水頭症における視野障害

VISUAL FIELD DEFECTS IN HYDROCEPHALUS

　抄録　水頭症における視野障害の出現は比較的稀である。我々は過去13年間に7例の非腫瘍性中脳水道狭窄症と1例の先天性交通性水頭症において各種視野障害の合併を経験した。全例に，CT上中等度から高度の第3脳室と側脳室の拡大を認めた。視神経あるいは視交叉部での障害が推定される5例中4例で第3脳室がトルコ鞍内に伸展していた。視索あるいは視放線での障害が示唆される3例では左右非対称の側脳室拡大がみられた。水頭症に対する治療として5名に脳室腹腔短絡術を行ない，3名で視野の改善が得られた。視野の改善した3例中1例で術後脳室系はslit-likeとなったが他の2例では脳室の大きさに変化は認められなかった。水頭症における視野障害では脳室拡大による視路への圧迫の他に頭蓋内圧の変化の重要性が示唆された。

Eight patients representing visual field defects associated with hydrocephalus are reviewed. Seven cases had aqueductal stenosis and one had con-genital communicating hydrocephalus.

We found five cases of defects in visual field typical of a chiasmal or optic nerve lesion :(1) inferior altitudinal hemianopia with inferior nasal quadrantanopia in the opposite eye;(2) inferiorbinasal quadrantanopia;(3) unilateral inferior nasal depression;(4) unilateral temporal defect ;(5) bilateral central scotoma. In these cases CTdemonstrated moderate or marked symmetrical dilatation of the third and lateral ventricles. Four out of five cases showed buldging of the third ventricle anteriorly into the sella turcica on CTor ventriculography.

Other three patients had incongruous homony-mous hemianopia. Characteristic asymmetrical dilatation of the lateral ventricles was noted in all three cases. The more enlarged lateral ventricles were ipsilateral with the affected visual pathways. The sites of lesion responsible for these field defects seemed to be optic tract in one case and optic radiation in two cases.

Ventriculoperitoneal shunt was placed in five out of seven cases. Impaired visual field improved in three patients after shunt insertion. A 28-year-old female who had had history of blurred vision fos 14 days showed improvement in visual acuity and field when the enlarged ventricles became slit-like by shunting. In the other two patients defects in visual fields improved in spite of consistent ventriculomegaly. These facts suggested that not only the mechanical forces with distended third ventricle but also increased intracranial pressure played an important role in producing visual field defects in hydrocephalic patients.