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About Epilepsy and Seizures

Epilepsy is defined as having two or more unprovoked seizures.

In the U.S., about 3.4 million people have epilepsy. Of this number, 3 million are adults and 470,000 are children. Worldwide, about 65 million people have epilepsy.

Epilepsy is a chronic disease characterized by recurrent seizures. Seizures are the results of a burst of uncontrolled electrical activity within damaged brain cells. Seizures can include changes of awareness, muscle control (your muscles may twitch or jerk), sensations, emotions, and behavior. However, having one seizure does not mean having epilepsy. Up to 10% of people worldwide can have 1 seizure in their lifetime without ever developing epilepsy.

The International League Against Epilepsy reclassified seizure types in 2017. Seizures are now described based on:

  • Where the seizure starts in the brain (generalized affecting both sides or focal starting on one side)
  • Level of awareness during a seizure (aware or impaired)
  • Whether movement occurs during the seizure (motor or non-motor) and what type of movement: muscles twitching (myoclonus), becoming limp (atonic), jerking (clonic) or becoming rigid (tonic)

Seizures are classified by where they begin in the brain.

  • Generalized: Generalized epilepsy is when seizures begin on both sides of the brain. Many times, generalized epilepsy is genetic and patients are treated with medication. In the event medication fails, some patients are treated with surgery to implant a device known as vagus nerve stimulation.
  • Localized/Focal: Localized epilepsy is when a seizure begins in a specific part of the brain. Many times, patients control their seizures through surgery to intervene at the part of the brain where the seizures begin.

Seizure Classification:

Focal Seizures: About 60 percent of all seizure types are focal (previously known as partial seizures). Focal means that they start in one small area of the brain. There are two types of focal seizures:

Focal onset aware seizure means you’re awake and aware during the seizure. Healthcare providers once called this a simple partial seizure. Symptoms may include:

  • Changes in your senses — how things taste, smell or sound
  • Changes in your emotions
  • Uncontrolled muscle jerking, usually in arms or legs
  • Seeing flashing lights, feeling dizzy, having a tingling sensation

Focal Onset Impaired Awareness Seizures: You’re confused or have lost awareness or consciousness during the seizure. This seizure type used to be called complex partial seizure. Symptoms may include:

  • Blank stare or a “staring into space”
  • Repetitive movements like eye blinking, lip-smacking or chewing motion, hand rubbing or finger motions

Generalized Seizures: Affect both sides of the brain at the same time. They account for about 30 percent of all seizure types. They can be further classified depending on different characteristics. 

Absence seizures: This seizure type causes a blank stare or “staring into space” (a brief loss of awareness). There may be minor muscle movements, including eye blinking, lip-smacking or chewing motions, hand motions or rubbing fingers. Absence seizures are more common in children, last for only seconds (usually less than 10 seconds) and are commonly mistaken for daydreaming. This seizure type used to be called petit mal seizures.

Atonic seizures: Atonic means “without tone.” An atonic seizure means you’ve lost muscle control or your muscles are weak during your seizure. Parts of your body may droop or drop, such as your eyelids or head, or you may fall to the ground during this short seizure (usually less than 15 seconds). This seizure type is sometimes called “drop seizure” or “drop attack.”

Tonic seizures: Tonic means “with tone.” A tonic seizure means your muscle tone has greatly increased. Your arms, legs, back or whole body may be tense or stiff, causing you to fall. You may be aware or have a small change in awareness during this short seizure (usually less than 20 seconds).

Clonic seizures: “Clonus” means fast, repeating stiffening and relaxing of a muscle (“jerking”). A clonic seizure happens when muscles continuously jerk for seconds to a minute or muscles stiffen followed by jerking for seconds up to two minutes.

Tonic-clonic seizures: A combination of muscle stiffness (tonic) and repeated, rhythmic muscle jerking (clonic). Healthcare providers may call this seizure a convulsion, and once called it a grand mal seizure. Tonic-clonic seizures are what most people think of when they hear the word “seizure.” You lose consciousness, fall to the ground, and your muscles stiffen and jerk for one to five minutes. You may bite your tongue, drool, and lose muscle control of bowels or bladder, making you poop or pee.

Myoclonic seizures: Causes brief, shock-like muscle jerks or twitches (“myo” means muscle; “clonus” means muscle jerking). Myoclonic seizures usually last only a couple of seconds.

As your healthcare provider learns more, your seizure type may change to focal or generalized onset seizure.


Non-epileptic Seizures

  • One-third of all patients admitted to an epilepsy monitoring unit for intractable seizures are found to have non-epileptic seizures, or NES (also known as psychogenic non-epileptic seizures, or PNES). 
  • Though they resemble epileptic seizures — either generalized seizures (falling and shaking) or focal seizures (staring spells, or other changes in perception or behavior) — nonepileptic seizures are not caused by abnormal electrical activity in the brain. 
  • Non-epileptic seizures may be associated with past traumatic experiences or other psychiatric or psychological factors. But sometimes none of these factors are identified by the patients at the time they come to the clinic.
  • Because NES do not respond to typical anti-seizure medications and are not under the person’s voluntary control, they can profoundly affect the quality of life. People with NES often require multiple trips to the ER or hospitalizations before being diagnosed with NES.