how do you get them to go to the doctor?

[sr]

i just found out my dad has been dealing with my mom who is experiencing sundowners syndrome very serverely.  she is yelling, screaming, crying for hours (3-4) in the middle of the night, wakes him up so she can do so, acuses him of all kinds of things, etc., and she refuses to go to a doctor. my dad has no idea how to get her to a doctor when she so strongly refuses to go.  i told him if it gets out of hand, he needs to call 911. i think it's his only option.   does anyone else have any other suggestions? thank you.