Neurosurgery notes/Anatomy/CSF anatomy/Cisternal triangles

Cisternal triangles

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CSF anatomy

1. Opticocarotid Triangle

  • Boundaries:
    • ICA
    • CN II
    • A1 segment of the Anterior Cerebral Artery (ACA).
  • Location:
    • in the anterior incisural space
    • It is situated in the suprasellar area and allows access to the deep structures of the Circle of Willis.
  • Contents:
    • Posterior Communicating Artery (PComA) is visible.
  • Clinical Significance:
    • Access the apex of the basilar artery.
    • This approach is effective if the triangle is sufficiently wide (which occurs if the ICA and A1 segments are long) and if the basilar apex aneurysm projects superiorly or anteriorly.
    • The exposure through this route includes the basilar artery, PComA, Posterior Cerebral Arteries (PCA), thalamoperforating arteries, Superior Cerebellar Artery (SCA), recurrent arteries, and the olfactory and optic tracts.
    • When viewed endoscopically, the chiasmatic cistern is positioned anterior to, and the interpeduncular cistern is behind, the diencephalic membrane when looking through this triangle.

2. Carotid-Oculomotor Interval

  • Rather than a fixed anatomical triangular membrane.
  • Borders
    • ICA
    • CN III
  • Clinical significance
    • This interval encompasses two distinct pathways used to approach basilar apex aneurysms via a pterional craniotomy:
      • The route above the posterior communicating artery (PComA), using the interval between the carotid artery and the oculomotor nerve.
      • The route below the posterior communicating artery (PComA), also using the interval between the ICA and the oculomotor nerve.
    • Maneuvers: Access through this interval often requires gently depressing or elevating the PComA, which typically crosses in front of the basilar artery, to increase the operating space around the basilar apex.
  • Limitation:
    • The posterior clinoid process can block the approach to the basilar artery through the carotidoculomotor interval.

3. Supracarotid Triangle

  • Location
    • Above the internal carotid artery
  • Borders:
    • Medially (inner boundary): A1 segment
    • Laterally (outer boundary): M1 segment
    • Superiorly (base): The basomedial frontal lobe (specifically the medial orbital gyrus).
  • Clinical significance
    • Using the supracarotid-infrafrontal approach to reach
      • Anteroinferior basal ganglia.
      • Ventral thalamopeduncular junction.
    • For Cavernomas
 
 
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