Venous drainage systems are really important for how blood flows in the brain. Here are some key points to understand:

1. Cerebral Venous Anatomy:

   • The way blood drains from the brain includes two systems: the superficial and deep venous systems.
   • There are important veins like the internal cerebral vein and the great cerebral vein (called Galen). These veins help carry blood from the brain to the internal jugular veins.

2. Impact on Cerebral Blood Flow:

   • About 25% of the blood pumped by the heart (around 1,000 mL per minute) goes to the brain.
   • Changes in how blood drains can affect the pressure inside the skull (this is called intracranial pressure or ICP).
   • If ICP rises by just 10 mmHg, it can cut blood flow to the brain in half.

3. Clinical Relevance:

   • When venous drainage doesn't work well, it can cause health issues like cerebral venous sinus thrombosis (CVST). This condition happens to about 2 to 3 people out of every million each year.