What Is Epilepsy?

A seizure is a brief burst of abnormal electrical activity in the brain. Epilepsy is a brain condition in which patients experience recurrent, unprovoked seizures.

Seizures may cause abnormal sensations (such as numbness, strange taste or smell), temporary disoriented feeling or sense of lost time, loss of consciousness or uncontrolled bodily movements. Often, patients are only partially aware of the seizure having occurred.

When seizures are provoked, or triggered by something in particular (drug or alcohol use, electrolyte imbalance, low blood sugar, etc.) they are not considered to be epileptic seizures.

Not everything which looks like a seizure, is actually an epileptic seizure. A variety of neurologic, cardiac, and psychological conditions can mimic seizure. Examples include migraines, movement disorders, fainting spells, chronic pain, and stress.

More than 25 percent of seizures seen at an epilepsy center turn out to be non-epileptic and often get better once the underlying cause is treated.

Types of Epilepsy

Generalized Epilepsy

Abnormal electrical discharges that involve all brain areas at the same time are called generalized seizures and are associated with generalized epilepsy.

In most cases, generalized epilepsy is associated with a completely normal appearing brain and no structural abnormality is found to explain the epilepsy. This type of generalized epilepsy is thought to be caused by a genetic (inherited) predisposition.

In some cases, generalized epilepsy can be associated with brain abnormalities. These brain abnormalities are sometimes caused by:

  • Brain infections
  • Head injuries
  • Lack of oxygen

Focal Epilepsy

Abnormal electrical activity that starts in a small area in the brain and spreads to the rest of the brain are called focal seizures.


Focal epilepsies start from a localized area in the brain, and can often be caused by an abnormal appearing area detectable on MRI scan. Typical abnormalities that can cause focal epilepsy are:

  • Hippocampal sclerosis (hardening of the hippocampus)
  • Scarring after stroke or trauma
  • Small area of disorganized brain tissue
  • Benign brain tumor
  • Malformed blood vessel

Related Resources


  • Video-EEG Monitoring: EEG portion of the test looks at electrical activity of the brain and the video recording shows how the body responds during a seizure.
  • Wada Testing: Learn more about this test, which examines each side of your brain.
  • Specialized Treatment for Epilepsy: The Northwestern Medicine Comprehensive Epilepsy Center maintains the highest designation by the National Association of Epilepsy Centers.


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