破裂脳動脈瘤術後早期に生じたIsolated Fourth Ventricleの1例

A Case of Isolated Fourth Ventricle in the Early Postoperative Period of Subarachnoid Hemorrhage

I．はじめに

　Isolated fourth ventricleとは，第4脳室から大槽への髄液の交通遮断に加え中脳水道の器質的もしくは機能的閉塞により第4脳室のみ拡大した状態で，頭蓋内圧亢進症状や意識障害，複視，失調などの後頭蓋窩の占拠性病変としての諸症候を呈するものである．一般に先行する水頭症に対しシャント手術を受け長期間経過した例に多いとされる．今回われわれは破裂脳動脈瘤術後早期に生じたisolated fourth ventricleを経験したので報告する．

An adult case of isolated fourth ventricle which developed in the early postoperative period of SAH is reported. A 72-year-old male with Hunt & Kosnik Grade 4 subarachnoid hemorrhage (SAH) underwent emergent neck-clipping of an anterior communicating artery aneurysm along with setting of external ven-tricular drainage (EVD) and cisternal drainage (CD). The lamina terminalis (LT) was opened. Preopera-tive study had showed diffuse SAH with intraventricular hemorrhage (IVH), and mild dilatation of the whole ventricular system on CT scan (Fisher Group 4). Twelve hours after surgery, both of the drainages were opened with the pressure setting of 20 cm H₂O for EVD and 10 cm H₂O for CD. Although his neu-rological state had been improving, 2 hours after the opening of the drainages he suddenly fell into res-piratory arrest and coma, when 20 ml of CFS through CD was drained. On CT scan, isolated fourth ventri-cle was recognized. The patient died on the ninth postoperative day.

In case of severe SAH with diffuse IVH, we should be careful when setting the pressure of EVD or CD with the LT opened, because of the possibility of occlusion of the fourth ventricle outlet and aqueduct, that results in fourth ventricle isolation.