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 .

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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.