The International PERForator ANeurysm Registry (PERFAN) - Natural History, Treatment, and Outcome of Intracranial Perforator Aneurysms

1. Background and current state of research

Lenticulostriate and basilar perforator aneurysms are extremely rare subtypes of intracranial aneurysms. Recent years have seen an increase in their diagnosis due to advancements in imaging technology. However, their low incidence has left a significant gap in the understanding of their natural history, diagnostic evaluation, management, and clinical outcomes. To date, the available literature consists mainly of case reports or small case series, with only a limited number of systematic reviews, such as those on lenticulostriate aneurysms (112 cases) and basilar perforator aneurysms (54 patients).

The most common presentation of perforator aneurysms is rupture, although unruptured aneurysms may be diagnosed as an incidental finding or as the cause of compressive symptoms. Initial angiography fails to identify approximately 30%-60% of perforator aneurysms. Various treatment approaches have been reported, including surgery and various endovascular techniques such as coiling, embolization with liquid embolic agents, flow-diverters, and even electrothrombosis with a microguidewire. However, all invasive strategies have inherent periprocedural risks that must be carefully weighed against the reported overall high rate of favorable outcomes in conservatively managed patients.

Despite the growing interest and knowledge in this field, an international multicenter registry that includes baseline patient characteristics, imaging, follow-up protocols, treatment strategies, and outcomes for both ruptured and unruptured intracranial perforator aneurysms is still lacking. 2. Research questions, hypotheses and aims

The research questions of this exploratory study are:

• To conduct a comparative analysis of clinical characteristics and outcomes among patients with intracranial lenticulostriate and basilar perforator aneurysms treated conservatively, endovascularly, and surgically.
• To assess the size and exact location of lenticulostriate and basilar intracranial perforator aneurysms.
• To gather information regarding the specific type of endovascular treatment employed.
• To compare patients with predominantly perimesencephalic SAH harboring a perforator aneurysm and those without an aneurysm.
• To investigate the occurrence of spontaneous occlusion in aneurysms treated conservatively.
• To perform a core lab analysis of lenticulostriate and basilar intracranial perforator aneurysms using different imaging modalities, including computed tomography (CT), magnetic resonance imaging (MRI), 2D digital subtraction angiography (DSA), and 3D DSA.
• To review and document observed changes of lenticulostriate and basilar perforator aneurysms (e.g. size) on follow-up imaging.
• To examine the association between aneurysm size and the incidence of bleeding.

3. Methods