Long Term effects

My daughter, 34, was diagnosed with epilepy when she was 3. She is mentally retarded due to anoxia at birth. Her medication has controlled her seizure activity . She recently changed medication ( about 6 mos.) with no increase in seizures. Until now... We have a nuerologist who monitors her meds. My question relates to the progression of the long term effects of the seizure activity as it relates to personality and cognitive ability. For the past several weeks, Kate has " lost her affect" and seems overall - slower and struggling more to perform tasks that she once enjoyed.
My concern and interest is to find stuidies relating to the organic changes that may/or can occur within the brain of people with this condition. Simply put - do they plateau and/or deteriorate oveer time? As a parent and advocate, I want to learn what information has been studied and written about. Any suggestions as to what material,cites, nuerologists or centers that are involved in this type of study would be appreciated. Thank you.  IMary Jane Coolidge