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Hello doctor! I went to the 29th week of pregnancy ultrasound and was diagnosed with a slight dilation of the posterior fossa 11.4mm. So the doctor asked me if this case is dangerous and what to do? Thanks for the advice doctor!
Anonymous customer question
Dear doctor, my son is 31 weeks and 6 days this month and went to the doctor for a checkup and concluded that he has a simple posterior fossa dilatation. So please ask the doctor is it dangerous, the size is 11.41mm. Looking forward to consulting your doctor. Thank you
Nguyen Thi Huong (1991)
Reply
Hello! The posterior fossa is the cerebrospinal fluid space located behind the cerebellum, normally measuring 2-10 mm in diameter. Dilatation of posterior fossa cistern in fetus is a condition in which ultrasound results show that the diameter of the posterior fossa cistern is larger than the mean posterior fossa cistern diameter according to gestational age. So your fetus at 29 weeks when this diameter is 11.4 mm is mild dilation.
Large dilatation of the posterior fossa in the fetus is common in the following phenotypes:
Blake's pouch cyst. Large tank with simple dilatation of the posterior pit (Megacisterna magna). Dandy–Walker syndrome (Dandy–Walker malformation). Vermian hypoplasia of the cerebellum. Cerebellar hypoplasia. Ultrasound can differentiate these cases with 80% accuracy. With the addition of MRI, more information can be obtained with 90% accuracy. Accordingly, the correct diagnosis is very important because each case has a completely different prognosis.
Blake pouch and simple posterior fossa dilation: 30-40% may spontaneously regress during pregnancy. Even in cases that persist after birth, the prognosis is good, up to 90%, with a good life without other abnormalities or mental retardation later on. Particularly, Dandy-Walker syndrome, nystagmus or partial cerebellar hypoplasia, the possibility of associated chromosomal abnormalities and mental retardation and balance and movement disorders later in life is up to 50 years. %. In the content of the question, you do not have information about the ultrasound results and how did the screening tests at the milestones do? Therefore, if these results are normal, you can rest assured to follow up and re-examine according to the appointment schedule.
You can also go to the nearest hospital under Vinmec Health System for consultation and examination by doctors and experts with many years of experience in diagnosing Obstetrics and Gynecology.
Thank you for trusting and sending questions to Vinmec. Best regards!
Answered by Specialist Doctor I Vo Cong Hien - Radiologist - Radiology Department - Vinmec Nha Trang International General Hospital
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