Inability to walk after a seizure

My daughter just started felbatol less then 2 months ago and we are weaning her off keppra. She's also on vigabatrin. THe doctors say these meds have no known "interactions". She has Tuberous Sclerosis so seizures have been impossible to control...probably lennox-gastaux. Her body is tolerating the felbatol well, and since she's tried 13 meds with no success (except vigabatrin which stopped her infantile spasms), the felbatol is really the last one we have to choose from. She is post frontal lobectomy to remove to tumors 2 years ago. She is severe MR, non-verbal, has autism but gross motor has always been very good. Since she is unable to tell us what happens during/after seizures, everything is a guess for us. She holds her hands to her ears during an absent seizure-we believe this is an aura and it gives us a few seconds to get to her if it advances into a myoclonic or tonic clonic. Since starting the felbatol though her tonic clonics have gotten worst and she is virtually unable to walk after even myoclonics anymore. The nuero thought at first it was med related-a side effect. Now she thinks it's a post-dictal effect. Funny thing is it doesn't happen every time and tonight she had no problems walking even after a tonic clonic. She is so multifocal that I'm thinking it could just be caused baesd on where the seizures happen to be originating from. Can anyone give me insight to this or had experiences they'd like to share? Since she is unable to speak, I'm hoping to get some insight from those who have personally experienced seizures and post-dictal problems as well as side effects. Has anyone ever heard of felbatol making grand mal activity worst? Thanks so much for your help.