Does anyone else know what I'm talking about when I say Mom's dementia is like Bipolar disorder?

The last two weeks mama has been very quite and not a lot of confusion, slept a lot, just seemed to be getting worse....THEN all at once it's like she is so hyped you can't leave her alone in a room...she talks loud, non stop, no sleeping, like for twenty four hours or more....and makes up these hugh stories about us and her life....she eats hugh meals and seems hungry all the time....she even eats pretend meals, and will say I've dropped my fork, do you see it...normally we can't get her to eat. she has us to call every one she can remember on the phone and talks...then she'll go to sleep and wake up back in her , mood of just sleeping for days not eating, and no talking....HELP us understand...please