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An Overview of Epilepsy

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Epilepsy has been around since ancient times. A Babylonian tablet that may date as far back as 2000 B.C. describes many of the seizure types that we see today, and associates each with a different god. The ancient Greeks also thought that people with epilepsy were being “seized” by the gods, so they called epilepsy “the sacred disease.” In about 400 B.C., Hippocrates criticized this view and wrote about epilepsy as a disorder of the brain that could in theory be treated with diet and drugs. The ancient Ayurvedic medical system of India also describes epilepsy as a physical disorder. Epilepsy is mentioned in the Bible; the book of Mark describes Jesus treating a young man with tonic-clonic seizures, and mentions fasting as a treatment. However, until the 19 th century A.D., when the first effective anti-epileptic drug was introduced, epilepsy was still considered a supernatural disease, and people with epilepsy were treated with fear and suspicion.

Epilepsy is common and exists all over the world. The World Health Organization estimates that approximately 50 million people in the world have epilepsy, and that it is a major cause of disability, especially in young people.

It is thought that about 1 in every 100 to 200 people has epilepsy. One study found that in 1990, about 47,000 people in Ontario had epilepsy. Among children under 12, about 1 in 320 had epilepsy, while 1 in 175 children aged 12 to 15 had epilepsy.

In Canada, around 15,000 people are diagnosed with epilepsy each year. Epilepsy most often starts either in childhood or in old age.

What is a Seizure?
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What happens in the brain when someone has a seizure?

The brain is made up of billions of neurons (nerve cells) working together to process input from the senses and to control the body’s voluntary movements (like walking and talking) and involuntary movements (like digestion and heartbeat). Each area of the brain is very specialized: for instance, body movements are controlled by the neurons in a strip of the brain called the motor cortex. One group of neurons controls the right hand, another group controls the left foot, and so on.

Normally, neurons fire singly or in small, controlled groups. For instance, when you decide to lift your hand, the neurons that send signals to the appropriate muscles fire in a controlled way -- like turning on a light switch -- and your hand moves.

When someone has a seizure, however, many neurons fire all together in an uncontrolled way. Neighbouring neurons may be drawn in as well — like a small electrical storm in the brain.

Different kinds of seizures

The old terminology of “petit mal” and “grand mal” seizures was incomplete and not always helpful. The new classification defines seizures as partial or generalized based on whether they begin in part of the brain or in the whole brain at once, with further separation based on the seizure symptoms.

Generalized seizures begin in the whole brain at the same time. They include:

  • absence seizures, in which the child briefly stares and does not hear or see what is happening around him
  • myoclonic seizures, in which the child has twitches or jerks in all or part of her body
  • atonic seizures, in which the child goes limp and falls
  • tonic-clonic seizures, in which the child goes rigid, then convulses (shakes or jerks rhythmically)

Partial seizures begin in only a part of the brain; they may remain there, or become secondarily generalized (that is, they may spread to involve the whole brain). They include:

  • simple partial seizures, in which the child is still aware of what is happening around her; these may have motor, somatosensory, autonomic, or psychic symptoms
  • complex partial seizures, in which consciousness is impaired

Finally, some seizures may not easily be classified because the doctor does not have enough information about the type of seizure (for instance, seizures in newborns may be difficult to classify).

Epilepsy syndromes

Sometimes seizures occur in a specific pattern. There are a variety of these patterns, which are called epilepsy syndromes. Some childhood epilepsy syndromes include:

  • infantile spasms
  • benign epilepsy of childhood with centrotemporal spikes (BECTS)
  • Rasmussen encephalitis
  • childhood or juvenile absence epilepsy
  • juvenile myoclonic epilepsy
  • Lennox-Gastaut syndrome
  • Landau-Kleffner syndrome
  • reflex epilepsy

Elizabeth J. Donner, MD, FRCPC

 

2/4/2010




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