Mechanisms of Healing in Coiled Intracranial Aneurysms: A Review of the Literature

Recanalization of intracranial aneurysms following endovascular coiling remains a frustratingly common occurrence. An understanding of the molecular and histopathologic mechanisms of aneurysm healing following coil embolization is essential to improving aneurysm occlusion rates. Histopathologic studies in coiled human and experimental aneurysms suggest that during the first month postcoiling, thrombus formation and active inflammation occur within the aneurysm dome. Several months following embolization, the aneurysm is excluded from the parent vessel by formation of a neointimal layer, which is often thin and discontinuous, across the aneurysm neck. Numerous coil modifications and systemic therapies have been tested in animals and humans in an attempt to improve the aneurysm-healing process; these modifications have met with variable levels of success. In this review, we summarize the histopathologic and molecular biology of aneurysm healing and discuss how these findings have been applied in an attempt to improve angiographic outcomes in patients with intracranial aneurysms.