Potty training for a sensory affected child can be a daunting task. It's frustrating to the parents too. I've read about children who don't manage it until as far as 18 years old. Most that I've read about are around 9 or 10.
What is it that causes potty training to be so difficult?
One theory is that the sensation of the open space of the bowl under them is disconcerting. They may not feel stable or safe sitting on the bowl. That could even take effect for child size potty chairs.
The change of not having the sensation of a soiled diaper may even have a little to do with it. Consider that all they've known up to this point is what if feels like to have the duty done next to their skin. The new effects can be disconcerting. Hey, it's only a theory.
What's really important to know (mostly for the high functioning with autism such as Asperger's) is that it's not impossible. Potty training can be done. It will take more dedication and perhaps longer than a typical child, but can be done.
Things that will help:
There are training programs geared for autism that you can find by internet search. Here are just a few sites to check out:
Seeing other kids the same age can inspire a child to do the same as they do. With all the attempts and programs used with my own son, it was seeing other five and six year olds use the potty that fixed the situation forever.
Use props, videos, toys and books. Read books on potty, watch videos, and get a baby doll that wets itself for demonstration.
Reinforce by pointing out that no one else in the house does the duty in their pants.
Consistency and repetition are key!
So, if you are looking at potty training, collect yourself and arsenal of information and tools and above all, don't give up!