The ILAE classification of seizures and the epilepsies: Modification for seizures in the neonate

Seizures are the most frequent neurological emergency in the neonatal period. Unlike those in infancy and childhood, they often result from acute, identifiable causes and may be electrographic-only, making them challenging to fit into classification systems developed for older age groups. The International League Against Epilepsy (ILAE) established a Neonatal Seizures Task Force to create a modified classification of seizures and epilepsies specifically for neonates. The new framework highlights the crucial role of electroencephalography (EEG).

For this report, the following terms are used:

• Gestational age (GA): The time from the first day of the last menstrual period to the day of delivery, measured in completed weeks.
• Postmenstrual age (PMA): The sum of gestational age and chronological age, also measured in weeks.
• Preterm infant: An infant born before 37 weeks of gestation.
• Neonatal period: The time from birth to 44 weeks of postmenstrual age.

Introduction

Seizures are the most common neurological emergency during the neonatal period, affecting 1–5 out of every 1,000 live births. Most neonatal seizures are provoked by acute illnesses or brain injuries, with an underlying cause either known or suspected. These are known as acute provoked seizures, replacing the previous term "acute symptomatic." They do not meet the criteria for epilepsy, which is diagnosed when:

• At least two unprovoked seizures occur more than 24 hours apart.
• One unprovoked seizure occurs with a probability of additional seizures similar to the general recurrence risk after two unprovoked seizures.
• An epilepsy syndrome is diagnosed.

Epilepsy syndromes can manifest in the neonatal period, and with the increasing availability of genetic testing, more neonatal epilepsies with genetic and metabolic origins are being recognized.

While numerous factors can cause neonatal seizures, a relatively small number are responsible for the majority. These include hypoxic-ischemic encephalopathy. The classification of seizures in neonates is based on their predominant clinical features. Many neonatal seizures are solely electrographic, with no observable clinical symptoms.

Given that neonatal seizures typically have a focal onset, a division into focal and generalized seizures is unnecessary. Seizures can present with motor symptoms (such as automatisms, clonic movements, epileptic spasms, myoclonus, or tonic stiffness) or non-motor symptoms (including autonomic changes or behavior arrest). The classification allows users to choose the level of detail appropriate for their needs when categorizing seizures in this age group.