So, before my younger brother passed of cancer last year, he had to have this thing called an 'ommaya catheter' inserted into his brain (a tiny tube that goes directly into the spinal fluid to administer chemo to the nervous system without having to do a spinal tap every time) well... long story short, it caused something called a 'sub dermal hematoma' (a clump of bleeding that puts pressure on the brain). In the week that this thing took to develop, even though it's fucking itty bitty,  my brother went from being the too-smart-for-his-own-good math master to not even being able to count to ten. A tiny, tiny, clump of bleeding made him retarded, literally, until he had an emergency brain surgery to have it removed (which fixed the issue entirely, thank God)  But just imagine...something less than the size of a dime can make someone literally retarded...just think what adipose fat does pushing all over the place. Crazy.