Liliequist membrane

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Done

Parent item

CSF anatomy

General

• The Liliequist membrane is the arachnoid membrane separating the chiasmatic and interpeduncular cisterns.

Boundaries

• Lower attachment:
• Dorsum sellae
• Posterior clinoid processes

• Upper attachment: Mamillary body

• Lateral attachment
• The oculomotor nerves (CN III) course along the lateral wall of the interpeduncular cistern and form the pillars to which the leaves of Liliequist’s membrane often attach.

Has two components

• Diencephalic membrane (Upper/anterior leaf)
• Attachment/Boundary:
• It extends upward and attaches to the floor of the third ventricle at the mamillary bodies.
• Cistern Separation:
• It separates the chiasmatic cistern (anteriorly) from the interpeduncular cistern (posteriorly).
• Variability in Attachment:
• Mamillary bodies
• Structure:
• It is typically the thicker of the two parts and is more frequently without perforations, allowing it to act as a more effective barrier to the passage of air or other substances through the subarachnoid space

• Mesencephalic membrane (Caudal/posterior leaf)
• Attachment/Boundary:
• It extends backward and attaches along the junction of the midbrain and pons.
• Cistern Separation:
• It separates the interpeduncular cistern (anteriorly) from the prepontine cistern (posteriorly).
• Contents:
• The basilar artery passes through an opening in the mesencephalic membrane to enter the interpeduncular cistern.
• Structure:
• This membrane is highly variable; while some are thick with small perforations, most are thinner, often incomplete, and have larger perforations

Clinical significance

• Aneurysms:
• Aneurysms arising at the basilar apex may project into the diencephalic and mesencephalic leaves of Liliequist’s membrane.

• Surgical Risk:
• Five arachnoid membranes, including the diencephalic and mesencephalic membranes, converge on the oculomotor nerve; thus, traction on any of these membranes may rupture associated aneurysms.

• Surgical Access:
• Opening the diencephalic leaf of Liliequist’s membrane provides surgical access into the interpeduncular cistern
• Opening the Sellar Segment is done to improve CSF flow during ETV.