What seizure names can tell you about a seizure:
This month’s episode of Epilepsy Explained features Dr. Kristen Park, Pediatric Epileptologist at Children’s Hospital of Colorado, explaining seizure names, what they mean, what they indicate about seizure types, and how your seizure type can inform your diagnosis, prognosis, and treatment. In “Naming Seizures Explained”, Dr. Park answers the following questions.
0:16 What is the difference between seizure type and epilepsy syndrome?
1:30 What is the difference between focal and generalized seizures?
3:08 What are impaired and aware seizures?
4:25 What are motor and non-motor seizures?
5:50 Can you explain the difference between tonic seizures, clonic seizures, and tonic-clonic seizures?
7:16 So, how does all of this fit together to describe your seizure type?
8:52 Why does knowing your seizure type matter?
More on the ILAE’s classification of seizure types
To learn more about seizures, watch Dr. Park’s first Epilepsy Explained episode “Seizures Explained”.
Look for new episodes of Epilepsy Explained on the third Wednesday of every month on CURE Epilepsy’s YouTube Channel and here on our website.
Video Transcript
What is the difference between seizure type and epilepsy syndrome?
Dr. Kristen Park: So that is an important distinction. And seizure type describes both clinically, meaning in the person’s body, and electrographically, meaning on the EEG, what is happening during a seizure. How does the seizure start? How does it spread? What areas does it implicate in its symptoms?
Whereas an epilepsy syndrome is a bit more complicated and describes kind of the totality of someone’s epilepsy. Typically, a syndrome includes when the seizure started, why the seizures are happening, sometimes there’s multiple seizure types within a single syndrome. It may also imply the prognosis for outgrowing or successfully treating that epilepsy.
And so with all of those factors together, people can often figure out what syndrome someone may have. So I think it’s important to know that today we’ll just be talking about seizure types and there’ll be a separate episode that will discuss epilepsy syndromes.
What is the difference between focal and generalized seizures?
Dr. Kristen Park: So that is a distinction that has existed for a long time and basically describes how the seizure starts in the brain. So focal seizures, they used to be called partial seizures, and they start from a specific part of the brain. And they may or may not spread to involve other parts of the brain, which is how you get the classification of focal with bilateral spread or with spread to a bilateral convulsion.
And then generalized seizures kind of start from the whole brain at the same time and involve both sides of the brain synchronously.
Sometimes we are not able to make that distinction because either no one saw the seizure, it doesn’t have any parts to it that allow people to determine how it started or the person’s EEG is normal and doesn’t give us any clues as to whether it’s one type or the other. And that’s where the classification of unknown seizure type comes in.
There are also a few seizure types. We don’t really understand how they work in the brain, or they can be part of multiple different categories, and that is often epileptic spasms or infantile spasms. We don’t really understand how they are generated and they can be seen in both focal lesions like dysplasias or in patients where there isn’t any brain abnormality where they presumably come from a more generalized onset.
What are impaired and aware seizures?
Dr. Kristen Park: So this distinction has to do with the person’s level of consciousness as they are experiencing the seizure. So aware seizures, the person is probably able to interact with their environment. They’re able to talk and hear people talking to them, move around. They may be experiencing something internally like an abnormal sensation in their arm or seeing something in a field of vision, but you might not otherwise know that they’re having a seizure. They could be having motor activity but still are able to talk and function through that.
Whereas an impaired aware seizure, the person has kind of lost that ability. It typically means that more of the brain has been involved in the seizure because it impairs their consciousness. So they may not be able to hear what someone is saying. They may not be able to respond to them.
This distinction is usually discussed in a visit with the epilepsy provider who asks both the patient and maybe a witness what happens during the seizure. Are you able to talk to them? Are they able to answer your questions or is there response time slow? Do they feel confused? And that would all indicate an impaired awareness seizure.
What are motor and non-motor seizures?
Dr. Kristen Park: So that’s another kind of dual distinction that we have. Motor seizures involving the body’s ability to move and what might happen could be a person turning their head or their body. Sometimes people can get up and move around and be agitated. Sometimes there can be twitching of one or more body parts or posturing of that body part. Those are motor features of the seizure, and they can be recognized and described by somebody else who sees the seizure.
As opposed to non-motor seizures, which can be anything from just that loss of awareness that we talked about to internal sensations that the person experiencing the seizure is having. So they could maybe feel deja vu or nausea. They could be seeing something. They could be hearing ringing in their ears. They could be having a sensation of tingling or numbness in one part of the body.
So those unfortunately are a lot more difficult to recognize as seizures because when most people think of seizures, they think of a convulsion. And those brief episodes of other types of experiences that are internal to the person often go undiagnosed until someone has a larger motor seizure or a convulsion.
Can you explain the difference between tonic seizures, clonic seizures, and tonic-clonic seizures?
Dr. Kristen Park: It’s actually not quite as complicated as it seems that it’s all in the name that it’s given. So a tonic seizure, tonic means stiffening, so any tonic seizure is going to have stiffening of either one part or all of the body. And that would be the distinction between a partial tonic seizure and a generalized tonic seizure. Those have a certain pattern on EEG as well that can help us to classify them.
And then clonic means jerking. So a seizure that has jerking, again, either in one part or the whole body, focal clonic or generalized clonic seizures involve twitching and jerking of that body part. Clonic also appears in myoclonic, which means muscle twitch. And those are brief twitches of the whole body, that’s a myoclonic seizure.
And then tonic-clonic is the typical convulsion that most people think of. So it involves usually stiffening of the whole body followed by jerking of the body, and that’s why it gets the name tonic-clonic. It can start in different ways, but most of the time a convulsion begins with a tonic phase, the stiffening, and then progresses to the jerking.
So, how does all of this fit together to describe your seizure type?
Dr. Kristen Park: So this is all part of the new classification system that came out in 2017 from the International League Against Epilepsy. And I would recommend going to their website. They have a lot of diagrams and explanations of this information, as well as what we’ve covered in this episode.
But basically, you meet with the provider, the neurologist or the epilepsy specialist to go over what is seen and what happens to the person during the seizure, if they can tell that, to kind of put all those pieces together. How does the seizure start? What is the first thing that the person experiences? If they can’t really remember anything, what did somebody else see? Did they stare off first and then start having twitching or did they remember feeling dizzy or off balance at the beginning of the seizure?
And using that information together with the EEG can help determine whether the seizure was a focal or generalized onset, whether it had motor features in it, whether the person’s awareness was impaired, all of those features that we talked about. And basically you just kind of string them to describe the seizure.
So, you could have, say, a focal onset, impaired awareness seizure, which progresses to a bilateral tonic-clonic convulsion. That’s a long name, but it basically describes essentially what happened to the person during their seizure.
Why does knowing your seizure type matter?
Dr. Kristen Park: So that’s a great question. I think it matters largely because of two main things. The first being that it helps to select the appropriate medication. So certain medications may only be good for certain seizure types, ethosuximide, or Zarontin is really only good for absence seizures. And knowing whether a seizure with impaired awareness is a generalized absence seizure or a focal onset temporal lobe seizure can help the provider to select the appropriate medication. So, it’s really important to be able to take the right medication.
The second part is that it can help to determine that epilepsy syndrome, that we’ll be talking about later, it is one part of that classification along with age of onset, family history and cause of epilepsy. And that can give you information about prognosis, whether other seizure types might come along. And so I think it’s also important for that.
Also, I think it can let people know, “Hey, I have generalized convulsions, but they have a focal onset. Maybe once I start to get treated, if I start experiencing something else like this weird nausea sensation or this thing in my vision, maybe that’s a focal seizure that is a bit different than what I started with, but I could be prone to because I have a focal onset convulsion.” So knowing that and then being able to take that information to your doctor is also really important.
