Carotid cistern

The carotid cistern is a rhomboidal space surrounding the supraclinoid inernal carotid artery, contiguous laterally to the lateral cerebral fossa (sylvian cistern).

In this cistern, the carotid artery may be observed underneath a thin arachnoid layer, the lateral carotid sheet, just proximal to the A1-M1 confluence.

Contents of the carotid cistern:

• Internal carotid artery: in its supraclinoid segment. it describes an anteromedial to the posterolateral trajectory, starting at the distal dural ring

• Posterior communicating artery: emerging from the posterolateral face of the internal carotid artery just next to the oculomotor nerve (CN III).

• Anterior choroidal artery: emerging from the last carotid segment before it bifurcates into the anterior and middle cerebral artery

• Ophthalmic artery: it can be seen accompanying the optic nerve, near the carotid emergence from the distal dural ring, beneath the medial carotid sheet.

Relationships - The carotid cistern is described as a rhomboid space :

• The posterior angle is represented by the oculomotor nerve cuff. The oculomotor nerve then runs in a separated cover until it enters the cavernous sinus.

• The anterior angle is at the optic nerve-chiasm junction, where medial and lateral carotid sheets join.

• Both lateral-sided segments of the rhomboid represent the shared limit with the sphenoidal deep part of the lateral cerebral fossa (sylvian cistern).

• Medial-sided segments of the rhomboid are contoured by the optic nerve-chiasm-tract. They connect the carotid cistern with the cistern of the lamina terminalis (superiorly), the interpeduncular cistern (posteriorly), and the chiasmatic cistern (medially).