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Interictal Epileptiform Discharges in Persons Without A History of Seizures: What Do They Mean?

So, Elson L.

Journal of Clinical Neurophysiology: August 2010 - Volume 27 - Issue 4 - p 229-238
doi: 10.1097/WNP.0b013e3181ea42a4
Invited Review

Interictal epileptiform discharge (IED) is rarely observed in healthy volunteers without a history of seizures, but higher rates of occurrence are reported in children than in adults. Higher rates are also observed among neurologic inpatients and outpatients without a seizure history, but the risk of subsequent unprovoked seizures or epilepsy is low in healthy volunteers and patients. An exception is the patients with autism spectrum disorders, attention deficit/hyperactivity disorder, or cerebral palsy, who are predisposed to epilepsy development. However, it is currently unclear whether epilepsy risk is higher for patients with incidentally detected IED than for the patients without IED. Hospitalized patients with IED but no prior seizures often have underlying acute or progressive brain disorders. Although they have increased risk of acute seizures, the risk for subsequent unprovoked seizures or epilepsy is unknown and requires assessment on an individual basis. For patients who have psychogenic spells but no seizure history, the rate of IED detection is low, similar to that of healthy volunteers. The association between IED and transitory cognitive impairment has not been established in nonepileptic persons. Evidence thus far does not suggest that routine EEG screening of pilot candidates reduces risk of flight-related accidents.

From the Department of Neurology, Mayo Clinic, Rochester, Minnesota, U.S.A.

Address correspondence and reprint requests to Elson L. So, MD, Department of Neurology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, U.S.A.; e-mail:

Copyright © 2010 American Clinical Neurophysiology Society