Lecture Notes: Dural Venous Sinuses

Introduction to Dural Venous Sinuses

• Understanding the drainage system of dural venous sinuses is essential for clinical problem-solving.
• Knowing the direction of blood flow helps in understanding clinical cases, e.g., tumor obstruction in the confluence of sinuses.

Dural Folds and Sinuses

• Dural Folds:
  • Falx Cerebri: Divides the two cerebral hemispheres.
  • Falx Cerebelli: Small fold between the cerebellum.
  • Tentorium Cerebelli: Separates cerebrum from cerebellum.
  • Diaphragma Sellae: Covers the sella turcica.

Major Dural Venous Sinuses

• Superior Sagittal Sinus

  • Located at the upper margin of falx cerebri.
  • Drains blood backward.

• Inferior Sagittal Sinus

  • Located at the lower margin of falx cerebri.
  • Drains blood backward and downward.

• Straight Sinus

  • Drains blood from inferior sagittal sinus backward.
  • Receives blood from falx cerebelli.

• Occipital Sinus

  • Drains blood upwards from the falx cerebelli.

• Confluence of Sinuses

  • Meeting point for superior sagittal, straight, and occipital sinuses.
  • Blood drained into transverse sinuses.

• Transverse Sinus

  • Located in the tentorium cerebelli.
  • Drains blood to sigmoid sinus.

• Sigmoid Sinus

  • S-shaped.
  • Joins inferior petrosal sinus to form internal jugular vein.

Petrosal Sinuses

• Superior Petrosal Sinus
  • Drains into transverse sinus.
• Inferior Petrosal Sinus
  • Joins sigmoid sinus.

Formation of Internal Jugular Vein

• Formed by the convergence of sigmoid sinus and inferior petrosal sinus.

Cavernous Sinus

• Drains through superior and inferior petrosal sinuses.
• Receives blood from:
  • Orbit: via ophthalmic veins.
  • Brain: via superficial middle cerebral and inferior cerebral veins.
  • Meninges: via spheno-parietal and middle meningeal sinuses.
• Outgoing channels include superior and inferior petrosal sinuses and superior ophthalmic vein.

Clinical Relevance

• Tumor obstruction in confluence of sinuses affects inflowing sinuses like superior sagittal sinus.
• Direction of blood flow is crucial for identifying affected sinuses in clinical scenarios.

Relations of Cavernous Sinus

• Medial: Pituitary gland, sella turcica, sphenoidal sinus.
• Lateral: Third, fourth cranial nerves, ophthalmic nerve, uncus.
• Floor: Foramen lacerum.
• Roof: Internal carotid artery, optic chiasm.
• Anterior: Superior orbital fissure.
• Posterior: Apex of petrous temporal bone.
• Inside: Internal carotid artery, abducens nerve.

Clinical Aspects

• Carotid-cavernous fistula can lead to pulsatile proptosis due to relationship with superior orbital fissure.

These notes summarize the key points regarding the anatomy, function, and clinical significance of dural venous sinuses.