How can I tell if these symptoms are due to my recent surgery or dementia?

I had a brain tumor and brain surgery. Both my in-laws have late-mid stage and early-late stage Alzheimers. In readying signs of demintia, I have many of the early signs. How can I tell if it is due to my tumor and surgery or dementia? I'm 47 and adopted, so I don't know if Alzheimers runs in my family.