The choroid plexus is a part of the brain that is responsible for the development of cerebrospinal fluid. It is like pockets that are called ventricles, which contains spongy layer of cells with blood vessels. It is present in the centre of the fetal brain. The cyst that occur within choroid plexus is called choroid plexus cyst. The fluid which is produced by the choroid plexus cells fills the ventricles and flows around the brain plus spinal cord to provide a cushion around these structures. The cysts form within these structures and the fluid trapped within this spongy layer of cells is much like a blister or a soap bubble. The choroid plexus cysts are often called as fetal ultrasound “markers” and “soft signs” , because it is found that there is a weak connection between fetal chromosomal abnormalities and choroid plexus cysts. The fetal chromosomal abnormalities are diagnosed by a procedure known as aminocentesis. The tiny choroid plexus cysts usually form in the brain as a normal part of the development in many fetuses, but disappears by the 32nd week of pregnancy.
The choroid plexus cysts are not true cysts as these have no epithelial lining, but are spaces filled with clear fluid within the choroid plexus. The size of these cysts range from a one to few mm to 1-2cm in diameter. Sometimes these cysts are responsible for obstructive hydrocephalus. This is caused by foramina blockage in the ventricular drainage system of central nervous system, which results in expansion of the ventricles and compressing the brain that cause severe damage.