Brief Answer:
PF dimensions in foetus

Detailed Answer:
Hi....
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I am Dr Ajeet XXXXXXX
Posterior fossa is a normal part of cranial cavity located between foramen magnum and tentorium cerebelli and houses most important part of brain called brain stem.
Brain stem has centres which control balance, coordination and respiration of the body.
Tiffa scan is done in second trimester of pregnancy to examine both the internal and external anatomy of foetus and helps to rule out defects,chromosome abnormalities and genetic syndromes.This tells about structural abnormalities that can cause physical and mental limitations later on.
Chiari malformations,dandy walker syndrome and cerebellar hypoplasia most commonly represent a group of abnormalities that affect the cranial vault as well as the posterior fossa contents.
Please send me the report of tiffa scan which will help me to evaluate further.
If the size of PF is abnormal,it is an important diagnostic tool to detect foetus with central nervous system malformations e.g. in Chiari malformation, it is small and in Dandy walker it is large.
But...you need not worry because prenatal sonographic assessment of PF size is mainly qualitative and depends on examiner's subjective impression.That's why further imaging is required for more information and to confirm the defects.Please go for MRI and revert.
Hope that I have answered your query.
All the very best.
Regards

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