De novo cerebral arteriovenous malformation in a child with previous cavernous malformation and developmental venous anomaly.

Although cerebral vascular malformations are traditionally considered to be congenital lesions, they often become clinically evident in the 3rd to 4th decades of life, leading to the assumption of a long silent clinical period. Unlike vein of Galen malformations, antenatal diagnosis of cerebral arteriovenous malformations (AVMs) is highly uncommon. Postnatal development of an AVM is an emergent concept supported by more clinical observations. Genetic and biological studies demonstrate that an environmental trigger ("second hit") in addition to genetic predisposition may be a key in understanding the pathophysiology of AVMs and other cerebral vascular lesions such as cavernous malformations (CMs). The authors describe a 6-year-old boy in whom a giant CM was diagnosed and a de novo AVM was detected 25 months after initial resection of the CM. This case seems to support the second-hit hypothesis.