There various types of seizures, and numerous things that can cause them—here's what to know.

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What Is a Seizure? Here’s What Happens When There’s a ‘Power Surge’ in the Brain
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Your brain cells need to communicate with each other—it's what enables you to think, act, feel, and experience the world around you. They do this through rapid electrical impulses, and that electrical activity is usually pretty well-controlled: Some brain cells send messages, others stop them, and this exchange allows your brain (and ultimately, your existence) to run smoothly.

A seizure, however, is a sudden change in how the brain typically works—it's an abrupt and uncontrolled burst of electrical activity in all or part of the brain, in which neurons (aka brain cells) begin firing at once, with no purpose.

In this case, it's helpful to think of a seizure as a sort of "electrical storm," Vikram Rao, MD, PhD, an associate professor of neurology at the University of California, San Francisco, tells Health. "One of my patients refers to a seizure as a power surge," he adds.

Here, neurologists help explain what's really going on during a seizure, what a seizure typically looks like, and how seizures can be diagnosed and ultimately treated.

What is a seizure?

A seizure is when there's an abnormal surge of electrical activity in the brain, due to complex chemical changes in nerve cells (this is technically known as electrochemistry, or when chemical reactions can produce an electrical current). Seizures are not considered a disease, but rather a symptom of some other issue, such as epilepsy, which is known as a seizure disorder, according to the Centers for Disease Control and Prevention (CDC).

A seizure is not just one thing—instead, there are quite a few types of seizures, and they're grouped together according to where a seizure starts in the brain (on one side or in both sides), how aware a person is during the seizure, and whether the seizure has motor or physical symptoms. Based on that criteria, there are three major groups of seizures, and certain types of seizures fall into each group, per the Epilepsy Foundation:

  • Focal onset seizures: These include both focal onset awareness seizures, focal onset impaired awareness seizures, and bilateral tonic-clonic seizures.
  • Generalized onset seizures: These include absence seizures, atypical absence seizures, tonic-clonic seizures, atonic seizures, clonic seizures, tonic seizures, and myoclonic seizures.
  • Unknown onset seizures: These seizures don't have a clear beginning, but one may be identified as more information is learned.

What happens during a seizure?

According to the Epilepsy Foundation, there is typically a beginning, middle, and end to seizures—even if those stages aren't easily separated or identified.

For some, there is a clear beginning stage of a seizure—they may even be aware of it days or hours before it actually happens. This is known as a prodrome, the Epilepsy Foundation says, and it can include changes in feelings, sensations, or behavior. While not everyone experiences a prodrome with a seizure, those who do may be able to identify an oncoming seizure to better treat it.

Another beginning phase of a seizure for some (but not all) people, is known as an aura. It can sometimes be an indescribable feeling, the Epilepsy Foundation says, but it can include feelings of déjà vu, racing thoughts, fear or panic, or certain tastes and smells. "The classic thing is smelling burnt toast or having a metallic taste in your mouth," Derek Chong, MD, MSc, vice chair of neurology at Lenox Hill Hospital in New York City, tells Health

The middle phase of a seizure—known a the ictal phase—comes next. This phase lines up with the abnormal electrical activity in the brain, and technically ranges from the first symptoms of a seizure (like an aura) to the ending of a seizure. During this middle phase, a person will likely experience the brunt of their symptoms. Those can include the more sensory or emotional changes (loss of awareness, blurry vision, flashing lights, unusual smells or tastes), or physical symptoms (difficulty talking; tremors, twitching, or jerking; lack of movement; loss of bowel control).

The final phase of a seizure—or the postictal phase—is the recovery period that follows a seizure. It can last minutes, hours, or days, depending on the type and severity of the seizure, as well as the person's age and health. Research published by the International League Against Epilepsy in 2020 shows that almost everyone experiences some degree of unresponsiveness during the postictal phase of a seizure. Other common symptoms include headaches, fatigue, memory loss, and anxiety.

What causes seizures?

We have to revisit those brain cells (aka, neurons) for this one. Anything that disrupts the brain's normal communication pathways can lead to a seizure—that can mean genetic mutations, certain infections, underlying conditions, or even just a change in routine for some people. And sometimes, there's no known cause of a person's seizure; in that case it's called an unprovoked seizure, the Epilepsy Foundation says.

According to the the Mayo Clinic, epilepsy is the main cause of seizures—that's why epilepsy is sometimes called a seizure disorder. But not every seizure is caused by epilepsy—in fact, a person isn't considered to have epilepsy until they've had two or more seizures, the CDC says. The agency lists the following as the most common causes of seizures, other than epilepsy:

  • Abnormal levels of sodium or glucose in the blood
  • Brain infection
  • Brain injury that occurs during labor or childbirth
  • Congenital brain defects
  • Brain tumor
  • Drug abuse
  • Electric shock
  • Head injury
  • Heart disease
  • Heat illness
  • High fever
  • Poisoning
  • Stroke
  • Preeclampsia
  • Kidney or liver failure
  • Very high blood pressure
  • Venomous bites or stings
  • Alcohol or medication withdrawal

What are the symptoms of a seizure—and what does one look like?

Because there are various types of seizures—mainly dependent on where they originate in the brain—they can present differently. Generally speaking, seizures can impact the way a person moves, thinks, speaks, or acts. But some seizures may only appear as a staring spell, and may go unnoticed.

The CDC says that specific symptoms of seizures depend on where the seizure originates in the brain, but many symptoms for many types of seizures can come on suddenly and may include any of the following:

  • A brief blackout followed by a period of confusion
  • Changes in behavior
  • Drooling or frothing at the mouth
  • Atypical eye movements
  • Grunting and snorting
  • Loss of bladder or bowel control
  • Mood changes
  • Shaking of the entire body
  • Suddenly falling
  • Tasting a bitter or metallic flavor
  • Teeth clenching
  • Temporary stop in breathing
  • Uncontrolled muscle spasms, or twitching and jerking movements

Going a bit deeper, tonic-clonic seizures (formerly known as a grand mal seizures), are how seizures are typically depicted in media. During one of these types of seizures, a person may suddenly drop to the ground (known as the "tonic" phase), and then start convulsing (known as the "clonic" phase). Though alarming, these seizures only last for about one to three minutes, according to the Epilepsy Foundation (though, if they last for a longer amount of time, emergency medical attention is necessary).

Tonic-clonic seizures, however, are on the most severe end of the seizure spectrum. But other seizures present much more subtly—a person may stare off into space, blink their eyes rapidly, experience changes in their breathing, or be unresponsive to noise or words. In some cases, a seizure may go completely unnoticed, as well.

How can you help someone having a seizure?

While it can certainly be scary to witness a seizure, you can (and should) only do a few things to help, so you don't end up injuring the person, or making it easier for them to injure themselves.

There are a few general steps to take if you witness a seizure of any kind, the CDC says. Those include:

  • Stay calm and keeping those around you calm
  • Stay with the person until the seizure ends and they are fully awake
  • Alert the person to what happened in a calm and comforting manner
  • Check to see if the person is wearing a medical bracelet or has other emergency medical information
  • Offer to help the person get home safely

Those guidelines change a bit when you recognize a person is having a tonic-clonic seizure (those are the ones in which a person will fall to the ground and begin shaking or jerking). In that case, the CDC says you should:

  • Ease the person onto the floor and turn them on their side
  • Clear the area of anything hard or sharp that could cause injury
  • Place something soft and flat under the person's head
  • Remove eyeglasses or anything that could restrict a person's breathing
  • Time the seizure, and call 9-1-1 if it lasts more than five minutes

Note that there are a few things the CDC says you should absolutely not do, as well, like holding the person down or placing anything between a person's teeth (a person having a seizure cannot and will not swallow their own tongue). The agency says you should also avoid giving the person food or drink until they are fully awake and alert.

How are seizures diagnosed and treated?

Diagnosing seizures can be difficult, especially because the types and causes vary so widely, and because doctors usually don't see a person's seizure in real time. According to Johns Hopkins Medicine, the best way for someone to get an accurate diagnosis is through a physician taking a medical history, and using brain imaging and other tests to assess any abnormal electrical activity in the brain.

If a person only has one seizure, and the cause is clear (like an infection or head trauma), treatment will likely only include treating the underlying issue. But if a person has had one or more seizures (or suspicious symptoms of a seizure), their doctor may refer them to a neurologist who can take a deeper look inside their brain. Johns Hopkins Medicine says patients may go through various tests, like an electroencephalography (EEG), which monitors electrical signals in the brain and can be used to find abnormal patterns. Other diagnostic imaging procedures—like magnetic resonance imaging (MRI), positron emission tomography (PET), and functional magnetic resonance imaging (fMRI) scans—can help doctors zero in on more specifics of a seizure, like where it originates in the brain.

In the best case scenario, a person's seizures will be identified at an early stage. "The importance of discovering the seizures when they're smaller is that then you might be able to prevent the bigger seizures," Dr. Chong says. While recurrent seizures don't always get worse over time, they can, which is why it's important to get them under control sooner rather than later through various treatments like anti-epileptic medications, certain surgeries, nerve stimulation, or lifestyle changes.

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