I have done a little research and I've not found any information stating it should not be used. Most of the info out there states that people with epilepsy, MS or other neurological conditions may not be able to handle the effects of the drug. Consult with your doctor before taking, etc.
It sounds to me like it would be based on a number of factors, like you said WhiteRose, depending on the severity of the epilepsy and the severity of the Crohn's. Would the possible benefit outweigh the possible risks? Something his doctor would have to discuss with him.
Good luck, I hope someone with a little more knowledge is able to help!