ABSTRACT
Since the area of the BBB is about 1000 times that of the blood-CSF barrier, it is more important to circumvent the impermeability of the BBB for delivering drugs to the brain [5,6]. e total surface area of the BBB constitutes by far the largest interface for blood-brain exchange, which is between 12 and 18 m2 for the average human adult [7]. Unlike these two tight blood barriers, the interface between the CSF and brain tissue along the ependymal surface of the ventricles and that between pia mater and brain tissue, the so-called brain-CSF barriers, are rather leaky, implying a possible route for drug delivery to the brain. e CSF is formed by the choroid plexuses of the ventricles, passes the ventricles to the subarachnoid space over the pia mater, and nally is absorbed to the venules in the dura mater through arachnoid microvilli and arachnoid granulations [8,9].
