Neonatal seizure

A neonatal seizure is a seizure in a baby younger than age 4-weeks that is identifiable by an electrical recording of the brain.^[1] It is an occurrence of abnormal, paroxysmal, and persistent ictal rhythm with an amplitude of 2 microvolts in the electroencephalogram,.^[2] These may be manifested in form of stiffening or jerking of limbs or trunk. Sometimes random eye movements, cycling movements of legs, tonic eyeball movements, and lip-smacking movements may be observed. Alteration in heart rate, blood pressure, respiration, salivation, pupillary dilation, and other associated paroxysmal changes in the autonomic nervous system of infants may be caused due to these seizures. Often these changes are observed along with the observance of other clinical symptoms.^[3] A neonatal seizure may or may not be epileptic (due to a primary seizure disorder). Some of them may be provoked (i.e. due to a secondary cause). Most neonatal seizures are due to secondary causes.^[4] With hypoxic ischemic encephalopathy being the most common cause in full term infants and intraventricular hemorrhage as the most common cause in preterm infants.^[4]

According to the International League against Epilepsy (ILAE), seizures are defined as excessive or synchronous neuronal activity in the brain that is manifested as signs or symptoms. As per the classification system by the American Clinical Neurophysiology Society, seizures can be classified into electroclinical (clinical signs of a seizure and electrical brain monitoring signs of a seizure), clinical only, and electrographic-only seizures (signs of a seizure on electrical brain monitoring without clinical-visual signs of a seizure). Some infants, especially critically ill ones, may experience electrographic-only seizures.^[5][6]

Neonatal seizures have been classified into various types. Neonates were found to experience either tonic or clonic seizures. If seizures were found to be focal, they were further classified into unifocal or multifocal.^[7] Seizures in the neonatal population can be mainly categorized into acute symptomatic seizures and neonatal epilepsy that is related to genetic or structural factors.^[8] Brain injury due to hypo-ischemic encephalopathy, ischemic stroke, intracranial hemorrhage or infection, inborn errors of metabolism, transient metabolic and brain malformations, lead to acute symptomatic seizures.^[9] Neonatal epilepsy may be credited to genetic syndromes, developmental structural brain abnormalities, or metabolic diseases.^[10]

The incidence of seizures is more common in the neonatal stage than in other stages of life.^[11] Neonatal seizures are comparatively rare and affect 1 or 3.5 in 1000 infants born.^[12] They are the most frequent neurological problem in the nursery that is associated with greater risks of morbidity and mortality,^[13][14] often requiring evaluation and treatment in a neonatal intensive care unit. Better care delivered in neonatal care units, with improved healthcare facilities, has decreased the mortality rate associated with these seizures. However, the long-term morbidity rate remains approximately the same.^[15]

Neonatal seizures are generally subclinical and their diagnosis based on the clinical observations is generally difficult.^[16][17] Diagnosis relies on identification of the cause of the seizure, and verification of actual seizure activity by measuring electrical activity with electroencephalography (EEG). The set of guidelines developed by the American Clinical Neurophysiology Society helps the healthcare providers know when the EEG is appropriate and corresponds to the seizures.^[18] Treatment depends generally on the underlying cause of the seizure if it is provoked. anti-epileptic drugs are also administered.

Neonatal seizures that are provoked (due to a secondary cause) usually resolve in the neonatal period when the secondary cause is treated. Neonates with epilepsy syndromes often have seizures later in life.^[4] It has been estimated that approximately 15% of neonatal seizures represent epilepsy syndrome.^[19] The incidence of seizures is higher in the neonatal period than at any other time of life,^[20] and most often occurs in the first week of life.^[21]