Epilepsy is a chronic condition produced by temporary changes in the electrical function of the brain, causing seizures, which can affect awareness, movement, or sensation.

Seizures occur when clusters of nerve cells in the brain, called neurons, signal or communicate with each other abnormally. During a seizure, the neurons' normal pattern of activity is disturbed. It causes them to fire as many as 500 times per second instead of the normal rate of about 80 times per second. This can cause strange sensations, emotions, and behavior, or convulsions, muscle spasms, and/or loss of consciousness.

Neurons in Nerve Tissue

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A diagnosis of epilepsy is usually not made until a person has a seizure more than once without a preventable cause.

The causes of abnormal brain wiring and imbalance of neurotransmitters are numerous. They can include:

• Head injury
• Stroke
• Brain abnormalities inherited at birth
• Gene abnormalities inherited at birth
• Brain injury at birth
• Hypoxia at birth
• Loss of neurons in the hippocampus, also called mesial temporal sclerosis
• Brain tumors
• Alcohol use disorder
• Metabolic conditions, such as low blood sugar, very high blood sugar, low calcium, high or low sodium, or low magnesium
• Alzheimer's disease
• Heart failure
• Liver failure
• Kidney failure
• Sickle cell anemia
• Vasculitis, which can occur with health conditions, such as systemic lupus erythematous
• Any condition that deprives the brain of oxygen, such as near drowning
• Infectious diseases, such as:
  • Meningitis
  • AIDS
  • Viral encephalitis
  • Malaria
  • Tetanus
  • Brain abscess
  • Syphilis
  • Subacute sclerosing panencephalitis (SSPE)
• Hydrocephalus —excess fluid in the brain
• Celiac disease —intolerance to wheat gluten
• Exposure to:
  • Lead
  • Carbon monoxide
  • Other environmental toxins
  • Chemical warfare agents
• Certain illegal drugs, such as cocaine, amphetamines, phencyclidine
• Overdose of antidepressants and other medicines
• Withdrawal from alcohol, sedatives, and hypnotics
• Certain medications can lower the seizure threshold and thus increase the risk of seizures, such as:
  • Tricyclics
  • Theophylline
  • Penicillin
  • Phenothiazine
• In children:
  • High fever
  • Maternal infections
  • Poor nutrition
  • Vitamin B6 deficiency in neonates, infants
  • Lead poisoning
  • Hereditary, including genetic syndromes and metabolic disorders

In many cases, the exact cause of epilepsy is not known.