Rage/aggressive episodes

Hi I have a 5 year old little girl, who was Dxed with pdd-nos around 19 months old. She had a bunch of sensory issues, almost completely none verbal, no eye contact, very aggressive and she head butted all the time.... Well she has come along way since then with us working with her, and lots of therapys....she doesnt head butt anymore, and shes verbal, shes still very hard to understand and she studders alot when shes trying to get the word out, but is she is trying to speak so thats the good thing...

anyhow heres the question I was wondering about.... Ive noticed for about a month a so that her aggression has come on full force.... its takes very very little to set her off. She gets angry very quick....and gets in this rage to were she tries to hurt me, kicking slapping, throughing things ate me, destroys things, shredding paper, and she says "hate you"

She has a little sister too I do what I can to keep her calm aroud her, and get onto her when shes mean to her, but she would go out of the blue and slap her, push her down, just very rough with her.

Im just concerened with this because these episodes seem to intense now and here lately they are so frequent.

I was just wondering if they could be linked to a seizure disorder.

Or what steps should I take, how to get started into looking into this....

she can be or should I say she is a very sweet little girl, until this rage takes over these episodes can last anywere from 10 minutes to 2 hours...just depends how upset she is....
but once she "calms down" shes back to a being a sweet little girl

She did have a eeg done around 2 years old, but was sedated for it.... (ive been told sedation medication can affect the results) and she sleeps with her eyes open too... ( I was also told-long after she had the test, that is something they needed to know for the eeg too,Im not sure if I told them that or not)

She has had a few "stareing " episodes too in the past, especially in her sleep...she has woken up in like a "trance" state.

Anyhow I know Im jumping all over the page with this. Im just concerned with her aggression, I dont want her to hurt somebody, and part of me feels like she does realize how "aggressive" she is being while shes doing it...

I just want to know were should I start about how to control this.

Takeing her to the drs are nightmare, shes gets all worked up about it.... I have noticed her having anxiety too. Anyhow I just do want to push something for her "a test" if its not necessary.

thank you for your time.  Jenn