Venous Drainage of the Brain

Summary

• Overview
• Venous sinuses
  • Cavernous Sinus

Overview of Venous Drainage

• The venous drainage of the brain tissue is done via the venous sinuses
  • These are endothelium lined spaces within the intradural space (i.e. between the two dural layers)

• Sinuses drain blood from the brain from two key sources via lacunae 
  1. Internal veins of the brain
  2. CSF via arachnoid granulations

• Finally, the sinuses then drain into the internal jugular vein

• Therefore the blood flows from CSF/internal veins => venous sinuses => IJV => heart

The Venous sinuses

• There are a number of sinuses to consider

1. Superior Sagittal sinus
   • Runs in falx cerebri
   • Drains directly into confluence of sinuses
2. Inferior Sagittal sinus
   • Drains into straight sinus
3. Great cerebral vein
   • Drains into straight sinus

• These drain into 2 structures

1. Straight sinus
   • Formed from ISS + GCV at union of falx cerebri and tentorium cereblli
   • Drains into the confluence of sinuses
2. Confluence of sinuses which is formed  from the straight sinus + superior sagittal sinus

• The Confluence of sinuses then drains into:

1. Transverse sinuses
   • Formed from confluence of sinuses
   • Run in attached border of  tentorium cerebelli
   • Drain into sigmoid sinus
2. Cavernous sinus
   • Drain into sigmoid sinus via superior petrosal sinus and IJV directly via inferior petrosal sinus
3. Sigmoid sinuses
   • Receives blood from transverse sinuses (from confluence) and the superior petrosal sinus (which drains the  cavernous sinuses)
   • Drains into IJV at jugular foramen

The Cavernous sinus

• This is a venous sinus  but important due to it’s anatomical relations – in particular the ICA, pituitary gland, and cranial nerves

• There are two cavernous sinuses, one for each side of brain
  • Separated by the sphenoid sinus & pituitary gland

• The cavity of the sinus is  bordered by:
  • Diaphragma sellae superiorly
    • Formed from meningeal dura
  • Sella turcica inferiorly (+ greater wing of sphenoid)
  • Temporal lobe laterally
  • Sphenoid sinus medially
  • Superior orbital fissure anteriorly
  • Petrous part of temporal bone posteriorly

• Contains several key structures besides venous blood
  1. Internal carotid arteries
  2. CNIII – VI (except V3)
  3. NB the pituitary is not within the sinus  itself