Median aperture

The median aperture of the brain (or foramen of Magendie) is an opening in the hollow nerve tube, connecting the fourth ventricle of the brain with the subarachnoid space.

The median aperture, along with the paired lateral apertures (foramina of Luschka) are the primary routes for cerebrospinal fluid to escape into the cisterna magna. The Foramen of Magendie is named for François Magendie, who first described it.