Epilepsy – EEG Testing

Transcript

The other thing that we’ll want, and equally important as the MRI, if not more important, is the electroencephalogram or EEG. An EEG is a test where what we’ll do is we’ll hook up electrodes to your head and usually it’s 21 electrodes through the head. They’re on the skin, nothing inserted into the skin, and they glue them on. So it’ll make your hair sort of messy for a couple of days or a day. And what you do is ideally you come in a little bit, sleep deprived. We tend to ask people to have a half nights sleep prior to the study. And the idea is we want you to come in, go into this nice dark room and take a nap. 20-30 minutes. And what we’re doing is we’re looking at all the brainwaves. And your brainwaves are incredibly small. You know, it’s interesting the eyeball has a charge that’s a hundred times more than the brainwaves that we see. So when you blink, we can actually see a huge change in the charge and the EEG. But what I’m looking for is what we call epileptiform discharges. What are epileptiform discharges? They are certain wave forms. They look like big spikes. And when I see those in someone who’s had a seizure, I know that there’s a high degree of likelihood they’re going to have another seizure. And that’s often something that we’ll use to treat someone for epilepsy. I will point out that one of the issues we have is the EEG is so useful, but it’s an insensitive test. It’s about 50% sensitivity. What does that mean? So if I take someone I know who has epilepsy and I do an EEG on them, half the time the EEG is normal. And so an abnormal test is really valuable because it’s so insensitive. When I see something abnormal, that’s something I can really use and sort of help understand what’s going on with you. But when it’s normal, you have to take it with a grain of salt because you can still have epilepsy and have a normal EEG. You can also have a normal MRI and have epilepsy. So this is sort of where we get into this difficult position where if someone comes in with a seizure, they have a normal MRI and EEG, we have a sometimes a difficult decision to make or we just, we can’t know for sure. And so we have to make our best judgment and sort of go from there.