Walsh & Hoyt: Veins of the Brain: Cerebral and Posterior Fossa Veins

The veins of the brain possess no valves, and their walls are extremely thin because they have no muscularis. These vessels pierce the arachnoid and the inner or meningeal layer of the dura mater to drain into the cranial venous sinuses. The veins of the brain are usually separated into those that drain the cerebral hemispheres and those that drain the posterior fossa.