Generalized Tonic-Clonic Seizure

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Overview, Causes, & Risk Factors

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 (this means the seizure has no identifiable cause)
  • usually beginning between ages 5 - 20
  • can occur at any age
  • no other neurologic abnormalities present
  • often a family history of epilepsy or seizures
• congenital defects (present from before birth) and perinatal injuries (occur near the time of birth)
  • seizures usually beginning in infancy or early childhood
• febrile seizure (children)
  • usually due to rapidly rising fevers in children
• Systemic illness
  • acute severe infections of any part of the body
  • chronic infections (such as neurosyphilis)
  • complications of AIDS or other immune disorders
• metabolic abnormalities
  • can affect people of any age
  • diabetes mellitus complications
  • electrolyte imbalances
  • kidney failure, uremia (toxic accumulation of wastes)
  • nutritional deficiencies
  • phenylketonuria (PKU)-- rarely causing seizures in infants
• brain injury
  • seizures are most likely if the brain membranes are damaged
  • seizures usually beginning within 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)
  • affecting any age, more common after age 30
  • partial (focal) seizures are most common initially
  • progressing to generalized tonic-clonic seizures
• use of alcohol or other recreational drugs, or withdrawal from alcohol or drugs
• low blood sodium or glucose
• disorders affecting the blood vessels (stroke, TIA), a common cause of seizures after age 60
• degenerative disorders (senile dementia Alzheimer type, or similar organic brain syndromes)
• nervous system infections (meningitis, encephalitis) or brain abscess

Risk factors include:

• any injury to the brain
• a family history of seizures
• severe medical problems that affect electrolytes
• exposure to illicit drugs and certain medications
• heavy alcohol use