Implantable EEG and Long-Term Seizure Monitoring - Prof. Norman Delanty, Beaumont Hospital & RCSI, Ireland
Routine EEG provides a brief snapshot of brain activity and may not capture seizures or epileptiform activity. In this episode, Norman Delanty explains the clinical limits of short-duration EEG, the role of inpatient video EEG, and how long-term and subcutaneous EEG monitoring can improve understanding of seizure burden and support more informed clinical decision-making when short recordings are insufficient.
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Episode Highlights
Why a normal routine EEG does not always rule out an epilepsy
How seizure under and over-reporting affects treatment decisions
What long-term and subcutaneous EEG monitoring adds beyond standard EEG
Which patients are most likely to benefit from extended EEG monitoring
About Prof. Norman Delanty
Norman Delanty is a consultant neurologist and Clinical Professor and principal investigator at the Research Ireland–funded FutureNeuro Research Centre at RCSI, with research interests spanning epilepsy diagnostics, genetics, and precision therapy. He has led multiple national epilepsy initiatives, published extensively, held senior roles within the ILAE, and was named one of the top 100 most influential individuals in Irish healthcare in 2025.
Full profile: norman-delante
Topics mentioned
routine eeg
video eeg monitoring
subcutaneous eeg
seizure underreporting
focal seizures with impaired awareness
idiopathic generalised epilepsy
seizure burden
diagnostic sampling limits
Related paper:
“Unilateral ultra long-term subcutaneous EEG monitoring in drug-refractory idiopathic generalized epilepsy”
https://onlinelibrary.wiley.com/doi/10.1111/epi.18644, Tudor Munteanu, et al. Oct 2025, Epilepsia, DOI:10.1111/epi.18644
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Trailer & intro
00:00 Norman Delanty
“In somebody with epilepsy, chronic epilepsy, difficult-to-control seizures, etc., clinically an issue with seizures being underreported. Patients may not be aware they're having seizures. And then you have the reverse problem where patients might be overreporting their seizures.”
00:16 Torie Robinson
I’m Torie Robinson, and I’m joined by Professor Norman Delanty, Consultant Neurologist in Dublin, with a longstanding focus on epilepsy care, research, and clinical innovation. This episode is presented in partnership with EASEE®, by Precisis GmbH.
What are EEGs?
00:30 Torie Robinson
Norman, can you tell us what are EEGs? We know there are heaps of different types. Can you give us a bit of an overview, please?
00:37 Norman Delante
EEG, of course, stands for electroencephalogram. The first EEG was done back, I think, in 1927, so, it's been around for nearly 100 years. So, the EEG basically is a method of putting recording electrodes on particular sites of a patient's scalp in a recognised pattern, left and right, etc. (there is a science behind it), and it measures essentially brainwaves, and it's measuring brainwaves in the awake state, it often tries to measure, importantly, brainwaves in the asleep state, and they can give us information in a variety of clinical circumstances. It's primarily used as a diagnostic “aid”, and I am emphasising the word “aid”, in the evaluation of the epilepsies. It is also used in other specific hospital environments, like, for example, in the intensive care units in patients who may be in coma, etc.. But for our purposes, it's a diagnostic aid in the evaluation and diagnosis of the epilepsies.
A normal, routine EEG does not rule out the diagnosis of epilepsy
01:45 Norman Delanty
It is important to point out that a routine EEG is just a very quick snapshot in time. A routine EEG in a hospital neurophysiology lab, somebody comes in for an outpatient test, really only is recorded for 30 or 40 minutes. And so, it's a very limited snapshot. And the person reporting an EEG will, certainly in our unit, and I'm sure most units around the world will say at the end of the EEG, if it's a normal EEG, we will add in the sentence “A normal routine EEG does not rule out the diagnosis of epilepsy”. And that's a really important statement. It's very basic, but a lot of physicians who are not epileptologists or neurologists, for example, referring general practitioners, and indeed patients and family members will sometimes default to, “Oh, my EEG was normal, I can't have epilepsy.”. So, there's really… that's not at all accurate. And that's important. An EEG, an outpatient EEG, is a very limited snapshot in time. It can provide very valuable information, but oftentimes it doesn't.
Other types of EEG for more informatoin
02:48 Norman Delanty
We then sometimes repeat EEGs. We do sometimes sleep-deprived EEG, because can you imagine if you're going in for an EEG recording that only takes 30 or 40 minutes at 11:00 o'clock in the morning, you may not fall asleep and we get valuable information by recording sleep. So, we sometimes repeat an EEG to get more information. Some units will have a one, two, three-day outpatient ambulatory EEG. So, we record, try to record EEG when the patient goes home for a day or two. We don't do that in our unit. There's one of our sister units in Dublin that does that. Sometimes that's problematic because the EEG electrodes break down and you get a lot of artefact. And then of course, traditionally over the last, probably 60 years, the gold standard for getting really nitty-gritty epilepsy information is inpatient continuous video EEG. So, for example, in our unit, we have four beds. It's open 24-7 (except it just closes for the 10 or 14 days around Christmas and New Year), and otherwise, we bring patients in for continuous video EEG monitoring. Our average length of stay would be maybe seven days, but you can appreciate that's a very high resource situation. And really, we only bring patients in primarily in two or three situations. One is the pre-surgical evaluation of patients with refractory epilepsy where we want to record their seizures. Secondly, where we want diagnostic clarification of the epilepsy syndrome. And then thirdly, related to that in the differential of diagnosis between epilepsy and Non-Epileptic Attack Disorder. So that's a potted version of EEG. And then we might talk about newer advances now in terms of long-term monitoring. So that's EEG in a very short nutshell.
Not seizing during video telemetry
04:41 Torie Robinson
Haha. I was one of those sorts of stereotypes of a person who showed no abnormalities with their EEG…
04:47 Norman Delanty
Yeah.
04:48 Torie Robinson
…for years until I had the video telemetry. And then even the first video telemetry showed no abnormalities because I did not seize! And that's quite common as well.
04:56 Norman Delante
Absolutely. We bring patients into the monitoring unit and we carefully reduce their medication. We try and sleep deprive them. And I've always… and I say this to patients in the monitoring unit, sometimes when I'm on service there, is that patients come into the monitoring unit (you've been through this experience), and the patient spends all their life in the real world, hoping that they don't have a seizure. And then they go into the monitoring unit and the whole psychology of it is switched because they're hoping that they have a seizure! Often, we would have patients saying to us in the monitoring unit, they're in there for four or five days and they're going, "You do believe me, don't you? I do have seizures." And I said, "I absolutely believe you. We just have to wait." And I think just as an aside, we have a seven-day unit, as I say, which is invaluable. We have fantastic nurses. We have fantastic EEG scientists. But some, and I would even be bold enough to say top units try to do video EEG five days a week and they're closing Saturday and Sunday. And I find that would be very difficult because we do need to have a good epoch of time to record patients and bring out their seizures, if you like. And we usually do get the information we need. Sometimes we have to say to patients after a certain amount of time, "Look, we'd have to just call it a day and maybe we'd consider doing it some other time." But most times, most admissions, we get very valuable information.
What’s an sqEEG (subcutaneous EEG)
06:15 Torie Robinson
Tell us what is an sqEEG or a “sqEEG” for people who might be reading it. [crosstalk] How does that differ?
06:19 Norman Delante
So sqEEG basically just means subcutaneous EEG. So, this is a unilateral device, one side of the scalp. So, it's only got a limited number of electrodes, not like a full scalp array. But it's subcutaneous EEG, basically a device that's inserted under the skin, but lying on the bone. So, it doesn't require any heavy-duty neurosurgical intervention. Although in our study that we will discuss, the device is put in by our neurosurgeons. And the great advantage is, although it's limited in terms of electrode coverage, let's say (we have to have a hypothesis before we put it in), and the great advantage is that it’s what we describe as ultra- long-term. So, it can be put in for months. And in our particular study, it was about three months for each patient. But now we can put this device in, and it's been approved recently for, and we're doing another study in different types of epilepsy at the moment, for up to three years. So, the thing then is your routine EEG is just very limited by sampling. As we just discussed, even inpatient video EEG monitoring, apart from the resources required, is very limited by sampling. So, this is a device that can record brainwaves in a particular patient for months and months now.
Sponsor mention
07:37 Torie Robinson
Before we move on - with thanks to EASEE®, by Precisis GmbH.
What’s an sqEEG (cont.)
07:42 Torie Robinson
And isn't it true that subcutaneous, it can actually identify more brain activity than something that's just external?
07:48 Norman Delante
The quality of the recording is generally very good. And obviously you're going to get more information because it's continuous over many months. So, absolutely, yes. But as I said, the slight limitation is that it's on one side of the scalp. So, it's unilateral and it's got limited electrode coverage. So, for example, if you're doing the subcutaneous EEG device in somebody with a focal epilepsy, you need to have a hypothesis or theory going into the study that, well, this person may have right temporal lobe epilepsy, we're not quite sure how often they have focal seizures with impaired awareness, so, we're going to ask our neurosurgeon to put the device over the right temporal region under the scalp or over the skull, obviously. So yeah, it's the timing or it's the long duration of monitoring. So ultra-long-term is the great advantage here.
Seizure under-reporting and over-reporting
08:38 Norman Delante
Now, we do need to also point out that in somebody with epilepsy, chronic epilepsy, difficult-to-control seizures, etc., we have… clinically an issue with seizures being underreported, right?
08:52 Torie Robinson
Huge.
08:53 Norman Delanty
For example, patients may not be aware they're having seizures, or somebody may be living alone, or [having] night-time seizures. So therefore, if they're being underreported, potentially they're being undertreated. And then you have the reverse problem where patients might be overreporting their seizures because they have other symptoms, and they may even have symptoms of drug toxicity, where sometimes the patients think they are having seizures. So that's one of the other issues.
More about sqEEGs
09:17 Norman Delanty
But, the device is small, it's under the skin, it's small, it's generally very comfortable. And then there's a Bluetooth device that picks up the EEG signal, and then that goes up to the cloud and down into the company. All that technology is beyond my knowledge, to be honest. But it's generally, first of all, from an implantation point of view, easy to insert (or neurosurgeons find it's a very short operation, or minimally invasive operation). It has to be done, of course, under a sterile technique to reduce the risk of infection, because at the end of the day, it's a foreign-object device. But it's generally very acceptable to the patient. Some patients find it comfortable. So, there's a little bit of just basic learning of how to use the device and a Bluetooth device. But it's generally very acceptable to the patient.
How accessible is an sqEEG?
10:10 Torie Robinson
How accessible is this device or this type of EEG to people? And, also, this is going to sound really shallow, but I can promise it matters to many people; what does it look like?
10:19 Norman Delanty
Well, it's translating now from clinical research into clinical usage. So, the last question, “how accessible is it to patients”, it's only really becoming accessible now. And of course, patients who are interested in this device, or where it might help their epilepsy management, would need to talk to their treating neurologist or epileptologist. So, it's not really available in every centre. And we've only used it so far in two different research study settings. There are specialist epilepsy centres in the UK and elsewhere, and in Europe and in the United States, who have already begun to use this device as a need to clinical care.
What are the outcomes of sqEEGs?
11:00 Torie Robinson
What's been the outcome so far?
11:02 Norman Delante
Well, overall, very positive. And as I said, it helps to identify underreported seizures, and it helps to identify over-reported events that are not seizures. So, the medication, the anti-seizure medicines, can either be increased appropriately in the first instance or potentially reduced appropriately in the second instance, and thus also reducing side effects.
11:24 Torie Robinson
I can imagine that because loads of people who have epileptic seizures have non-epileptic seizures as well,? So, can it be very useful for identifying when that's the case?
11:33 Norman Delante
Exactly. Yeah, exactly. It can be useful in that situation also.
Trial of sqEEGs for Idiopathic Generalised Epilespy
11:37 Torie Robinson
So, tell us about the paper that you published and what was the outcome of your study?
11:41 Norman Delante
When we heard about this device originally, the original thinking was that it's used for focal epilepsy. But we asked the question “Is this device going to be useful to detect seizures, the different seizure types within what we call idiopathic generalised epilepsy?”. Because in idiopathic generalised epilepsy, the seizure discharge is bilateral. Remember, this is a unilateral device.
12:01 Torie Robinson
Mmm.
12:02 Norman Delante
If it's put in on one side, it should pick up the unilateral signal from that bilateral discharge. So that was really the theory: how useful is this device in detecting seizures in idiopathic generalised epilepsy? And those seizure types primarily would be absence seizures…
12:18 Torie Robinson
Mm-hmm.
12:19 Norman Delanty
…of varying duration. These are usually short, or, of course, convulsive seizures. This study was led by my colleague, Dr. Tudor Munteanu, who was a fellow with me two years ago, he's now a consultant in Ireland also. We implanted nine patients with difficult-to-control seizures with idiopathic generalised epilepsy, and we had seven patients then to evaluate properly - because for each of these patients who had difficult idiopathic generalised epilepsy, we brought them into the epilepsy monitoring unit (we mentioned the epilepsy monitoring unit earlier on), and we were able to compare the gold-standard signal in the epilepsy monitoring unit with what we call the 24/7 Episight device.
Trial outcomes
13:03 Norman Delanty
And basically, the bottom line is we had very good longitudinal long-term data in seven patients with IGE (idiopathic generalised epilepsy) The bottom line is that the device was easy to put in. It was very acceptable to patients, and we were able to detect all convulsive seizures and 90% of absence seizures greater than three seconds in duration. It basically demonstrates that in selected patients, again, with difficult-to-control IGE, where you're not sure how much absence they're having - or there may be issues around even driving decisions, for example - this device can provide useful information out in the real world over several months of monitoring.
Which side should the electrodes go on?
13:45 Norman Delante
You have to have a theory of where the seizures, what side the seizures are coming from before you put in the device. So if you have a patient with right temporal lobe epilepsy and you don't know how frequent they're having subtle, let's say what we used to call complex partial seizures (in old money) and what we call now focal seizures with impaired awareness, you're not quite sure how… because some patients in that scenario are unaware that they become unaware, for example. So there’s…
14:08 Torie Robinson
Exactly.
14:08 Norman Delanty
…this phenomenon called “unawareness of unawareness”, which I talk a lot about. But because it's a real issue. You can detect focal seizures but you have to decide in advance which side you're going to put the device in. Because generally we don't put the device in on both sides, in other words…
14:26 Torie Robinson
Yes.
14:26 Norman Delanty
…two separate devices on both sides.
14:27 Torie Robinson
Of course.
14:27 Norman Delanty
Maybe in the future we might be, but you can use it. So that's the point; you can use this device, and I keep saying “appropriate patients”, and you might ask, we might talk about what an appropriate patient is in patients with either focal or generalised epilepsy. And that's what our recent paper showed, that it may also be of use in generalised epilepsy, not only in IGE, but perhaps in some patients with what we used to call symptomatic generalised epilepsy, or what we now tend to call the developmental and epileptic encephalopathies. So, it's a useful addition.
What’s an “appropriate patient” for an sqEEG?
15:30 Norman Delante
If I can get this, I suppose out of my system, when I say “appropriate patients”, not only, of course, are these patients who have difficult epilepsy (we're not going to put this device into somebody who's well controlled, for example…
15:15 Torie Robinson
Of course.
15:16 Norman Delante
…where everything would suggest that the patient is well controlled). So, the patient has to have difficult epilepsy where we don't have a full understanding of their seizure frequency or their epilepsy burden.
Who pays, who operates?
15:26 Norman Delanty
And then, of course, surprise, surprise, the challenge is resources. Both money, getting the system to pay for these devices. They cost money, surprise, surprise.
15:40 Torie Robinson
I'm really glad you brought that up, actually.
15:41 Norman Delante
And the reporting costs money. And then you have to get your unit and your business manager, as we would have in our hospital, to agree. And then, you of course, you have to get the neurosurgeons on board. Our neurosurgeons have been great in our studies, but in the cut and thrust of real clinical medicine, neurosurgeons are busy. Theatre times are difficult to get for the insertion of this device. So, you really want to be quite selective if you're starting this programme in your epilepsy unit of what patients you're going to pick. There's always going to be a challenge with advances in epileptology. It's fantastic. Genetics, whole-exome sequencing, new stereoEEG, new long-term, ultra-long-term monitoring EEG. But it's the resources in a system that's already, you know, in most hospitals, even in our part of the world, most neurologist units are under severe pressure. So, this is why we always have to pick the most appropriate patients.
Final thoughts and thanks
16:38 Torie Robinson
Thank you so much to Norman, for walking us through how EEGs are used in epilepsy, and where newer long-term monitoring tools can genuinely change clinical understanding and improve people’s quality of life.
With thanks again to EASEE®, by Precisis GmbH, for partnering with Epilepsy Sparks. If you found this conversation helpful, please give it a like and subscribe, and hit the bell so that you are notified when new episodes drop. I’d love to hear your thoughts or experiences in the comments below. Thank you for joining us, and see you next time.