Giant cavernoma of the brain stem: value of delayed MR imaging after contrast injection.

Cavernous angiomas are vascular malformations composed of slowly perfused, sinusoidal vessels which can be located in any part of the central nervous system. Whereas diagnosis is mostly straightforward in typical cases, some lesions may present in unusual locations or with unusual imaging characteristics. Because of the slow perfusion, contrast enhancement is not regarded as a characteristic imaging feature of cavernomas. We report a large brain stem cavernoma with signs of recent bleeding, in which the differential diagnosis against other mass lesions was facilitated by the demonstration of slow, but intense, contrast enhancement on MRI 1 h after contrast injection. We conclude that contrast enhancement in delayed images may contribute to a safe diagnosis of cavernous haemangiomas and should be performed in atypical cases.