What is a seizure, anyway?
The first episode of CURE Epilepsy’s new monthly video series Epilepsy Explained focuses on seizures. Dr. Kristen Park, Pediatric Neurologist at Children’s Hospital of Colorado, explains the basics of seizures.
Video Transcript
What happens in the brain when a seizure occurs?
Dr. Kristen Park: So I think this is actually one of the most difficult questions in epilepsy research. And I don’t know that anyone really knows at the cellular level what exactly is happening when a seizure starts. Why does it start on a particular Tuesday at 7:00 P.M. rather than last week when somebody had missed their medications or was under more stress? I don’t think anybody has those answers. But in general, in the brain, when a seizure is happening, a group of neurons are firing hypersynchronously. They are overactive and repetitively firing again and again and again.
And another way to think of that would be also that there exists an imbalance in kind of excitation and inhibition within the brain. So if you think of excitation as the gas that makes a car go, an inhibition as the brakes that make it stop. All of the activity of neurons within the brain is a balance of that, the gas and the brakes as we are learning and sleeping and talking. And when a seizure is happening, there’s an overactivity of the gas and not enough brakes, which are regulated by neurotransmitters within our brains. So chemicals within our brains, the excitatory being glutamate, and the inhibitory being largely GABA. And those are out of balance such that the seizure is allowed to spread and recruit other neurons within the connection that it is wired to and then grow and continue to propagate throughout the brain.
What is the difference between seizures and epilepsy?
Dr. Kristen Park: So seizures are a transient, a temporary alteration neurologic function that happens to someone and results in some symptoms, either twitching or jerking of the body or other things that will talk about, and that can happen to anybody. It can happen if someone has meningitis or they get a medicine they’re allergic to or they’re in a car accident. Any of those things can push the brain to have a seizure. It’s kind of the final common pathway for many different insults. Sometimes children whose brains are a bit different can have one when they have a high fever. All of those things are considered to be provoked seizures, meaning that whatever happened at that moment is what provoked the seizure to happen and is a response to whatever insult that is. Another term people use in that situation is an acute symptomatic seizure, meaning the seizure is a symptom of whatever else is going on, the car accident or the meningitis.
Epilepsy is the tendency of a brain to be able to produce seizures without any sort of inciting factor. Certainly people with epilepsy can have triggers. They can have more seizures when they have stress or when they’ve not gotten a good night of sleep. But there isn’t anything significant that’s causing the brain to be able to generate that seizure at that time other than it’s already wired to be able to do so. It used to be that the ILAE, which is the International League Against Epilepsy, defined epilepsy as two or more unprovoked, so seizures without a cause that are separated by more than 24 hours. They’ve since revised that definition to say that if you’ve had a single seizure and because of a variety of other factors, maybe your EEG or a family history or previous neurologic problems, you are kind of at risk to have another seizure, then the diagnosis of epilepsy can be given then after the first seizure with those other mitigating factors. But really epilepsy is the tendency of the brain to have unprovoked seizures over time.
How many different types of seizures are there?
Dr. Kristen Park: There are actually lots of different types of seizures. Typically, I think when people think of epilepsy and seizures, they think of convulsions where someone may fall and have generalized shaking of their body. And that is certainly one of the most dramatic types of seizures. A tonic-clonic seizure, but that’s not the only type of seizure. We typically divide seizures into several categories. So focal seizures which begin in one area of the brain and then may or may not spread to a larger area, generalized seizures that kind of start from the whole brain at the same time. And then seizures where we don’t exactly have enough information to make that determination or we’re not really sure how the seizure works to be able to put it into one of those categories. And the reason that seizures look so different from each other is that they engage different networks and affect different parts of the brain.
So for focal seizures in particular, the symptoms are very variable and they typically manifest as an effect of the area where the seizure is starting. So say if the seizure is starting in the occipital lobe, someone may see some flashing lights or they may see a form or a shadow come across their vision. If it starts over the temporal lobes, someone may hear some ringing in their ears or a buzzing sound because that’s where our sound processing is. They may have trouble talking because that’s where our language center is and kind of so on and so on.
So motor symptoms like twitching are from where the motor processes in the brain are and so forth. Generalized seizures are a little bit different and have to do with how the brain talks to each other. But they can range from absence seizures, which have people just staring off for a few seconds and not responding to brief twitches of the body called myoclonic seizures. Sometimes children can have atonic seizures where they drop suddenly to the ground. All of those are considered to be generalized seizure types because when you see them on EEG, they kind of come from everywhere at the same time.
How long does a seizure last?
Dr. Kristen Park: So the duration of a seizure really depends a lot on the type of seizure that it is. Some of the briefer seizures are myoclonic seizures, which can be just a second to absence seizures, which can be maybe five to 10 seconds and short enough that someone may not even realize that they’ve had one. Focal seizures and convulsions typically last for about one to three minutes at the most. And when we get worried about them, it’s when they last five or more minutes because then we wonder if the brain is going to be able to shut down the seizure on its own. And that’s why many rescue and emergency medicines are designed to be given at that point in time if the seizure had lasted more than five minutes, but most convulsions last just for a couple minutes. And then recovery time I think is variable.
So a short seizure, someone may be able to be back to themselves and doing whatever they were doing after an hour or so, whereas a longer convulsion may take some time to recover from. And I think recovery is also a spectrum. So after a seizure ends, someone may be confused or off balance or really tired, have a headache, all of those things can happen and last for 10, 20 minutes all the way up to an hour or so. But then the person may not feel back to themselves for another day or even longer after a convulsion happens. So each person’s experience of epilepsy, recovery and seizure types is pretty unique and variable depending on what kind of epilepsy they have and what kind of seizures they have.
What are the phases of a seizure?
Dr. Kristen Park: So phases of a seizure really only come into play when you’re talking about slightly longer seizures, focal seizures that may progress or convulsions. And there are several phases to a seizure. So the first one is something that not all people have, but people have referred to as a prodrome. And that can be a sense of that the person with epilepsy has, or someone in their family has that a seizure is going to happen sometime in the near future, in a couple of hours or during that day. There can be behavioral signs or maybe someone just looks a certain way and we don’t really know what causes that and we can’t really track it very well but many people talk about it. The next phase again, which not everyone has is something called an aura. And that’s actually a very small seizure. So it’s the beginning of the seizure in a very discrete portion of the brain that then spreads and causes the remainder of the symptoms that the person usually anticipates.
And that can allow them to maybe sit down or alert someone else that the seizure is going to happen. And then there’s actually the ictus itself, that’s the word we use for seizure. It’s an ictal phenomenon. And that’s when the person may have the tonic-clonic phase where they stiffen and then shake. And then the final phase would then be the post-ictal period, so after the seizure. And that’s when someone may again be tired or confused, have trouble talking, and that can last a variable amount of time, depending on the length of the seizure and the type of the seizure that it was.
