Taking folate will NOT interfere with the antiseizure properties of dilantin. You likely need an antiepileptic med on board given your neurological history, but it's your choice as to whether or not you want to take the folate. It's a relatively safe supplement and should not have any side effects if taken as directed (1mg a day). Also, checking homocysteine levels and bone density scans are not tests that we routinely order for patients on dilantin. In the past, we have ordered homocysteine levels for patients needing dilantin and who have risk factors such as those with a personal or family history of early coronary disease or strokes. And in those particular patients as well as some others we have recommended the folate supplement. Ultimately, it's a decision you and your doctor should make. In simple terms: the folate may help and it won't hurt. Good luck.
below is a link to more info on Folate (Folic Acid):
http://vvv.com/healthnews/folate.html