Generalised Tonic-Clonic Seizure

A generalised tonic-clonic seizure is a type of seizure that affects both sides of the brain, causing muscle stiffness, violent shaking, and loss of consciousness. These seizures are among the most feared types of seizures, but understanding what they are and how to respond can help manage them effectively.

Table of contents

• What is a Generalised Tonic-Clonic Seizure?
• Other Names
• Causes and Triggers
• How Common Are These Seizures?
• Signs and Symptoms
• The Two Phases of a Tonic-Clonic Seizure
• What Happens After a Seizure
• How Doctors Diagnose These Seizures
• Treatment and Management
• First Aid During a Seizure
• When to Call for Emergency Help
• Possible Complications

What is a Generalised Tonic-Clonic Seizure?

A generalised tonic-clonic seizure is defined as a seizure that has a tonic phase (muscle stiffening) followed by clonic muscle contractions (rhythmic jerking movements). These seizures affect both sides of the brain at the same time and usually cause a complete loss of consciousness^[1]. The abnormal electrical activity spreads quickly through both hemispheres of the brain, involving areas that control movement, consciousness, and other body functions^[1].

These seizures cause sudden muscle stiffness, involuntary jerking movements, and loss of consciousness. When this happens, abnormal electrical activity spreads through the brain^[4]. During normal brain function, nerve cells send electrical and chemical signals at different times. But during a seizure, many neurons fire all at once, creating a burst of uncontrolled electrical activity^[5].

Other Names

Grand mal seizure, tonic-clonic seizure, convulsion

These seizures were formerly known as grand mal seizures. The terms generalized seizure or convulsion are also often used to describe this type of seizure^[1][2].

Causes and Triggers

The most common cause of generalised tonic-clonic seizures is underlying epilepsy from genetic causes. Besides genetic causes, these seizures can happen due to problems with brain structure, infections, metabolic issues, or immune-related conditions^[1].

Several health conditions can trigger tonic-clonic seizures^[4]:

• Blood flow and circulation problems: aneurysms, arrhythmias, stroke, eclampsia
• Brain injuries or changes: concussion, traumatic brain injury, brain tumor, diseases that slowly damage the brain
• Imbalances: high blood sugar or low blood sugar (hypoglycemia), lack of oxygen
• Infections or immune responses: encephalitis, meningitis, sepsis, certain autoimmune conditions
• Poisoning: carbon monoxide poisoning, heavy metal poisoning
• Substances: substance use disorder, withdrawal from drugs or alcohol

Some seizures happen because of temporary medical problems, such as ischemic or hemorrhagic strokes, head injury, severe illness, metabolic problems, or substance abuse. These are called acute symptomatic seizures. They can appear as tonic-clonic seizures but do not mean the person has epilepsy, which involves repeated seizures without an immediate cause^[1].

Certain factors can increase the chance of having a seizure. These triggers include fatigue, poor nutrition, lack of sleep, high blood pressure, stress, diabetes, flashing lights or light patterns, hormonal changes, low blood sugar, anxiety, and antihistamines^[5]. In young children, fever can trigger seizures, known as febrile seizures^[4].

How Common Are These Seizures?

Seizures account for 1 to 2 percent of all emergency department visits in the United States^[1]. About 1 in 10 people in the United States may have a seizure in their lifetime^[6]. Common reasons for emergency visits after seizures include alcohol and drugs, head injury, and epilepsy^[1].

Signs and Symptoms

When most people think about seizures, they usually picture a tonic-clonic seizure because the symptoms are very noticeable. These seizures typically last 1 to 3 minutes^[3].

Some people experience warning signs just before a seizure begins. This warning is called an aura. During an aura, a person might have a feeling of already having been in this situation (called déjà vu), experience an unusual smell or taste, see flashing lights, feel a sudden intense emotion such as fear, or feel sick to the stomach^[3].

During the seizure, a person may^[4]:

• Make a groan or yell
• Experience sudden stiffening of muscles
• Fall to the ground
• Lose consciousness
• Have full-body rhythmic muscle jerks or shaking
• Lose control of bladder or bowels
• Bite their tongue or cheek, which may cause bloody saliva
• Have difficulty breathing or stop breathing temporarily
• Turn blue around the mouth

The Two Phases of a Tonic-Clonic Seizure

A generalised tonic-clonic seizure happens in two distinct parts^[3][4]:

Tonic phase (10 to 30 seconds): During this phase, the muscles suddenly become stiff. The person loses consciousness and falls to the ground. The muscles stiffen, causing the arms to bend and the legs, head, and neck to extend. The jaws clench sharply. The person might bite their tongue during this phase, but no one should put anything in their mouth as this can cause harm^[3].

Clonic phase (30 to 60 seconds): The arms and legs jerk quickly in rhythmic movements. This is when the body experiences periods of rhythmic shaking or jerking movements. During this time, breathing may become irregular, and the person may lose control of their bladder or bowels^[3][4].

What Happens After a Seizure

After a generalised tonic-clonic seizure, the person enters what is called the postictal phase. During this time, the person may feel confused or irritable, be very tired, have a headache, or experience other symptoms^[3]. They may also have memory loss about the seizure, feel drowsy or sleepy for an hour or longer, or experience weakness on one side of the body for a few minutes to a few hours^[4].

The postictal phase usually lasts just a few minutes but can be longer^[3]. Recovery usually occurs within 30 to 60 minutes but may be delayed^[12].

How Doctors Diagnose These Seizures

After a seizure, a doctor will perform a thorough review of symptoms and medical history. Because the person passed out during the seizure, they may not remember what happened. The doctor may ask witnesses about what they observed^[4].

The doctor will perform a physical exam that includes a detailed check of the brain and nervous system^[9]. Several tests may be needed:

Electroencephalogram (EEG): This test checks the electrical activity in the brain. People with seizures often have unusual electrical activity shown on this test. In some cases, the test shows the area in the brain where the seizures start. The brain may appear normal after a seizure or between seizures^[9].

Blood tests: A blood sample can check for signs of infections, blood sugar levels, or imbalances in body chemicals called electrolytes^[9].

Imaging tests: Head CT scan or MRI scan may be done to find the cause and location of the problem in the brain^[9].

Lumbar puncture (spinal tap): A sample of fluid surrounding the brain and spinal cord may be removed for testing^[9].

Treatment and Management

Some people who have a tonic-clonic seizure don’t have another one and don’t need treatment. However, someone who has repeated seizures may need treatment with daily medicines to control and prevent future seizures. Surgery and changes in diet may also be options to manage seizures^[2].

Several medicines called antiepileptic drugs (AEDs) or anticonvulsant medicines are used to treat generalised tonic-clonic seizures. The choice of medicine should be matched to each individual patient and the type of epilepsy, not just the seizure type^[10].

Commonly used medicines include^[10]:

• Valproic acid: Often considered a first choice for patients who have multiple seizure types, as it treats a broad range of seizure types
• Lamotrigine
• Topiramate
• Levetiracetam
• Phenytoin and carbamazepine: Used especially for seizures that start on one side of the brain and then spread
• Perampanel: Approved as additional treatment for primary generalised tonic-clonic seizures in adults and children aged 12 years or older

The selection of medicine must be personalized for each patient because of different side effects. For example, valproic acid can cause weight gain, so if a patient is already overweight, it might worsen that medical issue^[10].

Other treatment options may include^[10]:

• Vagus nerve stimulation: A device that sends electrical signals to the brain
• Ketogenic diet: A special high-fat, low-carbohydrate diet
• Surgery: In some cases, surgery may be considered

First Aid During a Seizure

Knowing how to help someone during a generalised tonic-clonic seizure is important. The following steps can help keep the person safe^[14][15]:

Stay calm and stay with the person. Most seizures stop on their own after a few minutes. Keep yourself and others calm. Remove anything nearby that could cause an injury^[15].

Protect from injury. Quickly look around for potential dangers such as furniture with sharp corners, hard surfaces, or objects that could pose a risk. Gently move objects away from the person to create a safe zone^[17].

Help them to the ground safely. If they appear to be falling, ease them to the ground^[15].

Turn them on their side. Place the person in a recovery position by turning them gently on their side, with their mouth pointing to the ground. This keeps their airway clear and prevents them from choking^[12][15].

Cushion their head. Put something soft and flat under their head, like a jacket^[15].

Loosen tight clothing. Remove eyeglasses and loosen anything around the neck that could block breathing^[15].

Time the seizure. Note when the seizure starts and how long it lasts^[12].

Check for medical information. Look to see if they are wearing a medical bracelet that has information about medical conditions, medicines, and emergency contacts^[15].

What NOT to do:

• Do not hold the person down or try to stop their movements. This could injure you or them^[15]
• Do not put anything in their mouth. This can hurt their teeth or jaw and cause harm^[3][15]
• Do not give mouth-to-mouth breaths during the seizure. People usually start breathing again on their own after a seizure^[15]
• Do not offer water or food until they are fully alert, as this could cause them to choke^[15]

After the seizure ends:

• Help them sit in a safe place to recover^[15]
• Once they are alert, comfort them and explain what happened^[15]
• Offer to call a friend or loved one to help them get home safely^[15]

When to Call for Emergency Help

Most seizures don’t require emergency medical attention. However, you should call emergency services (911 in the United States) if one or more of these things happen^[6][15]:

• The seizure lasts longer than 5 minutes
• They have another seizure soon after the first one without fully waking up between seizures
• They have trouble breathing or waking up after the seizure
• They are injured during the seizure
• The seizure happens in water
• The person has never had a seizure before
• The person has diabetes and loses consciousness
• The person is pregnant

A seizure that lasts over five minutes is called status epilepticus and is a medical emergency. Without quick treatment, it can cause brain damage or even death^[4][12].

Possible Complications

Complications from tonic-clonic seizures may include^[4]:

• Problems with thinking and memory (cognitive impairment)
• Heart disease
• Mental health conditions, such as anxiety and depression
• Sleep disorders
• Injuries from falls

The longer a seizure lasts, the more difficult it is to stop, and the greater the risk for permanent brain damage and death^[12].