overdose of dilantin

Are there any long term side effects from an overdose of Dilantin? My mother-in-law had a stroke and then several seizures. The hospital she is in has overdosed her with dilantin for 4 days. I have looked up the side effects and she has several. After realizing she was being overdosed, the hospital did not give her any dilantin last night and only gave her half a dose this morning. Yesterday, she had most of her memory, but today she can't remember having a stroke or anything following. She did have this memory the three days following the incident. My concern is that there might be permanent damage from the overdose. Is this possible?

Thanks