Understanding Your Baby's Tests: aEEG, MRI, and Blood Work
At a Glance
During HIE treatment, doctors monitor your baby's brain health using an aEEG for continuous electrical activity, blood tests to measure injury severity, and a brain MRI on days 4 to 10 to evaluate brain structure and help predict future development.
While your baby is being treated for Hypoxic-Ischemic Encephalopathy (HIE), the medical team uses a combination of real-time monitoring, blood tests, and advanced imaging to evaluate brain health and plan for the future.
aEEG: The Bedside Brain Monitor
In the NICU, you will see a monitor with a few wires attached to your baby’s head. This is the aEEG (amplitude-integrated EEG).
- What it does: It provides a continuous, simplified “snapshot” of the brain’s electrical activity at the bedside.
- Seizure Detection: Many seizures in babies treated with cooling are “subclinical,” meaning they don’t cause visible shaking. The aEEG helps doctors “see” these seizures so they can be treated with medication.
- Predictive Value: The “background pattern” of the aEEG is very important. If the brain activity returns to a normal, cycling pattern within 48 to 72 hours, it is a very positive sign for long-term recovery.
Blood Tests and Biomarkers
Doctors use specific substances in the blood, called biomarkers, to understand the severity of the initial oxygen loss:
- Lactate: High levels in the umbilical cord or the first hour of life indicate that the body was forced to use backup energy sources due to a lack of oxygen [1].
- LDH (Lactate Dehydrogenase): This enzyme is released when cells are stressed. High levels in the first 24 hours can help doctors predict the severity of the HIE.
- NSE (Neuron-Specific Enolase): This is a protein released specifically when brain cells (neurons) are injured [2].
The Brain MRI: The Gold Standard
A Magnetic Resonance Imaging (MRI) scan is the most detailed way to look at the brain’s structure.
- Timing: The optimal time for an HIE MRI is days 4 to 10 of life [3].
- Why wait?: The MRI is usually delayed until after the 72-hour cooling and rewarming period. This is because moving a baby while they are being cooled is difficult, and the full extent of the injury is often not clearly visible until the brain has had a few days to “evolve” after the event [4][3].
MRI Completeness Checklist
When you review the MRI report with your doctor, you may want to ask about these specific anatomical areas:
| Area of the Brain | Why it Matters |
|---|---|
| Basal Ganglia & Thalami | These deep areas use the most energy. Injury here is often seen in sudden, severe oxygen loss and can impact future motor skills. |
| Watershed Areas | These are the “end-of-the-line” areas for blood flow. Injury here is common in prolonged, partial oxygen loss and can affect cognitive development [5]. |
| PLIC (Internal Capsule) | The Posterior Limb of the Internal Capsule (PLIC) is a vital pathway for movement. A normal-looking PLIC is a very reassuring sign for a baby’s future motor ability. |
| Cerebellum | This area at the back of the brain helps with balance and coordination; it is also checked for volume and structure. |
Every baby’s brain is resilient, and the MRI is just one piece of the puzzle. It shows the brain’s structure at one moment in time, while your baby’s development will continue to unfold over the coming months and years.
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Common questions in this guide
What does an aEEG do for a baby with HIE?
Why is the brain MRI delayed until days 4 to 10?
What does a normal PLIC on an MRI mean?
What are biomarkers like lactate and LDH used for in HIE?
Questions to Ask Your Doctor
Curated prompts to bring to your next appointment.
- 1.What has the aEEG shown about my baby's brain activity 'background' in the first 48 hours?
- 2.When is my baby's brain MRI scheduled, and will it include a 'diffusion-weighted imaging' sequence?
- 3.Does the MRI report mention the 'PLIC' (internal capsule) and whether it looks normal?
- 4.Were any injuries found in the basal ganglia or the watershed areas of the brain?
- 5.What were the highest lactate and LDH levels recorded in the first 24 hours of life?
Questions For You
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References
References (5)
- 1
Predictions of Hypoxic-Ischemic Encephalopathy by Umbilical Cord Blood Lactate in Newborns with Birth Asphyxia.
Van Anh TN, Hao TK, Chi NTD, Son NH
Open access Macedonian journal of medical sciences 2019; (7(21)):3564-3567 doi:10.3889/oamjms.2019.581.
PMID: 32010377 - 2
Role of Netrin-1 in staging hypoxic ischemic encephalopathy.
Aycan N, Demir DÇ, Yürektürk E, et al.
Revista da Associacao Medica Brasileira (1992) 2025; (71(5)):e20241889 doi:10.1590/1806-9282.20241889.
PMID: 40531771 - 3
Prognostic Value of Brain Magnetic Resonance Imaging in Neonatal Hypoxic-Ischemic Encephalopathy: A Meta-analysis.
Sánchez Fernández I, Morales-Quezada JL, Law S, Kim P
Journal of child neurology 2017; (32(13)):1065-1073 doi:10.1177/0883073817726681.
PMID: 28925315 - 4
Hypothermia for newborns with hypoxic-ischemic encephalopathy.
Lemyre B, Chau V
Paediatrics & child health 2018; (23(4)):285-291 doi:10.1093/pch/pxy028.
PMID: 30657134 - 5
Long-term cognitive outcomes in term newborns with watershed injury caused by neonatal encephalopathy.
Lee BL, Gano D, Rogers EE, et al.
Pediatric research 2022; (92(2)):505-512 doi:10.1038/s41390-021-01526-2.
PMID: 34702974
This page explains HIE testing terminology for educational purposes. Your neonatologist and pediatric neurologist are the best sources for interpreting your baby's specific test results and imaging.
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