Neonatal seizures are seizures that occur in an infant during the first 28 days after birth. If the infant was born prematurely, the neonatal period is longer, and in a premature infant it extends to 44 weeks after the date of conception, regardless of the date of birth. Less than half of neonates who have seizures will go on to have seizures later in life, but neonatal seizures are often a sign of neurological dysfunction. They are a risk factor for neonatal mortality and the development of a cognitive or physical disability.
Seizures occur when a large group of neurons become depolarized at the same time. Depolarization means that the neurons have cell membrane changes that alter their net charge, causing the cells to transmit abnormal electrical signals to one another. The result of this is a change in electrical activity in these cells, which temporarily prevents normal function. Different types of seizures result, depending on the pattern of abnormal electrical activity.
Neonatal seizures occur with the greatest frequency in the first 10 days after birth. Neonates who have seizures often fail to thrive, are lethargic between seizures and appear to be generally ill. Many neonates appear neurologically normal between seizures; when abnormalities are noted, they are likely to be associated with a particular neurological syndrome.
There are many disorders and diseases that can cause neonatal seizures. These include metabolic disorders, infection, seizure syndromes and genetic disorders. One common cause of seizures in neonates is ischemia, the lack of oxygen. Ischemic seizures occur when the brain is deprived of oxygen and can develop in both premature and term neonates, most often in the first three days after birth. Another frequent cause is intracranial hemorrhage, a condition that is more common in premature neonates.
Neonatal intracranial infections such as encephalitis and meningitis are an important cause of early neonate seizures. Metabolic disorders which might cause seizures include dangerously low levels of blood glucose, calcium and magnesium. These disorders most often cause neonatal seizures after the first three days. Brain deformities are an uncommon cause of seizures in neonates; abnormal brain structure typically causes seizures later in life, but certain structural disorders can cause seizures within the first 28 days.
Seizures that occur in neonates are often treated with anti-seizure medication even if a diagnosis has not been made. The infant is then monitored for several months to determine when medication can safely be discontinued. Diagnostic tests might include an electroencephalogram to monitor patterns of electrical activity in the brain and blood tests to examine brain and body chemistry. Most infants also receive additional follow-up care to determine whether the seizures are an isolated occurrence or part of a syndrome or disorder.