Neonatal seizure
Seizures in infants under 4 weeks, often subclinical and difficult to diagnose.
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A neonatal seizure is a seizure that occurs in an infant under four weeks old and is confirmed through an electroencephalogram (EEG), which detects abnormal, sudden, and ongoing brain activity with a voltage of at least 2 microvolts. These seizures can appear as stiffening or jerking of the limbs or trunk, or as more subtle signs like random eye movements, leg cycling, tonic eye movements, or lip-smacking. They may also cause changes in heart rate, blood pressure, breathing, salivation, or pupil dilation, often alongside other visible symptoms. Some neonatal seizures are epileptic, stemming from a primary seizure disorder, while others are provoked by a secondary cause. Most are provoked, with hypoxic ischemic encephalopathy being the most common cause in full-term infants and intraventricular hemorrhage in preterm infants.
The International League against Epilepsy defines seizures as excessive or synchronous neuronal activity that produces signs or symptoms. The American Clinical Neurophysiology Society classifies neonatal seizures into three types: electroclinical (with both clinical signs and EEG evidence), clinical only, and electrographic-only (EEG evidence without visible signs). Critically ill infants, in particular, may have electrographic-only seizures. Seizures in newborns are categorized as tonic or clonic, and if focal, as unifocal or multifocal. They mainly fall into two groups: acute symptomatic seizures, caused by brain injury from conditions like hypoxic-ischemic encephalopathy, stroke, hemorrhage, infection, metabolic errors, or brain malformations; and neonatal epilepsy, linked to genetic syndromes, structural brain abnormalities, or metabolic diseases.
Seizures are more common in the neonatal period than at any other stage of life, though they are still relatively rare, affecting 1 to 3.5 per 1,000 live births. They are the most frequent neurological issue in newborn nurseries and carry high risks of illness and death, often requiring care in a neonatal intensive care unit. Improved care in these units has lowered mortality, but long-term morbidity rates have stayed about the same. Neonatal seizures are often subclinical, making diagnosis based on observation difficult.
- Incidence
- 1 to 3.5 per 1000 infants
- Most common cause full term
- hypoxic ischemic encephalopathy
- Most common cause preterm
- intraventricular hemorrhage
- Classification types
- electroclinical, clinical only, electrographic-only
- Epilepsy syndrome proportion
- approximately 15% of neonatal seizures
- Benign familial neonatal seizure inciden
- 1 in 100,000 newborns
Lore & Background
Neonatal seizures may manifest as stiffening or jerking of limbs or trunk, or as subtle signs such as random eye movements, cycling leg movements, tonic eyeball movements, and lip-smacking. Autonomic changes including alteration in heart rate, blood pressure, respiration, salivation, and pupillary dilation may also occur. Most neonatal seizures are due to secondary causes, with hypoxic ischemic encephalopathy being the most common cause in full-term infants and intraventricular hemorrhage in preterm infants.
Reader's Guide
Neonatal seizures are more common in the neonatal stage than in other stages of life, yet they are comparatively rare. Diagnosis relies on electroencephalography because clinical observation alone is often difficult—many seizures are subclinical or electrographic-only. The American Clinical Neurophysiology Society provides guidelines for when EEG is appropriate. Treatment depends on the underlying cause if the seizure is provoked; anti-epileptic drugs are also administered. Better neonatal intensive care has decreased mortality, but long-term morbidity remains approximately the same. Approximately 15% of neonatal seizures represent epilepsy syndromes, and those with provoked seizures usually resolve when the secondary cause is treated.
Did You Know?
- Neonatal seizures can be classified as electroclinical, clinical only, or electrographic-only.
- Benign familial neonatal seizures are inherited in an autosomal dominant manner and often resolve after 1–4 months.
- Myoclonic seizures must be distinguished from benign neonatal sleep myoclonus, a common mimicker.
- Generalized tonic seizures often mimic decorticate posturing and most are not associated with electrographic seizures.
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