Endoscopic anatomy of the tentorial membrane group. (A) The left posterior cerebral membrane through a left retrosigmoid approach. (B) The connection of the medial edge of the left posterior cerebral membrane in the interpeduncular fossa viewed through a left supraorbital approach. (C) The left lateral mesencephalic membrane viewed through a left supraorbital approach. The blue arrow-head points to the basal attachment of the membrane along the outer arachnoid over the posterior petroclinoid fold. (D) Relation of the left posterior cerebral artery to the lateral mesencephalic membrane viewed through the same approach. (E) Endoscopic view of the left lateral mesencephalic membrane from below, in the lateral part of the quadrigeminal cistern viewed through a right supraorbital appoach. Note the left trochlear nerve in the wall of the outer arachnoid. (F) The horizontal part of the left posterior mesencephalic membrane viewed through a left subtemporal approach. (G) The vertical part of the left posterior mesencephalic membrane viewed through the same approach. Note the penetration-point of the left posterior cerebral artery through the membrane (blue arrow-head). (H) The dorsal attachment of the vertical part of the right posterior mesencephalic membrane along the lateral side of the great vein of Galen and the basal vein of Rosenthal viewed from below, from the middle part of the quadrigeminal cistern. Right supracerebellar-infratentorial approach. (I) The ventral part of the left superior cerebellar membrane viewed from above, after preforation of the lateral mesencephalic membrane (blue arrow-head). Endoscopic view through left supraorbital approach. (J) Relation of the left superior cerebellar membrane to the superior cerebellar artery (above the membrane) and the trigeminal nerve (below the membrane, blue arrow-head). Its dorsal attachment to the pons is also visible. Left supraorbital approach. (K) The three-point junction (blue arrow-head) between the left anterior pontine and superior cerebellar membrane and the lateral edge of the Liliequist membrane complex (partly removed) on the left side. As the mesencephalic leaf was removed, it is possible to view into the lateral part of the quadrigeminal cistern. Right supraorbital approach. (L) The dorsal attachment of the left superior cerebellar membrane (blue arrow-head) in the cerebellomesencephalic fissure. Left sided subtemporal approach with angled-optic. (M) Junction between the left anterior pontine and superior cerebellar membrane viewed from below (from the direction of the left cerebellopontine cistern). Note the clival line (blue arrow-head) as the basal attachment of the anterior pontine membrane on the outer arachnoid. Left retrosigmoid approach. (N) The lateral portion of the trigeminal membrane on the left side, viewed from the direction of the left cerebellopontine cistern. In this case the lateral edge of the membrane is extremely far from the superior cerebellar membrane and forms an extraordinary big trigeminal cistern. Left retrosigmoid approach. (O) Medial portion of the right trigeminal membrane (blue arrow-head) viewed from left supraorbital approach.
AICA=anterior inferior cerebellar artery, APM=anterior pontine membrane, bas.=basal, cerebell.=cerebellum, cerebellomes.=cerebellomesencephalic, CNIII=oculomotor nerve, CNIV=trochlear nerve, CNV=trigeminal nerve, CNVI=abducent nerve, CNVII-VIII=vestibulocochlear and facial nerves, LMM=lateral mesencephalic membrane, mesenc.=mesencephalon, occ.=occipital, PCM=posterior cerebral membrane, PMM=posterior mesencephalic membrane, quadr.=quadrigeminal, Ros.=Rosenthal, SCA=superior cerebellar artery, SCM=superior cerebellar membrane, tent.=tentorium, v.=vein.