Amplitude integrated EEG monitoring in neonatal seizure care

Neonatal seizures are among the most common neurological emergencies encountered in the perinatal period, with the majority arising within the first week of life. Their clinical recognition is notoriously unreliable, as many events are subtle, electrographic-only or masked by concurrent sedation and illness. Continuous brain monitoring has therefore moved from being an optional adjunct to a near-essential component of contemporary neonatal intensive care.

For clinicians working across Australian perinatal centres, the question is no longer whether to monitor at-risk infants, but which modality best balances accessibility, accuracy and workflow. Conventional multichannel electroencephalography remains the gold standard for seizure detection, yet it is resource-intensive and rarely available outside tertiary referral hospitals. Amplitude integrated electroencephalography has filled this gap, providing a compressed, time-trended view of cortical activity at the cot side.

The technique gained traction throughout the era of therapeutic hypothermia for hypoxic-ischemic encephalopathy, when clinicians needed real-time reassurance that background activity was recovering and that subclinical seizures were being controlled. Over time its use has broadened to include preterm surveillance, metabolic disorders and post-cardiac-surgery neonates, transforming how neurocritical care is delivered in the newborn nursery.

The technology is not without controversy, particularly around interpretation variability and the risk of missing brief or low-amplitude events. Understanding its strengths, limitations and correct application is essential for any neonatal team aiming to deliver evidence-based neuroprotective care.

The clinical burden of neonatal seizures

Seizures in the newborn period affect roughly one to three per thousand live births in term infants and considerably more in preterm populations admitted to tertiary units. Hypoxic-ischemic encephalopathy remains the leading cause globally, followed by intracranial haemorrhage, stroke, infection, metabolic derangements and malformations of cortical development. Even when seizures themselves appear self-limited, they mark underlying brain injury and have been linked with worse neurodevelopmental outcomes, including cerebral palsy, epilepsy and cognitive impairment.

Australian data collated through the Australian and New Zealand Neonatal Network consistently show that infants with moderate to severe encephalopathy represent a significant proportion of neonatal intensive care workload in tertiary perinatal centres. Retrieval services such as the Newborn Emergency Transport Service in New South Wales, and counterparts in other states, routinely transport cooled infants across vast distances, where ongoing neurophysiological surveillance during transit has become an active topic among retrieval teams.

Early identification of seizure activity allows clinicians to initiate or refine anticonvulsant therapy, adjust sedation and reconsider the adequacy of neuroprotective strategies. Broader perinatal contributors, including the recognised impact of maternal obesity on neonatal outcomes, continue to shape the population of infants requiring such monitoring and reinforce the value of attentive neurocritical care.

How amplitude integrated EEG works

Amplitude integrated EEG, often abbreviated as aEEG, is derived from one or two channels of EEG signal that are filtered, compressed and displayed on a semi-logarithmic scale. The result is a continuous, time-trended tracing that emphasises changes in the lower and upper amplitude margins of the raw signal, which correspond to underlying background activity and seizure events. Most modern devices can also display the raw EEG beneath the trend, helping clinicians correlate suspected events with the source signal.

The technique was first popularised through the cerebral function monitor developed in the 1980s and has since evolved into more sophisticated digital systems with improved sampling rates, electrode configurations and artefact rejection. Two-channel recording, typically using parietal or central electrode pairs referenced to a distant site, has become standard because it improves detection of focal seizures that may be missed on a single channel.

Key practical advantages of the technique include:

• Continuous cot-side display without requiring a dedicated neurophysiologist
• Stability during transport and during therapeutic hypothermia
• Capacity for offline review across hours or days at a glance
• Lower cost and simpler electrode application than full multichannel EEG

These features have made aEEG especially attractive in regional centres where overnight EEG technician cover is unavailable, and for infants undergoing active cooling who cannot easily be moved to an EEG laboratory.

Applications in hypoxic-ischemic encephalopathy and cooling

The strongest evidence base for aEEG use lies in the management of term infants with hypoxic-ischemic encephalopathy undergoing therapeutic hypothermia. Background pattern within the first 24 to 48 hours of life is a robust predictor of neurodevelopmental outcome, and the early return of sleep-wake cycling during cooling is associated with better prognosis. Clinicians commonly use the Burdjalov score or similar tools to grade background activity, continuity, cycling and seizure burden, then track recovery across the cooling and rewarming phases.

Seizure detection during cooling presents particular challenges. Hypothermia itself reduces EEG amplitude and slows background activity, and many infants receive sedative infusions such as morphine and midazolam that further attenuate the tracing. Even so, the technique reliably identifies prolonged or recurrent electrographic seizures, enabling titration of anticonvulsants such as phenobarbitone, levetiracetam or midazolam infusions.

The use of aEEG also informs decisions about extending cooling beyond 72 hours, escalating care for infants with persistent suppression, and counselling families about likely neurological trajectory. In Australian units following Perinatal Society of Australia and New Zealand guidance, continuous monitoring throughout the cooling period has become standard practice where equipment is available.

Interpreting background patterns and seizure activity

Recognising the canonical patterns is the foundation of accurate aEEG interpretation. Background activity can be classified as continuous, discontinuous, burst-suppression, low voltage or flat, with each pattern carrying different prognostic implications. Sleep-wake cycling, when present, manifests as smooth sinusoidal variations in the lower margin of the tracing and is a particularly reassuring finding.

Seizures appear as sudden rises in both the lower and upper amplitude margins, producing a characteristic rhythmic elevation that usually lasts from several seconds to several minutes. Repetitive seizures within short periods constitute a high seizure burden, which itself is associated with adverse outcome independent of the underlying cause. Careful correlation with the raw channel helps distinguish true events from artefact caused by patting, suctioning or ventilation.

Common interpretive pitfalls include:

• Mistaking high-frequency artefact from servo-controlled mattresses for seizures
• Overlooking brief focal seizures that may not appear on the chosen channel montage
• Confusing cyclical sedative effects or respiratory artefact with seizure patterns

Accurate interpretation therefore benefits from regular review by clinicians with formal training, and ideally from intermittent confirmation with conventional EEG when atypical findings persist.

Use in Australian neonatal intensive care units

Practice across Australia varies according to centre size, retrieval infrastructure and local expertise. Large tertiary perinatal units such as the Royal Women's Hospital in Melbourne, the Royal Prince Alfred in Sydney and the Mater Mother's Hospital in Brisbane routinely perform aEEG monitoring as part of standard cooling protocols and high-risk preterm surveillance. Smaller regional units sometimes rely on telemetry-style monitoring during retrieval, with formal scoring on arrival at the receiving hospital.

The geographic spread of the Australian population introduces unique operational considerations. Retrievals from remote communities in the Northern Territory or far north Queensland often involve long flights, and maintaining electrode contact and signal quality throughout can be challenging. Teams increasingly carry portable cerebral function monitors on retrieval flights, allowing continuous recording that informs handover and guides subsequent therapy at the receiving centre.

Funding for monitoring equipment is generally managed within individual hospital budgets, although statewide perinatal networks have helped to standardise access. Collaboration through the Perinatal Society of Australia and New Zealand has supported the development of consensus guidelines on monitoring indications, electrode choice, scoring intervals and escalation to conventional EEG when findings are ambiguous.

Limitations and the role of conventional EEG

Although useful, amplitude integrated EEG is a screening and trend tool rather than a definitive diagnostic instrument. Short seizures under thirty seconds, low-amplitude focal discharges and seizures originating from deep midline sources may all be missed. Infants with abnormal backgrounds from congenital malformations, severe metabolic disease or profound sedation may have patterns that resist confident interpretation.

Conventional multichannel EEG remains the reference standard and is recommended when there is diagnostic uncertainty, when seizures persist despite treatment, or when atypical waveforms raise concern for non-seizure events. Many Australian centres now operate hybrid models, using aEEG for ongoing trend monitoring and reserving full EEG for specific clinical questions or for confirmation at key decision points such as consideration of withdrawal of intensive care.

Telemedicine and on-call EEG interpretation services are growing in some jurisdictions, but access remains uneven, particularly for rural and remote populations. Bridging this gap remains an active area of perinatal health system planning in Australia.

Training, quality and future directions

Interpretation of aEEG requires structured training, regular audit and ongoing exposure to maintain reliability. Several Australian centres have introduced credentialing pathways for neonatologists, fellows and senior nursing staff, often involving case review, scoring exercises and comparison with conventional EEG. Formal teaching modules delivered through the Perinatal Society of Australia and New Zealand and university-affiliated simulation programs have helped broaden expertise beyond the largest tertiary centres.

Emerging technologies are likely to refine the field. Quantitative EEG trends, automated seizure detection algorithms and machine-learning classifiers are increasingly integrated into commercial cerebral function monitors, promising more objective interpretation and earlier alerting. Combined with ongoing research into broader maternal and perinatal contributors, the discipline of neonatal neurocritical care continues to evolve.

Teams seeking to benchmark their protocols, access curated educational resources and engage with international colleagues are encouraged to explore the materials, abstracts and discussion forums hosted through FAOPS 2020. Such engagement helps translate technical advances into safer bedside practice and better long-term outcomes for vulnerable newborns across the region.