I have five children, all of whom have special needs and three of whom have some type of developmental disability. My oldest was a 24 week micro-preemie with multiple disabilities, among them low functioning autism and significant cognitive delays, my six year old has Aspergers (and was diagnosed with low functioning autism and had that diagnosis confirmed by a second and third opinion between the ages of 1 and 2 but has flourished with therapy), and one of my three year olds has a developmental delay and other disabilities also related to prematurity.
My six year old had the. most. out of control behavior that can be imagined when he was younger. I don't often go into great detail on public message boards because far too often people get one snapshot of the story and decide it's all simply because you are a lousy parent and if you'd JUST ______ (insert "perfect" parent behavior here) then your child would NEVER do ________ (insert unacceptable child behavior here), because THEIR child has NEVER __________ (insert unacceptable behavior) because they won't "allow" it!
However, I will share that my son was a wild-child. The hyperactivity was off the charts, as well as his aggression. He would randomly and impulsively bite people....whether he was angry, frustrated, happy, excited, or just happened to run by you....he would out-of-the-blue just bite people. It was bad enough at one point that when I was no longer capable of standing two inches behind him in public places (like a park, or zoo) because I had too many kids and not enough of "me" to be his personal follower, I hibernated us in my house for almost six months. We'd go to the park and if another child showed up, we'd leave.
For *years* and *years* I told people I thought he was over-tired. He had dark circles under his eyes and his behavior, especially the hyperactivity and impulsivity SCREAMED "I'm exhausted". And he was a frequent night-waker (as an infant up to 14 times a night even at a year old), a VERY early riser (up at 4 am) and would simply collapse at the end of the day, not gradually fall asleep, but just fall apart and crash. His behavior would consistently get worse as the day progressed. I kept bringing this up to pediatricians and therapists that this simply could not be considered normal. But, because he didn't snore, he was very thin for his age and his tonsils looked normal on examination, I kept being told it was a sensory issue related to his autism, and that sleep issues were common in autistic children and our treatments were all on the sensory side of the equation.
Finally, FINALLY when he was about to turn four, I had a new developmental pediatrician who listened to me explain my concerns about his sleeping and order the overnight sleep study I had been requesting for nearly three years. And sure enough, my son had severe sleep apnea. Even though his tonsils were normal size, doing a tonsillectomy and adenoidectomy is the standard recommendation for medical treatment, so we went ahead. The adenoids cannot be seen until they're actually *in* surgery, and the ENT came out to tell me that my son's adenoids were the largest she had seen in her career, and were actually entirely blocking the back of his nose and she was shocked he could breathe through his nose at all, never mind when sleeping.
I was told that within 3 months, I would have a brand new child. And I'm here to tell you, within 3 months, I absolutely had a brand new child. The hyperactivity? Gone. The biting? Gone. The impulsive pushing/shoving? About 80% gone. The late afternoon crazy-screaming hours? Gone. The constant crankiness and hypersensitivity? Drastically reduced.
Severe sleep deprivation in young children most often manifests itself as *hyperactive* and *impulsive* behavior. I would google "sleep apnea in children" and see if it resonates with you and your child at all. All it takes for a diagnosis is an overnight sleep study.
Having my son treated for sleep apnea did not cure his autism and he certainly still has behavioral and other challenges that come with an ASD diagnosis. But treating his sleep apnea literally changed both his life, and the quality of life for our entire family. I had actually broken down and put him on behavioral medication during that very same appointment where the developmental pediatrician ordered the sleep study, because dealing with his aggression was so constantly draining. Right after his surgery three months later, we took him off and have never looked back. All of his challenges now can be managed without the need for medication.
The bottom line--- while I bring up sleep apnea as an oft-undiagnosed and very real cause of this kind of behavior, the real moral of the story is that you are her mother. You have parented her for five years. If your gut tells you something is "wrong" and this goes beyond typical behavior, then trust your gut. You know your daughter better than ANYONE and you are going to be the first person who recognizes and understands that there is an issue that needs to be examined and treated. Children can be diagnosed with developmental disorders and other behavioral disorders as young as 12-18 months of age. I would start by researching developmental pediatricians in your area, find one I was most impressed with, and schedule a thorough assessment where you can bring your concerns directly to the person who will evaluate your daughter.
There are answers out there, and there is hope! It often times takes a lot of persistence on the part of parents to get correct and proper diagnoses, but with a diagnosis also comes answers and treatment options that better your child's life and your whole family. Trust your instincts.
Edit to add: here is a detailed list of the symptoms of sleep apnea in children http://www.stanford.edu/~dement/childapnea.html