Tocheck the anatomy and embriology development of posterior fossa that a radiology resident must know To review the MRI findings of the most frequent congenital cyst malformations of posterior fossa To sum up themost useful differential MRI findings in order to establish an accurate diagnosis

Posterior cranial fossa is delimited by the dorsum sellae, the apex of the petrous temporal, the mastoid process and the transverse sinus sulci in the occipital bone. The pons, medulla oblongata and cerebellum are the parenchymal structures held inside the posterior fossa. The fourth ventricle connected to the subarachnoid space via the foramen of Magendie at the midline and Luschka foramen laterally are the main cerebrospinal fluid (CSF) structures in the posterior fossa. Neural tube embryological development reaches a segmentation in three vesicles, the telencephalon,...

NORMALMRI POSTERIOR FOSSAAPPEARANCE The imaging assessment of the posterior fossa performed by the radiology resident should begin at the midline sagittal image (Fig 1): Size and content of the posterior fossa: to check absence of solid or cystic masses or increased amount of CSF. Shape and size of the vermis: should be divided by the primary and prepyramidal fissures (Fig 2 white arrows) in three sections approximately of the same size. The craniocaudal distance should be equal to the distance from the top part of...

Basic knowledge about anatomy and embryology of the posterior fossa helps to understand some differential findings that are relevant to guide the diagnosis. Size and shape of cerebellum and fourth ventricle, presence or absence of hydrocephalus and communication between fourth ventricle and the retrocerebellar or infravermian CSF space are key features to assess because they represent mandatory or discarding findings for each pathology. There could be another subtle findings for the diagnosis, but evaluating the aforementioned features cover differential findings and easy to identify even...

A. Gilabert-Ubeda - J. M. Felices-Farias - F. Barqueros-Escuer - M. Tovar-Perez - I. Cases-Susarte - R. Sanchez-Jimenez - C. Serrano-Garcia - A. Cuelliga-Gonzalez - G. Litrán-López All authors at Hospital Clínico Universitario Virgen de la Arrixaca; Murcia/ES

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