Cerebral arteriovenous malformations (AVMs) are generally attributed to congenital lesions that arise from aberrant vasculogenesis between the fourth and eighth weeks of embryonic life. However, this dogma has been challenged by several recent observations, one of which is de novo formation of AVMs. Forty cases of de novo AVMs were published between 2000 and 2019, all of which involved a history of intracranial insult, such as vascular abnormalities or nonvascular conditions, prior to AVM diagnosis. We hereby present two unique operative cases of ruptured de novo AVMs in older adult patients. Case 1 is novel in the sense that the patient did not experience any kind of environmental trigger (“second hit”) such as a previous intracranial insult, while Case 2 serves as the second report of a de novo AVM patient with a medical history of Bell's palsy.

Although the exact mechanisms of AVM formation remain to be elucidated, it is likely to be a multifactorial process related to environmental and hemodynamic factors.

脑动静脉畸形（AVM）通常归因于先天性病变，这些病变是在胚胎生命的第四周和第八周之间因异常血管生成而引起的。然而，这一教条已经受到最近的一些观察的挑战，其中之一是从头开始形成AVM。在2000年至2019年之间发表了40例从头开始的AVM，所有这些都涉及AVM诊断之前颅内损伤的病史，例如血管异常或非血管疾病。在此，我们介绍了老年患者中从头破裂AVM的两个独特的手术病例。从患者没有经历过任何类型的环境触发因素（“第二次发作”）（例如先前的颅内侮辱）的意义上讲，案例1是新颖的，而案例2则是具有病史的从头AVM患者的第二次报告钟'

尽管尚不清楚AVM形成的确切机制，但它可能是与环境和血液动力学因素有关的多因素过程。