Conditions InDepth: Epilepsy
by Rick Alan
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
- Alcoholism
- 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, such as systemic lupus erythematous
- Any condition that deprives the brain of oxygen, such as near drowning
- Infectious diseases, such as:
- 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, phencylidine
- Overdose of antidepressants and other medicines
- Withdrawal from alcohol, sedatives, and hypnotics
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Certain medicines 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
- Lead poisoning
- B6 deficiency in neonates, infants
- Hereditary, including genetic syndromes and metabolic disorders
In many cases, the exact cause of epilepsy is not known.
REFERENCES:
Berkow R. The Merck Manual of Medical Information . 17th ed. New York, NY: Simon and Schuster; 2000.
Epilepsy in adults. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed . Updated February 18, 2013. Accessed February 22, 2013.
Epilepsy in children. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed . Updated November 19, 2012. Accessed February 22, 2013.
Lowenstein DH. Seizures and epilepsy. In: Longo DL, Fauci AS, Kasper DL, Hauser SL, Jameson JL, Loscalzo J, 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: http://www.ninds.nih.gov/disorders/epilepsy/epilepsy.htm . Updated February 21, 2013. Accessed February 22, 2013.
What is epilepsy? Epilepsy Foundation website. Available at: http://www.epileps... . Accessed February 22, 2013.
Last reviewed March 2013 by Rimas Lukas, MD
Last Updated: 3/15/2013