Hi sallymanda,
Hirschsprung's disease is a congenital illness. The average age of diagnosis is 4 years and younger. For reason which are unknown there are no nerves in the affected section of intestines. This disease does not cause Neurological problems.
Information about Hirschsprung's Disease:
http://www.lpch.org/DiseaseHealthInf.../hirschpr.html
Best wishes to you and your son.