Median aperture

The median aperture (median aperture of fourth ventricle or foramen of Magendie) is an opening at the caudal portion of the roof of the fourth ventricle. It allows the flow of cerebrospinal fluid (CSF) from the fourth ventricle into the cisterna magna. The other openings of the fourth ventricle are the lateral apertures - one on either side. The median aperture varies in size but accounts for most of the outflow of CSF from the fourth ventricle.