Tela Choroidea of Fourth Ventricle Following Cerebellar Tonsil Removal. The right cerebellar tonsil has been resected to permit visualization of the tela choroidea and inferior aspect of the fourth ventricle. The tela choroidea is thin, double-layered membrane, made up of pia mater and ependyma, that forms the lower part of the roof of the fourth ventricle.  Suspended from the pial surface of the tela choroidea is a tuft of choroid plexus.  During a telovelar approach to the fourth ventricle, it is necessary to dissect through the tela choroidea to permit visualization of the fourth ventricular floor. (Image courtesy of AL Rhoton, Jr.)