Tonic-Clonic Seizures

By: Aliana Gordon

Tonic-clonic seizures, formerly known as grand mal seizures, embodies the social idea of seizures with the strong convulsions and foaming at the mouth that are common symptoms of this type of electrical disturbance in the brain. In this specific seizure, the body stiffens (tonic phase) and then there is a series of twitching or jerking motions of the body (clonic phase). But let’s break down what can occur when one experiences these seizures and what to do if you witness someone experiencing a tonic-clonic seizure.

A generalized tonic-clonic seizure consists of two phases, first the tonic phase when the muscles in the body stiffen then followed by the clonic phase of muscle spasms. The cause of these is believed to be a result of neurochemical and genetic abnormalities within the brain (1). The seizure could also arise from an abnormal electrical charge in a region of the brain, focal seizure, and then spread to both hemispheres of the brain turning it into a focal to bilateral tonic-clonic seizure (1). The cause or location of the focal onset may not be able to be determined by testing resulting in an idiopathic seizure, the cause is unknown (2). In addition, other health problems, such as extremely low blood pressure or a high fever, could trigger a tonic-clonic seizure (3).

tonic clonic seizures
Generalized vs. Focal Seizure Activity

The Tonic Phase

During the tonic phase, the muscles in the body stiffen which may cause the person to fall and lose consciousness. What may be viewed or experienced is the impairment of breathing which may sound like a cry or scream that is caused by the muscles surrounding the lungs to stiffen. This can cause their face to turn into a blue or gray color from the lack of oxygen. It is also common for there to be a formation of saliva appearing as foam to develop around the mouth with the addition of blood (4).

The Clonic Phase

In this phase, the body experiences twitching or jerking movements of the face, arms, and legs that can occur intensely and rapidly. This phase should diminish within 1-3 minutes and can be seen by the movements slowing down until the body fully relaxes. The relaxation of the body can lead to the loss of bowel or bladder control.

What should I do if I am witnessing someone have a tonic-clonic seizure?

If you know someone who could have unexpected seizures, talk to them beforehand to see how they would like your help in the situation, as the severity can differ from person to person.

Here is also a list of general rules when witnessing a seizure (3, 4):

  • Clear the area surrounding their body to prevent objects from harming them.
  • Turn their body onto their side if possible, to prevent choking on spit or other fluid.
  • Time the seizure, if the seizure lasts for more than 5 minutes, call 911.
  • Recurring seizures call 911 if a person is experiencing multiple seizures.
  • The person may be unresponsive after convulsions as the brain recovers; it may seem like they are sleeping or snoring.
  • Provide calm reassurance when they regain consciousness as they often feel disoriented and do not remember having a seizure. It is also common for them to experience fatigue and severe headaches. It can be an embarrassing experience to have in front of others especially with the chance of having a loss of bowel or bladder control.
  • DO NOT attempt to put any object in their mouth as it is impossible for one to swallow their tongue.
  • DO NOT attempt to hold one still during a seizure as it can cause harm to them and you.


A tonic-clonic seizure can occur as a generalized seizure affecting both sides of the brain or can arise from a partial seizure that spreads to both hemispheres of the brain from abnormally synchronized electrical activity. The first phase, referred to as the tonic phase, stiffens muscles in the body resulting in the possibility of falling and losing consciousness. It is important to remove potentially harmful objects away from the body during this time and to try to move the body onto their side while timing the length of the seizure. The second phase is the clonic phase which affects the face, arms, and legs by causing them to twitch or having intense jerking movements; should start diminishing within 1-3 minutes. If the seizure lasts more than 5 minutes or there are repetitive seizures, call 911. It is also important to provide reassurance to the person experiencing the seizure comes back to consciousness and to remain calm and supportive as they could be disorientated and embarrassed.


(1) “Tonic-Clonic Seizures.” Epilepsy Foundation, 2017, Accessed 4 Nov. 2020.

(2) DrupalAdmin. “FAQs.” American Epilepsy Society, 3 Dec. 2013, Accessed 4 Nov. 2020.

(3) “Grand Mal Seizure – Symptoms and Causes.” Mayo Clinic,  , 2019, Accessed 4 Nov. 2020.

(4) Tonic-Clonic (Grand Mal) Seizures. 2020, Accessed 4 Nov. 2020.

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