1. major angiographic recurrence of the lesion or the presence of a residual aneurysm at last angiographic follow-up, as determined by the core laboratory, blinded to treatment allocation;
2. retreatment of the same aneurysm by endovascular or surgical means during the 18-month follow-up period;
3. an intracranial bleeding episode, or the occurrence or progression of a mass effect in relation to the treated aneurysm during the follow-up period, as determined by the blinded Adverse Event Committee.

For the Platinum coils population (222):

Primary outcome available for 220/222 (could not attribute primary outcome for 2 participants)

For the Hydrogel coils population (225):

Withdrawn by physician right after Registration: 3/225 (remaining 222) Primary outcome available for 215/222 (could not attribute primary outcome for 7 participants)

Number of participants dead - All causes

For the Platinum coils population (222):

Secondary outcome measure applies to 222 participants.

For the Hydrogel coils population (225):

Withdrawn by physician right after Registration: 3/225 (remaining 222). Secondary outcome measure applies to 222 participants

Number of participants having experienced one or several Adverse Events. This measure is the number of participants having experienced Serious Adverse Events plus those having experienced other (not including Serious) Adverse Events.

For the Platinum coils population (222):

Secondary outcome measure applies to 222 participants.

For the Hydrogel coils population (225):

Withdrawn by physician right after Registration: 3/225 (remaining 222). Secondary outcome measure applies to 222 participants

Number of participants having experienced one or several Serious Adverse Events

For the Platinum coils population (222):

Secondary outcome measure applies to 222 participants.

For the Hydrogel coils population (225):

Withdrawn by physician right after Registration: 3/225 (remaining 222). Secondary outcome measure applies to 222 participants