Epilepsy causes brief changes in the electrical activity of the brain. Clumps of nerve cells in the brain (neurons) message each other in a way that is not normal. These are called seizures.

The neurons fire as many as 500 times per second instead of about 80 times per second. This can cause strange feelings, emotions, and actions. It can also cause shaking, muscle spasms, and loss of consciousness.

Neurons in Nerve Tissue Copyright © Nucleus Medical Media, Inc.

The diagnosis is made after a person has a seizure more than one time without a cause that could have been prevented.

Epilepsy may be from:

• A problem with your nerves and blood vessels:
  • Stroke
  • Brain injury at birth
  • Lack of oxygen (hypoxia) at birth
  • Loss of neurons in part of the brain
• Problems found at birth:
  • Brain abnormalities
  • Gene abnormalities
• Growths, such as brain tumors
• A breakdown of the nervous system in the brain, such as Alzheimer disease
• Some health problems:
  • Head injury
  • Metabolism problems, such as low blood glucose, very high blood glucose, low calcium, high or low sodium, or low magnesium
  • Heart failure
  • Liver failure
  • Kidney failure
  • Sickle cell anemia
  • Alcohol use disorder
• Problems with the body's immune system:
  • NMDA receptor encephalitis and health problems like it
  • Paraneoplastic syndromes from cancer
  • Vasculitis, which can happen with problems like lupus
• Any problem that keeps oxygen from getting to the brain, such as near drowning
• Diseases that can spread, such as:
  • Meningitis
  • AIDS
  • Viral encephalitis
  • Malaria
  • Tetanus
  • Brain abscess
  • Syphilis
  • Subacute sclerosing panencephalitis
• Hydrocephalus —too much fluid in the brain
• Celiac disease —an immune disease in which people cannot eat wheat gluten
• Exposure to:
  • Lead
  • Carbon monoxide
  • Other toxins
  • Chemical warfare agents
• Certain illegal drugs, such as cocaine, amphetamines, and phencyclidine
• Overdose of antidepressants and other medicines
• Withdrawal from alcohol, sedatives, and hypnotics
• Certain medicines can lower the seizure threshold and raise the risk of seizures, such as:
  • Tricyclics
  • Theophylline
  • Penicillin
  • Phenothiazine
• In children:
  • High fever
  • Infections in the mother
  • Not eating the right foods
  • Not enough vitamin B6 in newborns and infants
  • Lead poisoning
  • Hereditary, including genetic and metabolic problems

In many people, the cause is not known.