Dilated subarachnoid cisterna ambiens: A potential sonographic sign predicting cerebellar hypoplasia

In this report, a case is described in which dilation the subarachnoid cisterna ambiens was observed at ultrasonographic examination of 29 week's gestation in a fetus with trisomy 18 and normal TGD. Noenatal cranial sonographic scans revealed dilation of the subarachnoid cisterna ambiens associated with cerebellar hypoplasia. The findings have been confirmed on subsequent neoropathologic examination of the brain. This case suggests that pericerebellar cistern dilation is an early marker of cerebellar hypoplasia.