脳内出血にて発症したtwig-like middle cerebral arteryに対してECA-MCA double anastomosesを施行した1例

A Case of ECA-MCA Double Anastomoses for Hemorrhagic Type of Twig-Like MCA

Ⅰ．はじめに

　以前より，もやもや病の診断基準は満たさないが，もやもや様の異常血管網を伴う中大脳動脈（middle cerebral artery:MCA）閉塞症の存在が報告されており，本病態は“spontaneous MCA occlusion with moyamoya phenomenon”，“aplastic MCA”，“twig-like MCA”などと記されてきた．しかし，その病態は未だ定かではなく，治療方針に関しても統一されたものは存在していない^1-4,7,12-15)．今回われわれは，脳内出血で発症したtwig-like MCAの1症例を経験し，脳内血腫除去術後に時期をおいて浅側頭動脈（superficial temporal artery:STA）-，後頭動脈（occipital artery:OA）-MCA double anastomosesを施行し良好な経過を得ることができたので，文献的考察を加えて報告する．

　Herein, we describe the case of a superficial temporal artery（STA）- and occipital artery（OA）-middle cerebral artery（MCA）double anastomoses that we performed to treat a hemorrhagic twig-like MCA. A 55-year-old man presented to our hospital for investigation of an incidentally identified left MCA occlusion. Left cerebral angiography revealed a twig-like MCA. The ¹²³I-IMP-single photon emission computed tomography（SPECT）demonstrated no reduction in the cerebral blood flow（CBF), so the patient was initially observed with no treatment. Three months later, he was readmitted with a disturbance of consciousness. The cranial computed tomography revealed a subcortical hemorrhage in the left frontotemporal region and a subdural hematoma. The hematoma was removed via emergency craniotomy. The abnormal vessels were identified and resected, but the parietal branch of the STA was damaged during the skin incision. The histological examination did not reveal the marked fibrous thickening of the intima or wavy internal elastic lamina typically seen with Moyamoya disease. Six months after the initial surgery, a STA-MCA bypass surgery was planned to prevent a future hemorrhage by reducing the hemodynamic overload of the twig-like MCA and improving the cerebral ischemia in the MCA territory that was detected on the preoperative SPECT. However, the parietal branch of the left STA had been injured during the first operation, so we performed a double anastomoses to the MCA using the frontal branch of the STA and the OA. The patient's postoperative course was uneventful and he was discharged 2 weeks after surgery. The follow-up study performed 1 year postoperatively demonstrated no evidence of cerebral infarction and revealed an improvement in the resting CBF and vascular reactivity in the left cerebral hemisphere. No subsequent cerebrovascular events have occurred in this patient during the 7 years since the double anastomoses surgery. Direct bypass for flow conversion from the internal carotid artery to the external carotid artery can be an indispensable treatment for patients with a hemorrhagic twig-like MCA.