(I am trying harder than usual not to make any typing mistakes in this post, but I'll leave any in to show you what my uncorrected posts look like.)
I gave myself brain damage a few years ago by accidentally shutting myself in a CO-filled room and ever since I've suffered various tyrping (<--- where did that 'r' come from?) typing problems.
One is that I find myself adding 'e' to words ending in 'h' so 'both' becomes 'bothe', 'catch' becomes 'catche' and so on.
Another thing that I do unless I very carefully watch what I am typing is to transpose letters, so 'what' becomes 'waht', 'castle' becomes 'csalte', that kind of thing.
The third catgeory (<--- there you go - I just did it again!) category of mistake is the 'unrealted (<---) unrelated rhyming word'. My mind starts to wander when I'm typing and a word which sounds something like the one I want appears in its place. I might end up with 'Steam engines are fascinating matchings'.
I didn't suffer from any of those problems before the CO exposure. My memory was also affected. I now suffer from motion sickness, though fortunately, never when cycling!