Adult brain tumors are masses of abnormal cells that generally occur in adults, and result from the uncontrolled growth of those cells within the brain.
OK - let’s start with some basic brain anatomy. First off, there’s the cerebral cortex which is the part of the brain that’s supratentorial or above the tentorium, and the cerebellum, which is infratentorial or below the tentorium.
And the brain has four interconnected cavities called ventricles, which are filled with cerebrospinal fluid - a fluid that helps provide buoyancy and protection, as well as metabolic fuel for the brain.
Highest up, are two C-shaped lateral ventricles that lie deep in each cerebral hemisphere.
The two lateral ventricles drain their cerebrospinal fluid into the third ventricle, which is a narrow, funnel-shaped, cavity at the center of the brain.
The third ventricle makes a bit more cerebrospinal fluid and then sends all of the cerebrospinal fluid to the fourth ventricle via the cerebral aqueduct.
The fourth ventricle is a tent-shaped cavity located between the brainstem and the cerebellum.
After the fourth ventricle, the cerebrospinal fluid enters the subarachnoid space, which is the space between the arachnoid and pia mater, two of the inner linings of the meninges which cover and protect both the brain and spine.