Technology & Science

Seizures: What they are, and what causes them

"Seizure." It's a common term, but what exactly are seizures, and what causes them? The simple explanation is that seizures are symptoms of a problem that can happen because of sudden and abnormal electrical activity in the brain. Based on the type of behaviour and the brain activity, seizures fall into two wide-ranging groups. Partial seizures (also known as focal seizures) happen in just one part of the brain. Generalized seizures are a result of abnormal activity on both sides of the brain.

"Seizure." It's a common term, but what exactly are seizures, and what causes them?

The simple explanation is that seizures are symptoms of a problem that can happen because of sudden and abnormal electrical activity in the brain.  

Neurosurgeon Dr. P. David Adelson, right, and Dr. Brian Jankowitz, senior neurosurgical resident at the Children's Hospital of Pittsburgh, operate on a two-year-old child to remove abnormal brain tissue, blamed for seizures he suffered since he was 4 months old. ((Keith Srakocic/Associated Press))
Based on the type of behaviour and the brain activity, seizures fall into two wide-ranging groups. Partial seizures (also known as focal seizures) happen in just one part of the brain. Generalized seizures are a result of abnormal activity on both sides of the brain. 

Anyone can experience a seizure. Seizures can be caused by a blow to the head, an infection (meningitis, encephalitis), drug or alcohol toxicity, high fever, eclampsia (a condition in pregnant women), missed medication, strokes, heart attacks, complications of kidney disease, diabetes or brain tumors. They can also be the result of seemingly innocuous things like consuming large amounts of fluids or watching flashing lights.       Most seizures last from about 30 seconds to two minutes. If they continue for five minutes or more, they are considered a medical emergency.

A single seizure does not mean that it will ever happen again. Repeated brain seizures usually characterize a seizure disorder known as epilepsy.

Neurological disorder

Epilepsy is a neurological disorder, not a disease: it's not contagious and is not a mental illness.

According to Epilepsy Canada, approximately 0.6 per cent of the Canadian population has epilepsy. Every day in Canada, an average of 42 people learn that they have epilepsy.

Epilepsy by the numbers

  • 44 per cent of those with epilepsy are diagnosed before the age of five.
  • 75 per cent to 85 per cent have been diagnosed by age 18. 
  • One per cent of children will have recurrent seizures before the age of 14.
  • In 2003, when the Canadian population was around 31 million, the incidence of epilepsy was estimated at 15,500 new cases per year.
  • An estimated 40 million people in the world have epilepsy.
  • 32 million epilepsy sufferers have no access to treatment because services are non-existent or because epilepsy is not viewed as a medical problem or a treatable brain disorder in their part of the world.

Source: Epilepsy Canada

Dr W. McIntyre Burnham investigates seizures — why they occur, how they affect the brain, and how anticonvulsant drugs can suppress them. He heads the University of Toronto's Epilepsy Research Program and holds the Michael Bahen Chair in Epilepsy Research.

"Because the Bahen chair provides unearmarked research funds, we use it to support a wide range of work in my laboratory," Burnham says. "Our first project was the progesterone project. It evolved out of a consideration of catamenial epilepsy found in women. It is characterized by the fact that seizures occur at times in the female fertility cycle where estrogen is high and progesterone is low or falling."

Burnham says this suggests that estrogen is proconvulsant and progesterone is anticonvulsant.

"Particularly important is the fact that catamenial epileptics often have complex partial seizures, the most common seizures in adults," he said. "They are very drug resistant. The majority of people with intractable epilepsy have complex partial seizures, and prevention of them is the major goal of our lab."

Dorothy Collins, 74, of Guelph recalls the seizures her mother, Elizabeth Wagstaff, experienced throughout her life (she lived from 1898 to 1993). 

"My mother's epilepsy was linked to my birth and pre-eclampsia, we think," Collins said. "There was definitely a stigma attached in those days. I did not realize until we were in Greece visiting my cousin in 1999 that she, my cousin, didn't even know about it. My father never told anyone."

Wagstaff's seizures eventually went away with the onset of menopause, Collins said.

"Apparently, the doctors decided they had been caused by a hormonal problem," she said.

According to the Epilepsy Foundation, hormonal changes in men are less obvious than in women because they do not have a monthly menstrual cycle. "However, in men, hormones (testosterone and breakdown products) also influence brain function and may have an impact on seizures," says the foundation's website.

"Men versus women? It's about 50 per cent; there's no imbalance," says Burnham. "Both men and women tend to have problems with reproduction. If they're suffering from uncontrolled seizures of temporal lobe origin, both men and women tend to have less interest in sex, to get less physically aroused and to have less fertility. In women, the specific fertility problem is irregular and sometimes anovulatory [menstruation without ovulation] cycles, and in men it's a poor sperm count."

Seizures in children

When it comes to childhood seizure disorders, "epilepsy affects about one per cent of the population, and up to 30 per cent of children have seizures that are not controlled by medication," says Dr. Elizabeth J. Donner, a pediatric neurologist and medical director of the ketogenic diet program at the neurology department of SickKids Hospital in Toronto.

"When seizures fail to be stopped by medication, we consider other therapies. The treatment with the highest chance of 'cure' of seizures is resective surgery [removing the part of the brain that causes seizures]."

There appear to be some advantages to doing epilepsy surgery in children, rather than waiting for adulthood: children's brains are more "plastic" than adults' brains, with a greater ability to compensate for portions removed during surgery. In some children, treating seizures earlier may prevent brain damage or changes from repeated seizures and their detrimental effects on cognition and development.

Although surgery will not help every child with uncontrolled seizures, it can be a very effective treatment. Various studies suggest that 57 per cent to 69 per cent of babies, children and teenagers treated with surgery become seizure-free. Between 11 per cent and 24 per cent continue to have frequent seizures.

"Resective surgery for epilepsy involves identifying the region of the brain that is generating seizures and performing neurosurgery to remove that area," Donner explains.  "Children must undergo multiple investigations to identify the region of the brain. If a child is not a candidate for surgery, usually because the seizures are coming from more than one brain region or the whole brain, then we consider diet therapy.

"At SickKids, we offer three diet options: the classic ketogenic diet (high in fat and low in carbohydrate and protein, which results in ketosis), the medium chain triglyceride (MCT) diet and the modified Atkins diet." 

According to the Epilepsy Foundation website, the ketogenic diet, which is very high in fats and low in carbohydrates, was developed almost 80 years ago. It makes the body use fat instead of glucose for energy.

"When carefully monitored by a medical team familiar with its use, the diet helps two out of three children who are tried on it and may prevent seizures completely in one out of three. It is a strict diet and takes a strong commitment from the whole family," the site says.

Sandra Marchbank's son, Carson, was five years 11 months old when he began the ketogenic diet.

"Carson has had seizures since birth, and they were very difficult to manage," said the 37-year-old mother from Kensington, P.E.I. "He had been on several anticonvulsants over the years and still continued to have seizures. At the time we started the diet, he was having upwards of 30 to 40 seizures a day. He would just fall without warning, and the last straw was when he took a seizure while standing looking out the window and split his eyelid open and required three stitches. We knew we had to try something else. 

"Our neurologist mentioned the ketogenic diet and how Carson would be an ideal candidate for it as he is completely dependant on us for all aspects of daily living and wouldn't be able to cheat on the diet. Carson also has low functioning autism and has suffered brain damage from years of seizures."

Another option is the modified Atkins diet, which, Donner explains, is a simplified diet for epilepsy based on the popular Atkins Diet for weight loss.

"When used for epilepsy, it requires significant carbohydrate restriction combined with an increase in fat intake," Donner said. "The advantage of the Atkins diet is that it is less restrictive than the classic ketogenic diet and the MCT diet, and it requires less measuring and monitoring of food intake.

"The success that an institution has with the diet is related to how much they will customize and adapt the diet to suit the family and child."

Marchbank says the ketogenic diet has helped her son a lot but hasn't eliminated all of his seizures.

"It has greatly reduced them by about 80 per cent, and we are very pleased with that," she said. "Carson has gone from 30 to 40 seizures a day to approximately three to five seizures a week. The diet has certainly forced our family to change the way we do things, but at the end of the day, the extra effort is so very worth it.

"I'd definitely recommend trying the diet if anticonvulsants fail. It's not easy but neither is standing back helplessly watching your child have seizures. It's certainly worth the effort in my opinion."