Neonatal seizures and electrographic analysis: evaluation and outcomes

Classification of clinical semiology in epileptic seizures in neonates

The clinical semiology of 61 neonatal seizures with EEG correlates, in 24 babies was analysed. Most seizures (89%) had multiple features during the EEG discharge. The seizures were classified using the prominent clinical feature at onset, and all features seen during the seizure, using an extended classification scheme. Orolingual features occurred most frequently at onset (30%), whereas ocular phenomena occurred most often during the seizure (70%). Orolingual, ocular and autonomic features were seen at onset in 55% of the seizures. Seizure onsets with clonic, tonic and hypomotor features were seen in 20%, 8% and 18% respectively. Clinico-electrical correlations were as follows. The EEG discharge involved both hemispheres in 54% of all seizures, in clonic seizures this was 93%. Focal clonic seizures were associated with EEG seizure onset from the contralateral hemisphere. Majority of the clonic and hypomotor seizures had a left hemisphere ictal EEG onset. Orolingual seizures frequently started from the right hemisphere, whereas ocular and autonomic seizures arose from either hemisphere. There was no significant difference in mortality, morbidity, abnormal neuroimaging and EEG background abnormalities in babies with or without clonic seizures. This study provides insights into neuronal networks that underpin electroclinical seizures, by analysing and classifying the obvious initial clinical features and those during the seizure.

Ictal electroencephalograms in neonatal seizures: characteristics and associations

The characteristics of ictal electroencephalograms in 160 neonatal seizures of 43 babies were correlated with mortality and neurodevelopmental outcomes. Neonatal seizures are focal at onset, most frequently temporal, and often occur during sleep. Twenty-one percent of babies with seizures died, and 76% of survivors manifested neurodevelopmental impairment during 2-6-year follow-up. A low-amplitude ictal electroencephalogram discharge was associated with increased mortality, and a frequency of <2 Hz with increased morbidity. Status epilepticus, ictal fractions, multiple foci, and bihemispheric involvement did not influence outcomes. Of 160 seizures, 99 exhibited no associated clinical features (electrographic seizures). Neonatal seizures with clinical correlates (electroclinical seizures) exhibited a higher amplitude and frequency of ictal electroencephalogram discharge than electrographic seizures. During electroclinical seizures, the ictal electroencephalogram was more likely to involve larger areas of the brain and to cross the midline. Mortality and morbidity were similar in babies with electroclinical and electrographic seizures, emphasizing the need to diagnose and treat both types. Ictal electroencephalogram topography has implications for electrode application during limited-channel, amplitude-integrated electroencephalograms. We recommend temporal and paracentral electrodes. Video electroencephalograms are important in diagnosing neonatal seizures and providing useful information regarding ictal electroencephalogram characteristics.

Management of neonatal seizures

Seizures in the newborn period constitute a medical emergency. Subtle seizures are the commonest type of seizures occurring in the neonatal period. Myoclonic seizures carry the worst prognosis in terms of long-term neurodevelopmental outcome. Hypoxic-ischemic encephalopathy is the most common cause of neonatal seizures. Multiple etiologies often co-exist in neonates and hence it is essential to rule out common causes such as hypoglycaemia, hypocalcemia, and meningitis before initiating specific therapy. A comprehensive evidence based approach for management of neonatal seizures has been described in this protocol.

Neurodevelopmental outcomes in neonates with seizures: a numerical score of background encephalography to help prognosticate

There is a high incidence of mortality and neurodevelopmental sequelae in babies with neonatal seizures. The electroencephalography (EEG) background has been shown to be an excellent predictor of outcome by most studies, with a few suggesting limited value in prognostication. Previous studies suggest poor prognosis with severely abnormal backgrounds, but prediction was difficult with moderate abnormalities. The proposed numerical scoring system for the EEG background provides an objective method of evaluation with improved reproducibility, categorization, and prognostication. Our study showed that the numerical score of EEG background was a good predictor of outcome. Higher numerical scores reflecting greater abnormality of background EEG were associated with increasing incidence of mortality, neurodevelopmental impairment, cerebral palsy, vision and hearing impairment, and epilepsy. The numerical score also correlated with neuroimaging abnormalities. A numerical EEG score can help target interventional strategies for neonatal seizures.

Development of epilepsy in newborns with moderate hypoxic-ischemic encephalopathy and neonatal seizures

BACKGROUND

Hypoxic-ischemic encephalopathy (HIE) is one of the most frequent causes of neonatal death or neurological handicaps such as cerebral palsy, mental delay, and epilepsy. Moreover, an acute consequence of HIE are neonatal seizures which can cause an additional brain damage. The neurodevelopmental outcome is known in the mild or severe cases of HIE, but in the moderate conditions the predictivity results, to date, unsatisfying.

OBJECTIVE

The purpose of this prospective study was to appraise the development of post-neonatal epilepsy in a cohort of term infants with moderate HIE and neonatal seizures.

METHODS

This study considered all newborns admitted to Neonatal Intensive Care Unit of the University of Parma between January 2000 and December 2002 for perinatal asphyxia, then followed by Neonatal Neurology Service. In all patients, neonatal variables such as type of delivery, birth weight, gestational age, Apgar scores, the need for resuscitation and assisted ventilation soon after birth, and arterial-blood pH were analyzed.

RESULTS

Ninety-two newborns were enrolled in the study because of perinatal asphyxia. Of these, 27 subjects developed mild HIE, 25 moderate, and five severe HIE. Neonatal seizures were present in 13 subjects with moderate HIE and in all newborns with severe HIE. At the last follow-up, only three infants belonging to patients with severe HIE developed epilepsy.

CONCLUSION

Moderate HIE seems not to be related to post-neonatal epilepsy either if associated or not with neonatal seizures.

Seizures in the newborn

Seizures in the newborn period constitute a medical emergency. Subtle seizures are the commonest type of neonatal seizures, other types being clonic, tonic, and myoclonic. Myoclonic seizures carry the worst prognosis in terms of long-term neurodevelopmental outcome. Hypoxic-ischemic encephalopathy is the most common cause of neonatal seizures. Multiple etiologies often co-exist in neonates and hence it is essential to rule out conditions such as hypoglycemia, hypocalcemia, and meningitis before initiating specific therapy. A comprehensive approach for management of neonatal seizures has been described.

A single episode of neonatal seizures permanently alters glutamatergic synapses

OBJECTIVE

The contribution of seizures to cognitive changes remains controversial. We tested the hypothesis that a single episode of neonatal seizures (sNS) on rat postnatal day (P) 7 permanently impairs hippocampal-dependent function in mature (P60) rats because of long-lasting changes at the synaptic level.

METHODS

sNS was induced with subcutaneously injected kainate on P7. Learning, memory, mossy fiber sprouting, spine density, hippocampal synaptic plasticity, and glutamate receptor expression and subcellular distribution were measured at P60.

RESULTS

sNS selectively impaired working memory in a hippocampal-dependent radial arm water-maze task without inducing mossy fiber sprouting or altering spine density. sNS impaired CA1 hippocampal long-term potentiation and enhanced long-term depression. Subcellular fractionation and cross-linking, used to determine whether glutamate receptor trafficking underlies the alterations of memory and synaptic plasticity, demonstrated that sNS induced a selective reduction in the membrane pool of glutamate receptor 1 subunits. sNS induced a decrease in the total amount of N-methyl-D-aspartate receptor 2A and an increase in the primary subsynaptic scaffold, PSD-95.

INTERPRETATION

These molecular consequences are consistent with the alterations in plasticity and memory caused by sNS at the synaptic level. Our data demonstrate the cognitive impact of sNS and associate memory deficits with specific alterations in glutamatergic synaptic function.

The current etiologic profile and neurodevelopmental outcome of seizures in term newborn infants

OBJECTIVES

The objectives of this study were to delineate the etiologic profile and neurodevelopmental outcome of neonatal seizures in the current era of neonatal intensive care and to identify predictors of neurodevelopmental outcome in survivors.

METHODS

Eighty-nine term infants with clinical neonatal seizures underwent neurologic examination, electroencephalography (EEG), neuroimaging, and extensive diagnostic tests in the newborn period. After discharge, all infants underwent regular neurologic evaluations and, at 12 to 18 months, formal neurodevelopmental testing. We tested the prognostic value of seizure etiology, neurologic examination, EEG, and neuroimaging.

RESULTS

Etiology was found in 77 infants. Global cerebral hypoxia-ischemia, focal cerebral hypoxia-ischemia, and intracranial hemorrhage were most common. Neonatal mortality was 7%; 28% of the survivors had poor long-term outcome. Association between seizure etiology and outcome was strong, with cerebral dysgenesis and global hypoxia-ischemia associated with poor outcome. Normal neonatal period/early infancy neurologic examination was associated with uniformly favorable outcome at 12 to 18 months; abnormal examination lacked specificity. Normal/mildly abnormal neonatal EEG had favorable outcome, particularly if neonatal neuroimaging was normal. Moderate/severely abnormal EEG, and multifocal/diffuse cortical or primarily deep gray matter lesions, had a worse outcome.

CONCLUSIONS

Mortality associated with neonatal seizures has declined although long-term neurodevelopmental morbidity remains unchanged. Seizure etiology and background EEG patterns remain powerful prognostic factors. Diagnostic advances have changed the etiologic distribution for neonatal seizures and improved accuracy of outcome prediction. Global cerebral hypoxia-ischemia, the most common etiology, is responsible for the large majority of infants with poor long-term outcome.

Wavelet analysis for neonatal electroencephalographic seizures

Electroencepholographs (EEGs) of neonatal seizures differ from those of children and adults. This study evaluated whether wavelet transform analysis, a nonstationary frequency analysis of EEG, can recognize and characterize neonatal seizures. Twenty-second segments were analyzed from 69 EEG seizures in 15 neonatal patients whose seizures lasted 10 seconds or longer. The wavelet transform results were examined, as were EEG seizure durations and dominant frequencies. The wavelet transform results were correlated with the occurrence, after an 18-month follow-up, of postneonatal seizures. Wavelet transform analysis identified 40 seizures (58%) with a "sustained dominant frequency component" that lasted 10 seconds or longer and 29 seizures without a sustained dominant frequency component. The mean seizure duration of the 40 seizures with sustained dominant frequency components was 63.3 seconds, longer than the mean duration (33.6 seconds) of the seizures without sustained dominant frequency components, P < 0.01. Eleven patients manifested postneonatal epileptic seizures. Fifty-two EEG seizures in these 11 patients revealed more sustained dominant frequency components (74%) than 17 seizures in the 4 patients without postneonatal seizures (only 12%), P < 0.05. Wavelet transform analysis can identify neonatal EEG seizures and characterize their epileptic components. The presence of sustained dominant frequency components may predict postneonatal epileptic seizures.

Seizures in the newborn

Seizures in the newborn period constitute a medical emergency. Subtle seizures are mild paroxysmal alterations in motor or autonomic activity and are unique to the neonatal period. They are likely to be missed or confused with benign movements observed commonly in preterm children. Focal clonic seizures have a better prognosis as compared to myoclonic seizures for long-term neuro-developmental outcome. Seizures due to sub-arachnoid hemorrhage and late onset hypocalcemia carry a better prognosis as compared to seizures due to hypoglycemia, meningitis and cerebral malformations. Hypoglycemia and hypocalcemia are common causes and should be excluded in all neonates with seizures. Multiple etiologies can co-exist in neonatal seizures and a comprehensive approach for management of neonatal seizures has been described.

Epilepsy in children with cerebral palsy

Epilepsy occurs in 15-60% of children with cerebral palsy; however, its clinical course is not well defined. This retrospective study reviewed the prevalence, nature, and prognosis of epilepsy in cerebral palsy. Thirty-two of 85 children with cerebral palsy seen in the Neurodevelopmental Clinic in Tuen Mun Hospital between 1990 and 1995 had epilepsy. A control group of 59 epileptic children with normal neurodevelopment status was seen during the same period. Epilepsy most commonly affected patients with spastic tetraplegia and those with mental subnormality. When compared with controls, children with cerebral palsy had a higher incidence of epilepsy with onset within the first year of age (47% vs 10%), history of neonatal seizures (19% vs 3%), status epilepticus (16% vs 1.7%), polytherapy (25% vs 3%), and treatment with second-line antiepileptic drugs (31% vs 6.7%). They had a lower incidence of generalized seizures (28% vs 59%) and remaining seizure free (37% vs 90%). Factors associated with a seizure-free period of 1 year or more in epileptic children with cerebral palsy were normal intelligence, single seizure type, monotherapy, and spastic diplegia. Epilepsy was common in children with cerebral palsy. Further larger studies are required to delineate other prognostic factors.

Regional cerebral blood flow during seizures in neonates

With the use of 99mTc-D, L,-hexamethylpropylenamine oxime and single photon emission computed tomography, regional cerebral blood flow was measured ictally in 12 mature infants with recurrent seizures and compared with a reference group of nine interictal studies. The study indicates that both clinical and electrical seizures in neonates are associated with a focal cerebral hyperperfusion of the same amount as seen in adults.

Ictal and interictal SPECT in a newborn infant with intractable seizure

Neonatal seizures can be difficult to classify according to partial vs generalized onset based on clinical appearance, electroencephalogram (EEG) or other adjunctive imaging techniques. Single-photon emission computed tomography (SPECT) has proven to be useful in adults; however, its use is limited in the paediatric age group, particularly in neonates. A case of a 12-d-old infant with intractable seizures is reported, on whom an interictal Tc-99m HMPAO SPECT showed an area of hypoperfusion in the left temporal cortex, whereas the ictal SPECT revealed prominent hyperperfusion in the same area. The EEG of the infant demonstrated generalized epileptiform activity, while computed tomography and magnetic resonance (MR) imaging findings were normal. This case indicates that the use of SPECT may provide valuable data in evaluation of neonatal seizures, particularly with poorly localized EEG changes and normal MRI scans.

Status epilepticus in children and adults

Status epilepticus (SE) in children and adults is one of the most common neurology problems confronting the intensivist. Recognition of SE is usually straightforward, but may be complicated by the effects of other diseases or therapies. Emergent treatment is necessary to prevent further brain damage. This article reviews protocols for standard treatments of SE patients and includes recommendations for the management of refractory SE.

The contribution of EEG to the understanding of neonatal seizures

The neonatal EEG is a thread that has linked past and present studies of neonatal seizures that have emerged over the last several decades. Instead of experiencing a waning of value or interest, the neonatal EEG has grown in significance for characterization and quantification of seizures in the neonate. At present, it serves as the ideal theoretical end point of antiepileptic drug (AED) therapy and provides invaluable prognostic information in the analysis of its interictal EEG background. The needs of the near future are to learn the real behavior of the electrographic neonatal seizure (ENS) burden as it erupts on the scene of an acute encephalopathy. The response of the neonatal seizure burden to AED treatment requires careful quantitative description and reliable, automated ENS detection by cerebral function monitors, which are on the technologic horizon.

Spatial and temporal characteristics of neonatal seizures

Thirty-two neonates (26 term and 6 premature) having seizures were prospectively recruited and studied. Using prolonged video/EEG monitoring, we quantified seizure variables (electrographic and clinical seizure durations, interictal periods and electrographic seizure spread) for all 1,420 seizures recorded. The effects of time and antiepileptic drug (AED) therapy were analyzed statistically. Seizures were generally frequent, with limited electrographic spread. However, some neonates had consistently longer interictal periods and 13% had mean interictal periods > 60 min. Seizure variables were relatively stable over time, but they changed with AED therapy. There was a trend to decreased seizure duration, increased length of interictal periods, and decreased electrographic spread. Furthermore, there was evidence of reduced clinical features after sequential AED infusions. Seizures ceased during the monitoring period in 22 neonates. Eighty-five percent of all seizures had no clinical manifestations. Among neonates with clear clinical correlates, clinical observations underestimated electrographic seizures in individual neonates by a mean of 54% (range 0-95%). Seizures generally had limited electrographic spread. Use of only four recording electrodes, characteristic of some portable EEG systems, underestimated seizures in 19 neonates, and missed all seizures in 2.