• These seizures are called secondary generalized because they start in one area and spread to both sides of the brain. 
  • They usually last 1 to 3 minutes, but it may take a lot longer for a person to recover.
  • A secondary tonic clonic seizure lasting longer than 5 minutes is a medical emergency. 

What is a secondarily generalized seizure?

These seizures are called "secondarily generalized" because they only become generalized (spread to both sides of the brain) after the initial event (a partial seizure) has already begun. They happen when a burst of electrical activity in a limited area (the partial seizure) spreads throughout the brain. Sometimes the person does not recall the first part of the seizure. These seizures occur in more than 30% of people with partial epilepsy.

The generalized, convulsive phase of these seizures usually lasts no more than a few minutes, the same as primary generalized seizures. The preceding partial seizure is usually not very long. Sometimes this part is so brief that it is hard to detect.

Who is at risk for secondarily generalized seizures?

They can affect people of all ages who have partial seizures.

What is it like to have a secondary generalized seizure and how can I tell if someone is having one?

  • These seizures are dramatic cannot be missed due to their sudden and forceful nature. 
  • The seizure may begin with an aura or simple partial seizure or they begin with a complex partial that continues and changes into the secondary generalized seizure.
  • The secondary generalized part begins usually with stiffening of the muscles. Air being forced past the vocal cords causes a cry or groan. The person loses consciousness and falls to the floor. The tongue or cheek may be bitten, so bloody saliva may come from the mouth. The person may turn a bit blue in the face.
  • After the tonic phase comes the clonic phase. The arms and usually the legs begin to jerk rapidly and rhythmically, bending and relaxing at the elbows, hips, and knees. After a few minutes, the jerking slows and stops.
  • Bladder or bowel control sometimes is lost as the body relaxes. Consciousness returns slowly, and the person may be drowsy, confused, agitated, or depressed.
  • These seizures generally last 1 to 3 minutes.
  • A tonic-clonic seizure that lasts longer than 5 minutes is a medical emergency. 
  • It may be difficult to distinguish these seizures from primary generalized tonic-clonic seizures, especially if they occur during sleep or are not seen by anyone else. Most convulsive seizures during sleep are secondarily generalized seizures that do begin as partial seizures.

What happens after a secondarily generalized seizure?

After the seizure, consciousness returns slowly and the person may be drowsy, confused, agitated or depressed immediately after the seizure. If the person does not return to normal, or if another seizure occurs before they return to normal, this may be a sign of an emergency situation known as status epilepticus that requires immediate attention in a hospital. Call 911.

How often will secondarily generalized seizures occur?

It depends and varies among people. Some people can have seizures one a day and others, several times a week, to several times a month or year.

How are secondarily generalized seizures diagnosed?

The EEG and MRI are often helpful in telling the difference between these seizures and primary generalized tonic-clonic seizures.

How are secondarily generalized seizures treated?

Many seizures of this kind can be controlled with medication. If a person has tonic-clonic seizures that are not well controlled with medication, testing may be needed to see whether they might be secondarily generalized seizures that begin in a limited area of the brain. If they do begin in one area, surgery could be an option. Devices and diet therapy are also used to treat secondarily generalized seizures.

What should I do if I think, my child loved one or myself may have secondarily generalized seizures?

If you think your child, loved one or yourself may be having secondarily generalized seizures, it is important to let your doctor know your concerns right away. Uncontrolled secondarily generalized seizures may lead to injury, memory impairment and in some rare cases death. Getting a diagnosis and treatment is of utmost urgency.

Authored by: Orrin Devinsky, MD | Joseph I. Sirven, MD on 7/2013
Reviewed by: Joseph I. Sirven, MD | Patricia O. Shafer, RN, MN on 3/2014
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What Does It Look Like?

Seizures of this kind start as a partial seizure—that is, they start in one limited area of the brain. The forms they take vary as much as other partial seizures. But then (sometimes so quickly that the partial seizure is hardly noticed) the seizure spreads throughout the brain, becoming "generalized." Here's how a couple of people with epilepsy described their secondarily generalized seizures:

  • "The seizures start with a tingling in my right thumb. In seconds, my thumb starts jerking. Soon, my whole right hand is jerking. I have learned that by rubbing and scratching my forearm I can sometimes stop the seizure. Other times the jerking spreads up my arm. When it reaches my shoulder, I pass out and people tell me that my whole body starts to jerk."
  • "I see this colored ball on my right side. It seems to grow until it fills up my whole view. Everything becomes like a dream and I don't feel real. It is the strangest feeling. Sometimes the seizure stops then, and sometimes it goes all the way and I fall to the floor and have a grand mal [tonic-clonic seizure]."
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