I found this tweet today. It links to a nice simple overview video of the blood brain barrier and how it is an obstacle in treating to neurological diseases.

https://www.youtube.com/watch?v=aNliYYWXNQU

Here's the tweet

Daniel Carlson (@DanCarlson33) Oct 27th

Here's a great overview of the #Blood Brain Barrier. #bioasis gets drugs across the barrier. #cancer #herceptin

https://twitter.com/DanCarlson33/status/791767236981633024