has a mRS score > 2 (i.e., mRS scores of 3 to 5) prior to procedure (in case of unruptured IA) or prior to rupture (in case of ruptured IA).
6. Subject has an SAH from a non-target aneurysm or any other intracranial hemorrhage within 90 days.
7. Subject, of child-bearing potential, is pregnant (confirmed with a positive pregnancy test) or plans to become pregnant during the 1 year follow up period after the index procedure.
8. Subject is enrolled in another device or drug study in which participation could confound study results.
9. The treating physician determines that the health of the subject or the validity of the study outcomes (e.g., high risk of neurologic events, conditions that may increase the chance of stroke) may be compromised by the subject's enrollment.
10. Subject has a known hypersensitivity, which cannot be medically treated, to any component of the study device, procedural materials, or medications commonly used during the procedure.
11. Subject is taking anticoagulants (e.g., warfarin) that cannot be discontinued for a minimum of 7 days post-procedure or have a known blood dyscrasia, coagulopathy, or hemoglobinopathy.
12. Subject has acute or chronic renal failure (unless on dialysis) that would prevent them from undergoing digital subtraction angiography (DSA).
13. Subject has a life expectancy of less than 5 years due to an illness or condition other than the index IA.