What is a Blake’s Pouch Cyst?

It is a cystic appearing structure at the back lower part of the fetal brain, called the cisterna magna in the posterior fossa. It occurs in 1 in 1,000 pregnancies and is usually an isolated finding, although around 5% may be due to a chromosomal condition. The fetal medicine doctor will perform regular scans during pregnancy to monitor the size of the cyst and assess to see if it is spontaneously going away (this happen in half of all cases). Very occasionally the cyst may grow during pregnancy and cause a build of fluid in the brain, this may require drainage by a neurosurgeons after birth. Children with this condition generally have a normal outcome with around 90% having normal brain development.