In my experience, it's helpful to ask questions that are more inclusive rather than pointing out a "disability."
For example, "As with all of our employees, we want to make sure that the workplace is user-friendly. Do you have any requests to help accommodate your employment with us?"
In this way, you facilitate the person being the expert on his needs, not you. I find that people with special needs often become quite comfortable talking about the scenario. They will let you know accordingly, most of the time.