Neonatal EEG transients (also called graphoelements) are common in premature and full-term infants, and they can often be mistaken for abnormalities if the observer is not familiar with their normal timelines. Below is an expanded explanation of the more commonly seen neonatal transients and their significance:

1. Premature Temporal Theta

  • Appearance: Temporal theta appears as bursts of moderately high-amplitude theta waves. These bursts often have a sharp contour and can be observed primarily in the bitemporal regions (both sides of the brain's temporal lobes).
  • Significance: Temporal theta is seen predominantly in very premature neonates and is a part of the normal maturation of the brain's electrical activity. It is considered a transient and disappears as the baby reaches full term.
  • Clinical Relevance: While theta activity is a normal rhythm for adults, in neonates, it is expected only in the premature stages of development. If seen in full-term infants or older, it could be considered abnormal.

2. Monomorphic Occipital Delta

  • Appearance: This pattern consists of slow, delta waves that are uniform or "monomorphic." These waves are most prominent in the occipital region (the back of the brain) and are typically more pronounced in preterm neonates.
  • Significance: Monomorphic occipital delta is a normal finding in the EEG of premature infants. The presence of delta waves here reflects the immature neural activity that is expected in the earlier stages of brain development.
  • Clinical Relevance: This waveform pattern typically fades away as the brain matures and should not be seen in full-term or older infants. If it persists in older children, it may raise concerns of underlying neurological issues.

3. Delta Brush

  • Appearance: Delta brush is a combination of slow, delta waves (2-3 Hz) with faster, higher-frequency activity (8-20 Hz). The fast activity overlays the delta waves, resembling the bristles of a brush.
  • Significance: This pattern is common in mildly premature neonates and represents an ongoing developmental process where more complex brain rhythms are starting to emerge. Delta brush usually starts in the central and posterior areas of the brain, and as the infant matures, it moves to the posterior regions.
  • Clinical Relevance: Delta brush is generally benign in neonates, but its appearance in adult patients, particularly in those with NMDA receptor encephalitis (a form of autoimmune encephalitis), can indicate pathology. This makes its presence in neonates distinct from other conditions where it could be a marker of illness.

4. Frontal Sharp Transients (Encoches Frontales)

  • Appearance: These are sharp, sudden bursts of electrical activity that originate in the frontal regions of the brain. The discharges are synchronous (both sides of the brain are activated simultaneously).
  • Significance: Frontal sharp transients appear at 34 weeks PMA and are part of the normal neonatal EEG pattern. They are typically seen in healthy premature infants as their frontal lobes develop. These transient bursts are part of the maturation process and should not cause concern unless they become irregular.
  • Clinical Relevance: Frontal sharp transients should always be synchronous (both sides of the brain firing at the same time). If they become asynchronous, it could indicate that the pattern is abnormal, possibly pointing to epilepsy or other neurological conditions.

5. Centrotemporal Sharp Transients

  • Appearance: Centrotemporal sharp transients are brief bursts of sharp waves that originate from the centrotemporal region, which is located near the motor cortex of the brain.
  • Significance: These sharp transients are typically seen in neonates and are most commonly observed during the first month of life. They are considered part of the normal range of developmental patterns in the neonatal EEG.
  • Clinical Relevance: These transients are usually benign and resolve as the infant grows older. However, if they persist or increase in frequency after the first month, further investigation may be required, as they could be a sign of developing epilepsy.

6. Multifocal Sharp Transients

  • Appearance: Multifocal sharp transients are sharp bursts of electrical activity that can occur in multiple regions of the brain. These transients are generally seen in neonates and tend to be widespread across different areas of the brain.
  • Significance: In the first month of life, multifocal sharp transients are typically considered normal, especially if they are transient and do not appear excessively in one location. They reflect the process of neuronal maturation where different brain regions are still "wiring" together and developing.
  • Clinical Relevance: While multifocal sharp transients are normal in the early stages of life, if they persist beyond the first month, or if they are particularly localized or frequent, they may indicate an underlying neurological condition, such as a seizure disorder.