[A case of hemorrhagic mixed cerebrovascular malformation of the brainstem draining through a transpontine vein].

A case of mixed cerebrovascular malformation of the brainstem with pontine hemorrhage is reported. The mixed cerebrovascular malformation was composed of medullary venous malformation, one hemorrhagic and another non-hemorrhagic mass. The latter masses were thought to be cavernous venous malformations by their MR findings. The medullary venous malformation drained to the anterior pontomesencephalic vein through a transpontine vein. A 70-year-old man, complaining of aggravation of left hemiparesis, was admitted to our department. His past history included traumatic cervical myelopathy and diabetic neuropathy. CT revealed a pontine hemorrhage with linear enhancement. Depending on MRI findings, the hemorrhage was thought to be an intratumoral hemorrhage within the cavernous venous malformation. Cerebral angiogram demonstrated medullary venous malformation. The malformation drained to the anterior pontomesencephalic vein through a transpontine vein. The linear enhancement was the transpontine vein itself. Medullary venous malformations in the brainstem are rare. With MRI, the transpontine vein is thought to be a characteristic feature of medullary venous malformation of the brainstem. We suggest that most cases of hemorrhagic medullary venous malformations are mixed cerebrovascular malformations. We emphasize the need for precise examination of other types of vascular lesions coexisting with medullary venous malformations.