I am so sorry to hear about your father. I know that the uncertainty is very hard to deal with. I know you are worried and that is understandable so I hope I can ease your mind a little. Quickly about me - I had a major stroke in 2010 and this year I was diagnosed with epilepsy as a symptom from my stroke, so all of those tests your father has been through I am very aware with. It sounds like a stroke is out because of all the tests. In my case the stroke was easily seen as a black spot on my brain from an MRI. People can have TIA's (mini strokes) that do not show on MRI film, but are a warning of a major stroke. And even TIA's can cause temporary confusion and paralysis.
From what you wrote, in my opinion your father may have the onset of epilepsy. I am not a doctor obviously, but I have learned a lot through my own experiences. The good thing is that it is found early. For you, I would not be worried about the Ativan they are giving to him. I am sure he must be sedated while they are trying to figure out what is wrong. They don't want him to have a grand mal seizure. He will hurt himself even in the hospital if that happens. Apparently epilepsy is a hard thing to diagnose. I had 4 grand mal seizures 3 trips to ER and weeks of hospital stays and tests until a neurologist finally figured out I have epilepsy and it was caused by me stroke.
Now I am on medication that control my seizures. They are very strong can make me spaced out at times, but I am getting used to it.
As far as your father goes. Find a good neurologist. That is the only way that I finally go some results and satisfaction after seeing dozens of different kinds of doctors. Even that neurologist took months to find a diagnoses of epilepsy, but he is the only Dr. that finally got it right. When dealing with the brain there a so many variables, that you really have to find the best one that knows what he is talking about. About the Ativan. My doctor gave me a very strong script. Not to take everyday, but have with me all the time and if a feel a seizure coming on to take it, if there is not water, just chew it. And you know I have had to use it a few times. They are called triggers that warn you before a seizure. A trigger could be anything to each person. Mine, I start feeling dizzy and I can't talk. I try to talk, but it is like my brain is frozen. Some other ones I have heard are tastes of rhubarb, smelling like something burning, or listening to music that isn't there. Your dad's headache could have been a trigger too. Can you ask him if he remembers anything unusual before his seizure? Like a taste or smell? That may help pinpoint things down if that is the case.
Jennalyn, I am not saying he has epilepsy at all. I don't know. Just some of the things you wrote sounded very similar to some things that have happened to me. Whatever happens I wish you well and you father as well. I hope you get some resolve soon. Let me know if I can help, and I will try if I can.