What is the role of electroencephalogram in the diagnosis of pediatric first seizure?

Updated: Aug 16, 2018
  • Author: Shelley R Waite, MD; Chief Editor: Amy Kao, MD  more...
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Answer

Electroencephalogram (EEG) can be useful in the acute setting if there is a concern for subclinical seizures (electrographic seizures without clinical correlate) or if the patient has persistent altered mental status. An EEG is also important if a nonreactive patient received paralytics for intubation and does not show awakening in the critical care unit after an expected timeframe. Clinical signs such as appropriate pupil reactivity and withdrawal to pain/stimulation can be helpful clues that the patient is not in continuous nonconvulsive status epilepticus. Long-term (24 h or greater) EEG monitoring should be considered to identify nonconvulsive seizures in at-risk patients, including infants or children with persistent unexplained altered mental status.

If the child is clinically stable, it may not be necessary to perform the EEG on an emergent basis. However, EEGs are an important tool in determining prognosis (see Long-Term Prognosis) for future seizures and should be strongly considered for all children with a first seizure on a nonurgent basis. [6] In the nonacute setting, there is still debate as to whether an EEG performed within the first 24 hours is more sensitive to identify epileptiform abnormalities. However, current practice does not mandate early EEG, as untreated patients with epilepsy tend to have persistent EEG abnormalities. EEG yield can be increased by including sleep and activating procedures, such as hyperventilation and photic stimulation. If there is a high suspicion for a seizure disorder and routine EEG is normal, repeat EEG or prolonged EEG monitoring can be obtained. Repeating the EEG a second time may increase the sensitivity to 80–90%. [8]

It is important to remember that an EEG does not determine whether the patient had a seizure, as this is a clinical diagnosis. EEGs may be abnormal in up to 10% of healthy individuals, and 50% of patients with epilepsy have a normal first EEG. EEGs can be helpful in classifying seizure types and identifying epilepsy syndromes with specific electroclinical features, such as benign rolandic epilepsy or juvenile myoclonic epilepsy. This classification system can help both with prognosis and determining appropriate anticonvulsant therapy. For more information regarding EEG findings in specific childhood epilepsy syndromes, see EEG in Common Epilepsy Syndromes.


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