EEG in the neonatal unit

Quantitative analysis of high-frequency activity in neonatal EEG

OBJECTIVE

To determine the presence and potential utility of independent high-frequency activity recorded from scalp electrodes in the electroencephalogram (EEG) of newborns.

METHODS

We compare interburst intervals and continuous activity at different frequencies for EEGs retrospectively recorded at 256 Hz from 4 newborn groups: 1) 36 preterms (<32 weeks' gestational age, GA); 2) 12 preterms (32-37 weeks' GA); 3) 91 healthy full terms; 4) 15 full terms with hypoxic-ischemic encephalopathy (HIE). At 4 standard frequency bands (delta, 0.5-3 Hz; theta, 3-8 Hz; alpha, 8-15 Hz; beta, 15-30 Hz) and 3 higher-frequency bands (gamma1, 30-48 Hz; gamma2, 52-99 Hz; gamma3, 107-127 Hz), we compared power spectral densities (PSDs), quantitative features, and machine learning model performance. Feature selection and further machine learning methods were performed on one cohort.

RESULTS

We found significant (P < 0.01) differences in PSDs, quantitative analysis, and machine learning modelling at the higher-frequency bands. Machine learning models using only high-frequency features performed best in preterm groups 1 and 2 with a median (95% confidence interval, CI) Matthews correlation coefficient (MCC) of 0.71 (0.12-0.88) and 0.66 (0.36-0.76) respectively. Interburst interval-detector models using both high- and standard-bandwidths produced the highest median MCCs in all four groups. High-frequency features were largely independent of standard-bandwidth features, with only 11/84 (13.1%) of correlations statistically significant. Feature selection methods produced 7 to 9 high-frequency features in the top 20 feature set.

CONCLUSIONS

This is the first study to identify independent high-frequency activity in newborn EEG using in-depth quantitative analysis. Expanding the EEG bandwidths of analysis has the potential to improve both quantitative and machine-learning analysis, particularly in preterm EEG.

Polygraphic EEG Can Identify Asphyxiated Infants for Therapeutic Hypothermia and Predict Neurodevelopmental Outcomes

Background: Neonatal encephalopathy due to perinatal asphyxia is one of the leading causes of neonatal death and morbidity worldwide. The neurodevelopmental outcomes of asphyxiated neonates have considerably improved after therapeutic hypothermia (TH). The current challenge is to identify all newborns with encephalopathy at risk of cerebral lesions and subsequent disability within 6 h of life and who may be within the window period for treatment with TH. This study evaluated the neurodevelopmental outcomes in surviving asphyxiated neonates who did and did not receive TH, based on clinical and polygraphic electroencephalographic (p-EEG) criteria. Methods: The study included 139 asphyxiated newborns divided into two groups: 82 who received TH and 57 who were not cooled. TH was administered to asphyxiated newborns (gestational age ≥ 35 weeks, birth weight ≥ 1800 g) with encephalopathy of any grade and moderate-to-severe p-EEG abnormalities or seizures. Neurodevelopmental outcomes between the groups at 24 months of life and the risk factors for severe outcomes were assessed. Results: Severe neurodevelopmental impairment occurred in 10 (7.2%) out of the 139 enrolled neonates. Nine out of the 82 cooled neonates (11.0%) had severe neurodevelopmental impairment. All but one neonate (98.2%) who did not receive TH had normal outcomes. The multivariate logistic regression analysis showed that abnormal p-EEG patterns (OR: 27.6; IC: 2.8-267.6) and general movements (OR: 3.2; IC: 1.0-10.0) were significantly associated with severe neurodevelopmental impairment (area under ROC curve: 92.7%). Conclusion: The combination of clinical and p-EEG evaluations in hypoxic-ischemic encephalopathy contributed to a more accurate selection of patients treated with therapeutic hypothermia. When administered to infants with moderate to severe p-EEG abnormalities, TH prevents approximately 90% of severe neurodevelopmental impairment after any grade of hypoxic-ischemic encephalopathy.

Comparative analysis of background EEG activity based on MRI findings in neonatal hypoxic-ischemic encephalopathy: a standardized, low-resolution, brain electromagnetic tomography (sLORETA) study

Background

It is important to assess the degree of brain injury and predict long-term outcomes in neonates diagnosed with hypoxic-ischemic encephalopathy (HIE). However, routine studies, including magnetic resonance imaging (MRI) and conventional encephalography (EEG) or amplitude-integrated EEG (aEEG), have their own limitations in terms of availability and accuracy of evaluation. Recently, quantitative EEG (qEEG) has been shown to improve the predictive reliability of neonatal HIE and has been further refined with brain mapping techniques.

Methods

We investigated background EEG activities in 29 neonates with HIE who experienced therapeutic hypothermia, via qEEG using a distributed source model. MRI images were evaluated and classified into two groups (normal-to-mild injury vs moderate-to-severe injury), based on a scoring system. Non-parametric statistical analysis using standardized low-resolution brain electromagnetic tomography was performed to compare the current density distribution of four frequency bands (delta, theta, alpha, and beta) between the two groups.

Results

Electrical neuronal activities were significantly lower in the moderate-to-severe injury group compared with the normal-to-mild injury group. Background EEG activities in moderate-to-severe HIE were most significantly reduced in the temporal and parietal lobes. Quantitative EEG also revealed a decrease in background activity at all frequency bands, with a maximum in decrease in the delta component. The maximum difference in current density was found in the inferior parietal lobule of the right parietal lobe for the delta frequency band.

Conclusions

Our study demonstrated quantitative and topographical changes in EEG in moderate-to-severe neonatal HIE. They also suggest possible implementation and evaluation of conventional EEG and aEEG in neonatal HIE. The findings have implications as biomarkers in the assessment of neonatal HIE.

Expert consensus on minimum technical standards for neonatal electroencephalography operation and report writing

Electroencephalography (EEG) monitoring is an important examination method in the management of critically ill neonates, which can be used to evaluate brain function and developmental status, severity of encephalopathy, and seizures and predict the long-term neurodevelopmental outcome of high-risk neonates with brain injury. EEG monitoring for neonates is different from that for adults and children, and its operation and interpretation are easily affected by the number of recording electrodes, electrode montage, and monitoring quality. Therefore, standard operation must be followed to ensure the quality of signal acquisition and correct interpretation, thereby ensuring proper management of critically ill neonates. The Subspecialty Group of Neonatology, Society of Pediatrics, Chinese Medical Association established an expert group composed of professionals in neonatology and brain electrophysiology to perform a literature review, summarize the minimum technical standards for neonatal EEG monitoring, and develop the expert consensus on minimum technical standards for neonatal EEG operation and report writing. This consensus will provide guidance for neonatal EEG operation, including technical parameters of EEG monitoring device, operation procedures of EEG monitoring, and specifications for report writing.

Technical recommendations and interpretation guidelines for electroencephalography for premature and full-term newborns

Electroencephalography (EEG) of neonatal patients is amongst the most valuable diagnostic and prognostic tool. EEG recordings, acquired at the bedside of infants, evaluate brain function and the maturation of premature and extremely premature infants. Strict conditions of acquisition and interpretation must be respected to guarantee the quality of the EEG and ensure its safety for fragile children. This article provides guidance for EEG acquisition including: (1) the required equipment and devices, (2) the modalities of installation and asepsis precautions, and (3) the digital signal acquisition parameters to use during the recording. The fundamental role of a well-trained technician in supervising the EEG recording is emphasized. In parallel to the acquisition recommendations, we present a guideline for EEG interpretation and reporting. The successive steps of EEG interpretation, from reading the EEG to writing the report, are described. The complexity of the EEG signal in neonates makes artefact detection difficult. Thus, we provide an overview of certain characteristic artefacts and detail the methods for eliminating them.

Developmental EEG hallmark or biological artifact? Glossokinetic artifact mimicking anterior slow dysrhythmia in two full term newborns

The aim of this paper is to describe an uncommon physiological EEG artifact in newborns caused by tongue movements (TM), mimicking anterior slow dysrhythmia (ASD). The subjects are two full-term newborns (39 weeks gestational age (GA)), admitted to the Neonatal Intensive Care Unit for respiratory distress. Both underwent polygraphic video-EEG recording in order to better characterize tremor-like movements of all four limbs that appeared 48 hours after birth. Multichannel video-EEG polygraphy was performed using the 10-20 electrode montage modified for neonates. Ninety minutes of EEG was recorded for each subject, capturing different behavioral states. Background EEG activity was normal for both subjects. During active sleep (AS), synchronous and symmetric slow activity was recorded over bifrontal head regions. For subject 1, bursts of monomorphic 2Hz delta waves, with an amplitude between 50-100μV lasting two seconds, were recorded and identified as anterior slow dysrhythmia. For subject 2, polymorphic 1-2Hz delta waves, 50-100μV in amplitude and lasting for 20 seconds, were recorded only during suction. After thorough analysis of simultaneous digital video recording synchronized with the EEG trace, this activity was thought to be compatible with glossokinetic artifact. Interpretation of neonatal EEG can be challenging; the background activity is frequently intermixed with physiological artifacts, such as ocular, muscle and movement artifacts, complicating the interpretation. Even continuous video-recording might not make the diagnosis immediately obvious. Therefore, when a rhythmic monomorphic pattern without evolution in amplitude or frequency is seen, we suggest that tongue movement artifact should be considered.

Models for Preterm Cortical Development Using Non Invasive Clinical EEG

The objective of this study was to evaluate the piglet and the mouse as model systems for preterm cortical development. According to the clinical context, we used non invasive EEG recordings. As a prerequisite, we developed miniaturized Ag/AgCl electrodes for full band EEG recordings in mice and verified that Urethane had no effect on EEG band power. Since mice are born with a “preterm” brain, we evaluated three age groups: P0/P1, P3/P4 and P13/P14. Our aim was to identify EEG patterns in the somatosensory cortex which are distinguishable between developmental stages and represent a physiologic brain development. In mice, we were able to find clear differences between age groups with a simple power analysis of EEG bands and also for phase locking and power spectral density. Interhemispheric coherence between corresponding regions can only be seen in two week old mice. The canolty maps for piglets as well as for mice show a clear PAC (phase amplitude coupling) pattern during development. From our data it can be concluded that analytic tools relying on network activity, as for example PAC (phase amplitude coupling) are best suited to extract basic EEG patterns of cortical development across species.