Neonatal EEG Flashcards
PCA and post-menstrual age
Postconceptional age (PCA) = gestational age (prenatal) + chronological age (postnatal)
Postmenstrual age is also used (usually postmenstrual age = PCA + 2 weeks)
Neonatal montage
Special montage for preterm or newborn with head circumference<35cm
It is modified 10–20 system with a minimum of 9electrodes. Cz electrode plays an important role because abnormal positive sharp waves (and sometimes seizures) can be confined to this single electrode without involving or spreading to nearby regions
Usually, 16 channels recording are done, which should include 2 or more non-cerebral channels.
Non-cerebral electrodes include EKG, EMG, ocular, and respiratory belt. It helps in staging the sleep cycle, abnormal body movements, and also to identify the artifacts.
60-min recording is mandatory in an attempt to capture EEG in various behavioral states. EEG abnormalities are usually the most prominent in quiet sleep.
In a term neonate, the total sleep cycle lasts anywhere between 45 and 60min (active sleep:~25min; quiet sleep:~20min; transitional sleep:~15min).
Developmental landmarks
Best categorized in 3 phases:PCA <30weeks, 30–37weeks, and>37weeks.
<30weeks: EEG may be indistinguishable from awake and sleep in extremely premature infants of PCA<30weeks. A discontinuous EEG pattern termed trace discontinue is noted in all behavioral states.
Approximately IBI lasts anywhere between 20 and 35 for neonates with PMA<30–33 [PCA 28-31]weeks with<25µV.
30–37weeks: EEG starts showing variation in different behavioral states around 35weeks of PCA. Identifying different sleep stages in a newborn’s EEG is critical for optimal interpretation. EEG maturational changes occur first in active sleep (REM); after a lag of about 2weeks, the awake periods start showing more mature patterns. Quiet sleep (NREM) is the last stage to show more mature changes. For these reasons, the abnormalities are most frequently seen in the quiet sleep phase.
Trace alternant: These are characterized by high-amplitude (50–150µV) synchronous burst of mixed frequencies predominantly delta activity for 3–10s followed by 3–5s of low-amplitude burst (25–50µV) of predominant theta activity. This patterns replaces the trace discontinue with advanced PCA. This pattern is seen only in quiet sleep in neonates between PCA of 36 and 38weeks (Fig.4.3). TA usually starts appearing in neonates>35weeks and can be seen until 42weeks but no longer than 44weeks of PCA.
After 34weeks [32 weeks PCA], IBI significantly reduces, and closer to the term, it ranges anywhere between 6 and 10s and has higher voltage>25µV.
> 37weeks.
In active sleep (and later in wakefulness), TA is replaced by more continuous pattern characterized by uninterrupted, low-to-medium amplitude, mixed EEG activity with<2s of voltage attenuation (<25µV), and seen in mostly neonates with PCA>30weeks.PCA between 38 and 44weeks. Awake and sleep contains continuous, low-to-medium voltage, mixed frequency predominantly theta and delta with overriding beta activity (activite moyenne); Rudimentary spindles starts appearing in sleep state; and Sleep–wake cycling is more distinctive in terms of neonates after 37weeks.
Trace discontinue
Tracé discontinue pattern is a predominant pattern seen in preterm neonates with PCA<30weeks. It is characterized by high-amplitude (50–300µV) bursts of mixed frequency (theta and alpha riding over delta) which are seen simultaneously on both the hemispheres followed by low-amplitude periods of quiescence (<25µV) which can last anywhere between few seconds and 1min (inter-burst interval—IBI)
Inter-burst interval (IBI)
The key factor that determines the IBI in healthy babies is the postconceptional age. As the PCA increases, the IBI decreases. Approximately 30weeks or older, median IBI of 8s or less has higher survival than those with longer median IBI.
Approximately IBI lasts anywhere between 20 and 35 for neonates with PMA<30–33weeks with<25µV. After 34weeks, it significantly reduces, and closer to the term, it ranges anywhere between 6 and 10s and has higher voltage>25µV.
Prolonged IBI is seen in acute encephalopathy secondary to any type of brain injury, but is also commonly seen in moderate-to-severe hypoxic ischemic encephalopathy.
Trace alternant
These are characterized by high-amplitude (50–150µV) synchronous burst of mixed frequencies predominantly delta activity for 3–10s followed by 3–5s of low-amplitude burst (25–50µV) of predominant theta activity. This patterns replaces the trace discontinue with advanced PCA. This pattern is seen only in quiet sleep in neonates between PCA of 36 and 38weeks (Fig.4.3). TA usually starts appearing in neonates>35weeks and can be seen until 42weeks but no longer than 44weeks of PCA.
TA usually starts appearing in neonates>35weeks and can be seen until 42weeks but no longer than 44weeks of PCA.
In active sleep (and later in wakefulness), TA is replaced by more continuous pattern characterized by uninterrupted, low-to-medium amplitude, mixed EEG activity with<2s of voltage attenuation (<25µV), and seen in mostly neonates with PCA>30weeks.
TA pattern is replaced by medium-to-high voltage delta slow wave sleep after PCA of 44–48weeks.
Excessive discontinuity
Abnormal discontinuous tracing separated by prolonged IBI for PCA. This is usually seen in neonates with severe hypoxic ischemic encephalopathy, meningitis, encephalitis, and severe intraventricular hemorrhage.
Burst suppression
Burst suppression pattern is a pattern with high-amplitude burst (50–300µV) of delta and theta frequency with sharp waves and spikes followed by severe background suppression (<5µV). Usually, the background shows no reactivity to stimuli. In certain conditions like non-ketotic hyperglycinemia, the EEG bursts may be accompanied by myoclonic jerks (Fig.4.5).
Voltage amplitudes
Synchrony
Burst of morphological similar activity in the homologous head regions is separated by<1.5s.
<28 weeks: no asynchrony
28–32 weeks: 70% synchrony
>37 weeks: mostly synchronous Abnormal finding: Asynchrony of>1.5s may be significant if in excess for the PCA (Fig.4.6).
Delta brush
Delta brush is characterized by 0.3–1.5Hz delta activity superimposed with beta or fast activity (18–22Hz).
Other names are beta-delta complexes, ripples of prematurity, spindles/delta bursts.
They usually appear in the central region first followed by temporal and occipital and also disappear in the same order.
Most commonly seen during 24–34weeks and starts to disappear first in the active sleep after 30weeks.
They can be present in the quiet sleep up to 38weeks.
Abnormal findings: Delta brushes are often asynchronous, but when consistently absent on one side, a concern for some cerebral dysfunction is raised; if it is persistently present beyond 44weeks then it is consistent with dysmaturity (Fig.4.7).
Frontal sharps (Encoches Frontales):
These are blunt isolated biphasic broad sharp transients (0.5–0.75s) seen in the frontal region with initial smaller negativity followed by prominent positivity phase.
They are usually symmetric and synchronous;
Frequently seen in the transitional stage of sleep;
Usually seen between 33 and 46 weeks of PCA with peak around 35weeks;
Mostly associated with rhythmic bi-frontal delta;
Abnormal findings: Consistently absent on one side or any asymmetry raises concern for structural lesion on the other side.
Asymmetry
Asymmetry is defined as a persistent difference in amplitude/voltage of>50% between homologous regions of right and left hemispheres. It should be interpreted with cautions as extracranial factors such a caput succedaneum, cephalhematoma, and subgaleal hemorrhage may result in similar findings.
Positive sharp waves
These are abnormal positive polarity sharp waves seen mostly in the rolandic and central vertex regions around the 5th–8th postnatal day in preterm neonates with severe intraventricular hemorrhages. Examples seen in neonates with interventricular hemorrhage, hydrocephalus, and periventricular leukomalacia. It is an electrographic marker often linked to parenchymal white matter injury and usually disappears in 3–4weeks.
Sharp transients
These are frequently seen in temporal, central, and frontal regions, and less frequently in vertex and occipital regions.
Abnormal sharp transients are differentiated from the Encoches Frontales by the presence of associated frontal slowing, usually asymmetric and seen mostly in active sleep and awake state.
Normal vs abnormal sharp transients
