When common lesions behave like a rare disease: The case for orphan status in brain aneurysm research

Brain aneurysms occupy a unique and somewhat paradoxical position in cerebrovascular disease. Although unruptured aneurysms are relatively common, affecting approximately 2–5% of the adult population, their most catastrophic consequence, aneurysmal subarachnoid hemorrhage (aSAH), remains comparatively rare, with an estimated global incidence of 7.9 (95% CI 6.9 to 9.0) per 100 000 person-years.1 This imbalance yields a condition that carries profound neurological morbidity and mortality, disproportionately affecting individuals in midlife, yet occurs with too low a frequency to command the research attention, infrastructure, and funding typically devoted to high-burden disorders such as ischemic stroke. As a result, brain aneurysms function in many respects—scientifically, structurally, and economically—like an orphan disease.