Crural cistern

The crural cistern is a paired subarachanoid cistern at the tentorial/mesencephalic level, midway between interpenduncular cistern and ambient cistern.

Classical anatomic references describe this cistern as located in front of the ambient cistern and just lateral to the interpeduncular cistern. Nevertheless, the FIPAT/IFA nomenclature does not name it particularly in TA1, TA2 or TNA. 

The anterior choroidal artery (as an anterolateral limit with the carotid cistern) and the posterior communicating artery (as the posteromedial limit with the interpeduncular cistern) demarcates the cural cistern location.

Crural cistern and cistern ambiens can be denominated as one as “lateral mesenchepalic cistern".

The intracrural membrane runs anteromedially dividing crural cistern in a superior and inferior compartment (anterior choroidal artery and posterior communicating artery belong to each one of them in that order). 

The crural membrane (separating ambiens from crural cistern) must be differentiated from the intracrural membrane (separating crural cistern in superior and inferior compartments), both appearing as incomplete and not always present membranes.

Boundaries:

• Lateral: anterior and mid part of the uncus

• Medial: the lateral surface of the mesencephalon.

• Anterior: anterior choroidal artery (as an anterolateral limit with the carotid cistern) and the posterior communicating artery(as the posteromedial limit with the interpeduncular cistern) 

• Posterior: crural membrane (separating ambiens cistern from crural cistern)

Contents:

• Anterior choroidal artery (carotid last branch previous to bifurcation)

• Posterior choroidal artery (PCA branch)

• P2a segment of the posterior cerebral artery

• Proximal part of the Basal Vein of Rosenthal