an attack of rotational vertigo at night
Are you sure, the term is "rotational" vertigo? The type of vertigo which is fairly common is "positional" vertigo. The latter is related to the position of the head. If the head ( and middle ear) are situated in a specific position, the body of the patient will tend to be swung out in a centripetal direction.
So, if the patient is standing, when the centripetal action takes place, the patient tends to fall over ( towards his left or right side), if he/she doesn't catch himself/herself.
This disorder is related to the middle ear, problems of which are common in the elderly. I don't know if the "exact cause"of the disease is known. While all of your tests haven't yielded much information, one area not mentioned was the boney structure of the ear.
One unique cause of positional vertigo that's been suggested is arthritis of the ear. Another explanation offered has been sudden and probably forceful changes in air pressure within the eustachian tube .
Of all the meds you've mentioned, has anyone thought of using a NSAID to treat the problem, especially if it's caused by arthritis?
Finally, when treated in the US, positional vertigo is commonly treated by having the patient undertake excercises that involve the head and neck.
Finally, we don't know the exact cause of your friend"s vertigo and we may never find out what it is. I find it strange that it occurs at night. Does this mean, it never takes place during the daytime?
Lastly, while I'm not an MD, I wonder if the polypharmacy, your friend is being treated with is really necessary....You might consult a clinical pharmacist to discuss the possibility of removing some of the drugs used in treatment.