This 29 year old lady , primi, non consanguinous marriage was referred for a routine scan around 34 weeks .
The posterior fossa scan showed cisterna magna to be mildly enlarged ; cerebellar vermis and both lobes of cerebellum were identified normally. No other associated anomaly was found out .
In general isolated mild cisterna magna enlargement ( between 10 to 13 mms ) is associated with good prognosis in the child after birth .
For comparison with cerebellar vermis hypoplasia that picture is also given in the end.( this was posted last week in this blog )
The absent vermis and the communication is well seen in the picture given below.