Record eye movements electro-oculogram, EOG either with frontal EEG electrodes then no additional electrodes are needed , or with separate EOG electrodes attached near the lateral corners of the eyes.
In the youngest premies, however, it may be sometimes needed to use piezo sensors attached to eyelids not shown in this video , because their retina may not be polarized enough to cause detectable electric fields. Monitor respiration movements with a stretch-sensitive transducer belt that is wrapped around the trunk over abdomen or chest.
Make sure that the transducer is tight enough to show respiratory movements in the recording, and yet loose enough to allow unrestricted respiration. If clinically needed, add also a movement-sensitive piezo sensor to any body part that is expected to show unusual movements.
Position the EEG-synchronized video camera so that the whole baby is well seen in the picture. During specific parts of the EEG study, one may choose to focus on selected body parts, such as hands or feet during their tactile stimulation. Recording 1. During the entire recording session, keep an eye on the signal quality, and make corrections if any signal deteriorates. Follow the baby as well, and add annotations of any event eg. Should artefacts occur during the recording, troubleshoot them and make corrections to the recording immediately.
Many artefacts may permanently compromise the later use of EEG signal. Adjust the recording length individually so that the EEG study includes at least one epoch of all vigilance states: awake, active sleep and quiet sleep. In most cases, this will take 40 to 90 minutes. Perform sensory stimulations see section 5 below when the baby is well asleep. It is preferable to wait until quiet sleep period. In the end of the EEG recording session, remove the cap and other sensors, and clean the excess gel from baby's scalp by wiping with a wet cloth.
Clean the EEG cap and other accessories first mechanically, then sterilize them according to hospital instructions. Sensory stimulations 1. Note that all sensory responses in the young preemies have a long several seconds refractory period, and the responses decline rapidly with short interstimulus intervals or in the presence of other ongoing EEG activity in the sensory cortex. Hence, deliver sensory stimuli at moments when the EEG has been relatively silent for at least few seconds, which is easiest to do during quiet sleep exhibiting trace discontinue activity.
If possible, use stimulation devices that automatically generate a mark trigger into the EEG trace. Perform first the tactile stimulations, then the visual stimuli, and at last the auditory stimuli, which may wake up the baby. To study the visual evoked responses, give single flashes with a device integrated to the EEG system.
You may also show any transient light, such as moving a torch beam over the face. A response is readily generated even from distance, such as through the transparent incubator walls. Observe the response with at least one second duration in several occipital and parietal electrodes.
To study the somatosensory evoked responses, apply gentle tactile stimuli to the palm or sole of the baby. It is helpful to use a device that automatically generates a mark trigger into the EEG trace. Observe the response in the contralateral centro-temporal C and T electrodes after hand stimulation, and in the midline Cz electrodes after foot stimulation. To assist later analysis, add manual annotation to EEG recording any time when you see a spontaneous limb movement, because it produces responses similar to stimulated ones.
To study auditory responses, you may use almost any sound with relatively low intensity,such as hand clapping near baby's head. Avoid using the traditional horn stimulation, because its high sound intensity will lead to both auditory activation and sleep arousal, with often ensuing movement artefacts. Analysis 1. Start preliminary analysis during the EEG recording already. Add annotations of clinical events that are not obvious from the EEG signal eg. Make note also of all EEG artefacts eg.
Finally, add your preliminary considerations as they arise online, as they may often involve insights that are difficult to perceive later. Make sure that you have recorded both active and quiet sleep, and that the number and quality of sensory stimuli are sufficient.
The actual, thorough review of neonatal EEG is done offline in a workstation where EEG findings can be processed and described in more detail. Representative Results Figure 1. For details, see Discussion. Figure 2.
Comparison of the increase in information obtained by adding the number of electrodes. This spatial information is negligible in the conventional 8 channel middle recording, and completely lost in the common one channel EEG monitoring left. Please click here to see a larger version of this figure. Left: An example is shown from single trial responses to tactile sensory stimulations of hands as seen in the raw EEG trace. Right: Comparison of the preterm and fullterm somatosensory responses both C4-Fz derivation demonstrates the magnitude of preterm cortical reactions.
The preterm response is shown from a single trial trace, while the fullterm response is generated by averaging, since it would not be distinguished at single trial level. In the fullterm trace, the arrow depicts the N1 response that is conventionally used as the representative measure for clinical diagnosis.
For further details, see refs 4,6,10, Discussion Recording of neonatal EEG in the way shown here is safe, and hence doable from any baby and in any condition that allows handling associated 1 with routine care procedures. The intensive care unit is a challenging environment to the sensitive EEG devices. A key to a technically good quality recording is a proper use of well-functioning dense array EEG cap, such as the one shown in this video.
NICU environment is unique in that the study subjects are critically ill, vulnerable babies, which undergo demanding care and diagnostic procedures. While they are readily seen with the FbEEG technique see Fig 1 and refs 8,9 , they are ignored or distorted in the conventional EEG using an AC coupled amplifier that permanently cuts them at the time of signal collection, because AC coupled amplifiers act as highpass low cut filters.
It is notable in clinical context, that the caps used in our presentation are fully compliant with FbEEG recording, while many other clinical EEG caps are unsuitable 16 because of their inappropriate electrode materials eg.
Adequate assessment or monitoring of the early preterm brain must be based on a thorough understanding of the nature and specific characteristics of the immature brain activity itself see above. Such an approach is largely lacking in the current clinical practice and literature. To meet this need, the protocol for a multimodal neurophysiological assessment of preterm babies was developed in our laboratory. The present paper bridges together the latest knowledge of developmental neurobiology, the relevant advances in neurophysiological techniques, as well as the pressing need for novel clinical research.
Our work hences opens the window for translational studies to be performed in a bidirectional manner from bench to bedside and back. In addition, clear demonstration of the protocol aims to open a venue for larger scale collection of clinically relevant datasets, including studies to define the elusive criteria of normality.
Our clinical experience in the Helsinki University Hospital has shown that i multimodal studies of this kind have rapidly become an integral part of clinical routine, ii that they have significantly increased the interest in neonatal EEG studies, and iii that the developments in recording techniques shown here have made performance of such recordings as readily attainable as any limited, conventional EEG.
Most importantly, understanding the relationships between developing brain function and structure makes it possible to assess brain maturation at a time when the 17 baby is not yet able to communicate with the outside world. Better brain care at an early stage of development is likely to lead to a permanent increase in health and in overall quality of life of the preterm baby.
Acknowledgements We want to thank Mr. Jyri Ojala for the technical production of the film, including its animations, graphical design, as well as all technical editing. We also want to thank the parents who gave permission to have their baby be starring in this video, as well as the nurses especially Mr. References 1. Vanhatalo, S. High fidelity recording of brain activity in the extremely preterm babies: feasibility study in the incubator. Stjerna, S. Evaluation of an easy, standardized, and clinically practical method SurePrep for the preparation of electrode-skin contact in EEG recordings.
Physiological Measures. Julkunen, P. Hrbek, A. Development of visual and somatosensory evoked responses in pre-term newborn infants. Milh, M. Rapid cortical oscillations and early motor activity in premature human neonate.
In recent years, digital technology has replaced analog equipments, and it is now possible to easily record and store EEG tracings and to quickly recall previously acquired material for subsequent analysis.
In addition, not only static figures, but also electronic supplementary materials can be included in books, enabling EEGs to be viewed in real-time.
In clinical practice, EEG still represents the most important functional examination in the study CNS development and its anatomical and physiological integrity throughout life. In the pathological context, EEG provides indispensable diagnostic information for classification of epileptic syndromes, and it is also valuable in all the other CNS diseases infectious, cerebrovascular, neurodegenerative, etc.
Furthermore, monitoring EEG can be widely used in emergency settings, such as emergency departments or intensive care units.
In comatose patients, EEG provides information regarding prognosis and evaluation of the sedative effect of anesthetic drugs. Written by a group of leading national and international experts, it offers a substantial, yet practical, EEG compendium, which serves as a reference resource for physicians and neurodiagnostic technologists as well as physicians-in-training, researchers, practicing electroencephalographers and students.
His main area of interest is electroencephalography and clinical epileptology. Skip to main content Skip to table of contents. Advertisement Hide. This service is more advanced with JavaScript available.
Clinical Electroencephalography. Editors view affiliations Oriano Mecarelli. Offers a ready consultation text for physicians and neurodiagnostic technologists Introduces readers to the technical and methodological aspects of EEG Defines the physiological patterns of awakeness and sleep Uses a didactic and systematic method to demonstrate the electrophysiological and clinical patterns of epileptic syndromes Provides practical examples of the most appropriate EEG methods for different pathologies video EEG, back averaging, neuromonitoring, etc.
Supplies indications for immediate and correct interpretation of EEG patterns in emergency situations, during neuromonitoring in Intensive Care Unit and surgery Defines the EEG peculiarities of the different etiologies of coma Includes an updated section on EEG in brain tumors Offers a practical, easy-to-use approach to using and interpreting polysomnography in epileptic and non-epileptic disorders.
Front Matter Pages i-xix. Front Matter Pages Pages Neurophysiological Basis of EEG.
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