An amplitude-integrated electroencephalogram (aEEG) is a bedside tool used in neonatal intensive care units (NICUs) to continuously monitor a newborn’s brain activity. It functions as a simplified version of a traditional electroencephalogram (EEG), recording and processing the brain’s electrical signals. This information is then displayed on a screen as a compressed tracing, allowing medical staff to observe trends in brain function over several hours or days. The monitor filters and amplifies the brain’s natural electrical waves, creating a visual pattern that is easier to interpret at a glance. This non-invasive method has become a routine part of care for many critically ill infants.
Purpose of Neonatal aEEG
The primary purpose of a neonatal aEEG is to help medical teams assess brain function and detect potential problems early. One of its most important uses is in identifying sub-clinical or “silent” seizures. These are seizure activities in the brain that do not cause the outward physical convulsions associated with seizures, making them impossible to detect through observation alone. The aEEG can reveal these hidden events, allowing for prompt treatment.
This monitoring is particularly useful for infants who have experienced a difficult birth, such as those with hypoxic-ischemic encephalopathy (HIE), a type of brain injury caused by oxygen deprivation. The information helps doctors gauge the extent of the brain injury and monitor the infant’s response to treatments like therapeutic hypothermia, a cooling therapy designed to protect the brain.
The aEEG also provides ongoing information about the brain’s functional integrity. It is used for infants with suspected brain injuries, certain metabolic disorders, or severe infections like meningitis. This real-time view of cerebral activity helps clinicians make more informed decisions about an infant’s immediate medical needs.
The aEEG Procedure
The process of setting up an aEEG is designed to be gentle and is not painful for the baby. A nurse or specialized technician will attach a few small sensors called electrodes to specific locations on the baby’s scalp. These electrodes may be small, sticky pads or tiny needles placed just under the skin. In some cases, a soft cap with the electrodes already embedded in it is used.
Before placing the electrodes, the baby’s head is cleaned, and a special gel may be used to ensure good contact between the sensor and the scalp. The electrodes are then connected by wires to a portable monitor at the baby’s bedside. Parents can often hold their baby during the monitoring as long as the infant’s condition is stable.
The aEEG can remain in place for hours or even several days, depending on the baby’s condition. This extended recording period allows doctors to see trends and changes over time that might be missed with a shorter test. Once the monitoring period is over, the electrodes are gently removed.
Understanding aEEG Patterns
While interpreting an aEEG tracing requires specialized training, parents can understand the basic concepts of what the medical team is observing. The two main components doctors analyze are the background pattern and any seizure activity. The background pattern can be thought of as the brain’s continuous, baseline electrical hum.
In a healthy, full-term baby, this pattern will show gentle, wave-like cycles as the baby moves between sleep and wakefulness. This is called sleep-wake cycling (SWC), and its presence is a reassuring sign of normal brain function. Conversely, patterns that are abnormally flat, showing very low electrical voltage, or patterns of “burst-suppression,” where short bursts of activity are followed by periods of flatness, can indicate that the brain is suppressed or has been injured.
Seizure activity appears on the tracing as a sudden and repetitive change from the baby’s normal background pattern. It often looks like a dramatic rise in both the top and bottom edges of the tracing, creating a distinct shape that stands out. By identifying these events, doctors can confirm the presence of seizures.
Role in Treatment and Prognosis
The information gathered from an aEEG directly influences a newborn’s medical care and helps doctors form a prognosis. When the aEEG detects seizures, the medical team can administer anti-seizure medication and then use the monitor to see if the treatment is effective. This real-time feedback allows for timely adjustments to the baby’s care plan.
For infants with HIE undergoing cooling therapy, an improving background pattern on the aEEG is a positive sign that the treatment may be helping to protect the brain. The evolution of the aEEG tracing over the first few days of life provides prognostic information. For instance, the earlier a suppressed background pattern begins to normalize, the better the potential outcome.
The aEEG is one piece of a larger diagnostic puzzle. Doctors use the aEEG findings in combination with clinical examinations, other imaging tests like MRI, and the baby’s overall condition. This comprehensive approach helps them make treatment decisions and discuss the likely long-term outlook with parents.