Following on from Don's post:
healthunlocked.com/blf/post....
New research from Boston University suggests that tonight while you sleep, something amazing will happen within your brain. Your neurons will go quiet. A few seconds later, blood will flow out of your head. Then, a watery liquid called cerebrospinal fluid (CSF) will flow in, washing through your brain in rhythmic, pulsing waves.
Issues sleeping, and other things
”Till we meet again “ 
exacerbation here we go again 
Have we all gone back to the playground 
My 4 year old awaiting sleep study for suspected OSA diagnosis
