What is a seizure?

A seizure is a temporary episode of uncontrolled, abnormal electrical activity in the brain that affects physical and mental function. Epilepsy is a neurological condition that makes a person more likely to experience recurrent, unprovoked seizures.

Seizure symptoms

Signs and symptoms of seizures vary depending on the area of the brain affected and the type of seizure. Some seizure symptoms are obvious, while others might not be noticeable at all.

People with seizures may experience one or more of the following symptoms:

  • Abnormal or unpleasant taste or smell
  • Hearing or seeing things that are not there
  • Strange thoughts or experiences, such as déjà vu or sudden behavioral changes
  • Involuntary movements of the arms or legs
  • Spells of staring or unresponsiveness during which the person has difficulty communicating and may remember nothing
  • Lip smacking or repetitive movements, for example picking or grasping movements
  • Whole-body stiffening or shaking
  • Drooling or frothing from the mouth
  • Loss of bladder or bowel control

Seizure triggers

Certain events or exposures called triggers may set off the abnormal electrical brain activity that causes seizures.

Common seizure triggers include:

  • Alcohol/drug use or withdrawal
  • Certain foods and medications
  • Dehydration/physical exertion or malnutrition
  • Flashing lights or patterns (photosensitivity)
  • High environmental temperatures
  • Hormonal changes (such as those during menstruation)
  • Illness or fever
  • Sleep disturbance or stress

Seizure types

Doctors categorize seizures into two main types—generalized seizures and focal seizures. The type of seizure depends on what part of the brain is affected and the symptoms a person has during the seizure.

What causes a seizure?

All seizures are caused by abnormal electrical activity in the brain. That abnormal activity can be caused by many different factors. In some cases, the cause of seizures is unknown.

Known factors that affect the brain and promote this abnormal electrical activity include:

How are seizures diagnosed?

Some seizures have obvious symptoms, but others are subtle. Even when seizure symptoms are obvious, the cause often isn't. Precise diagnostic testing is the only true way to determine the cause of seizures.

We begin with a review of your and your family's medical history. You will be asked questions about your seizures, including how often they occur, what seems to trigger them, and what you experience during your seizures. Since many people with seizures do not remember them, we also ask family members or other witnesses what they observe when you have a seizure.

Your doctor will likely order brain imaging and other tests to pinpoint where abnormal electrical activity is happening in the brain and what is causing it.

Learn more about advanced diagnosis testing for seizures at Penn Medicine's Comprehensive Epilepsy Center.

Seizure treatment at Penn Medicine

The specialists at Penn Medicine's Comprehensive Epilepsy Center offer a variety of treatment options.

Related specialties

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