Neonatal seizures: diagnosis and treatment

Neonatal seizures: stepping outside the comfort zone

Seizures are the most common neurological disorders in newborns. Managing neonatal seizures is challenging, especially for neurologists who are not neonatal specialists. Acute brain injury during ischemic insult is a key component of seizure occurrence, while genetic and metabolic disorders play less prevalent but more severe roles. The diagnosis of neonatal seizure is ambiguous, as the subjective differentiation between seizure and nonepileptic events is difficult; therefore, electrographic recording is the gold standard for diagnosis. The detection of electrographic seizures by neonatologists is currently facilitated by amplitude-integrated electroencephalography availability in many neonatal intensive care units. Although it is less sensitive than conventional electroencephalography, it is better to record all risky neonates to filter the abnormal events as early as possible to enable the initiation of dedicated therapy at proper dose and time and facilitate the initial response to antiepileptic drugs. This, in turn, helps maintain the balance between unnecessary drug use and their neurotoxic effects. Moreover, the early treatment of electrographic seizures plays a vital role in the suppression of subsequent abnormal brain electricity (status epilepticus) and shortening the hospital stay. An explicit understanding of seizure etiology and pathophysiology should direct attention to the proper prescription of short- and long-term antiepileptic medications to solve the challenging issue of whether neonatal seizures progress to postneonatal epilepsy and long-term cognitive deficits. This review addresses recent updates in different aspects of neonatal seizures, particularly electrographic discharge, including their definition, etiology, classification, diagnosis, management, and neurodevelopmental outcomes.

Independent role of neonatal seizures in subsequent neurological outcomes: a population-based study

AIM

This population-based study aimed to estimate the impact of neonatal seizures on subsequent neurological outcomes, regardless of underlying etiology.

METHOD

We performed a retrospective cohort study (1st January 2009-31st December 2014), using a USA nationwide claims database. Newborn infants enrolled in 2009 were followed for up to 6 years. Neonatal seizures were identified by combining the International Classification of Diseases, Ninth Revision, Clinical Modification diagnosis code of 779.0 (convulsions in newborn), procedure codes of electroencephalogram and brain imaging, and antiepileptic drugs claims. Cox regression models were built to estimate the independent impact of neonatal seizures on developing epilepsy, intellectual disability, psychiatric/behavioral disorders, and headache.

RESULTS

Out of 490 071 newborn infants (251 850 males [51.4%], 238 221 females [48.6%]), 800 neonatal seizure cases were identified. After controlling for sex, birthweight, preterm birth status, and underlying etiology, neonates with seizures were more likely to have epilepsy (hazard ratio=32.7; 95% confidence interval [CI]=27.7-38.7; p<0.001), intellectual disability (hazard ratio=2.0; 95% CI=1.8-2.3; p<0.001), and headache (hazard ratio=1.6; 95% CI=1.1-2.2; p=0.013) than those without seizures.

INTERPRETATION

Observed covariates being equal, seizures in neonates appeared to play a significant role in developing epilepsy, intellectual disability, and headache. The findings showed a detrimental impact of the event in the very early life on neurological outcomes in later life.

WHAT THIS PAPER ADDS

Seizures had their own impact on the development of adverse neurological outcomes. The magnitude of impact was quite large in epilepsy.

Phenobarbital use in an infant requiring extracorporeal membrane life support

Over the past two decades, there has been an increased use of extracorporeal membrane life support (ECLS) for critically ill neonates and infants. Approximately 20% of these children will experience seizures as a complication of ECLS or the comorbid condition which necessitated extracorporeal support. While phenobarbital is one of the most common drugs used to treat seizures in children, little is known about its dosing while on ECLS. We present a 3-month-old girl who required ECLS after cardiac arrest in the postoperative period following surgery for complex congenital heart disease. The patient subsequently developed seizure activity, which was treated with phenobarbital. Following an initial loading dose of 30 mg/kg, the serum concentration was 47.9 mcg/ml. A supplementary loading dose of 10 mg/kg was administered 8 h later with an increase of the maintenance dose to 8 mg/kg/day. The phenobarbital serum concentrations were 65.9 and 72.8 mcg/ml on the subsequent days. Despite therapeutic levels of phenobarbital, the patient continued to exhibit clinical and electroencephalographic evidence of seizure activity and a midazolam infusion was started at 0.3 mg/kg/h. Because of continued seizure activity, the patient ultimately required titration of midazolam to 1.2 mg/kg/h by day 7 of ECLS to control seizure activity. Due to severe intracerebral bleeding on day 9, ECLS was withdrawn and the patient expired. Our experience demonstrates some of the challenges of medication titration during ECLS. Previous reports of phenobarbital dosing during ECLS are reviewed and considerations for the dosing of anticonvulsant medications during extracorporeal support are discussed.

Neonatal Seizures: Gaps Between the Laboratory and the Clinic

Seizures in neonates (NBs) remain the most frequent neurological problem in the nursery. Considerable debate about their consequences exists between data and deductions reached through animal experimentations and those obtained through clinical investigations. The main conflicting issues are whether seizures in NBs can plant the roots for epileptogenesis and cause long-term deficits. The purpose of this chapter is to evaluate both laboratory and clinical results.

METHODS

Clinical data will be presented, including a 20-year-long cohort of NBs. This will be followed by the main seminal discoveries obtained in neonatal models. The phenomenon of transient or persistent dysmaturity following NB seizures will be discussed in relation to etiological factors.

RESULTS

The findings and deductions from animal models support the notions that epileptogenesis and cognitive deficits result from NB seizures. These conclusions contrast with clinical investigations maintaining that NB seizures, per se, are symptomatic markers of preexisting or of ongoing morbidities. The reasons for contrasting views will be discussed. Suggestions will be advanced for more animal models whose seizures are consistent with the etiologies and the phenotypes of human NB seizures.

Seizure recurrence and developmental disabilities after neonatal seizures: outcomes are unrelated to use of phenobarbital prophylaxis

This study investigated treatment patterns at discharge in infants with neonatal seizures and evaluated the impact of outpatient phenobarbital prophylaxis on the frequency of seizure recurrence and the long-term neurodevelopmental outcome at 1 to 11 years. Infants with neonatal seizures during a 12-year period were identified retrospectively (n = 146), and data were obtained by medical chart review. Outcomes were ascertained by standardized telephone survey. Thirty-three infants (23%) were taking phenobarbital, and 99 infants (68%) were taking no anticonvulsants at discharge. Comparisons were made between these 2 groups. Phenobarbital prophylaxis did not improve neurologic outcomes, either with respect to seizure recurrence or neurologic development. These data have important implications at a time when many are questioning the practice of prophylaxis after neonatal seizures and when newer anticonvulsants are being recommended for treatment of acute neonatal seizures.

X-linked lissencephaly with abnormal genitalia as a tangential migration disorder causing intractable epilepsy: proposal for a new term, "interneuronopathy"

X-linked lissencephaly with abnormal genitalia is the first human disorder in which deficient tangential migration in the brain has been demonstrated. Male patients with X-linked lissencephaly with abnormal genitalia show intractable seizures, especially clonic convulsions or myoclonus from the first day of life, but neither infantile spasms nor hypsarrhythmia on electroencephalograms so far. Brain magnetic resonance imaging shows anterior pachygyria and posterior agyria with a mildly thick cortex, agenesis of the corpus callosum, and dysplastic basal ganglia. ARX, a paired-class homeobox gene with four polyalanine sequences, is a responsible gene for X-linked lissencephaly with abnormal genitalia. The brain of Arx knockout mice shows aberrant tangential migration and differentiation of gamma-aminobutyric acid (GABA)ergic interneurons. In human X-linked lissencephaly with abnormal genitalia, a neuropathologic study has suggested a loss of interneurons. Meanwhile, polyalanine expansion of ARX causes symptomatic or nonsymptomatic West's syndrome and nonsyndromic mental retardation. The striking epileptogenicity of X-linked lissencephaly with abnormal genitalia and West's syndrome associated with ARX mutations i s considered to be caused by a disorder of interneurons involving a tangentialmigration disorder. We propose "interneuronopathy" as a term for this.

Phenytoin and phenobarbital stable isotope studies in neonates

A pharmacokinetic study of phenytoin and phenobarbital with nonradioactive isotopes was performed in nine neonates in an intensive care unit setting. A single-pulse dose of either labeled phenobarbital (1,3-(15)N, 2-(13)C) or labeled phenytoin (2-(13)C, 1, 3-(15)N) was administered to neonates who manifested gestation between 25 and 40 weeks and were receiving maintenance medication. Blood samples were collected at fixed intervals, and with a computerized gas chromatography mass spectrometry system, plasma concentrations of the labeled and unlabeled drug in relation to time administered were obtained. According to the calculations obtained from labeled analogue, several kinetic characteristics related to drug absorption, clearance, and elimination were determined. The use of a nonradioactive labeled isotope overcomes the limitations of conventional pharmacokinetic methodology and can be specifically useful in neonates and infants in whom volumes of distribution are rapidly changing and steady state is not achieved.

Prediction of outcome based on clinical seizure type in newborn infants

OBJECTIVE

To determine whether the clinical features of neonatal seizures are of value in predicting outcome.

STUDY DESIGN

Demographic features, clinical seizure types, etiologic factors, and laboratory findings of all 77 patients with seizures admitted to our neonatal intensive care unit over a consecutive 7-year period were extracted from the medical records.

RESULTS

Twenty-three (30%) died; 59% of the survivors had abnormal neurologic examinations, 40% were mentally retarded, 43% had cerebral palsy, and 21% were epileptic at mean follow-up of 3.5 years. Compared with patients with other seizure types, those with subtle and generalized tonic seizures had a significantly higher prevalence of epilepsy (P =.04 and P =.01 respectively); mental retardation (P =.02; P =.007), and cerebral palsy (P =.03; P =.002). Subtle seizures were, in addition, more likely to be associated with abnormalities on the neurologic examination at follow-up (P =.03). Similar outcome comparisons for those with focal and multifocal clonic, focal tonic, and multifocal myoclonic seizures revealed no significant differences. However, patients with >or=2 seizure types were significantly more likely to have epilepsy (P =.02), mental retardation (P =.001), cerebral palsy (P =.001), and abnormal examinations (P =.05).

CONCLUSIONS

Clinical semiology is predictive of outcome in neonates with seizures and suggests the presence of unique pathophysiologic processes for different seizure types.

Prenatal and perinatal determinants of neonatal seizures occurring in the first week of life

To evaluate prenatal and perinatal risk factors for early neonatal seizures, we conducted a case-control study including 100 newborns with neonatal seizures in the first week of life and 204 controls randomly selected from a list of healthy newborns born in the same hospital during the study period. Generalized tonic seizures were the most common seizures observed (29%), although the majority of newborns (71%) experienced more than one type of seizure. The most frequent presumed etiology of neonatal seizures was hypoxic-ischemic encephalopathy (30%). A history of epilepsy in first-degree relatives was found only for cases. Neonatal seizures were found to be associated with maternal disease in the 2 years before pregnancy, mother's weight gain > 14 kg during pregnancy, placental pathology, preeclampsia, low birthweight, low gestational age, and jaundice in the first 3 days of life. The need for cardiopulmonary resuscitation was found only for cases (37%). The causal pathways for neonatal seizures often begin before birth, and some of the factors identified may be preventable.

Neonatal seizures and neonatal epileptic syndromes

The neonatal period is defined as the first 28 days of life of a term infant; for premature infants the limit of this period is 44 completed weeks of the infant's conceptional age (CA)-defined as the chronological age plus gestational age (GA) at birth. The clinical and electroencephalographic (EEG) manifestations of seizures during this period are determined primarily by the development features of the immature brain at the time of seizure onset, but are also related to the type and diversity of etiologies and risk-factors for seizures neonates may face early in life. Neonatal seizures may be strikingly different from the clinical and electrical seizures of older children and adults. In addition, findings from basic science investigations suggest that immature animals are more likely to experience seizures in response to injury than more mature animals, although the developing brain is less susceptible to seizure-induced injury.

Phenytoin administration in the newborn and infant

To evaluate the efficacy and safety of phenytoin (PHT) in the treatment of situation-related seizures and epilepsies in the newborn and infant; the clinical histories of 82 patients were retrospectively reviewed. Sixty patients received for status epilepticus (SE), intravenous PHT followed by long-term oral administration for 27 of them. The other 22 patients had oral treatment only. Intravenous administration made 55% of these patients seizure-free, whereas oral administration produced lasting seizure control in only 9.1%. During chronic oral treatment, it was most difficult to obtain adequate plasma concentrations in 69.1% of the patients, and 43.6% had side effects, most of which were related to very high plasma concentrations. In conclusion, in the first 2 years of life, intravenous administration of PHT is useful for SE, but oral treatment is poorly effective with difficulty to achieve appropriate and stable therapeutic plasma concentrations, and with frequent side effects.

[Treatment of neonatal convulsions]

Three important measures are concommitantly recommended in the treatment of neonatal seizures. 1) The maintenance of vital functions by supplying oxygen and using mask ventilation in addition to cardiac monitoring and placing an intravenous line. 2) The search for an etiology through metabolic and infectious laboratory tests. In many cases this will lead to an etiological treatment. 3) The specific treatment of the seizures: intravenous or intrarectal diazepam is the first line treatment. Phenobarbital, then phenytoin and clonazepam are used when diazepam is unsuccessful. Indications and duration of a secondary prophylactic treatment are controversial and must be discussed on the basis of the electroencephalographic data and the risk factors for epileptic seizures during the neonatal period and at 3 months of age.

Neonatal seizures and electrographic analysis: evaluation and outcomes

Issues exist in the diagnosis, evaluation, management, and outcome of neonatal seizures. Electroencephalographic data are essential in the characterization, description, and classification of these events, as clinical inspection alone may lead to significant errors in underestimation or overestimation of seizures. This review discusses ictal characteristics of neonatal seizures as well as electrographic status epilepticus. The long-term benefit of treatment of electrographic seizures has never been proved. Prognosis is of critical concern in neonates with seizures and electroencephalographic data yield significant predictive information. Background analysis is most reliable in infants with normal or markedly abnormal recordings. Other ictal features may provide insight into specific outcomes (e.g., development of cerebral palsy). Mortality and neurologic morbidity (including postnatal epilepsy) remain major risks.