Neonatal EEG is the measurement of the electrical activity of the newborn brain. It provides a sensitive, real time, continuous measure of cerebral activity and, therefore, brain function. The EEG is capable of detecting changes in oxygenation and blood pressure, detecting electrical signs of seizure and determining the neurodevelopmental outcome of neonates with hypoxic ischaemic injury.
The measurement of brain activity via the EEG is performed by attaching several electrodes (or sensors) to the head of the newborn. These electrodes are placed according to the International 10-20 system. Our montages are built from recordings of F3, F4, Cz, C3, C4, T3, T4, O1, O2 as shown in Figure 1.
Electrode placement for measuring neonatal EEG.
This signal that is picked up by each electrode is then amplified, stored and displayed on a monitor. We also measure several other physiological signals in conjunction with the EEG such as the ECG (heart function), respiration (lung function) and EMG (muscle function), as these recordings can influence the EEG.
We then analyse the EEG by visual inspection to assist in the diagnosis and prognosis of the newborn. Our analysis usually involves locating abnormal EEG in a recording. The normal EEG appears to be a random signal without any obvious pattern. The EEG becomes abnormal when certain patterns appear in the EEG and it loses the underlying randomness of a normal recording. The normal EEG pattern and several abnormal EEG patterns are shown in Figure 2.
Figure 2: Examples of normal and abnormal neonatal EEG.
In addition to pattern analysis we also analyse more general characteristics of the EEG such as continuity, amplitude, frequency, synchrony and symmetry as well as more clinical features such as maturational characteristics, sleep state differentiation and reactivity.
We have been collecting EEG data at the neonatal intensive care unit of the Cork University Maternity Hospital since 2003.
Our neonatal EEG database contains; long duration, continuous, multiple channel recordings with synchronised video that were recorded from within 6 hours of birth. We have also measured the heart rate and respiration of the neonate. Our EEG recordings contain;
- Seizure EEG patterns
- Abnormal EEG patterns
- Normal EEG patterns
We have recorded EEG from newborns with
- Hypoxic-Ischemic Encephalopathy
We have followed up these newborns at 2 and 5 years.
We are also investigating new montages, that reveal the maximum amount of information with the minimum amount of electrodes, and different techniques for attaching the electrodes.
Further reading on neonatal EEG can be found in,
- G.B. Boylan, "Principles of EEG and CFM" in Neonatal Cerebral Investigation, Chapter 2, Eds: J.M. Rennie, Robertson and Hagmann. Cambridge University Press, UK, 2008.
- G.B. Boylan, J.M. Rennie, and D.M. Murray. "The normal neonatal EEG" in Neonatal Cerebral Investigation, Chapter 6, Eds: J.M. Rennie, N.J. Robertson and C.F. Hagmann. Cambridge University Press, UK, 2008.
- G.B. Boylan, "Neurophysiology in the Neonatal Period", in Neonatal and Paediatric Clinical Neurophysiology, Eds: R.M. Pressler, C.D. Binnie, R. Cooper and R. Robinson, Churchill Livingstone Elsevier, The Netherlands, 2007