My Mother has PPA (primary progressive aphasia) along with other aspects of dementia. She has begun having excessive moods in which she becomes quite agitated. How do I deal with these mood swings?

My Mother has PPA (primary progressive aphasia) along with other aspects of dementia. She has begun having excessive moods in which she becomes quite agitated. She cries and makes fearful sounds and says she is scared or that she doesn't know what is wrong. Then a few minutes later she is okay. Her mood goes up and down, mostly down and she becomes quite distressed. We try talking to her, holding her, letting her know she is safe. It is hard to know exactly what she is afraid of because of her inability to use language. We tried Paxil with no success and now are trying Lexapro but it doesn't seem to be helping either. We will be going back to the doctor in a week or so to see what else we can try. Does anyone have any suggestions as to how we can deal with her issues now, before we get to the doctor? Her distress is making my husband and I very stressed because we just don't seem to be able to ease her suffering. Thanks for any suggestions.