Tests to Diagnose Focal Onset Seizures in Children

Medically Reviewed by Dan Brennan, MD on March 15, 2022
4 min read

When your child has a seizure, there are two main things your doctor wants to find out. The first is what type of seizure it was. The second is what caused it.

Diagnosing a focal seizure, which used to be called a partial seizure, is often straightforward. Your doctor might be able to tell what it was based just on what you and your child share about it.

The bigger challenge is usually finding out what's behind it. Seizures may be a symptom of another problem. To get the best treatment, you have to get at the root cause. For that, your child may need any number of tests.

This is the typical first step. The doctor will check how alert your child is and take vital signs, like heart rate, temperature, and blood pressure.

Your child will also get a neurological exam, which checks their brain and nerves. This may include things like testing reflexes and looking for differences in strength between the two sides of their body.

Your doctor will ask about the health of your child and other people in your family. It helps to know if anyone in your family has had seizures or any related conditions.

Your doctor will ask a lot of questions about your child, on things like:

  • Head or brain injuries
  • Health conditions your child was born with
  • How your child does in school
  • If your child was born much earlier than expected
  • Medicines your child takes
  • Recent infections or fevers
  • Your child's development

And, of course, there will be lots of questions about any seizures your child has had. You know your child better than anyone else, so you have the best sense of what's normal and what behaviors seem off. It may help to write things down ahead of time. And if it's possible, it can be valuable if you take a video of their seizure on your cell phone.

If your child is old enough, your doctor will ask that they share as many details as they can remember. What happened before, during, and after the seizure all matter.

This is a common test for seizures that measures brain activity. If something is off, it can show up as an unusual spike or wave on a graph.

Doctors use the test to help confirm the type of seizure your child had. In some cases, it will also show if your child has epilepsy. But it's often not the whole story. Many kids who have epilepsy have perfectly normal EEG results. And many others who have something off in their EEG don't have epilepsy.

During the test, your child gets a number of small disks placed on the head and face. Each one is attached to a wire. It's not painful.

In some cases, your child will get the test while asleep. In others, your child will be awake. And for some, you'll have to keep your child awake well past bedtime so they're short on sleep before the test. That can help get the best results.

The test typically takes about an hour. But your doctor may want to record things for a longer period, like 24 hours. In this case, the wires connect to a small device that your child carries around in a little pouch as it records the results.

If your doctor suspects a focal onset seizure, it's very common to follow up with a CT or MRI. Both can help find out where in the brain it happened and what caused it.

An MRI is more likely if your doctor needs an image with fine detail. For example, it can help show part of the brain that might not have developed as usual.

A CT can spot things like scars or tumors on the brain. They're common if a head injury triggered the seizure.

Both types of imaging are painless. For a brain MRI, your child has to lie in one position for up to an hour or the images come out blurry. Kids under age 5 may get drugs to help them stay still.

Doctors use these tests to check on possible causes of your child's seizure, such as:

Your child would likely only need this test if it seems like an infection, such as meningitis, is to blame for the seizure. Your doctor puts a needle in the lower back to draw out spinal fluid for testing.