Reinvestigation of the ambient cistern and its related arachnoid membranes: an anatomical study

Abstract

This study updates some information about the ambient cistern and its arachnoid membranes. The perimesencephalic membrane was identified and described in detail. The ambient cistern was verified to be a supratentorial cistern above the perimesencephalic membrane. The borders and contents of this cistern, as well as its relationship with adjacent cisterns, were also redefined.

Anatomical variations and neurosurgical significance of Liliequist’s membrane

“…The medial ML extends between the oculomotor nerves, and is referred to as the ML in previous studies, separating the interpeduncular and prepontine cisterns [15]. Similar division was also applied by Qi [23] who used the name anterior perimesencephalic membrane to describe the medial ML [23].…”

“…Moreover, when supratentorial approaches are used to gain access to the posterior ambient cistern, it is also important to preserve the perimesencephalic membrane (which was described by Qi [23] as part of the ML) in order to protect the superior cerebellar artery and the trochlear nerve below it from surgical injury [23].…”

Arachnoid membranes in the posterior half of the incisural space: an inverted Liliequist membrane–like arachnoid complex

“…Second, the PPM is not continuous with the lateral part of the APM. 7 Therefore, we abandoned the name "superior cerebellar membrane" and redefined the CPM in this study. The CPM is confined within the posterior half of the incisural space and has no relationship with either the oculomotor nerve or the lateral part of the APM.…”

“…The 2 lateral parts of the posterior arachnoid complex are composed of the bilateral horizontal parts of the PPM, which are identical to the lateral parts of the Liliequist membrane. 7,16 The main differences are as follows. First, the CPM and the diencephalic membrane travel in opposite directions, which makes the posterior arachnoid complex an inverted Liliequist membrane-like structure.…”

“…7 The similarity between the APM and PPM has prompted us to further investigate the construction of the arachnoid membranes in the posterior and posterolateral incisural spaces. In this study, the incisural space is divided into the anterior and posterior halves by the posterior edge of the cerebral peduncle.…”