The most striking component of a neonatal background is discontinuity, or periods of essentially flat activity in between bursts of activity. In reviewing neonatal studies, you should assess all of these components just as you do with adult studies, so let's get started. Morphology describes the shape of a given waveform. Amplitude refers to the height of a given waveform, while frequency (in hertz, Hz) is the number of times a set of waves happens per second. Reactivity refers to a response or change in the tracing due to external stimuli. Synchrony describes bursts of activity happening at the time in both sides of the brain (note that this is different than symmetry, in which the activity is the same in frequency and amplitude on both sides). Continuity refers to continuous waves across the page, without flat periods.
Before we delve into neonatal development, lets review some key terms regarding the background. After that, things start to change rapidly. However, for up to 29 weeks of postmenstrual age the neonatal EEG looks essentially the same across the awake, active sleep and quiet sleep states. Awake is marked simply by the presence of the eyes being open, and asleep by the eyes being closed. The background of a neonatal EEG is grossly broken down into awake, quiet sleep, and active sleep states. So, a 4 week old baby who was born at 34 weeks would have a PMA of 34 + 4 = 38 weeks. The PMA is calculated by adding the gestational age (the time from the mother’s last menstruation, aka the length of the pregnancy) to the chronological age (the time since the baby’s birth). The timeframe for changes is measured by the postmenstrual age (PMA also called conceptual or conceptional age), rather than chronological age, to take into account prematurity or delayed delivery. These differences, marked as they are, progress into a more classic childhood and then adult EEG, and knowing the timeframe of such changes is critical because what is normal one week for a neonate may be abnormal by the next week. Sleep is also different in a neonate, being broken down into quiet and active sleep as opposed to the four stages in adults.
Neonatal studies are read at a faster page speed of 15mm/sec, with a low frequency filter of 0.01 - 0.5Hz.Īs stated above, neonatal EEGs are starkly different than adults, showing diffuse slowing, discontinuity, asynchrony, and minimal reactivity.
In the neonate, in addition to the brain and ECG electrodes, there are also extraocular electrodes (electro-oculogram, EOG) placed lateral to the eyes, electromyography electrodes (EMG) on the chin, and leads to assess chest movements for breathing (pneumograph).
EEG ON BABY FULL
This version is used until the baby is full term, or at most 46 weeks postmenstrual age (see below for PMA definition). So, the neonatal montage is a pared down version of the 10-20 system that focuses on the central areas, which tend to be more active in neonates, and includes a transverse chain going across from T3 to T4. Given the small and sometime alien appearing head size of neonates, a full 10-20 montage puts the electrodes too close together and risks forming salt bridges (discussed in the artifact section) between them.
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