頸部内頸動脈にみられた窓形成

FENESTRATION OF THE INTERNAL CAROTID ARTERY IN THE NECK

　抄録　脳血管の一部に重複するbypass血管の存在する走行異常である窓形成（fenestration｝が，内頚動脈に認められたとする報告は極めて少ない。本論文では本異常の2症例の脳血管写所見を中心に，文献的に発生学的考察を加え報告した。症例1は47歳女性。破裂右中大脳動脈瘤の精在中，脳血管写で右頸部内頸動脈のC2レベルより遠位側の著明な蛇行と径の拡大，およびC1レベルに窓形成を認めた。さらに右外頸動脈も総頸動脈からの分岐部でlateral positionの異常を示した。症例2は51歳男性。右側頭葉腫瘍（glio—blastoma multiforme）の精査中，脳血管写で右頸部内頸動脈がC1-2レベルで拡大し，C1／2間レベルに窓形成を認めた。これら2症例の窓形成とも，それ自体は無症候性であった。文献上，頸部内頸動脈は胎生期aortic arch 3とdorsal aortaの吻合により形成され，C2レベル付近に相当するその吻合部位へは将来退縮するductus caroticusも連結する。これらより報告した2症例でみられた窓形成の発生機序として，aortic arch 3とdorsal aortaの吻合の錯誤か，ductus caroticusの遠位部の遺残が示唆されることを述べた。

Fenestration or duplication of the internal caro-tid artery is extremely rare. A review of the lite-rature revealed only two such cases by angio-graphy. We present two further cases of internal carotid artery fenestration, incidentally disclosed by angiography. The embryological basis and theclinical significance of this anomalous condition were discussed.

Case 1. A 47-year-old woman was admitted to hospital on May 13, 1982, after the first attack of subarachnoid hemorrhage. Four-vessel angiography showed a saccular aneurysm arising at the trifur-cation of the right middle cerebral artery. In ad-dition, a fenestration of the right internal carotid artery was demonstrated at the level of the atlas : the cervical portion of the vessel distal to the level of C-2 was markedly elongated and dilated in caliber. Moreover, the right external carotidartery occupied a dorso-lateral position relative to the internal carotid artery.

Case 2. A 51-year-old man was admitted to hos-pital on April 20, 1983, for evaluation of grand mal seizures. CT scans and four-vessel angiograms showed a malignant glioma of the right temporal lobe. Additionally, a fenestration of the right in-ternal carotid artery was identified at the level of the atlantoaxial joint, and the vessel was dilated in caliber at the level of C-1 to C-2.