Rare aneurysms. No patient enrolled at site.

The purpose of the DIVERT study is to provide a prudent, controlled clinical context for the use of flow diversion, a promising option of yet unproven benefit, in the care of patients with acute blood blister-like and dissecting intradural aneurysms. Hence DIVERT is a simple, multicenter, randomized trial integrated into daily practice. DIVERT addresses the clinical dilemma of whether the use of PED FD truly is a safe and effective alternative to best standard treatment, defined as conventional methods of treatment or in some cases, observation. Selection criteria are few, to facilitate the recruitment of most affected patients confronted with these difficult aneurysms that their physician judges suitable for PED FD. The trial does not obstruct clinical care, does not include extra tests or risks beyond what is necessary and proven beneficial. Endpoints are simple, clinical, meaningful, valuable and resistant to bias. Follow-up visits and tests are "routine', imposing no extra burden on clinical transactions. Data is collected in simple case-report forms filled by physicians.

Ruptured blood blister-like (BB) and dissecting vertebral aneurysms are infrequent but devastating causes of subarachnoid hemorrhage (SAH), prone to acute rebleeding with poor clinical outcomes despite current surgical or endovascular treatment. Flow diversion (PED FD) with the Pipeline Endovascular Device (PED) is a promising treatment alternative to conventional management options.

The DIVERT trial is designed to provide a prudent, controlled clinical framework for offering the PED FD , a promising yet unproven option in the care of patients with acute blood blister-like or dissecting vertebral aneurysms. DIVERT is a care trial, designed as a simple, pragmatic, multicenter, randomized trial integrated into daily practice with inclusive selection criteria.

The investigators hypothesize that PED FD can decrease poor outcomes from 30 to 15%, compared to 'best standard treatment' (BST). BST is chosen prior to randomization amongst 4 options: observation, coiling with or without stenting, parent vessel occlusion or surgical clipping or wrapping. Patients are enrolled within 48 hours of SAH using standard 1:1 randomization between PED FD and BST after informed consent has been obtained from the patient or surrogate decision maker(s). Patients for whom no other option than PED FD appears feasible and safe will be included in a registry conducted alongside the trial.

Blister-like aneurysms and intradural dissections presenting with SAH have a high propensity for rebleeding and outcomes are poor in approximately one third of the cases, despite treatment using surgical or endovascular techniques.

Inclusion Criteria:

• A patient affected with a blood blister-like aneurysm or a dissecting aneurysm, vertebral or at other sites, responsible for a recent subarachnoid hemorrhage (<14 days) for whom PED FD is considered an appropriate therapeutic option by the participating clinician. Current indications may be (but not restricted to) symptomatic blister-like aneurysms and dissecting intradural vertebral aneurysms.

Exclusion Criteria:

1. Severe allergy, intolerance or bleeding disorder that prohibit the use of Acetyl Salicylic Acid (ASA), clopidogrel or other platelet inhibitors
2. Acute hydrocephalus or intracranial hematomas necessitating urgent ventricular drainage or surgical evacuation (patients may be recruited after these urgent interventions have been performed)
3. Absolute contraindication to endovascular treatment or anesthesia.