1) The document describes cerebrospinal fluid (CSF), including its production in the choroid plexus at a rate of 20 cm3/h, composition, flow through the ventricles and absorption via arachnoid granulations into the dural sinuses.
2) It then discusses two clinical cases of young women presenting with headaches and the differential diagnoses of intracranial hypotension and idiopathic intracranial hypertension.
3) Intracranial hypotension is described as being caused by a CSF leak leading to decreased CSF volume and pressure, with characteristic MRI findings of dural enhancement and venous distension.