I am a nervous speaker and can't string together thoughts and ideas effectively. I usually end up stammering while i search for words with which to express myself. It can be torturous when I am put on the spot. It's not an impediment in the sense of a medical condition, but it definitely impedes.
I also have something similar. I have to think for a while before I can output what I'm thinking as words.
It's like having to translate it first from some foreign language... Maybe that's why I was always the "smart kid"? I managed to decouple my thinking process from any kind of language? ._.