Epilepsy

Alternative names:

seizure disorder

Definition:

A brain disorder involving recurrent seizures.

Causes, incidence, and risk factors:

A seizure disorder includes any condition in which there are repeated episodes of seizures of any type. Epilepsy (idiopathic seizure disorder) is a term used when the seizure disorder has no identifiable cause such as brain disease. A seizure disorder affects about 0.5% of the population. It can affect people of any age.

Transmission of information from nerve cell to nerve cell occurs by an electrochemical process. This process can be detected as electrical activity by an electroencephalograph (EEG). Abnormal patterns of electrical activity are associated with seizures.

The cause of the seizure correlates to some extent with the age of onset. In some people, seizures may be triggered by hormone changes such as pregnancy or menstruation. They may also be triggered by illness or by sensory stimuli such as lights, sounds, and touch. In many cases, no trigger is found for the seizures. Given sufficient circumstances, any person will have a seizure. The amount of stimulation required to cause a seizure is called the seizure threshold. Many people with epilepsy are considered to have a low seizure threshold.

Some of the more common causes of seizures include:

• Idiopathic (no identifiable cause)
  • usually begin between ages 5 to 20
  • can occur at any age
  • no other neurologic abnormalities present
  • often a family history of epilepsy or seizures

• Congenital defects and perinatal (near the time of birth) injuries--seizures usually begin in infancy or early childhood
• Metabolic abnormalities
  • may affect any age
  • diabetes mellitus complications
  • electrolyte imbalances
  • kidney failure, uremia (toxic accumulation of wastes)
  • nutritional deficiencies
  • phenylketonuria (PKU)--can rarely cause seizures in infants
  • use of or intoxication from alcohol or drugs
  • withdrawal from alcohol
  • withdrawal from drugs

• Brain injury
  • may affect any age, highest incidence in young adults
  • most likely if the brain membranes are damaged
  • seizures usually begin 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 that occupy space (such as hematomas)
  • may affect any age, more common after age 30
  • partial (focal) seizures most common initially
  • may progress to generalized tonic-clonic seizures

• Disorders affecting the blood vessels (stroke, TIA, and so on)
  • most common cause of seizures after age 60

• Degenerative disorders (senile dementia Alzheimer type, or similar organic brain syndromes)
  • mostly affect older people

• Infections
  • may affect all ages
  • may be a reversible cause of seizures
  • brain infections (meningitis, encephalitis)
  • brain abscess
  • acute severe infections of any part of the body
  • chronic infections (such as neurosyphilis)
  • complications of AIDS or other immune disorders

There may be changes in mental status (such as alertness and awareness) and/or focal neurologic symptoms (localized symptoms of changes in brain function) associated with the seizures. The type of seizure that occurs varies depending on the location and type of the problem causing the seizure and with individual response to the problem.

Seizures may occur in a generalized form (affecting all or most of the brain) or in a partial form (affecting only a portion of the brain). Epilepsy is typically generalized (except in some cases that develop in childhood and have a specific focus). Generalized seizures include variations of generalized tonic-clonic seizures and petit mal seizures. Partial seizures include focal seizures (during which the person remains alert but there are abnormal movements or sensations) and partial complex seizures (during which the abnormal movement or sensation is accompanied by changes in consciousness).