Angle glaucoma and vertigo

Hello,

I have open angle glaucoma and vertigo.
To find out why I always feel dizzy and my legs are instable when walking, I had MRI, but nothing was found. Now I will have to undergo EEG, EMG and NCS.
I have 3 questions:

1. Can any of the above procedures worsen my glaucoma?
2. Which pain medication should I take before undergoing EMG and NCS? My doctor told me both procedures were extremely painful. Can these procedures be done under general anesthesia?
3. Which side effects do EMG and NCS have? I heard that myasthenia gravis could be induced by NCS. The electric impulses could damage neuromuscular transmission.
How often does that happen after an NCS?

Thanks for any answers.
Amy