Doctor  i've a serious problem. my kid sister suffers 4rm frequent convulsion i mean violent. we've gone 2 a specialist hospital but they refered 2 mental institution so as to verify if it was epilepsy it came back negative the doctors then said that it would subside with time but it's  getting ever violent through the years which has been eleven years if i may add my questions
1 is it a medical condition  
2 dose it have a cure
HELP PLEASE

go to a better doctor for a second opinion!!!!

Oh dear! I feel for you concerning your sister's ill health. It definitely won't be easy on the family.
The little I know about that is that it has to do with some brain nerves etc but I ain't no doctor so you need to hear from doctors. More violent over the years?? meaning that it needs serious attention. You can ask around to see whether there are doctors that are very knowledgeable at that, research intensively in the internet, you may get helpful info from write-ups or health forums.
Do take good care of her the best you can, she should avoid standing on heights(elevated places) especially open ones, she mustn't drive (okay she is a kid as you said). She needs good attention, I pray she recovers from it very soon.

@poster,is your sister presently on medications?
i mean anti-seizure drugs.

^^^^ CHARLATAN!!