General
- The Liliequist membrane is the arachnoid membrane separating the chiasmatic and interpeduncular cisterns.
- Remnant of primitive tentorium
- Forming of a competent barrier in only 20%
- Separates the interpeduncular cistern from
- Chiasmatic cistern medially
- Carotid cistern laterally
- There is a communication between carotid cistern ↔ crural cistern ↔ interpeduncular cistern
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
- Form by 3 leaflets
- Inferior leaflet (M):
- 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
- Posterior leaflet (D):
- Diencephalic membrane (Upper/anterior leaf)
- Thicker and more competent
- 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
- Anterior leaflet (S):
- Sellar membrane
Clinical significance
- SAH
- Bld in carotid or prepontine cistern: low pressure pretruncal source of bleed
- Bld in chiasmatic cistern: high pressure aneurysmal bleed
- 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.