Dilated subarachnoid cisterna ambiens: a potential sonographic sign predicting cerebellar hypoplasia.

Received October 26, 1995, from the Perinatology Research Facility, Department of Obstetrics and Gynecology (A.G., R.A.F., ].T., D.M.S.), <tnd Dep<~rtment of Pathology <J.A.W., H .J.M.), Georgetown University Medical Center, Washington, DC . Revised manuscript accepted for publication February 2, 1996. Address correspondence and reprint requests to Alessandro Ghidini, MD, Dep<~rtment of Obstetrics and Gynecology, Georgetown University Medical Center-3PHC, 3800 Reservoir Road , NW, Washington, DC 20007. This project has lx."'!n funded in whole or in part with federal funds from the National Institute of Child Health and Human Development, Perinatology RL'Search Branch, National Institutes of Health under contract NOl-HD-3-3198. The content of this publica· tion doL'S not necessarily reflect the views or policies of the Department of Health and Human Services, nor does mention of trade names, commercial products, or org;miz.1tions imply endorsement by the U.S. Government. drome,6 and trisomies 15 and 18.7 It is unknown, however, if TCD is a useful index for the diagnosis of cerebellar hypoplasia. We describe a case in which dilation of the subarachnoid cisterna ambiens was observed at ultrasonographic examination at 29 weeks' gestation in a fetus with trisomy 18 and normal TCD. Neonatal cranial sonographic scans revealed dilation of the subarachnoid cisterna ambiens associated with cerebellar hypoplasia, findings confirmed on subsequent neuropathologic examination of the brain. This case suggests that pericerebellar cistern dilation may be an early marker of cerebellar hypoplasia.