Susan,
 Good point: the diagnosis is made clinically.
 You can't image the vestibular system--when I go to Mass Eye and
Ear, they have brochures for you to donate your temporal bones after
death, for research, in the waiting room of the otology department.
 So, as my ENT has explained to me: when you can't image the system,
and no one goes into it, except otologists who are killing it off when
they do Meniere's surgery, all vertigo diagnoses are by inference.
I've had ENG's, fancier stuff like rotational chairs and balance
machines, and they interpret them as showing decreased vestibular
function in my "bad" ear.
 A potential reason for vertigo with vacations is mal de
disembarkment: the illusion of movement after movement stops. I would
have it every summer when I sailed, and never made the connection: for
months, the room wouldn't stop moving. It can occur with flying, and
the pressurization of flying can make it worse.
 The latest common diagnosis is migraine associated vertigo. I do
believe in it, but as it is a diagnosis of exclusion, and migraine is
so common, I think it's being a bit over used currently. A member of
my family truly has it: her migraines are 99% vertigo, and she spent
many years in really bad shape until she started on a low dose of
medication to suppress migraines. She started with bouts of vertigo as
child. In her case, she was hospitalized with intractable migraine,
and the neurologist couldn't fathom why she was having terrible
vertigo. My ENT "got it" instantly.
 Interesting about the muscle spasms--I have a few woppers lately,
and I"ve had the nasty lingering virus--keeps threatening to be a
"real" sinus infection, but doesn't get there, and I've been dizzy and
having some major leg cramps. And, I'm using my asthma inhaled
steroids....
 For me, my first symptoms of sinusiits used to be severe nausea,
which was associated with the vertigo, When I had a really bad time
with vertigo: about 5 years ago I had a huge episode of BPPV in a yoga
class, and the rehab (I did it to extreme--trying to reposition the
otolith) likely did further damage to my inner ear--I was so nauseated
for a couple of years. My medical director at the time couldn't stand
to look at me in meetings because she said it made her feel car sick.
Think how I felt.
 I did call out one day this week when the virus was at it's peak,
and when I came back the office, I got the common statement from
patients that makes me crazy: "I didn't think doctors get sick." No,
we just deal with high volumes of ill people, and have some secret
defense weapon. My internist earned my high regard when she admitted--
and she's trained in ID as well as medicine--that she asked a patient
to cover her mouth. I've never had the guts to directly say it. It
makes my husband---who as a dentist is masked, gloved and gowned,
nuts.
 Judy

Duke,
 I just got mine redone:
Ironically, same numbers as 5 years ago, different lab with different
reference #
IgG1=352 (low) range=382-929
IgG2=451  (ok) range=241-700
IgG3=22 (low nl)--range=22-178
IgG4-2.7 (low) range=4-86
IgE=1.7
Unfortunately I don't have the reference range on this print out--but
the numbers are the same values were Subclass 1/3 low in the past.
We agreed that I'm essentially low in 1/3/4--with 1 the most
clinically important value.
I found a good handout--for a patient with zero 2/4.
I'll post it.
Judy