High-density electroencephalogram monitoring in the neonate

EEG in neonatal seizures: where to look and what to see

INTRODUCTION

Neonatal seizures are frequent and carry a detrimental prognostic outlook. Diagnosis is based on EEG confirmation. Classification has recently changed.

AREAS COVERED

We consulted original papers, book chapters, atlases, and reviews to provide a narrative overview on EEG characteristics of neonatal seizures. We searched PubMed, without time restrictions (last visited: 31 May 2022). Additional papers were extracted from the references list of selected papers. We describe the typical neonatal ictal EEG discharges morphology, location, and propagation, together with age-dependent features. Etiology-dependent electroclinical features, when identifiable, are presented for both acute symptomatic neonatal seizures and neonatal-onset epilepsies and developmental/epileptic encephalopathies. The few ictal variables known to predict long-term outcome have been discussed.

EXPERT OPINION

Multimodal neuromonitoring in critically ill newborns, high-density EEG, and functional neuroimaging might increase our insight into the neurophysiological bases of seizures in newborns. Increasing availability of long-term monitoring with conventional video-EEG and automated detection methods will allow clinicians and researchers to gather an ever expanding bulk of clinical and neurophysiological data to enhance accuracy with deep phenotyping. The latest classification proposal represents an input for critically revising our diagnostic abilities with respect to seizure definition, duration, and semiology, possibly further promoting clinical research.

Cohort profile: the Neonatal Intensive Care Unit Hospital Exposures and Long-Term Health (NICU-HEALTH) cohort, a prospective preterm birth cohort in New York City

PURPOSE

The Neonatal Intensive Care Unit Hospital Exposures and Long-Term Health (NICU-HEALTH) longitudinal preterm birth cohort studies the impact of the NICU exposome on early-life development. NICU-HEALTH collects multiple biospecimens, complex observational and survey data and comprehensive multisystem outcome assessments to allow measurement of the impact of modifiable environmental exposures during the preterm period on neurodevelopmental, pulmonary and growth outcomes.

PARTICIPANTS

Moderately preterm infants without genetic or congenital anomalies and their mothers are recruited from an urban academic medical centre level IV NICU in New York City, New York, USA. Recruitment began in 2011 and continues through multiple enrolment phases to the present with goal enrolment of 400 infants. Follow-up includes daily data collection throughout the NICU stay and six follow-up visits in the first 2 years. Study retention is 77% to date, with the oldest patients turning age 8 in 2019.

FINDINGS TO DATE

NICU-HEALTH has already contributed significantly to our understanding of phthalate exposure in the NICU. Phase I produced the first evidence of the clinical impact of phthalate exposure in the NICU population. Further study identified specific sources of exposure to clinically relevant phthalate mixtures in the NICU.

FUTURE PLANS

Follow-up from age 3 to 12 is co-ordinated through integration with the Environmental Influences on Child Health Outcomes (ECHO) programme. The NICU-HEALTH cohort will generate a wealth of biomarker, clinical and outcome data from which future studies of the impact of early-life chemical and non-chemical environmental exposures can benefit. Findings from study of this cohort and other collaborating environmental health cohorts will likely translate into improvements in the hospital environment for infant development.

TRIAL REGISTRATION NUMBERS

This observational cohort is registered with ClinicalTrials.gov (NCT01420029 and NCT01963065).

EEG Source Imaging: A Practical Review of the Analysis Steps

The electroencephalogram (EEG) is one of the oldest technologies to measure neuronal activity of the human brain. It has its undisputed value in clinical diagnosis, particularly (but not exclusively) in the identification of epilepsy and sleep disorders and in the evaluation of dysfunctions in sensory transmission pathways. With the advancement of digital technologies, the analysis of EEG has moved from pure visual inspection of amplitude and frequency modulations over time to a comprehensive exploration of the temporal and spatial characteristics of the recorded signals. Today, EEG is accepted as a powerful tool to capture brain function with the unique advantage of measuring neuronal processes in the time frame in which these processes occur, namely in the sub-second range. However, it is generally stated that EEG suffers from a poor spatial resolution that makes it difficult to infer to the location of the brain areas generating the neuronal activity measured on the scalp. This statement has challenged a whole community of biomedical engineers to offer solutions to localize more precisely and more reliably the generators of the EEG activity. High-density EEG systems combined with precise information of the head anatomy and sophisticated source localization algorithms now exist that convert the EEG to a true neuroimaging modality. With these tools in hand and with the fact that EEG still remains versatile, inexpensive and portable, electrical neuroimaging has become a widely used technology to study the functions of the pathological and healthy human brain. However, several steps are needed to pass from the recording of the EEG to 3-dimensional images of neuronal activity. This review explains these different steps and illustrates them in a comprehensive analysis pipeline integrated in a stand-alone freely available academic software: Cartool. The information about how the different steps are performed in Cartool is only meant as a suggestion. Other EEG source imaging software may apply similar or different approaches to the different steps.

High density electroencephalography in sleep research: potential, problems, future perspective

High density EEG (hdEEG) during sleep combines the superior temporal resolution of EEG recordings with high spatial resolution. Thus, this method allows a topographical analysis of sleep EEG activity and thereby fosters the shift from a global view of sleep to a local one. HdEEG allowed to investigate sleep rhythms in terms of their characteristic behavior (e.g., the traveling of slow waves) and in terms of their relationship to cortical functioning (e.g., consciousness and cognitive abilities). Moreover, recent studies successfully demonstrated that hdEEG can be used to study brain functioning in neurological and neuro-developmental disorders, and to evaluate therapeutic approaches. This review highlights the potential, the problems, and future perspective of hdEEG in sleep research.

Cortical potential imaging of somatosensory evoked potentials by means of the boundary element method in pediatric epilepsy patients

The aim of the present study was to assess the feasibility of identifying the primary hand sensory area and central sulcus in pediatric patients using the cortical potential imaging (CPI) method from the scalp recorded somatosensory evoked potentials (SEPs). The CPI method was used to reconstruct the cortical potential distribution from the scalp potentials with the boundary element (3-layer: scalp, skull and brain) head model based on MR images of individual subjects. The cortical potentials estimated from the pre-operative scalp SEPs of four pediatric patients, were compared with the post-op subdural SEP recordings made in the same subjects. Estimated and directly recorded cortical SEP maps showed comparable spatial patterns on the cortical surface in four patients (spatial correlation coefficient >0.7 in the SEP spikes). For two of four patients, the estimated waveforms correlated significantly to the waveforms obtained by direct cortical recordings. The present results demonstrated the feasibility of the cortical potential imaging approach in noninvasive imaging spatial distribution and temporal waveforms of cortical potentials for pediatric patients. These also suggest that the CPI method may provide a promising means of estimating the cortical potential and noninvasive localizing the central sulcus to aid surgical planning for pediatric patients.

EEG functional connectivity in term age extremely low birth weight infants

OBJECTIVE

The hypothesis is tested that electrocortical functional connectivity (quantified by coherence) of extremely low birth weight (ELBW) infants, measured at term post-menstrual age, has regional differences from that of full term infants.

METHODS

128 lead EEG data were collected during sleep from 8 ELBW infants with normal head ultrasound exams and 8 typically developing full term infants. Regional spectral power and coherence were calculated.

RESULTS

No significant regional differences in EEG power were found between infant groups. However, compared to term infants, ELBW infants had significantly reduced interhemispheric coherence (in frontal polar and parietal regions) and intrahemispheric coherence (between frontal polar and parieto-occipital regions) in the 1-12Hz band but increased interhemispheric coherence between occipital regions in the 24-50Hz band.

CONCLUSIONS

ELBW infants at term post-menstrual age manifest regional differences in EEG functional connectivity as compared to term infants.

SIGNIFICANCE

Distinctive spatial patterns of electrocortical synchrony are found in ELBW infants. These regional patterns may presage regional alterations in the structure of the cortex.

Frequency domain analyses of neonatal flash VEP

A battery of frequency-dependent measures was made for high-density electroencephalographic recording measured in response to a flash stimulus in 12 normal term infants within 2 d of birth. Significant changes recorded in posterior electrodes in the same time window as the visual evoked potential (VEP) included increased local synchrony at approximately 40 Hz, increased power at approximately 16 Hz, the emergence of nonlinear coupling of lower (approximately 2 Hz) and higher frequency oscillations, and phase locking over a wide range of frequencies. This research provides evidence of neural synchrony and nonlinear coupling in response to a simple visual stimulus. These mechanisms are functional in early development. It is proposed that the frequency domain metrics of this study may augment current diagnostic measures of cortical function at birth.