A generalized tonic-clonic seizure is a seizure involving the entire body, which usually involves muscle rigidity, violent muscle contractions, and loss of consciousness.

Generalized tonic-clonic seizures (also called grand mal seizures) are the type of seizure that most people associate with the term "seizure," convulsion, or epilepsy. They may occur in people of any age, as a single episode or as a repeated, chronic condition (epilepsy). The majority of seizures that do occur as just a single episode are generalized tonic-clonic seizures rather than other types.

Generalized seizures are caused by abnormal electrical activity at multiple locations in the brain and/or over a large area of the brain. This results in loss of consciousness and body stiffening, which is followed by shaking of the arms and legs.

Abnormal electrical activity may start in one part of the brain and cause isolated symptoms (see partial seizures). Sometimes this abnormal electrical activity spreads through the brain, resulting in a generalized seizure. Seizures can be caused by a specific area of the brain that is injured or inflamed, or they can be due to stress on the brain from a more widespread systemic process, such as severely low blood sugar.

Some of the more common causes of seizures include:

• Idiopathic seizures have no identifiable cause. They usually begin between ages 5 and 20, but can occur at any age. There are no other neurological problems, but the patient often has a family history of epilepsy or seizures.
• Congenital defects (present from before birth) and injuries that occur near the time of birth can cause seizures to begin in infancy or early childhood.
• Febrile seizure (in children) are usually caused by rapidly rising fevers in children.
• Acute severe infections of any part of the body, chronic infections (such as neurosyphilis), and complications of AIDS or other immune disorders can cause seizures.
• Seizures related to metabolic problems can occur at any age, and may be due to:
  • Diabetes mellitus complications
  • Electrolyte imbalances
  • Kidney failure, uremia (toxic accumulation of wastes)
  • Nutritional deficiencies
  • Phenylketonuria (PKU)-- rarely causing seizures in infants
  • Low blood sodium or glucose
• Brain injury usually causes seizures 2 years after the injury. Early seizures (within 2 weeks of injury) do not necessarily indicate that chronic seizures (epilepsy) will develop
• Tumors and brain lesions (such as hematomas) are more common after age 30. They most commonly cause partial (focal) seizures at first, then progress to generalized tonic-clonic seizures.
• Other causes include:
  • Use of alcohol or other recreational drugs, or withdrawal from alcohol or drugs
  • Disorders affecting the blood vessels (stroke, TIA), a common cause of seizures after age 60.
  • Degenerative disorders (senile dementia Alzheimer type)

Risk factors include:

• Any injury to the brain
• Family history of seizures
• Severe medical problems that affect electrolytes
• Using recreational drugs and certain medications
• Heavy alcohol use

Many patients have an aura (sensory warning sign) preceding the seizure. This can include a visual, taste, smell, sensory, or other hallucination or dizziness.

• Loss of consciousness or fainting, usually lasting between 30 seconds and 5 minutes
• General muscle contraction and rigidity (tonic posture), usually lasting 15-20 seconds
• Violent rhythmic muscle contraction and relaxation (clonic movement), usually lasting for 1-2 minutes
• Biting the cheek or tongue, clenched teeth or jaw
• Incontinence (loss of urine or stool control)
• Stopped breathing or difficulty breathing during seizure
• Blue skin color

Almost all people lose consciousness, and most people have both tonic and clonic muscle activity.

After the seizure, the person usually has:

• Normal breathing
• Sleepiness lasts for one hour or longer
• Loss of memory (amnesia) regarding events surrounding the seizure episode
• Headache
• Drowsiness
• Confusion, temporary and mild
• Weakness for 24-48 hours following seizure (Todd's paralysis)

Diagnosis of a grand mal seizure is based on the symptoms and excluding other medical problems that can look like a seizure (such as heart arrhythmia). A neuromuscular examination may or may not reveal neurologic deficits (decreases in brain functions) when the person is not actively having seizures.

An EEG may show characteristic changes and in some cases may show the focus (location of the cause of the seizure). An EEG can be normal in between seizures and a normal EEG does not rule out a seizure disorder.

Tests for the cause may include various blood tests (depending on the suspected cause), including:

• Complete blood count
• Blood chemistry, blood glucose
• Liver function tests
• Kidney function tests (BUN, creatinine, etc.)
• tests for infectious diseases (depending on the suspected cause)

• Head CT or MRI scan
• Lumbar puncture (spinal tap)

Disorders that may cause symptoms resembling seizures include transient ischemic attacks, rage, or panic attacks.