Neurosurgery notes/Anatomy/Skull base anatomy/Meningeal anatomy/Tentorium

Tentorium

View Details
Status
Done
logo
Parent item
Meningeal anatomy

Tentorial incisura spaces

  • Important landmarks
      • Space
      Neural Structures
      Vascular Structures
      Lateral
      Lateral surface of midbrain
      Anterior choroidal artery
      ㅤ
      Upper pons
      Posterior cerebral artery
      ㅤ
      Medial surface of temporal lobe
      Superior cerebellar artery
      ㅤ
      Fourth and fifth cranial nerves
      Basal vein of Rosenthal
      Posterior
      Pineal region
      Internal cerebral veins
      ㅤ
      Quadrigeminal plate
      Posterior basal veins
      ㅤ
      Fourth cranial nerve
      Vein of Galen
      ㅤ
      ㅤ
      Straight sinus

Tentorial Incisura

  • The lateral and third ventricles are situated above the tentorial incisura, the triangular space situated between the free edges of the tentorium and the dorsum sellae
  • The apex of the incisura is dorsal to the midbrain in the area posterior to the pineal body, and the base is on the dorsum sellae.
  • The midbrain is situated in the center of the incisura.
  • The area between the midbrain and the free edges is divided into
    • The three incisural spaces contain some of the basal cisterns and are so intimately related to the lateral ventricles that some operative approaches to the basal cisterns situated within the incisura are directed through the lateral ventricles and choroidal fissure.
      • Anterior incisural space
      • Located anterior to the midbrain
      • The frontal horns are located above the anterior incisural space
      • Extends obliquely upward around the optic chiasm along the anterior wall of the third ventricle to the area below the rostrum of the corpus callosum and the floor of the frontal horn.
      • Contains the
        • Interpeduncular cistern, which is situated between the cerebral peduncles,
        • Chiasmatic cistern, which is located below the optic chiasm.
          • The chiasmatic cistern communicates around the optic chiasm with the cisternal laminae terminalis, which lies anterior to the lamina terminalis in the area below the floor of the frontal horn.
      Middle incisural spaces (paired)
      • Located
        • Lateral to the midbrain
        • Between the temporal lobe and the midbrain
          • Is so intimately related to the temporal horn and temporal part of the choroidal fissure that some operative approaches to this space are directed through the temporal horn.
      • Ventricular relations
        • The bodies of the lateral ventricles are located directly above the central part of the incisura, where they sit on and are separated from the central part of the incisura by the thalamus.
        • The temporal horns
          • Are situated superolateral to the middle incisural space.
          • Ends approximately 3 cm from the anterior pole of the temporal lobe.
      • Cisterns within the space
          • Crural cistern (2)
          • Has been named as the space limited laterally by the uncus, medially by the crus cerebri, and superiorly by the optic tract
          • Borders
            • Located between the cerebral peduncle and uncus
            • Roofed by the optic tract
            • It connects the carotid cistern anteriorly to the ambient cistern posteriorly.
          • Ends with the entry of the anterior choroidal artery into the temporal horn
          • The crural cistern cannot be reached through the choroidal fissure because the fissure ends just behind the uncus at the inferior choroidal point.
            • The crural cistern can be exposed from the temporal horn by an incision extending forward from the inferior choroidal point through the amygdala.
          • Contents
            • Basal vein
            • Cisternal segment of the anterior choroidal artery
            • P2A segments of the posterior cerebral artery
          Ambient cistern (3)
          • Continues posteriorly between the parahippocampal gyrus and the brainstem
          • Borders
            • Medially by the midbrain
            • Above by the pulvinar
            • Laterally by the parahippocampal and dentate gyri and the fimbria of the fornix.
          • The cisternal side of the temporal portion of the choroidal fissure is located in the superolateral part of the ambient cistern between the fimbria and the lower thalamic surface.
          • There are still some controversies regarding the boundaries between the crural and ambient cisterns.
      Posterior incisural space
      • Located
        • Medial to the atrium.
        • Located behind the midbrain.
      • Ventricular relations
        • The atria are located above the posterior incisural space.
      • Contains
          • Quadrigeminal cistern (4)
          • Aka: Pineal region
          • Has a roof, floor, and anterior and lateral walls.
            • The choroid fissure lies at the junction of the anterior and lateral walls of the quadrigeminal cistern.
            • Lateral walls
              • Of the quadrigeminal cistern separate the cistern from the atria.
              • Each lateral wall has 2 parts:
                • Anterior part is formed by the crus of the fornix
                • Posterior part is formed by the part of the medial surface of the occipital lobe situated below the splenium.
            • Anterior wall of the cistern
              • 2 parts.
                • Medial part:
                  • Formed by the quadrigeminal plate and pineal body.
                  • The suprapineal recess of the third ventricle bulges into the cistern above the pineal body.
                • Lateral part:
                  • Formed by the part of the pulvinar that lies medial to the crus of the fornix.
              • Below the colliculi, the cistern extends into the cleft between the midbrain and cerebellum called the cerebellomesencephalic fissure.
              • This fissure cannot be reached through the choroidal fissure.
              • The trochlear nerves arise below the inferior colliculi and course laterally around the midbrain and below the pulvinars to enter the ambient cisterns.
            • Roof of the cistern is formed by the lower surface of the splenium and the broad membranous envelope that surrounds the great vein and its tributaries.
              • This broad envelope of arachnoid tissue is applied to the lower surface of the splenium and is continuous anteriorly with the velum interpositum.
                • It is within this envelope, in the superomedial part of the cistern, that the venous structures are found in the greatest density.
                • The superomedial location of the major veins in the cistern contrasts with the location of the large arteries that are found in the inferolateral part of the cistern.
          • Communications with the quadrigeminal cistern
            • The quadrigeminal cistern opens anteriorly below the pulvinars into the ambient cisterns.
            • The quadrigeminal cistern may communicate with the velum interpositum.
            • Another potential cavity that may communicate with the quadrigeminal cistern is the cavum vergae, which is located immediately above the velum interpositum between the hippocampal commissure and the splenium.
              • The cavum vergae is infrequently present because the hippocampal commissure commonly fuses to the lower surface of the splenium
Oblique view of the left tentorial incisura (lateral space) showing its neurovascular structures. The left tentorial edge is elevated with a dissector, displaying the trochlear nerve (tr.n.) running parallel to the tentorial margin to its entrance into the cavernous sinus. The oculomotor nerve (oc.n.) enters into the roof of the cavernous sinus. Beneath the trochlear nerve, the trigeminal nerve (tg.n.) passes through Meckel’s cave. Note the close relationship between the trigeminal nerve and the superior cerebellar artery (sca). Basilar artery (ba); internal carotid artery (ica); midbrain (mb); optic nerve (o.n.); posterior communicating artery (pca); and third ventricle (3v).
Oblique view of the left tentorial incisura (lateral space) showing its neurovascular structures.
The left tentorial edge is elevated with a dissector, displaying the trochlear nerve (tr.n.) running parallel to the tentorial margin to its entrance into the cavernous sinus.
The oculomotor nerve (oc.n.) enters into the roof of the cavernous sinus.
Beneath the trochlear nerve, the trigeminal nerve (tg.n.) passes through Meckel’s cave. Note the close relationship between the trigeminal nerve and the superior cerebellar artery (sca).
Basilar artery (ba); internal carotid artery (ica); midbrain (mb); optic nerve (o.n.); posterior communicating artery (pca); and third ventricle (3v).
Superior view of the tentorial notch displaying its neurovascular relationships. Basilar artery (ba); cerebellum (ce); internal carotid artery (ica); midbrain (mb); oculomotor nerve (oc.n.); optic nerve (o.n.); pituitary stalk (ps); posterior communicating artery (pca); superior cerebellar artery (sca); and trochlear nerve (tr.n.).
Superior view of the tentorial notch displaying its neurovascular relationships.
Basilar artery (ba); cerebellum (ce); internal carotid artery (ica); midbrain (mb); oculomotor nerve (oc.n.); optic nerve (o.n.); pituitary stalk (ps); posterior communicating artery (pca); superior cerebellar artery (sca); and trochlear nerve (tr.n.).
notion image

Dural septa

Function

  • Partition and maintain the positions of the intracranial neural structures

Falx cerebri

  • Lies in the deep fissure between the two hemispheres of the cerebrum.
  • Attachment
    • Anterior attachment at the crista galli of the cribriform plate
    • Posterior attachment superior surface of the tentorium.
    • Superiorly it attaches to the midline of the frontal, parietal, and occipital bones,
    • Inferiorly it remains unattached.
      • Posteriorly the inferior free edge closely opposes the corpus callosum,
      • Anteriorly there is a wide space between the two structures where the cerebral hemisphere can herniate beneath the free edge
  • The sickle-shaped falx is shorter in its anterior portion.

Tentorium cerebelli

  • Divides the cranium into the supratentorial and infratentorial compartments.
  • Incisura: Free edge of the tentorium
  • A dural duplication
  • Attachment
    • Posteriorly
      • To the transverse ridges on the inner surfaces of the occipital bone
      • Encloses the transverse sinuses
    • Anterolaterally
      • To the superior ridge of the petrous portion of the temporal bone,
      • Enclosing the superior petrous sinus on both sides.
    • Anteriorly
      • To the posterior and anterior clinoid processes.
      • The free edges of the incisura pass over the trigeminal ganglion to insert onto the petrous apex and the anterior and posterior clinoid processes.
        • These insertions form three dural fold/ligaments: (Aka oculomotor trigone, through which the oculomotor nerve enters the cavernous sinus)
          • Anterior petroclinoid fold/ligaments
          • Posterior petroclinoid fold/ligaments
          • Interclinoid fold/ligaments
            • The medial extension of the dura covering the oculomotor trigone is the diaphragma sellae. Dura extending anteriorly from the free edge will form the lateral wall of the cavernous sinus and cover the middle cranial fossa.
    • Medially
      • Incisura tentorii
        • Preservation structures around the incisura by surgical dissecting the arachnoid layers forming the lateral walls of the chiasmatic, crural, ambient, and interpeduncular cisterns and is important to obtain a good surgical result.
        • For transmission of the midbrain.
        • Divided into
            • Anterior incisural space
            • Located in front of the brain stem
            • Important structure
              • Oculomotor nerve,
              • Basal vein,
              • Posterior communicating artery,
              • Anterior choroidal artery,
              • P1 and proximal P2 segments of the posterior cerebral artery,
              • Superior cerebellar artery.
              • Optic nerve and the optic chiasm may be involved
                • Less often involved
            Middle incisural space
            • Located lateral to the brain stem
            • Bounded medially by the cerebral peduncle and upper pons.
            • Important structure
              • Crural cistern, located between
                • Uncus and cerebral peduncle anteriorly,
                • Ambient cistern situated between the midbrain and parahippocampal gyrus posteriorly
              • Trochlear nerve
                • Tiny trochlear nerve located just beneath the tentorium because it may be damaged in the subtemporal or petrosal approach.
              • Anterior choroidal artery
              • P2 segment of the posterior cerebral artery
              • Superior cerebellar artery
              • Basilar vein constitute
            Posterior incisural space
            • Located behind the brain stem
            • Important structure
              • Ambient cistern into the quadrigeminal cistern
                • This space forms the pineal region and is related to anterior falcotentorial meningiomas.
              • PCA and SCA: Trunks and branches
              • Vein of Galen
                • Which receives the paired internal cerebral and basal veins.
              • Trochlear nerve
                • Exits from below the inferior colliculi, curves around the dorsal midbrain, and enters the ambient cistern in the middle incisural space.
    • Superiorly
      • The falx cerebelli
        • A small triangular dural process that arises in the midline from underneath the tentorium.
        • It indents between the two cerebellar hemispheres.
        • The upper surface of the tentorium connects to the posterior end of the falx cerebri in the midline,
        • Enclosing the straight sinus along the line of junction.
          • Straight sinus receives the vein of Galen and the inferior sagittal sinus at the tentorial apex and runs posteriorly to meet the transverse sinuses from both sides and the superior sagittal sinus from above at the torcular Herophili.
  • Arterial supply from
    • Basal tentorial artery (artery of Bernasconi-Cassinari) originating from
      • Meningohypophyseal trunk
      • Marginal tentorial artery arising from the inferolateral trunk of the intracavernous carotid
    • Tentorial branches originating from
      • SCA
      • PCA
  • A peculiarity of the tentorium is the presence of interdural venous sinuses, which may become particularly prominent when major venous channels are occluded by tumor.
    • Brisk bleeding from these venous lakes may be anticipated during incision of the tentorium in the occipital transtentorial approach.
    • This bleeding can be controlled by bipolar coagulation.
    • In the authors’ experience, no neurological sequelae have been caused by their occlusion.
    • The surgeon should study the venous drainage pattern of the temporal lobe and the point of termination of the subtemporal veins into the venous sinuses when planning for a subtemporal or petrosal approach.
A diagram of the internal organs AI-generated content may be incorrect.
notion image
notion image

Diaphragma sellae

  • Layers of the dura also separate around the sella and parasellar regions and the Meckel cave.