An amplitude-integrated electroencephalogram (aEEG) is a specialized method for continuously observing brain function. Primarily used in the neonatal intensive care unit (NICU), it provides healthcare professionals with insights into the neurological state of newborn infants. By examining variations in brain electrical signals over an extended, compressed period, aEEG effectively monitors a baby’s brain activity. It helps medical teams assess brain function, especially when a baby experiences stress or injury.
What an aEEG Test Monitors
The aEEG test serves several purposes in neonatal care, offering insights into a newborn’s brain health. It is frequently used to detect and monitor subclinical seizures, which lack obvious physical symptoms but impact brain function. Early identification allows for timely intervention, potentially improving outcomes.
A primary application is assessing brain injury, particularly from events like hypoxic-ischemic encephalopathy (HIE), caused by oxygen deprivation at birth. The test helps determine injury severity and guides treatment. It also monitors brain development in very premature infants and evaluates treatment effectiveness, such as therapeutic hypothermia, a cooling therapy used to protect the brain after oxygen deprivation.
The aEEG Testing Process
The aEEG testing process is gentle and non-invasive for the newborn. Small, soft electrodes are carefully placed on the baby’s scalp, typically using a special paste or soft cap for secure contact. Two to four electrodes are commonly used, often positioned over specific brain areas like the biparietal regions (P3 and P4). These electrodes capture brain electrical signals without causing discomfort.
Once applied, they connect to a bedside monitor, displaying continuous brain activity. Monitoring can extend over many hours or several days, providing a comprehensive record of brain function trends. Throughout, the baby can be held, fed, and receive routine care, ensuring minimal disruption and consistent observation by the medical team.
Understanding the aEEG Output
When healthcare professionals review aEEG output, they observe a compressed visual representation of brainwave activity, displayed as a continuous band. This trace is presented on a semi-logarithmic scale, compressing long periods of data into a manageable view. The band’s width and characteristics provide information about the baby’s brain function over time.
For instance, a “continuous normal voltage” pattern, with the upper margin above 10 microvolts (mcV) and the lower margin above 5 mcV, indicates healthy and active brain function. A continuous or slightly discontinuous pattern within the first six hours indicates a higher likelihood of cerebral recovery and a favorable outcome.
In contrast, “burst-suppression” shows intense activity followed by very low activity, while a “flat trace” indicates consistently very low brain activity. These patterns suggest varying degrees of brain compromise or injury.
The aEEG also helps identify seizures, which appear as an abrupt and sustained rise in both the minimum and maximum amplitude of the trace, sometimes followed by decreased activity. Interpreting these visual patterns provides insights into the baby’s neurological state, allowing assessment of encephalopathy severity and brain maturational development.