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 injuryStrokeBrain abnormalities inherited at birthGene abnormalities inherited at birthBrain injury at birthHypoxia
Loss of neurons in the hippocampus, also called mesial temporal sclerosisBrain tumorsAlcohol use disorder
Metabolic conditions, such as
low blood sugar
, very high blood sugar, low calcium, high or low sodium, or low magnesium
Alzheimer's diseaseHeart failureLiver failureKidney failureSickle cell anemia
Vasculitis, such as
systemic lupus erythematous
Any condition that deprives the brain of oxygen, such as
Infectious diseases, such as:
MeningitisAIDSViral encephalitisMalariaTetanusBrain abscessSyphilisSubacute sclerosing panencephalitis
—excess fluid in the brain
—intolerance to wheat gluten
LeadCarbon monoxideOther environmental toxinsChemical warfare agents
, such as
, amphetamines, phencyclidine
Overdose of antidepressants and other medicines
alcohol, sedatives, and hypnotics
Certain medications can lower the seizure threshold and thus increase the risk of seizures, such as:
High feverMaternal infectionsPoor nutritionLead poisoningB6
deficiency in neonates, infants
Hereditary, including genetic syndromes and metabolic disorders
In many cases, the exact cause of epilepsy is not known.
Lowenstein DH. Seizures and epilepsy. In: Longo DL, Fauci AS, et al, eds.
Harrison's Principles of Internal Medicine.
18th ed. New York, NY: McGraw-Hill; 2012.
NINDS epilepsy information page. National Institute of Neurological Disorders and Stroke website. Available at:
Updated February 21, 2013. Accessed February 22, 2013.
Seizure disorders. Merck Manual Professional Version website. Available at: http://www.merckmanuals.com/professional/neurologic-disorders/seizure-disorders/seizure-disorders. Updated May 2012. Accessed February 22, 2013.
What is epilepsy? Epilepsy Foundation
website. Available at:
http://www.epilepsy.com/learn/epilepsy-101/what-epilepsy. Accessed February 22, 2013.
Last reviewed March 2016 by Rimas Lukas, MD
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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