Spontaneous Regression of Intracranial Aneurysms-Case Report and Systematic Review of the Literature.

Background/Objectives: The natural course of intracranial aneurysms (IAs) remains unclear. Many of them remain stable over time and few experience patterns of growth. The spontaneous regression of IAs without any microsurgical or endovascular treatment is a very rare phenomenon. This paper reports the case of a 56-year-old female who experienced spontaneous regression of her IA. Furthermore, it contains a systematic literature review to explore reported cases of spontaneous IA regression. Methods: The case of a 56-year old female patient who presented with an anterior communicating artery (ACom) IA that thrombosed spontaneously after 108 months follow-up is reported. Additionally, a systematic literature search was conducted using the Medline database to identify reported cases. Results: The IA showed spontaneous regression without any surgical or endovascular intervention. We identified 33 articles describing IAs with spontaneous regression. Reported reasons for spontaneous IA thrombosis included (1) anatomical factors like narrow aneurysmal necks; (2) coagulation pathway modifications, including antifibrinolytic activity that promotes thrombosis; and (3) hemodynamic changes such as altered blood flow dynamics and external vascular compression. These findings suggest that spontaneous regression, while rare and unpredictable, can be associated with distinct physiological and anatomical conditions. Conclusions: The spontaneous regression of IAs is an extremely rare phenomenon. It cannot reliably be predicted and may be associated with changes in the hemodynamic situation, specific anatomical constellations, or coagulation pathways.