Anatomical and Histological Study of Liliequist's Membrane: with Emphasis on Its Nature and Lateral Attachments

Purpose: In previous studies, some disagreements regarding the nature (inner or outer arachnoid membrane) and lateral boundaries (temporal uncus or tentorial edge) of Liliequist's membrane remain. The aim was to clarify whether Liliequist's membrane is an inner or outer arachnoid membrane, and the distribution of Liliequist's membrane with emphasis on its lateral attachments.

Methods: Liliequist's membrane was investigated by microsurgical dissection in 24 formalin-fixed adult cadaver heads and by histological sections of sellar-suprasellar specimens from another four formalin-fixed adult cadaver heads.

Results: The results obtained in the present study indicated that 1) Liliequist's membrane arises from the basal arachnoid membrane and has two components: a basal part comprising a folding inner layer of the arachnoid mater and an attaching part consisting of accumulated arachnoid trabeculae; 2) similar histological features are also present in other inner arachnoid membranes with attachments on basal arachnoid membrane, demonstrating Liliequist's membrane is an inner arachnoid membrane; 3) laterally, Liliequist's membrane attaches to the anterior tentorial edge constantly and to the mesial temporal uncus in more than half; 4) the oculomotor nerve courses above Liliequist's membrane and is fixed on Liliequist's membrane by the oculomotor membrane, which can also attach on temporal uncus and should be differentiated from the true temporal attachments of Liliequist's membrane.

Conclusion: Liliequist's membrane is an inner rather than outer arachnoid membrane. Understanding of its individual variation and topographic relationships with surrounding neurovascular and arachnoid structures is important for neurosurgical practice.