The fourth ventricle communicates with the cistern via the unpaired midline median aperture.

[2][3] It is continuous inferiorly with the subarachnoid space of the spinal canal.

[2] The Terminologia Anatomica classifies the terms cisterna magna and posterior cerebellomedullary cistern as synonyms.

[6] The 42nd edition of Gray's Anatomy (2020) and 12th edition of Last's Anatomy (2011) recognise the cisterna magna and cerebellomedullary cistern as synonyms, and do not describe a separate lateral cerebellomedullary cistern.

[7] The cisterna magna may be tapped with a needle inserted superior to the posterior arch of atlas.