Understanding the Different Types and Causes of Seizures

One sunny day in mid-October I realized that I was in the hospital. I didn't know why, and I didn't know how long I had been there, but I was definitely in the emergency ward at Vancouver General Hospital.

By the end of the day I had learned that my wife, Susan, had found me on the dining room floor in my dressing gown, that she had called the paramedics and that through the examinations and the ambulance journey, my eyes had been open and I was answering questions.

A week later, my new neurologist, Oscar Benavente, M.D., told me that I had probably suffered a seizure. The "probably" was because the event had happened days earlier, and he hadn't been there to see it.

According to the Cleveland Clinic, there's a one in 10 chance you will have a seizure at some point in your life. The likelihood increases depending on underlying medical conditions, a family history of seizures or if you are over 50. Children can also experience seizures.

A seizure is, at its simplest, a surge of electrical activity in your brain that causes affected brain cells to quick-fire random signals to other surrounding cells. Your seizure can be a one-off event, or if it is caused by epilepsy, may be one in a continuing series. Your doctor might be able to say why your seizure happened, or it may remain a mystery. And those electrical signals can cause all kinds of symptoms.

In the broadest of terms, you'll want to know if you are suffering from epileptic seizures, meaning you're prone to having repetitive attacks, or if your seizure is likely an isolated episode. How your doctor will determine this is through observation over a long period of time. In my case this meant that for the following six months I was prohibited from driving, and was monitored for further seizures.

Seizures are first categorized by type of onset. Your doctor will ask whether your seizure began on one side of your brain (a focal-onset seizure) or on both sides (a generalized-onset seizure). If you can't tell, it may initially be classed as an unknown-onset seizure. The neurologist will try to answer this and other questions by booking a variety of tests including a CT brain scan (computed tomography, using X-rays to scan the brain), an MRI (magnetic resonance imaging, using magnets), and possibly an EEG (electroencephalogram), a test that measures electrical activity in the brain.  

Those three broad categorizations are useful, but seizures fall into dozens of different categories and combinations depending on your specific symptoms — and whether anyone was on hand to note what was happening. Most seizures last only a minute or two, so there's every chance that it will be over before anyone else could notice how you behaved, or what parts of your body were moving in which fashion.

Most people associate a seizure with (what used to be called ) a grand-mal seizure, where an unconscious person's limbs shake and jerk. These seizures — now termed "tonic-clonic seizures" —are just one of a variety of generalized-onset motor seizures. These seizures include both clonic behaviors — rhythmic jerking — and tonic stiffening, where parts of your body become rigid. Generalized-onset seizures can also include spasms, or loss of muscle tone or combinations of behaviors.

There are also generalized-onset non-motor seizures, (formerly petit-mal seizures) which still originate on both sides of the brain, but include absence seizures, where a patient "blanks out" for a few seconds but without any lasting symptoms.

Focal-onset seizures begin in only one area of the brain and can be categorized by the patient's level of awareness. If awareness is impaired during any part of the seizure, the seizure is classified as a focal impaired-awareness seizure. As with generalized-onset seizures, jerking and stiffening of parts of the body are common events although often only one limb or one side of the body will be involved. It is common for an initially focal seizure to spread to other parts of the brain, creating a focal to bilateral tonic-clonic seizure.

If clinicians are unsure about a seizure, they may choose to describe it as an unknown-onset seizure. After further testing and scans they may be able to reclassify it as either general- or focal-onset seizure. This is important for choosing the correct approach to treatment.

Just as there is a long list of seizure types, the possible causes of a seizure can vary widely, and it's not always possible to be certain of the cause. Merck & Company's MSD Manual lists risk factors such as head trauma, neurological disorders, family history, alcohol or drug use (or withdrawal) or not following prescribed anti-seizure drug schedules. More factors can include a high fever or heat stroke; brain infections from malaria, HIV, rabies or a variety of other bacterial or viral conditions. High or low levels of glucose or sodium can be a cause, as can kidney or liver failure. 

Various cardiac problems may cause inadequate oxygen supply to the brain, as can near-drowning or carbon monoxide poisoning. Damages to the structure of the brain, such as strokes or tumors, can trigger a seizure, as can fluid accumulation, and poisoning from lead or strychnine also will cause a seizure.

In other words, just as a doctor may not ever determine exactly what type of seizure a person had, the patient also may never know what caused it.

The initial follow-up treatment for a seizure will usually include three things: regular brain scans to identify repetitive brain activities; monitoring to detect other seizures and determine what type of seizure it was; and continuing anti-seizure drugs to prevent seizures from reoccuring.

As a patient, learn to look out for the warning signs of an impending seizure. This may include experiencing an aura — an abnormal sensation or feeling — or unusual motor activity or sensory sensations. Patients also may sense odd smells or feel a sense of déjà vu (familiarity) or jamais vu (where a familiar place or activity feels unfamiliar).

Family members and co-workers can be instructed to watch for signs, and to video record a seizure for doctors to examine after the fact. The clues and descriptions that the people around you can provide could be valuable diagnostic aids, and help decide treatment options.

It's likely you will be told that your anti-seizure medication is permanent – you'll take it for the rest of your life. These can be powerful drugs, and it may take a few weeks before you've adjusted to them and no longer suffer side effects. 

Even though most patients can rely on anti-seizure drugs, some 30% of patients progress to brain surgery to help control seizures. Sometimes the portion of the brain that triggers epilepsy can be removed. There are also devices for controlling seizures. One stimulates the vagus nerve, sending regular pulses, or activated with a magnet when the patient feels a seizure beginning. The vagus nerve extends from the brain throughout the body to the colon, and interacts with many organs. Another option uses brain responsive neurostimulation using the RNS System, an implanted device that can detect activity and disrupt it before the seizure can happen.

For now, I'm learning to get around Vancouver using transit, and walking a lot more. So far the medication I've been given has kept my brain functioning properly, and I'm hopeful that I'll be able to avoid surgery and further seizures. And I'm optimistic that after my next checkup with my neurologist I'll be allowed to drive once again.

Barry Rueger is a writer with ties to Canada, France, and Appalachia. Barry’s writing focuses on how people live and how their environment influences their choices. With a special focus on development and municipal government, this invariably leads to the discussion of housing and transportation. Barry also writes about technology and dogs, both from an end-user perspective and on a more philosophical level. Follow Barry’s work at https://appalbarry.com. Read More