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Occult neonatal seizures
R R Clancy1, A Legido, D Lewis
1Division of Neurology, Children's Hospital of Philadelphia, PA 19104.
Insights
Most neonatal seizures are subclinical, meaning they are not visible to the naked eye. Routine electroencephalogram (EEG) monitoring is crucial for accurately diagnosing neonatal seizures and assessing treatment effectiveness.
Area of Science:
- Neonatal neurology
- Clinical neurophysiology
Background:
- Neonatal seizures are a significant concern in clinical practice.
- Accurate detection of electrographic seizures is essential for effective management.
- Previous studies suggest a discrepancy between electrographic and clinical seizure manifestations.
Purpose of the Study:
- To determine the frequency of occult (subclinical) electrographic seizures in neonates.
- To investigate the relationship between seizure duration and clinical visibility.
- To examine the influence of neonatal mental status on the clinical detection of seizures.
Main Methods:
- Analysis of routine electroencephalogram (EEG) recordings from 41 infants with neonatal seizures.
- Correlation of electrographic seizure events with observed clinical seizure activity.
- Assessment of seizure duration and infant mental status (consciousness level).
Main Results:
- The majority of electrographic seizures (79%) were occult, lacking distinctive clinical signs.
- Only 21% of electrographic seizures were accompanied by visible clinical activity.
- No significant differences were found in seizure duration or the proportion of occult seizures based on infant consciousness levels.
Conclusions:
- Unaided clinical observation significantly underestimates the true frequency of neonatal seizures.
- Long-term EEG monitoring is recommended for accurate seizure frequency assessment and treatment evaluation in neonates.
- Subclinical seizures may require specific therapeutic considerations.
Abstract:
Forty-one infants with neonatal seizures frequent enough to be captured by randomly recorded routine EEG examinations were studied to determine how often their electrographic seizures were occult (subclinical) and to examine the effects of seizure duration and mental status on their clinical visibility. Seizures were the result of diverse etiologies and most infants had received one or more antiepileptic drug prior to the EEG recordings. The majority of electrographic seizures were occult: only 84 of 393 (21%) were accompanied by distinctive clinical seizure activity; the remaining 79% were occult. There was no significant difference between the duration of EEG seizures with distinctive clinical signs and those without. There was no significant difference in the proportion of occult seizures in neonates with preserved consciousness compared with lethargic or comatose infants. We conclude that unaided visual inspection of infants seriously underestimates true seizure frequency. Long-term EEG monitoring may be necessary in many infants to determine their real seizure frequency and to judge the adequacy of antiepileptic drug treatment.