EEG - hyperventilating component

[CtResident]

So today I had an EEG and one of the components was this: I had to breathe out after the technician counted. 1 - puff. 2 - puff. 3 - puff. Up to 10.

Again. And again. Again. Again.

I lost count around 7 units of 10. My legs started to shake and shake, my whole body got chills. And he breezes in, okay, all done.

I was really annoyed at the blinking lights part of it and said I wanted to know about that, was that the VEP part? Um, no. Silly me, they forgot to schedule the latter two. Off I go to another appt. next Tuesday. I tell you what, it's a good thing they are only 10 minutes from me and I'm a stay-at-home mom, or I'd bill them for my mileage.

Question: what does this part of the EEG look for? And what did my response mean?

Suzanne

[Super_sally888]

Hi Suzanne,

someone else will comment probably, but I think the feeling your felt are quite easy to bring on with hyperventilation.  Hyperventilation blows out carbon dioxide from your blood.  If carbon dioxide levels change it has effect on blood pH and affects nerve transmissions etc - which I guess is why it can stimulate seizure activity in someone susceptible.

Actually pretty harmless.  If someone hyperventilates till they pass out (the body's protective mechanism to prevent things getting to a level where they cause damage), they will actually stop breathing for a few breaths while the carbon dioxide levels in their body build up to normal again.

I remember this from physiology years ago..... we students thought it was a great lark!  Hoping I got it right.  If not, someone will correct me.

Sally

[Rena705]

I remember back even as recent at 1993 when I was first diagnosed and presented with Grand Mal seizures I was told that I should never use a computer and avoid strobe lights.  I personally never had a connection between flashing lights and I never did stop using the computer...it was part of my job!  I am on meds, maybe that is why?? who knows but no seizure problems with these things for me.

[CtResident]

Why did my legs shake and I got cold? But it was short-lived, I walked out of there just fine.

Suzanne

[Quixotic1]

During the EEG when they flash the strobe lights and have you hyperventilate they are trying to bring on seizure activity.  Those are two things known to precipitate certain kinds of seizures.  So they watch the recording very carefully.  

When I discuss the difference between evoked potentials and EEG I state that the EEG is mostly passive.  But, twice during an EEG they attempt to evoke a response - these are during the strobe lights and the hyperventilation.

In the late 60's it was very fashionable to use strobe lights during performances and concerts and they ended up causing a whole bunch of seizures in audiences.  I don't know if that's when they discovered it, but I remember being at a play and having the announcer ask anyone with a seizure disorder to cover their eyes for the duration of the strobe work.  It's a particular frequency that affects people.

The hyperventilation will especially bring out absence (or petit mal) seizures.

If your brain is "twitchy" (pediatrician term for a brain prone to having seizure activity) you might have a particular aversion to either of these maneuvers.

Quix

[CtResident]

Meaning they forgot to schedule my VEP and the BAER.

It's just as well; I left the house at 10:30 for my 11 appt., got seen around 11:30 (to be expected, right?) and was home around 1:30 (waiting for my MRI CD and the accompanying records). If I'd had the VEP and BAER, it might have been quite longer?
How long do those tests take?

Suzanne