Every family situation is different; I don't know the dynamics between your brother and you.
First: I am not a medical doctor. I have a doctorate, but I am not a MD so take what I say as a potential starting point; I am speaking from my experience, and my experience is just mine, not your's.
A couple of questions:
Who is the primary person helping your mom? You or your brother? If it is you, get your mom to verbally tell her doctors, the retirement center, etc that YOU are to be included as a person helping your mom to make the decisions. It is NOT that you WILL be making the decisions, but you are to be included (they can talk to you, they have your mom's permission!). You can also act as your mom's "memory", meaning that you might remember to ask things that your mom doesn't (or won't). I'm not saying that your mom's memory is bad, but it doesn't hurt to have someone else there (if possible). I know that sometimes it is just not possible, so don't beat yourself up about it.
Regarding the Medical Power of Attorney. You say your brother holds it; are you on it at all? I know when I had it drawn for my mom I was listed first, then my brother and finally my sister. I ask, because some medical providers are more willing to include you if you are listed on it. In any case, it applies when your mother has been judged as not being able to make her own decisions medically--you cannot use it to "force" anyone to do anything. It just doesn't work that way.
I'm glad that your mom is out of the hospital. How bad was the stroke? Were there any severe (or not so severe) consequences she suffered? Is she ambulatory?
Alert! I am not a psychiatrist either!! The following is my 2cents:
As others have said, depression is quite common in the elderly. Some of the depression may stem from the stroke. You stated previously that she suffers from depression, OCD, and anxiety, but doesn't want to take any meds for it because of how it makes her feel. This is an area that not many of us can help you with. On the one hand, you cannot be with her 24 hours a day to help relieve her depression and anxiety; on the other, you feel you need to be there 24 hours a day to help relieve her depression and anxiety! (My mom wanted me to be there all the time to keep her "entertained" and keep company; that's a fast way to become an enabler instead of a helper. Quite frankly, her issues weren't something that I could "fix.") Does she perk up with family visits? Does she have friends around who would be willing to check in on her on a more frequent basis for a while until her mood "stabilizes"? Would your mom be amenable to talking to a counselor about her issues? Basically, getting out of the house and being around people will help to some degree, both for depression and anxiety; making sure she is eating (and eating well) is another issue, as diet and depression have been linked. Any idea what her anxiety issues are, and how bad it may be and what may trigger it? You certainly want to help alleviate it, but it may be a function of "getting old and now she's been put in the nursing home" issue. When my mom fell and broke her hip, we were able to get her into a retirement village where she could get better care; she didn't want to be there (she called it the nursing home, even though she was living independently) and so that ratcheted up her anxiety. You mom may be in the same boat.
Finally, try to have a sit down with your brother. It will be difficult for both of you. You appear to be quite invested in your mom (absolutely nothing wrong with that!), and your brother appears to have taken a step or two back. In your case, it will be quite easy for you to get sucked into the situations that may unfold around your mom where the more you try to help, the less you actually get done. It is tiring, frustrating, and ultimately not good for you. Try to step back. Don't let your fears drive you in this journey. His reticence to talk to you may be simply because he is having a hard time with this too.
Good luck, and let us know how it goes.
Diana