[Spontaneous cerebral ventriculostium (author's transl)].

Two cases of spontaneous cerebral ventriculostium are presented. The first case is that of a 3 year-old girl with a thumb-sized soft scalp tumor of the occipital region (dural hypertrophy) and hydroencephalodysplasia (Picaza). PVG revealed noncommunicating hydrocephalus with asymmetrical deformity of the lateral ventricle and agenesis of corpus callosum (Fig. 1). Ventriculoatrial shunt was performed. Three years passed under the useful life when she readmitted to our clinic complaining headache, nausea and vomiting. On the first hospital day she fell into respiratory arrest accompanied with coma after the tonic convulsion, and eventually, she died on the fourth hospital day. Postmortem examination revealed spontaneous cerebral ventriculostium which communicated with the posteromedial trigone of the left lateral ventricle (Fig. 3). Combined other malformations such as dysgenesis of the corpus callosum and only one anterior cerebral artery, etc. were found. The second case is that of a young adult, a 22 year-old male with rapidly progressing intracranial hypertension. PVG revealed marked dilatation of the lateral and the third ventricle, non-filling of the aqueduct and spontaneous cerebral ventriculostium which communicated with the posterior part of the third ventricle (Fig. 4). And insidiously he fell into akinetic mutism. After suboccipital exploratory craniotomy and ventriculo-peritoneal shunt akinetic mutism improved gradually, and he was discharged on foot after 7 months. PEG performed on June 8, 1973, showed no evidence of aqueduct obstruction and injected air passed from the fourth ventricle to the third one smoothly. He lives on now under a useful condition. These 2 cases are the first report on literatures in Japan, but presumably there must be many other cases. Since W. H. Sweet reported his own two cases of spontaneous cerebral ventriculostium on 1940, more than thirty cases have been published on literatures. However, there are found various expressions to describe the same condition (Table 1). We would like to propose that the most suitable expression is "ventriculostium" not only in deference to the originality of W. H. Sweet but also not to confuse this pathogenetic state with other similar conditions. The author's next interest is the chronological fact that from W. H. Sweet (1940) to A. Torkildsen (1948), all but one ostiums reported situated at the posteromedial trigone of the lateral ventricle, whereas after A. Torkildsen, they were found at the posterior part of the third ventricle in many cases. The reason is unknown. It would appear that three main conditions are necessary for the development of ventricluostium just beneath the tentorium. The first, there must be increased pressure within the lateral or the third ventricle. The second essential feature is the lack of any large space occupying lesion in the the infratentorial space. The third, there must be wider space between the tentorial incisura and the brain stem.