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Method Article

Ultrasound-Measured Optic Nerve Sheath Diameter Predicts Cognitive Dysfunction After Resuscitation: A Retrospective Study

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DOI:

10.3791/70156

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April 24th, 2026

 ,  ,  ,  ,  ,  ,  ,  ,  , 
1Department of Ultrasound, The Third Hospital of Wuhan, 2Department of Public Health, The Third Hospital of Wuhan

* These authors contributed equally

In This Article

Summary

This retrospective observational study evaluated optic nerve sheath diameter (ONSD) as a predictor of cognitive dysfunction in post-resuscitation neurological ICU patients. Persistently elevated ONSD values were associated with poor neurological outcomes, supporting its role as a rapid and non-invasive prognostic tool.

Abstract

Optic nerve sheath diameter (ONSD) measured by bedside ultrasonography has emerged as a promising non-invasive surrogate marker of intracranial pressure and may have prognostic value in post-resuscitation patients. This retrospective observational study evaluated the utility of ONSD in predicting cognitive dysfunction among neurological intensive care unit (ICU) patients following cardiac arrest. A total of 60 adult patients who achieved return of spontaneous circulation (ROSC) were initially identified, of whom 48 patients with complete follow-up data were included in the final analysis. Serial ONSD measurements were obtained at baseline (within 6 h post-ROSC), 24 h, and 72 h using standardized transorbital ultrasound techniques. Neurological status was assessed using the Glasgow Coma Scale (GCS), and cognitive outcomes were evaluated using the mini-mental state examination (MMSE) and the Montreal cognitive assessment (MoCA) after recovery of consciousness. Patients with favorable neurological outcomes demonstrated significantly lower baseline ONSD values and a progressive decline over time, which correlated with improvement in GCS scores. In contrast, persistently elevated ONSD values were associated with poor cognitive outcomes, minimal neurological recovery, and higher early mortality. Receiver operating characteristic analysis identified an ONSD cutoff value of 5.8 mm for predicting poor outcomes, with a sensitivity of 42.9% and specificity of 85.9%. These findings suggest that serial ONSD measurements are a rapid, reproducible, and non-invasive bedside tool that may aid early neurological prognostication following cardiac arrest. Integration of ONSD with clinical parameters may enhance risk stratification in critical care settings.

Introduction

Cardiac arrest (CA) is one of the main causes of mortality and long-term neurological disability in the world, and survivors often have post-resuscitation brain injury that is defined by cognitive impairments, encephalopathy, and lack of functional recovery1,2. Timely detection of patients at risk of adverse neurological outcomes is necessary in the right direction to inform therapeutic interventions, prognostic counseling, and intensive care resources. Nevertheless, prognostic tools currently in use, such as the neurological examination, serum biomarkers, such as neuron-specific enolase, and neuroimaging, such as computed tomography (CT) and magnetic resonance imaging (MRI), have significant limitations of latency, low sensitivity or specificity, high cost, and infeasibility in continuous bedside use3,4,5.

The combined objective of this methodology is to develop a standardized, reproducible, non-invasive, bedside technique of measuring intracranial dynamics by using the ultrasound-measured optic nerve sheath diameter (ONSD) and to determine its capacity to predict cognitive dysfunction in post-resuscitation intensive care unit (ICU) patients. The reasoning behind ONSD implementation is that there is an anatomical continuity between the optic nerve sheath and the intracranial subarachnoid space so that alterations occurring in intracranial pressure (ICP) can be passed over to the optic nerve sheath and measured with ultrasonography6,7. Since Cerebral edema and increased ICP are closely related to post-cardiac arrest brain injury, ONSD measurement is a physiologically applicable surrogate endpoint of early neurological impairment.

The ONSD assessment using ultrasound has a number of distinct advantages as compared to alternative methods. In comparison with invasive ICP monitoring, it means the absence of complications of the procedure (infection or hemorrhage). Compared to CT and MRI, it can be performed at the bedside, is repeatable, inexpensive, portable, and does not require radiation or the transportation of the patient. Further, ONSD measurement makes it possible to monitor dynamically and serially, which is especially helpful in patients with unstable neurological states who are critically ill and have a rapidly changing condition8,9,10. Past research has shown that ONSD is strongly correlated with high ICP and is a prognostic factor in patients with traumatic brain injuries and post-cardiac arrests11,12. Nevertheless, the imprecision of measurement methods and the absence of unified procedures have contributed to its absence in clinical use.

In the larger literature, ONSD is now being identified as an accurate non-invasive biomarker of intracranial hypertension, with systematic reviews and meta-analyses showing good diagnostic accuracy in measuring elevated ICP13,14,15. However, it has not been comprehensively studied as a predictor of cognitive impairment after resuscitation, especially when it comes to serial measures and standard methods of acquisition.

This approach is especially applicable to clinicians in emergency and critical care environments in need of a fast, reproducible, non-invasive instrument to evaluate early neurological status. It is particularly useful in cases where sophisticated neuroimaging or invasive monitoring is not easily available and practicable. Nevertheless, accurate training of the operator, following standardized measurement procedures, and taking into account confounding factors, including orbital pathology or edema, is necessary to achieve measurement accuracy and reproducibility. Thus, the aim of the study is to standardize the use of ultrasound-based ONSD and determine its clinical potential as a bedside prognostic variable assessing the predictability of cognitive impairment in post-resuscitation ICU patients.

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Protocol

Retrieved records of adult patients admitted to the neurological intensive care unit (ICU) following cardiac arrest over a defined 12-month period. Confirmed that all patients had achieved return of spontaneous circulation (ROSC). This study was approved by the Ethics Committee of The Third Hospital of Wuhan (No.: KY2025-044). Consent requirements were waived for retrospective data collection in accordance with the Declaration of Helsinki and good clinical practice guidelines.

1. Inclusion and exclusion criteria

  1. Include adult patients aged ≥18 years who achieved return of spontaneous circulation (ROSC) following cardiac arrest and were admitted to the neurological ICU within 6 h.
  2. Exclude patients with pre-existing optic nerve disorders (e.g., optic neuritis or glaucoma), ocular trauma, prior orbital surgery, significant facial or orbital edema interfering with ultrasound probe placement, or inadequate ultrasound windows.
    NOTE: A minimum of 60 patients were enrolled based on feasibility and prior literature evaluating the relationship between ONSD and intracranial pressure (ICP).

2. Extracted baseline demographic and clinical data

  1. Collect baseline data from medical records, including age, sex, comorbidities, cause of cardiac arrest, initial cardiac rhythm (shockable or non-shockable), duration of resuscitation, time to ROSC, and sequential organ failure assessment (SOFA) score.
  2. Record initial Glasgow Coma Scale (GCS) scores at ICU admission.

3. Preparation of the patient for transorbital ultrasound examination

  1. Position the patient in the supine position with the head elevated at approximately 20–30°.
  2. Ensure that the patient’s eyes remain closed.
  3. Apply sterile ultrasound gel over the upper eyelid and avoid excessive probe pressure to prevent distortion of optic nerve sheath diameter measurements.

4. Optic nerve sheath diameter (ONSD) measurement using ultrasound

  1. Use a high-frequency linear ultrasound probe (7.5–13 MHz).
  2. Place the probe gently over the closed eyelid and obtain transverse and sagittal views of the optic nerve.
  3. Identify the optic nerve as a hypoechoic structure posterior to the globe and measure the optic nerve sheath diameter at a standardized distance of 3 mm posterior to the retina.

5. Bilateral ONSD measurements and mean value calculation

  1. Obtain three measurements from each eye in both transverse and sagittal planes.
  2. Calculate the average value for each eye and then compute the overall mean ONSD from both eyes to minimize variability.

6. Serial ONSD measurements at predefined time points

  1. Perform ONSD measurements at baseline (within 6 h after ROSC) and repeated measurements at 24 h and 72 h.
  2. Maintain consistency in measurement technique and anatomical landmarks across all time points.

7. Assessment of neurological status using the Glasgow Coma Scale (GCS)

  1. Evaluate the neurological status at ICU admission and conduct daily assessments using the Glasgow Coma Scale.
  2. Record the changes in GCS scores throughout the ICU stay.

8. Evaluation of cognitive function using standardized assessment tools

  1. Assess the cognitive function after recovery of consciousness using the Mini-Mental State Examination (MMSE).
  2. Conduct additional evaluation using the Montreal Cognitive Assessment (MoCA) when patients were clinically stable and able to participate reliably.

9. Storage of clinical and imaging data in a structured database

  1. Document all the ultrasound measurements, clinical variables, and outcome data in a standardized data collection form.
  2. Ensure the accuracy and completeness of the dataset for analysis.

10. Primary and secondary outcome measures

  1. Define the primary outcome as post-resuscitation cognitive dysfunction based on standardized cognitive assessment scores.
  2. Defined secondary outcomes as the association between ONSD and neurological status (GCS), temporal trends in ONSD measurements, and patient mortality during ICU stay. The specific material information covered by the plan can be found in the Table of Materials.

11. Statistical analysis and evaluated correlations

  1. Analyze the data using statistical software (SPSS version 26.0).
  2. Express the continuous variables as mean ± standard deviation and categorical variables as frequencies and percentages.
  3. Perform Pearson correlation and regression analyses to evaluate associations between ONSD and clinical outcomes.
  4. Conduct receiver operating characteristic (ROC) curve analysis to determine optimal ONSD cutoff values, with statistical significance set at p < 0.05.

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Results

A total of 60 patients were enrolled in the study as per the available database. Of these, 48 completed full follow-up and were included in the final analysis. While 12 were excluded due to incomplete follow-up or poor ultrasound visualization. The mean age of participants was 56.4 ± 10.7 years, with a male-to-female ratio of 1.8:1.

Positive outcomes
In patients who demonstrated good neurological recovery (defined as regaining full consciousness with mini-mental state exam...

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Discussion

This paper reveals that measurement of optic nerve sheath diameter (ONSD) by means of ultrasound is a viable, fast, and non-invasive method of predicting cognitive impairment in post-resuscitation ICU patients. Continuous high ONSD levels corresponded with unfavorable neurological and cognitive results, and declining tendencies were linked with recovery, indicating that it can be utilized as a surrogate endpoint of intracranial pressure (ICP). The results are consistent with the findings of earlier studies which indicate...

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Disclosures

The authors declare that there are no conflicts of interest related to this study or its publication.

Acknowledgements

The authors sincerely thank the reviewers and the editor for their valuable comments and guidance, which have greatly helped improve the quality of this manuscript.

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Materials

List of materials used in this article
NameCompanyCatalog NumberComments
Portable Ultrasound SystemMindray Medical International Co., Ltd.M9 or TE7 seriesUsed for bedside ultrasonographic measurement of ONSD in ICU settings. Compact and high-resolution imaging capability.
High-frequency Linear Probe (7.5–13 MHz)Mindray / Philips / GE Healthcaree.g., L12-4 (Philips), L10-5 (Mindray), or ML6-15 (GE)Required for precise visualization of the optic nerve and sheath; allows measurement 3 mm posterior to globe.
Sterile Ultrasound GelParker Laboratories Inc.AQUASONIC® 100 (Ref 01-08)Sterile coupling gel applied over closed eyelid to ensure acoustic contact; avoids infection risk.
Sterile Ultrasound Probe CoversCIVCO Medical SolutionsCIV-FCV-610Sterile single-use cover for eye scanning; ensures infection control and patient safety.
Patient Monitor (ECG, BP, SpO2)Philips IntelliVue MX550 / Mindray BeneVision N12–Continuous monitoring of vital signs during and after ultrasound measurement.
GCS Assessment Chart / Cognitive Scales––Standardized Glasgow Coma Scale scoring sheet for serial assessment.
Mini-Mental State Examination (MMSE) ToolkitPsychological Assessment Resources, Inc.MMSE-2™Used to evaluate global cognitive function after patient regains consciousness.
Montreal Cognitive Assessment (MoCA) FormMoCA Test Inc. (Official license)–Used for screening mild cognitive impairment; translated and validated in Chinese population.
Data Collection Sheets / Electronic CRFSelf-designed (SPSS-compatible)–Used to record demographic data, ONSD, cognitive scores, and clinical variables.
Statistical SoftwareIBM CorporationSPSS v26.0Used for correlation and regression analyses (ONSD vs. cognitive outcome).
Hospital Information System (HIS)Wuhan Third Hospital HIS platform–Source for retrieving patient demographics and clinical parameters post-ROSC.

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ONSD MeasurementIntracranial PressureBedside UltrasoundCardiac ArrestNeurological PrognosticationGlasgow Coma ScaleMini Mental StateMontreal Cognitive Assessment
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