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Updated: Aug 2, 2025
Optic Nerve Sheath Point of Care Ultrasound: Image Acquisition
Published on: August 18, 2023
Effect of General Anesthesia on MR Optic Nerve Sheath Diameter in the Pediatric Population
Israel Cohen1,2, Matan Kraus1,2, Gahl Greenberg1,2
1Section of Neuroradiology, Division of Diagnostic Imaging, Sheba Medical Center, Ramat-Gan, Israel.
Insights
General anesthesia can increase optic sheath diameter (OSD) on brain MRI, mimicking signs of increased intracranial pressure (ICP). This finding is particularly relevant in pediatric patients, necessitating cautious interpretation of OSD in relation to anesthesia status.
Area of Science:
- Neuroimaging
- Pediatric Radiology
- Ophthalmology
Background:
- Papilledema is a key indicator of increased intracranial pressure (ICP).
- Optic nerve sheath distension on MRI is an indirect sign of elevated ICP.
- General anesthesia and positive pressure ventilation may influence optic sheath diameter (OSD) measurements.
Purpose of the Study:
- To investigate the impact of general anesthesia on optic sheath diameter (OSD) in pediatric patients.
- To evaluate the correlation between OSD, optic nerve diameter (OND), and peri-optic cerebrospinal fluid (CSF) with papilledema.
- To differentiate imaging findings related to anesthesia from those indicative of increased ICP.
Main Methods:
- Retrospective analysis of 154 MRI scans from 145 pediatric patients.
- Manual measurement of OSD, OND, and peri-optic CSF on T2-weighted MR images (1.5T or 3.0T).
- Comparison of measurements between patients with and without general anesthesia, and with or without papilledema.
- Receiver operating characteristic (ROC) analysis to evaluate diagnostic correlation.
Main Results:
- General anesthesia was associated with significantly larger mean OSD in both papilledema and non-papilledema groups.
- In the non-anesthesia group, higher OSD and larger peri-optic CSF rim were observed in papilledema patients.
- In the anesthesia group, OND was larger in papilledema patients, but peri-optic CSF rim showed limited correlation with increased ICP.
Conclusions:
- Increased OSD on pediatric brain MRI may be attributable to general anesthesia rather than elevated ICP.
- Anesthesia status must be considered when interpreting optic nerve sheath distension, especially in pediatric imaging.
- Further cautious reporting of OSD findings in conjunction with anesthesia is recommended.
Background:
Papilledema is thought to be the hallmark sign of increased intracranial pressure (ICP). Distension of the subarachnoid space within the optic nerve sheath is also commonly reported in MR studies as an indirect sign of increased ICP.
Hypothesis:
General anesthesia and positive pressure ventilation might result in changes in optic sheath diameter (OSD) observed on clinical brain MRI.
Study Type:
Retrospective.
Population:
One hundred forty-five patients (154 MRI scans, 7.3 years ± 5.1); 97 studies in the anesthesia group (4.4 years ± 3.4) of which 22 had papilledema, and 57 in the non-anesthesia group (12.3 years ± 3.2), of which 28 had papilledema.
Field Strength/Sequence:
1.5T or 3.0T volumetric T2 images. T2 images were obtained from different vendors.
Assessment:
OSD, optic nerve diameter (OND), and peri-optic cerebrospinal fluid (CSF) were measured manually on T2-weighted MR images for various population subgroups (with and without anesthesia; with or without papilledema). The correlation between these measurements and the clinical diagnosis of papilledema was evaluated via receiver operating characteristic (ROC) analysis.
Statistical Tests:
Chi-square test; Mann-Whitney Test; Spearman's test and ROCs; Interclass correlation coefficient, P = 0.05.
Results:
General anesthesia resulted in significantly larger mean OSD in patients with or without papilledema (7.3 ± 1.0 mm vs. 6.1 ± 1.1 mm and 6.7 ± 1.0 mm vs. 5.4 ± 0.9 mm, respectively). In the non-anesthesia group, the average OSD values (6.1 ± 1.1 mm) were significantly higher in papilledema patients compared to non-papilledema patients (5.4 ± 0.9 mm), with larger peri-optic CSF rim (1.6 ± 0.4 mm vs. 1.3 ± 0.3 mm). In the anesthesia group, OND was significantly larger in papilledema patients (3.4 ± 0.4 mm vs. 3.1 ± 0.5 mm), though the average peri-optic CSF rim did not reach a significance in papilledema compared with non-papilledema patients (2.0 ± 0.3 mm vs. 1.8 ± 0.4 mm, P = 0.06). In patients with general anesthesia, peri-optic CSF rim had a limited correlation with increased ICP.
Data Conclusion:
In the pediatric population, imaging findings of increased OSD on brain MRI might be related to general anesthesia rather than increased ICP. The interpretation of optic nerve sheath distention should be reported cautiously in conjunction with anesthesia status, especially in the pediatric population.
Evidence Level:
4 Technical Efficacy: 5.
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