Unusual Presentation of Cerebral Cavernous Malformation.

Cerebral cavernous malformations (CMs) are vascular malformations of the central nervous system, which can be detected in the absence of any clinical symptoms. Nodules and cysts with mixed signal intensity and a peripheral hemosiderin rim are considered brain magnetic resonance imaging (MRI) findings typical of CMs. A 48-year-old man was admitted to our hospital because of abnormal MRI findings without significant neurological symptoms. A cyst with an internal fluid-fluid level was found in the left basal ganglia on the initial brain MRI. We decided to observe the natural course of the asymptomatic lesion with serial MRI follow-up. On MRI at the 5-month follow-up, the cystic mass was enlarged and showed findings consistent with those of cystic CM. Surgical resection was performed and the pathological diagnosis was CM. Our experience suggests that the initial presentation of a CM can be a pure cyst and neurosurgeons should consider the likelihood of CMs in cases of cystic cerebral lesions with intracystic hemorrhage.