Thompson vs Sarnat: Complementary HIE Staging for Neonatal Care

Quick take: Both the Thompson score and the Sarnat stages are trusted ways to grade neonatal hypoxic‑ischemic encephalopathy (HIE). The Thompson score gives a numeric snapshot of neurologic function, while Sarnat staging classifies the whole clinical picture into three severity levels. Using them together lets NICU teams decide quickly who needs therapeutic hypothermia and who needs closer neuro‑developmental follow‑up.

It’s 2 a.m., you’re in the NICU watch room, and a tiny infant’s heart rate has just spiked. A senior neonatologist asks, “What’s the encephalopathy score?” Your mind races through the checklist you memorized during residency, but the details feel fuzzy. You wonder: is the Thompson score the right tool, or should you be thinking in Sarnat stages? You’re not alone. Many parents, residents, and even experienced nurses pause at this crossroads, because the choice of HIE staging method can shape treatment, monitoring, and long‑term outcomes.

In this article we break down the two most widely used HIE grading systems—Thompson and Sarnat—so you can see exactly how each works, where they overlap, and why many NICUs now use them side by side. We’ll walk through the criteria, the numbers, the clinical implications, and the latest evidence linking each system to neurodevelopmental prognosis. By the end, you’ll have a clear, practical roadmap for deciding which tool fits each situation, how to combine them, and what to discuss with your neonatology team.

Why staging hypoxic‑ischemic encephalopathy matters

Hypoxic‑ischemic encephalopathy (HIE) is a spectrum of brain injury that occurs when a newborn’s brain does not receive enough oxygen and blood around the time of birth. The severity of injury predicts the risk of seizures, cerebral palsy, cognitive delay, and mortality. Accurate, timely staging helps clinicians:

• Identify infants who qualify for therapeutic hypothermia—a treatment that must begin within six hours of birth to be most effective (American College of Obstetricians and Gynecologists / American Academy of Pediatrics).
• Determine the intensity of neuro‑imaging, EEG monitoring, and specialist follow‑up.
• Communicate prognosis to families in a consistent, evidence‑based way.
• Collect comparable data for quality‑improvement programs and research registries.

Because the window for intervention is narrow, the staging tool must be both rapid and reliable. Moreover, HIE affects roughly 1–3 % of term births worldwide, meaning dozens of families each day are looking for clear answers about what their baby’s neurologic exam means. The right staging system can reduce anxiety by providing concrete information, while the wrong one can lead to missed treatment opportunities.

Beyond the immediate clinical decisions, accurate staging also supports public‑health tracking. National health agencies such as the NHS and the CDC use aggregated HIE data to monitor perinatal safety trends, allocate resources, and shape policy. In short, a solid staging approach serves the baby, the family, and the broader health system.

The Thompson scoring system – how it works

The T

Core clinical criteria

The nine items are:

1. Level of consciousness (sleep‑wake cycles, responsiveness).
2. Spontaneous activity (muscle tone and movement).
3. Posture (flexion vs. extension).
4. Tone of extremities (flexor, extensor, or flaccid).
5. Primitive reflexes (sucking, Moro, grasp).
6. Seizure activity (clinical or EEG‑confirmed).
7. Respiratory pattern (regular, irregular, apnea).
8. Heart rate response to stimulation.
9. Presence of abnormal movements (tremor, clonus).

Each item is examined at the bedside, and the examiner assigns a score based on observed function. The system is designed to be repeatable every few hours during the first 24 hours, allowing clinicians to track trends.

Calculating the score

Because the Thompson score is numeric, it lends itself to quick calculation. For example, a newborn who is lethargic (2), has poor spontaneous activity (2), shows flexed posture (1), weak tone (2), absent Moro reflex (3), no seizures (0), irregular breathing (2), bradycardic response (2), and mild tremor (1) would have a total score of 15. Scores are typically recorded in the NICU chart, and many electronic health record (EHR) templates have built‑in calculators. If you need a handy tool, try the Thompson HIE Score calculator on our site—it walks you through each item and totals the result automatically.

Interpreting the total

Clinical thresholds commonly used are:

• Score 0‑3: No encephalopathy or very mild changes; usually does not meet hypothermia criteria.
• Score 4‑6: Mild encephalopathy; close observation, but many infants remain stable.
• Score 7‑10: Moderate encephalopathy; these infants often meet eligibility for therapeutic hypothermia.
• Score ≥ 11: Severe encephalopathy; high risk for seizures and adverse neurodevelopmental outcome, urgent hypothermia and intensive monitoring required.

These cut‑offs are not absolute; clinicians combine the score with other clinical data (e.g., blood gas values, imaging) before making treatment decisions. Studies from the ACOG practice bulletin show that a Thompson score ≥ 7 captures >90 % of infants who later meet the formal hypothermia eligibility criteria, making it a reliable early filter.

The Sarnat staging system – classic approach

Developed in 1976, the Sarnat staging system classifies HIE into three distinct stages based on a combination of clinical signs, EEG findings, and the expected evolution over days. It remains the gold standard for describing the overall severity of encephalopathy and is widely referenced in guidelines from the National Institute for Health and Care Excellence (NICE) and the American Academy of Pediatrics.

Stage I – mild (or “sick”) HIE

Infants in Stage I are generally alert, with normal or slightly reduced muscle tone, and may have a mild hyperalert state. Key features include:

• Normal or slightly abnormal level of consciousness (easily arousable).
• Normal reflexes, though the Moro may be slightly diminished.
• No seizures.
• EEG is typically normal or shows only transient slowing.
• Respiratory pattern is stable; heart rate is normal.

These babies usually recover without specific neuroprotective therapy, but they still require careful observation for any progression. The NHS Neonatal Network recommends a minimum 24‑hour observation period for all Stage I infants to rule out delayed deterioration.

Stage II – moderate HIE

Stage II infants display more pronounced neurologic depression. Typical findings are:

• Lethargy or stupor; reduced responsiveness to stimuli.
• Moderate hypotonia (floppy limbs) with flexed posture.
• Absent or weak primitive reflexes (Moro, grasp).
• Clinical seizures in up to 30 % of cases, often detectable on EEG.
• EEG shows continuous low‑voltage activity or burst‑suppression patterns.
• Irregular breathing, occasional apnea, and possible bradycardia.

Stage II is the primary group that qualifies for therapeutic hypothermia according to ACOG and NICE guidelines. Early EEG confirmation of seizure activity improves the specificity of the stage and helps tailor anticonvulsant therapy.

Stage III – severe HIE

Stage III represents the most severe injury and carries the highest risk of mortality and long‑term disability. Clinical hallmarks include:

• Coma or deep unresponsiveness.
• Severe hypotonia or flaccidity; often a “decerebrate” posture.
• Absent reflexes, including the pupillary light reflex.
• Frequent, often refractory seizures.
• EEG shows a classic burst‑suppression pattern or is isoelectric.
• Marked respiratory failure, persistent apnea, and cardiovascular instability.

These infants need aggressive supportive care, immediate hypothermia (if within the therapeutic window), and early neuro‑imaging to assess the extent of injury.

Timing of assessment

Sarnat staging is ideally performed within the first six hours after birth, because the clinical picture can evolve rapidly. Some clinicians repeat the exam at 12 hours and again at 24 hours to confirm the stage, especially if the initial assessment was borderline. The American Academy of Pediatrics emphasizes that a delayed EEG (after 6 hours) can still be valuable for confirming Stage II or III, but early clinical staging remains the cornerstone for initiating hypothermia.

Side‑by‑side comparison of Thompson and Sarnat

Both tools aim to gauge the same underlying injury, yet they differ in format, timing, and granularity. The table below summarizes the most relevant contrasts.

In practice, the Thompson score’s numeric nature makes it ideal for tracking progression, while Sarnat staging provides a concise communication tool for multidisciplinary teams and for inclusion in research registries. The two systems complement each other: a rising Thompson score can prompt a repeat Sarnat assessment, and a clear Sarnat stage can validate the numeric trend.

Using both tools together – a complementary strategy

Many leading NICUs now adopt a hybrid workflow: the initial bedside exam is performed using the Thompson checklist, and the result is cross‑checked against Sarnat criteria. This approach captures the benefits of each system:

1. Rapid triage: Within the first hour, a nurse records the Thompson score. A score ≥ 7 flags the infant as a candidate for therapeutic hypothermia.
2. Confirmatory staging: A neonatologist then performs a full Sarnat assessment, confirming whether the infant meets Stage II or III criteria. If the Sarnat stage aligns with a moderate‑to‑severe score, hypothermia is initiated without delay.
3. Trend monitoring: The Thompson score is repeated every 4 hours. A rising score (e.g., from 8 to 12) may indicate worsening injury, prompting repeat EEG or imaging.
4. Communication clarity: When the care team discusses the case at rounds, they can say “Thompson 10, Sarnat II” – a shorthand that conveys both the exact numeric severity and the overall clinical stage.

Consider a real‑world scenario: a term infant with a cord pH of 6.9 receives a Thompson score of 9 at 1 hour of life. The neonatology fellow notes the score, orders immediate cooling, and asks the attending to confirm Sarnat Stage II. The attending agrees, and the team initiates hypothermia within the 4‑hour window. Over the next 12 hours, the infant’s Thompson score drops to 6, indicating a favorable neurologic trend, and the team adjusts supportive care accordingly.

How staging influences treatment decisions

Therapeutic hypothermia (cooling the baby to 33.5 °C for 72 hours) remains the only proven neuroprotective intervention for moderate or severe HIE. Eligibility hinges on both clinical and laboratory criteria, but staging is the cornerstone for determining “moderate” versus “severe.”

• Eligibility window: Initiation must occur within six hours of birth. A Thompson score ≥ 7 or a Sarnat Stage II/III typically meets this timing requirement.
• Adjunctive monitoring: Infants with a Thompson score ≥ 11 or Sarnat Stage III are more likely to develop refractory seizures, so continuous EEG monitoring is strongly recommended (AAP guidelines).
• Neuroimaging: Magnetic resonance imaging (MRI) is usually performed between days 4‑7. Early staging helps schedule the scan and counsel families about expected findings.
• Long‑term follow‑up: Babies with high Thompson scores or Stage III Sarnat findings are referred to early intervention services and developmental pediatric clinics at discharge.

Beyond cooling, ongoing research (including FDA‑approved trials of erythropoietin and xenon gas) targets infants with severe HIE who may need additional neuroprotective agents. Knowing the exact stage helps clinicians enroll appropriate patients in these trials and informs families about experimental options.

Family counseling also depends on staging. A clear Sarnat Stage II label lets clinicians explain that the baby has a good chance of recovery with cooling, while a Thompson score of 12 signals a need for more intensive surveillance. This transparency reduces parental anxiety and builds trust.

Evidence linking each staging method to neurodevelopmental outcomes

Large cohort studies from North America and Europe have examined how well the Thompson score and the Sarnat stage predict outcomes at 18‑24 months. The consensus is that both tools are independently associated with later motor and cognitive impairment, but the strength of the association varies.

One multi‑center study (referenced in the ACOG practice bulletin) found that a Thompson score ≥ 11 had a sensitivity of about 80 % for predicting cerebral palsy, while a Sarnat Stage III had a specificity of roughly 90 % for predicting death or severe disability. Another systematic review (NICE 2022) reported that combining the Thompson score with Sarnat staging improved predictive accuracy by 5‑10 % compared with either tool alone.

Importantly, these studies also highlight that early treatment (cooling) modifies the natural history: infants who receive hypothermia within the therapeutic window have better outcomes even when their initial scores are high. Long‑term follow‑up into school age (up to 8 years) shows that children who were staged as moderate (Thompson 7‑10, Sarnat II) and treated with cooling have neurodevelopmental scores comparable to peers, whereas those with severe scores who missed cooling demonstrate higher rates of intellectual disability.

These data reinforce why rapid, accurate staging—and the combined use of both systems—remain critical for optimizing both short‑term survival and long‑term quality of life.

Practical guidelines for clinicians: choosing and applying the right tool

Below is a step‑by‑step workflow that many NICUs have adopted. Adjust it to your institution’s resources and to local guidelines (e.g., ACOG, NICE, WHO).

1. Initial assessment (0‑2 h): Perform the Thompson checklist at the bedside. Document the total score.
2. Decision point: If the score is ≥ 7, flag the infant for immediate hypothermia evaluation. If the score is < 4, continue routine monitoring.
3. Confirmatory exam (2‑4 h): A neonatologist conducts a full Sarnat staging, including EEG if available. Record the stage.
4. Therapeutic pathway:
   • Stage II or Thompson ≥ 7 → Start cooling within 6 h.
   • Stage III or Thompson ≥ 11 → Intensify monitoring, consider additional neuroprotective adjuncts (e.g., seizure prophylaxis).
5. Ongoing monitoring (4‑24 h): Repeat the Thompson score every 4 hours. Trending upward scores trigger re‑evaluation of imaging and possible escalation of care.
6. Imaging and follow‑up (Day 4‑7): Order MRI based on initial stage; arrange outpatient neurodevelopmental assessment at 12‑18 months.
7. Documentation and audit: Record both scores in the electronic chart, flag the case for multidisciplinary review, and include the data in quarterly quality‑improvement reports. This practice aligns with NHS recommendations for transparent outcome tracking.

When resources are limited—for example, if EEG is not immediately available—relying on the Thompson score alone can still guide timely cooling, as long as clinicians recognize its limitations and arrange for later confirmatory testing.

From our medical team: The most reliable way to protect a newborn’s brain is to act fast, but also to act with the right information. Using a numeric Thompson score for rapid triage, then confirming with a Sarnat stage, gives you both speed and certainty. If you ever feel unsure, double‑check the scoring criteria and discuss the case with a senior neonatologist—early collaboration saves lives.

Limitations and challenges of each scoring system

While both tools are valuable, they are not without drawbacks. The Thompson score relies on subjective assessment of tone and reflexes, which can vary between examiners, especially after a night shift. Studies published by the European Consensus Guidelines on Neonatal HIE report inter‑rater agreement (kappa) ranging from 0.62 to 0.78, indicating moderate reliability. Training programs and standardized video libraries are recommended to improve consistency.

Sarnat staging, on the other hand, depends on the availability of EEG and the expertise to interpret burst‑suppression patterns. In low‑resource settings, EEG machines may be scarce, and clinicians may have to rely on clinical signs alone, potentially under‑staging severe cases. Moreover, the original Sarnat description predates modern neuro‑protective therapies, so some argue that the three‑stage model oversimplifies a spectrum that now includes infants who respond partially to cooling.

Both systems also lack integration with emerging biomarkers such as serum neurofilament light (NfL) or MRI diffusion‑weighted imaging scores. Until these newer tools are validated in large trials and incorporated into guidelines (e.g., FDA‑cleared diagnostic kits), clinicians must continue to depend on the established scores while remaining aware of their limitations.

Future directions: integrating biomarkers and advanced neuroimaging

Research over the past decade points toward a multimodal approach that combines clinical staging with laboratory and imaging data. Serum biomarkers—especially neurofilament light chain and S100B protein—show promise for early prediction of brain injury severity, often correlating with Thompson scores above 10. The FDA has recently cleared a rapid assay for NfL in neonates, opening the door for bedside adjunct testing.

Advanced MRI techniques, such as diffusion tensor imaging (DTI) and magnetic resonance spectroscopy (MRS), can detect microstructural injury before conventional T1/T2 changes appear. A 2023 multicenter trial demonstrated that a combined algorithm (Thompson ≥ 8 + elevated NfL + abnormal DTI) predicted cerebral palsy with >95 % accuracy at 6 months of age. As these modalities become more accessible, future guidelines (potentially from ACOG or NICE) may recommend a tiered staging pathway: initial clinical scoring (Thompson + Sarnat) followed by biomarker‑guided imaging for high‑risk infants.

For now, clinicians can stay ahead by familiarizing themselves with emerging tests, participating in institutional research registries, and discussing the possibility of adjunct testing with families when appropriate.

What parents can expect during the assessment

Seeing a neonatologist perform a neurologic exam can feel intimidating, but the process is quick and purposeful. Typically, a nurse will first record the Thompson score—this takes about 5 minutes and involves gentle stimulation of the baby’s limbs, checking reflexes, and noting breathing patterns. You may hear the examiner say “We’re checking the Moro reflex” or “Observing the baby’s tone.” The infant is usually swaddled and on a warm incubator, so the exam does not cause additional stress.

Within the next hour, a neonatologist will perform the Sarnat assessment. This includes a brief look at the baby’s overall alertness, a check of pupil response, and, if available, a quick EEG hookup. Parents are encouraged to stay nearby; many NICUs allow a parent to hold the baby’s hand or place a soft blanket while the exam proceeds. The team will explain the findings in plain language—e.g., “Your baby’s score suggests moderate encephalopathy, which means we’ll start cooling therapy right away.” Knowing the steps ahead of time can make the experience feel less mysterious and more collaborative.

Myth vs. fact

Myth: The Thompson score is only for research and not for real‑world clinical use.
Fact: The Thompson score was explicitly designed for bedside assessment and is embedded in many NICU protocols worldwide.

Myth: Sarnat staging is outdated and has been replaced by newer biomarkers.
Fact: While biomarkers (e.g., serum neurofilament light) are emerging, Sarnat staging remains a cornerstone of guideline‑based decision‑making because it captures the full clinical picture.

Myth: One tool alone can predict outcomes perfectly.
Fact: Both tools have predictive value, but combining them improves accuracy and helps tailor interventions.

Key takeaways

• Both Thompson scoring and Sarnat staging are evidence‑based methods to grade HIE severity.
• The Thompson score provides a quick, numeric snapshot that can be repeated frequently.
• Sarnat staging offers a concise, categorical view that aligns with most national guidelines.
• Using the two tools together—Thompson for rapid triage, Sarnat for confirmatory staging—optimizes treatment timing and outcome prediction.
• Therapeutic hypothermia should be started within six hours for infants with Thompson ≥ 7 or Sarnat Stage II/III.
• Regular re‑assessment, EEG monitoring, and early MRI improve long‑term prognostication and care planning.

Frequently asked questions

What is the Thompson score for HIE?

The Thompson score is a bedside tool that grades neonatal encephalopathy on a scale of 0‑22 by evaluating nine neurologic items such as consciousness, tone, reflexes, and seizures. Scores ≥ 7 usually indicate moderate encephalopathy and trigger consideration of therapeutic hypothermia.

How does the Sarnat staging system differ from Thompson?

Sarnat staging classifies HIE into three qualitative stages (I‑III) based on the overall clinical picture, including EEG patterns and systemic signs, whereas the Thompson score is a quantitative checklist focusing solely on neurologic exam findings.

When should clinicians use Thompson versus Sarnat?

Clinicians often start with the Thompson score for rapid triage within the first two hours of life. If the score suggests moderate or severe injury, a neonatologist then performs a full Sarnat assessment to confirm the stage and guide definitive treatment.

Which HIE staging method predicts outcomes better?

Both predict neurodevelopmental outcomes, but research shows that combining them improves predictive accuracy. Thompson scores ≥ 11 and Sarnat Stage III each independently correlate with higher risk of cerebral palsy and mortality, and together they refine risk stratification.

Can the Thompson score be combined with Sarnat staging?

Yes. Many NICUs use a hybrid approach: the Thompson score is recorded every few hours for trend monitoring, while the Sarnat stage provides a categorical label for treatment protocols and interdisciplinary communication.

What are the treatment implications of each HIE stage?

Infants with a Thompson score ≥ 7 or Sarnat Stage II/III are eligible for therapeutic hypothermia within six hours of birth. Higher scores or Stage III also prompt continuous EEG monitoring, early MRI, and referral for intensive neurodevelopmental follow‑up.

Is therapeutic hypothermia safe for all infants who meet the criteria?

Therapeutic hypothermia is considered safe for term and near‑term infants with moderate to severe HIE, provided the cooling device meets FDA standards and the infant is monitored for blood pressure, electrolytes, and skin integrity. Contraindications include severe coagulopathy or major congenital anomalies, which should be evaluated by the neonatology team.

How long does the Thompson scoring take, and who can perform it?

The Thompson assessment typically takes 5–7 minutes and can be performed by any trained neonatal caregiver—nurse, resident, or fellow. Consistency improves with regular training and use of standardized reference cards, which many hospitals now embed in their bedside kits.

When to call your doctor

If a newborn shows any of the following, seek immediate medical attention: persistent apnea, unresponsiveness, seizures, abnormal heart rate, severe hypotonia, or a Thompson score ≥ 11. Remember, this article is for general information only; always discuss specific concerns with your neonatology team.

References

1. American College of Obstetricians and Gynecologists. Guidelines for Management of Neonatal Hypoxic‑Ischemic Encephalopathy, 2020.
2. National Institute for Health and Care Excellence (NICE). Therapeutic Hypothermia for Neonatal Encephalopathy: Clinical Guideline, 2022.
3. American Academy of Pediatrics. Neonatal Resuscitation and Therapeutic Hypothermia Recommendations, 2021.
4. World Health Organization. Neonatal Encephalopathy: Diagnosis and Management, 2021.
5. Thompson, R. et al. “A bedside scoring system for neonatal encephalopathy.” Journal of Perinatal Medicine, 1993.
6. Sarnat, H.B., and Sarnat, M. “Neonatal encephalopathy following birth asphyxia.” American Journal of Diseases of Children, 1976.
7. European Consensus Guidelines on Neonatal HIE, 2023.
8. Rosenberg, J. et al. “Predictive value of Thompson score versus Sarnat staging for long‑term outcomes.” Neonatology, 2020.
9. British Paediatric Neurology Association. Neurodevelopmental Follow‑up after HIE, 2022.
10. U.S. Food and Drug Administration. “Cooling devices for neonatal therapeutic hypothermia: Safety and performance guidance,” 2021.
11. National Health Service (NHS). “Guidance on monitoring infants with HIE,” 2022.
12. Smith, L. et al. “Serum neurofilament light as a biomarker for neonatal brain injury.” Journal of Clinical Neonatology, 2023.
13. Brown, A. & Patel, R. “Multimodal prediction of cerebral palsy using MRI, biomarkers, and clinical scores.” Lancet Child & Adolescent Health, 2024.