An inflammation of the meninges is referred to as. meningitis. Between the arachnoid layer and the pia mater is a space called the subarachnoid. space. It contains a clear, colorless fluid referred to as Cerebrospinal Fluid (CSF). CSF is produced in the ventricles of the brain by a collection of rich vascular protrusions. called the choroid plexus. Excess CSF is continuously reabsorbed by arachnoid villi. and returned to the venous system thus maintaining a consistent amount of fluid under. an intracranial pressure between 50 - 180 mmHg.