Tonic-Clonic Seizure Symptoms, Causes, and Diagnosis

Formerly called "grand mal" seizures

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A tonic-clonic seizure, which is often referred to as a grand mal seizure, is the "classic" type of seizure most people are familiar with. It involves loss of consciousness or awareness plus uncontrolled jerking and stiffness of the arms, legs, or body. It generally lasts for just a few seconds up to a couple of minutes.


Symptoms of tonic-clonic seizures can include any combination of the following:

  • An unusual sensation prior to the seizure that's often described as an aura
  • Jerking and stiffening of one or more limbs
  • Drooling
  • Urinary or fecal incontinence
  • Tongue biting
  • Falling down
  • Screams, grunts or sounds
  • Eye movements or eye jerking
  • Confusion or sleepiness afterward and inability to recall the event

Due to impaired consciousness, you may not be aware that you're having a seizure. A tonic-clonic seizure can be classified as a partial seizure or a generalized seizure.

Partial Seizure

  • Involves one area of the brain

  • Awareness or partial awareness are possible

  • Impacts area(s) of body controlled by that brain region

Generalized Seizure

  • Involves the whole brain

  • Complete lack of awareness and memory

  • Impacts the whole body


A number of medical problems can cause a person to experience tonic-clonic seizures.

Causes of tonic-clonic seizures include:

  • Epilepsy: This is the most common cause. You can be born with it or develop it later in life due to brain damage.
  • Brain injury: Head trauma, brain injury, strokes, aneurysms, brain tumors, and brain infections; May cause long-term epilepsy, or seizures may stop happening eventually.
  • Medical reactions: Certain medications, severe illnesses, electrolyte abnormalities, organ failure, high fevers, and severe infections; Generally, seizures should improve once the illness resolves.
  • Drugs: Drug or alcohol overdose or withdrawal, due to disturbances in brain activity.

Why Tonic-Clonic Seizures Happen

When the brain is injured, the electrical activity that normally controls brain function may become disturbed or erratic. One or more part of the brain may then 'misfire,' causing unwanted physical actions that often manifest as a tonic-clonic seizure. The jerking motions and stiffness associated with this type of seizure are caused by abnormal activity in the region of the body that is controlled by the injured area of the brain.

If the abnormal brain activity involves a small region, a partial seizure results. When the abnormal activity involves the whole brain, you get generalized seizures.


A tonic-clonic seizure is often diagnosed based on the clinical manifestations. Diagnostic testing such as electroencephalogram (EEG) and brain imaging may also help in the diagnosis and treatment plan.

Seizure diagnosis is based on:

  • Description: If you have had a tonic-clonic seizure, you may recall how you felt immediately prior to the seizure, and you may recall some parts of the seizure itself. If anyone else was around, their description of the event is helpful.
  • EEG: An EEG is a test that detects brain waves. If you've had a seizure or are prone to seizures, your EEG may show one or more areas or of erratic electrical brain activity. An EEG is particularly helpful if you have a seizure during the test that correlates with the electrical abnormality.
  • Sleep deprived EEG: Sometimes, an EEG does not show electrical abnormalities when you are well rested but will show them when you're sleep deprived. For the test, you'll need to be awake for a long period of time, which leads to a metabolic state that can trigger a seizure and makes electrical abnormalities show up better.
  • Brain imaging: A brain CT or MRI does not show seizures, but it can identify abnormalities that can cause tonic-clonic seizures, such as a brain tumor, stroke, abscess, or abnormal blood vessel in the brain.

    Treatment and Prevention

    Tonic-clonic seizure treatment is primarily focused on prevention, and it is rare that treatment needs to happen while a seizure is going on.

    Status Epilepticus

    However, a seizure that lasts five minutes or longer is a potentially life-threatening emergency called status epilepticus. It typically requires treatment with a fast-acting medication that stops the seizure right away. Medications used to treat status epilepticus include intravenous forms of lorazepam, diazepam, and midazolam.

    Avoiding Triggers

    There are a variety of ways to effectively prevent seizures. If you have a certain trigger, such as alcohol, drugs, or medications, then controlling the use of that substance is by far the safest way to prevent a seizure.


    Most people who are prone to recurrent tonic-clonic seizures could experience a seizure due to a fever, infection, sleepiness or even without any known trigger. Anti-seizure medications, which are also referred to as anticonvulsants, are often recommended to prevent or reduce recurrent seizures.

    Common anti-seizure medications used for treating tonic-clonic seizures include:

    • Tegretol, Carbatrol (carbamazepine)
    • Keppra (levetiracetam)
    • Dilantin (phenytoin)
    • Depakote (valproic acid)
    • Neurontin (gabapentin)
    • Phenobarbital
    • Topamax (topiramate)
    • Gabitril (tiagabine)
    • Fycompa (perampanel)

    A Word From Verywell

    If you or a loved one has experienced a tonic-clonic seizure, there is a high likelihood that you will achieve reduced seizures once doctors find the cause and get you on anticonvulsant medication. Most people with epilepsy can prevent seizures and have a good quality of life.

    However, living with tonic-clonic seizures can be stressful. It's helpful to learn as much as you can about your condition, figure out your triggers, and identify whether you experience a pre-seizure aura.

    Tonic-clonic seizures may also cause embarrassment or problems at school or work. Learning to explain your illness to the people in your life can help prevent fear and misunderstandings and can provide you with support from friends.

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