Aims and hypothesis: Giant intracranial aneurysms have a poor prognosis mainly due to their high risk of rupture. Because their incidence is low, clinical trial evidence for adequate treatment is lacking. The Giant Intracranial Aneurysm Registry is designed to document current treatment strategies in giant aneurysm care and to monitor the course of the disease over five-years. It aims to evaluate the hypothesis that all three possible branches of therapy (conservative/endovascular/surgical) lead to equal rupture rates.

Design: The Giant Intracranial Aneurysm Registry is an interdisciplinary multicenter observational study. Each center recruits patients diagnosed with a giant intracranial aneurysm both prospectively and retrospectively. Primary outcome will be the aneurysm rupture rate at five-years of follow-up.

Study outcome: Patient enrollment has begun at 20 neurovascular centers throughout Germany, with 19 further centers applying for local ethics approval to take part in the study. The first nine months are designed as a pilot phase followed by the integration of study centers throughout the EU and the initiation of separate sub-studies.

Discussion: Giant intracranial aneurysms have often been ignored or marginalized due to their low incidence. The Giant Intracranial Aneurysm Registry aims to lead to a better understanding of these complex lesions and to serve as a basis for the development of future clinical studies.