橋出血にて発症した，transpontine veinを導出路にもつ脳幹部mixed cerebrovascular malformationの1例

A Case of Hemorrhagic Mixed Cerebrovascular Malformation of the Brainstem Draining through a Transpontine Vein

I．はじめに

　近年，出血で発症したvenous angiomaの手術標本やMRI所見の検討の結果，cavernous angiomaなどの他の種類の脳血管奇形の隣接併存が明らかとなった例が，報告されている^{1,8,9,12,14）}．この場合，出血の責任を，venous angioma自身よりも，併存する他の易出血性脳血管奇形に，求める報告が増えている^1,8,12）．われわれは，このような多種類の脳血管奇形の隣接併存を，Awardの提唱に基づいて^1），mixed cerebrovascular malformation（MCVMと略す）と呼ぶことが適切と考えている．なお，Huangは，腫瘍性病変との混同しやすい“angioma”との用語を避けるため，cavernous an—gioma，venous angiomaを，それぞれcavernous venous malformation（CVMと略す），medullary venous mal—formation（MVMと略す）と呼称することを主張しており，以下これに従う^3,13）．

　MRIの普及に伴い，脳血管奇形の発見に著しい発達をみているが，脳幹部MVMの報告は，非常に少ない^2,4,10）．最近，transpontine veinと呼ばれる，脳幹部を貫いて走る髄内静脈を導出路とした特徴的な画像を呈する脳幹部MVMの報告があり，注目されている^2）．

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 hemor-rhage with linear enhancement. Depending on MRI findings, the hemorrhage was thought to be an intratu-moral hemorrhage within the cavernous venous mal-formation. Cerebral angiogram demonstrated medullary venous malformation. The malformation drained to the anterior pontomesencephalic vein through a transpon-tine 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 malforma-tion 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 mal-formations.