Epilepsy vs. Isolated Seizure: What’s the Difference?

They both involve seizures, but they’re not the same.

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If you look inside the brain during the seizure, it resembles a full-on lightning storm. The brain contains billions of neurons (nerve cells) that communicate with each other by creating and receiving electrical impulses.

“In the normal human brain that doesn’t have a seizure, the nerve cells fire off separately. In a seizure, they’ll go off at the same time,” says Padmaja Kandula, MD, neurologist at Weill Cornell Medicine and NewYork-Presbyterian. This storm of abnormal electrical activity can cause body movements as well as changes in behavior and awareness.

There are many different types of seizures, depending on where this electrical storm started in the brain. There are also many different causes of seizures.

When someone comes to the emergency room with a seizure, doctors need to determine if the seizure was a one-time, correctable event, if there’s a chance the person may have another seizure, or if they may have a condition called epilepsy.

The Difference Between an Isolated Seizure and Epilepsy 

Isolated seizures are one-time seizures, meaning the seizure occurred for the first time. Once the underlying problem is remedied, isolated seizures don’t often recur. “Isolated seizures are actually more common than we think, up to 10 percent of people can have an isolated seizure,” says Dr. Kandula.

Isolated seizures may be provoked by something such as drugs, alcohol withdrawal, or low blood sugar. These are called provoked seizures.

Epilepsy, also called seizure disorder, is when you have recurrent seizures. Epilepsy may be inherited or caused by a brain injury brought on by a tumor, infection, trauma, or stroke. Sometimes, the cause of epilepsy isn’t clear.

The traditional rule to diagnose epilepsy was if someone had two or more seizures in a 24-hour period. “That definition has been extended to one seizure with a high risk of a second seizure,” says Dr. Kandula.

Another category of seizures are nonepileptic seizures. Unlike seizures caused by epilepsy or provoked by drugs, alcohol withdrawal, or low blood sugar, these seizures aren’t associated with abnormal electrical activity in the brain—even though from the outside, it can look just like the other seizure types. These seizures may be due to fainting spells, a muscle disorder, or a psychological condition.

If Someone Has a First-Time Seizure

“If someone has their first seizure, the first thing to do is get immediate [medical] attention,” says Dr. Kandula. “The emergency room [is] best equipped to handle the problem, whether that will be just a single seizure or whether that will develop into epilepsy.”

How the Cause of Seizure Is Diagnosed

Blood test: When a person arrives in the emergency room, they’ll likely get a blood test to help determine the cause of the seizure, and to see if it’s correctable. Doctors may look for:

  • Low blood sugar

  • Low sodium

  • Low calcium

  • Low magnesium

Urine tests: “In some cases, if somebody took a non-prescribed medication that may have caused a problem, a urine drug screen may also be helpful,” says Dr. Kandula.

Imaging tests: To get a more detailed look and check for abnormalities in the brain, the patient may also get imaging tests, such as a CT scan or MRI.

“When patients are first diagnosed with epilepsy or seizure disorder, it’s traumatic, but we tell them that the good news is you can lead a very normal life,” says Dr. Kandula. “Most people with epilepsy can be treated with medications.”