anyone know about neurological disorders?

my daughter is 4 almost 5 and has been having problems for the last 8 months, and is getting worse. the dr.s can't figure it out. here is some symptoms she is having:

the onset is much worse when she is tired. she gets clumsy in the feet, trips a lot, toes curl under causing her to drag her feet when she walks. and her legs fall asleep a lot. she sways back and forth when trying to stand still. we know she is having some kind of neurological problems that seems to be isolated in her lower legs, but even the specialists can't seem to figure it out. i was just wondering if anyone else have had any of these problems, or any suggestions on what we might want to look for. we do know there is NO tumor of any kind, we had an mri on her whole body.