Choroid plexus of fourth ventricle

At the rear end of the brainstem, the tela choroidea extends upward between the anteroinferior cerebellum and the back of the medulla and fourth ventricle. When it intrudes into the cavity of the fourth ventricle, it is surrounded by a cuboidal ependyma. This three-layered structure forms the choroid plexus of fourth ventricle, which consists of a vascular endothelium, pia mater, and cuboidal ependymal lining. These layers together create a blood-cerebrospinal fluid barrier, filtering the blood to produce cerebrospinal fluid in the third ventricle. Initially, the choroid plexus is oriented sagittally but it bends and extends laterally withing the fourth ventricle to reach the lateral apertures.

The posterior and anterior inferior cerebellar arteries, mainly the PICA, supply blood to the choroid plexus of fourth ventricle.