Correct me if I'm wrong, but isn't bell's palsy more a symptom? And usually a virus (like epstein barr or herpes virus) or sometimes lyme disease is the cause of the bell's palsy?

I think the cause is also a diagnosis of exclusion. They test for lyme, they make sure its not a stroke or tumour, etc.

Electromyography is a nerve test they do to test the electrical activity of the nerves, I think the electrodes go on your face. I think they can tell which nerves are affected and how much they are affected.

I assume your face is only affected on one side? I know if you are having trouble closing the eye on the affected side that artificial tears are necessary to protect the eye while you recover.

Best of luck, I hope it resolves quickly.
Starr