Seizures are mysterious. They cause the body to act strangely. They’re hard to predict and they can’t be seen, except with special tests of the brain. So, what causes seizures?
As a neurologist with special training in epilepsy, CHOC epileptologist Dr. Maija-Riikka Steenari has dedicated her career to understanding seizures and epilepsy, which affects 470,000 children nationwide. In recognition of National Epilepsy Awareness Month, she provides a look into the mystery of seizures.
Brain cells, called neurons, communicate by electrical activity. If there is a dysfunction, the brain can get overexcited. The electrical activity in the brain surges, causing the neurons to get out of control. The surge of electricity can start in one spot and spread, called a focal onset seizure, or it can happen throughout the brain, called a generalized seizure.
A seizure can manifest in many different ways. When a family comes to us, we ask them what they saw when their child had a seizure. What happened first? Was one arm stiff, were both arms jerking, did the child fall down, did their head turn to one side, were they unresponsive? It’s very helpful if the family has video of a seizure happening. A seizure can make you see, feel and taste weird things. We will ask the child, do you remember having a seizure or not? All these details help us determine if the seizure started from one focus and from which area of the brain, or if it was generalized onset.
Focal onset seizures can be caused by multiple different things, for example a malformation in the brain or an injury to the brain. Other causes could be a genetic or metabolic disorder which affects how the brain works, or causes a buildup of toxic materials, or is preventing the brain from getting what it needs. Many seizures or epilepsies are considered idiopathic, which means they have no known cause. We are learning more about them and why they happen, and as we do more testing, we find explanations to previous mysteries, often caused by genetic mutations.
We always start with an EEG. That looks at the electrical activity in the brain. We can often see epileptiform discharges on the EEG, which tells us a patient has a tendency of having seizures. I often describe these discharges as sparks of electrical activity. I like to use the lawn analogy when I am talking to families. Think of a brain that has a tendency of having seizures as dry grass. Epileptiform discharges, or sparks, can easily cause a fire (I.e. seizure) on the dry grass. We may also use an MRI to look at the structure of the brain, to look for any abnormalities like a cortical malformation, tumor, or scar tissue from an infection or brain injury such as a stroke.
If the seizure was unprovoked, and after the initial evaluation we have a high suspicion that seizure will reoccur, we recommend starting a medication to treat the seizures. Referring back to the lawn analogy, medication can be considered as watering the lawn, to make the environment more difficult for the sparks to cause more fires. About 60-70 percent of the time, the first medication works when picked correctly. If the seizures continue despite appropriate dosing, we often try a second one. With adding a second medication, the chance of being seizure free is much less likely and If they fail two medications, we need to consider other treatment options, for example epilepsy surgery, diet treatments or vagal nerve stimulator.
Prior to surgery, we gather a lot of information about the seizures, the cause of the child’s epilepsy and the brain structure. We capture typical seizures during an inpatient video EEG study, and we will often lower medication to encourage a seizure to happen. We use detailed imaging techniques to look at the brain structure and how the brain uses energy, to see if we can pinpoint a focal seizure onset zone. We will also do neuropsychological testing, to understand if a child has difficulties in certain brain functions. We will discuss the results with our multidisciplinary epilepsy team, and evaluate if the child could benefit from epilepsy surgery.
No. Most brains are generally mapped the same but it’s not always the case, and sometimes the cause of the seizure has also caused the brain to map differently. A child’s brain is very plastic, and it has adapted around the injury or abnormality. Seizures cause disruption of typical brain development and the more seizures you have and the longer you have them, at some point your brain has learned to have seizures and they are much harder to control. Disruption of normal brain networks can also cause learning difficulties and developmental delays. That’s why it’s important to treat epilepsy as early as possible in children.
For more about CHOC’s Neuroscience Institute