The detailed anatomy of the venous circulation and the tentorial incisura and classification of the tentorial meningiomas

1. Tentorial meningioma
Mohamed Elsayed Elsebaey
Neurosurgery Registrar
Egypt, Ismailia
Ministry of Health
Seba3y700025@gmail.com
Mohamed E Elsebaey

2. • Meningiomas of the posterior cranial fossa is
about 9% of all intracranial meningiomas
• Tentorial meningiomas is about 30% of the
posterior fossa meningiomas
• First described by Andral in 1833
• Reviewing the deep venous system and
venous drainage of the temporal lobe is the
cardinal step when planning for the
subtemporal and petrosal approach.

3. Tentorium
Surgical Anatomy
• Tentorial cerebelli is dural duplication that
covers the upper surface of the cerebellum
and supports the occipital lobes
• Separating the supra from infra tentorial
compartments

4. Borders
• Posterior
attaches to the transverse ridges on inner surface of occipital
bone.
Enclosing the transverse sinuses
• Anterolateral
Attaches to the superior ridge of the petrous portion of the
temporal bone
Enclosing the superior petrous sinuses on both sides
• Anterior
Attached to the anterior and posterior clinoid processes
• Medial
Medial free concave border that forms the tentorial incisura
and bounding the midbrain.

5. Falx cerebelli
• Small triangular dural process
• Arises in midline from underneath the
tentorium in-between the cerebellar
hemispheres
• Upper surface connects to the posterior end of
falx cerebri in midline
• Enclosing the straight sinus along the line of
this junction

6. • The straight sinus receives
Vein of Galen & Inferior sagittal sinus ISS
at the Tentorial apex and runs posteriorly to
meet
the transverse sinuses from both sides
And
the SSS from above at the torcular Herophili.

19. Incisural space
is divided into
Anterior
In front of brain stem
Middle
Lateral to brain stem
Posterior
Behind brain stem

20. Tentorium Incisura

21. Arachanoid dissection to get the lateral walls of
the chiasmatic, crural, ambient and
interpeduncular cisterns is crucial step in
surgery.

22. Neurovascular structures
Anterior Incisural space:
1. 3rd cranial nerve
2. Basal vein
3. Posterior communicating artery
4. Anterior choroidal artery
5. Posterior cerebral artery (P1 & P2)
6. Superior cerebellar artery

24. Neurovascular structures
Middle tentorial incisura
Cerebral peduncle & Upper pons medially
Crural cistern: between uncus and cerebral peduncle anteriorly
Ambient cistern: between midbrain and parahippocampal gyrus
posteriorly
1. 4th cranial nerve
2. Anterior choroidal artery
3. Posterior cerebral artery P2
4. Superior cerebeller artery
5. Basilar vein

26. • 4th cranial nerve: tiny nerve that exits from below the inferior
colliculi and curves around the dorsal midbrain and enters the
ambient cistern in the middle incisural space, supposed to be
injured in subtemporal and petrosal approaches.
• Ambient cistern continues posteriorly into the quadrigeminal
cistern.

27. Neurovascular structures
Posterior incisural space
quadrigeminal cistern is the main cistern
This space forms the pineal region
Related to the falcitentorial meningiomas
1. Posterior cerebral artery
2. Superior cerebellar arteries
3. Vein of Galen

30. Blood supply
• ICA  intracavernous segment C4 
meningiohypophyseal trunk  basal tentorial
artery (A. of Bernasconi – Cassinari)
• Superior cerebellar artery
• Posterior cerebral artery

31. • There are intradural venous sinuses inside the
tentorium, that become more prominent when
the major venous channels are blocked by the
tumor.
• Those sinuses are source of brisk massive
bleeding during dissection especially while using
the occipital transtentorial approach.
• Bipolar coagulation can control this bleeding.
• No neurological deficit happens while occlusion
of those intradural sinuses

32. Yasargil Classification
• T: Incisural
Anterior (T1) Middle (T2) Posterior (T3)
• T4: Intermediate tentorial surface
• T5: Torcular herophili
• T6: Lateral outer tentorial ring anteriorly
• T7: Lateral outer tentorial ring posteriorly
• T8: Falcotentorial

33. Yasargil Classification
T1
T2
T3
T4
T5
T6
T7
T8

34. Classification
Supra tent.
-------------
Infra tent.

38. Supracerebellar infra tentorial
Occipital trans tentorial

40. Subtemporal Approach

41. Area that must be known before dealing with
the T1, T2, T3