EEG in Epilepsy With Dr. Daniel Weber

EEG is the single most useful ancillary test to support the clinical diagnosis of epilepsy, but if used incorrectly it can lead to misdiagnosis and long-term mental and physical health sequelae. Its application requires proper understanding of its limitations and variability of testing results.

In this episode, Katie Grouse, MD, FAAN, speaks with Daniel Weber, DO, author of the article “EEG in Epilepsy,” in the Continuum® February 2025 Epilepsy issue.

Dr. Grouse is a Continuum® Audio interviewer and a clinical assistant professor at the University of California San Francisco in San Francisco, California.

Dr. Weber is the director of adult epilepsy and vice chair of clinical affairs at the St. Louis University in St. Louis, Missouri.

Additional Resources

Read the article: EEG in Epilepsy

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Guest: @drdanielweber

Full episode transcript available here

Dr Jones: This is Dr Lyell Jones, Editor-in-Chief of Continuum, the premier topic-based neurology clinical review and CME journal from the American Academy of Neurology. Thank you for joining us on Continuum Audio, which features conversations with Continuum's guest editors and authors who are the leading experts in their fields. Subscribers to the Continuum journal can read the full article or listen to verbatim recordings of the article and have access to exclusive interviews not featured on the podcast. Please visit the link in the episode notes for more information on the article, subscribing to the journal, and how to get CME.

Dr Grouse: This is Dr Katie Grouse. Today, I'm interviewing Dr Daniel Weber about his article on EEG and epilepsy, which appears in the February 2025 Continuum issue on epilepsy. Welcome to the podcast and please introduce yourself to our audience.

Dr Weber: Hi, thanks for having me. My name is Dan Weber and I'm an epileptologist at Saint Louis University. I direct the adult epilepsy program here and also serve as the vice chair for Clinical Affairs. Been my pleasure to work on this article.

Dr Grouse: I'm so happy to have you today. I read your article. I found it to be incredibly useful as someone who often orders EEG in the general neurology clinic. So, I wanted to start with asking, what is the most clinically relevant message or takeaway from your article that you'd really like neurologists to know? 

Dr Weber: Yes, when I was asked to write this article, I looked back at the previous Continuum on epilepsy and just the general literature. And there's a lot of good articles and books out there on EEG and epilepsy and sort of giving you a primer on what you might see and how to interpret it. So, we wanted to try to go a slightly different direction. This article gives you some of that gives you the background of EEG and some of the basic things that you may see, but the real thrust of it is more about the limitations of EEG in the clinical picture of epilepsy and common things you might avoid. There are some things that we get hammered into our brains in training that aren't always true and there's plenty of examples in the literature to review, and this article sort of tries to encapsulate as many of those as possible in a digestible format. The main takeaway would be that EEG is an extremely helpful tool in the diagnosis of epilepsy, is the best tool we have to help supplement your clinical acumen. But it does not make the diagnosis of epilepsy. And there are certain circumstances when it may not be as helpful as you may have been led to believe in residency.

Dr Grouse: Maybe not the most comforting of messages, but certainly an important one, very important to learn more about this. So, we appreciate that. Can you tell us your decision-making process when deciding whether to order a routine EEG, an extended EEG, prolonged ambulatory EEG, or inpatient video EEG?

Dr Weber: Sure. So, it's a multi-part question because each one, I think, has a different clinical scenario. In the current state, our best data for estimating risk of recurrence after an initial seizure comes with routine EEG abnormalities. So, often I will order routine EEGs in those scenarios. So new patient presentation, new patients coming in with an initial seizure who want to know what's their risk of recurrence. So, risk stratification, I use a lot of routine EEG for, often sleep deprived if possible to increase the sensitivity. If you'd like, the extended EEG does offer higher sensitivity, or you can repeat the routine EEG if the first routine EEG is nonconclusive.

For generally extended EEGs, I tend to order them in my practice if patients have come to see me with a suspected diagnosis of epilepsy but haven't yet had any electrographic confirmation.

Maybe they've already had routine EEGs done in the past, so we'll try to obtain just a little more data. The longer-term EEGs I tend to use in different clinical scenarios, in patients usually who already have established diagnosis or people who have become refractory and we haven't yet confirmed their diagnosis. I tend to do inpatient EEGs in those situations. Ambulatory EEGs I do more when there are certain characteristics of the patient or the patient 's presentation that may not fit well on the inpatient side. Patients who are reliant on substances who can't use while they're inpatient and may have withdrawal effects complicating the stay. Or people who have a strong activation component to their epilepsy where activity really draws it out, certain activities that they do at home that they might not do during the inpatient stay. Those are the sorts of people I'll do ambulatory EEGs on. There are a couple other scenarios as well that come up less commonly, but everything has its own little niche.

Dr Grouse: That's a really helpful review as we sort of think about which way we want to go as we're working up our patients in the inventory setting. Can you tell me a little more about the difference between sensitivity of, for instance, doing maybe two routine EEGS versus prolonged ambulatory EEG?

Dr Weber: Generally speaking, the longer you're recording someone's brain waves, the higher the sensitivity is going to be. So routine EEG is twenty to forty minutes at most places. One of those gives you a certain sensitivity. More of them will give you more sensitivity. And there was a recent study highlighted in the article that compared routine EEGs to initial multi-day ambulatory EEG, and the ambulatory EEG obviously, as would be expected, has a higher sensitivity than either of the routines. So, there may be some cases with that initial evaluation where an ambulatory EEG may be held and we get into that in more detail in the article. But with the caveat, a lot of this article is about limitations, and the data that we have to talk about increased risk of recurrence was based off seeing epileptic form discharges on routine EEG. So you could hypothesize that if you only have one epileptic form discharge in three days on an ambulatory EEG, that may not carry the same recurrent significance as catching one on a twenty minute EEG. But we don't have that knowledge.

Dr Grouse: Getting a little bit more into what you mentioned about the limitations, when is the scalp EEG less useful or limited in the evaluation of epilepsy?

Dr Weber: So, one thing I see a lot in my residence at here and other places where I've worked is, I get them very excited about EEG and they may order it a bit too much. So, if patients have a known, established diagnosis of epilepsy, electrographically confirmed, and they come in with a breakthrough seizure and they're back to their baseline, there's really not a strong reason to get an EEG. We often seem to in the emergency department as part of our evaluation, but we already know what happened to the patient. The patient's not doing poorly right now, so the EEG is not going to give you any additional information. Just like really any test, you should think, what are the possible outcomes of this test and how would those outcomes alter the care of this patient? And if no outcome is going to affect the care of the patient or give you any additional diagnostic information, then probably don't need to be doing that test.

Dr Grouse: This is probably a good segue into asking, what is an area of confusion or common pitfalls that you've seen in the clinical application of EEG and epilepsy?

Dr Weber: So, a lot of times on the inpatient service, we'll get longer-term EEGs for patients who are having spells that are occurrent while they're in the ICU or other places or altered in some way, encephalopathic. And these patients will have their spell, and in my report, I'll say that there is not any electrographic correlate. So, there's no EEG finding that goes along with the movement that they're doi