De novo cavernoma developing from an asymptomatic thalamic microhemorrhage.

Cavernomas are low-flow vascular lesions affecting approximately 0.5% of the population. Historically these have been considered congenital lesions, but numerous reports have demonstrated de novo formation. The phenomenon is well documented in patients with the familial disease form and after cranial radiotherapy, but outside of these circumstances there is scant evidence as to the potential etiology. The authors present a 5 year MRI series of a 56-year-old woman with no known risk factors demonstrating cavernoma formation and growth from previously normal brain. The patient was consistently asymptomatic during follow-up. Given the history and imaging findings, we propose that cavernomas can arise directly from angiogenic proliferation secondary to microhemorrhage from unrelated causes.