I can't even imagine how frustrating his condition must be for him though. To have full mental capabilities but have so little (and slow!!) means of communicating his ideas.
In IT we tend to train our brains to commit processes (eg ways to research information) rather than facts. But we also have the luxury of being able to be lazy (internet, functioning limbs so can write notes, etc). Heck, before IDEs and the internet I used to remember every function name and order of parameters for any particular programming languages I was proficient in. These days I just learn the function name and let the IDE remind me of the rest (sometimes I don't even learn the function name and just search for it in the package namespace).
He's not at all disabled for what he does, which is think, and he does that better than (I'm guessing here) any of us.
Also no ability to use paper and pencil, and still only a low bandwidth mechanism to store and retrieve notes to increase your effective memory.