Viral encephalitis is a common disease in children's neurology. The clinical symptoms just like headache, vomiting and hyperspasmia are related to ICP. In severe cases, increased ICP can lead to cerebral hernia and consciousness disorder. Accurately monitoring changes in intracranial pressure, early identification of moderate to severe intracranial pressure elevation, and timely appropriate intervention are of great significance to improve the prognosis of brain function and reduce mortality in children.

This study recruited children who were diagnosed with viral encephalitis from May 2022 to June 2024 in the Department of Pediatrics, Yuyao Branch of the Second Affiliated Hospital of Zhejiang University. The diagnosis of viral encephalitis was based on the criteria of the International Encephalitis Collaboration Group. The study has been approved by the Ethics Committee of the Yuyao People's Hospital. All children participated voluntarily and had informed consent signed by their legal guardians. The exclusion criteria were as follows: (1) >16 years old; (2) anterior fontanel is not closed; (3) suffered from eye disease, open head trauma or intracranial tumour; (4) history of medication affecting intracranial pressure; (5) other conditions that do not cooperate with the inspection. Sex, age, body mass index (BMI), blood pressure, symptoms, signs and disease duration were be recorded.

The ultrasound examinations were conducted by a clinical physician who had received professional theoretical and practical training in critical ultrasound, which proved that he can perform measurements. All examinations were conducted simultaneously under the supervision of an ultrasound physician skilled in neurovascular examination. The measurements were obtained by a Mindray M9 ultrasound device with a high-frequency linear transducer (frequency 7.5 MHz). The patient was placed in a supine position with the head between 20° and 30°, the protocol was started with the right eye. The ultrasound gel was applied to the surface of the patient's closed upper eyelid, and the probe was gently placed on the eyelid without pressure. The probe was placed on the transverse section of the eyeball, and the optimal plane was scanned from the frontal end to the nasal end to fully demonstrate the path of optic nerve entering the eyeball. The maximum outer diameter of optic nerve sheath at 3 mm behind the ball and the maximum transverse diameter of eyeball in this plane were measured respectively, namely ONSD and ETD. The procedure was repeated three times on the transverse section; then, the probe was positioned on the vertical section, and the measurement of ONSD was again repeated three times. The entire ultrasound assessment was performed for the contralateral eye later. To reduce measurement errors, the final ONSD/ETD values were averaged. The mean values of right and left eyes were used for statistical analysis. Ultrasound examinations were performed before, 3 days and 7 days after clinical treatment.

The lumbar puncture was performed within 30 min after the ultrasound examination by a senior physician. The children were placed in the left lateral decubitus position with the neck and knees fixed by the assistant. L3–L4 or L4–L5 was selected as puncture point, and after disinfection, wrapping, and local anesthesia, a puncture needle was inserted from the puncture point along the anesthesia canal until a breakthrough is felt. After seeing the outflow of the cerebrospinal fluid, connecting the pressure-measuring tube, and making the children straighten their legs slowly, the ICP was read after the water column stabilized. All children were divided into the increased ICP group and the normal ICP group, where ICP >200 mmH2O was considered to be increased.

Statistical analyses were performed using IBM SPSS 19.0 software. Normally distributed continuous variable were expressed as mean ± standard deviation (SD) and non-normally distributed continuous variables were represented by median and interquartile range (IQR). One-way ANOVA analyses of variance were applied to evaluate the differences in ONSD/ETD before and after treatment. The differences between each time point were analyzed using Student's t-tests when the overall difference has statistical significance. ROC curve was used to evaluate the accuracy of visual ONSD/ETD ratio in increased ICP assessment, and the area under the curve and 95% confidence interval (CI), threshold, sensitivity and specificity were calculated. Statistical significance was set at p < 0.05.

Most viral encephalitis in children causes increased ICP and the increased ICP group accounted for 73.21% of the total as shown in this study. A mild elevation in ICP can cause symptoms like headache and vomiting. As the ICP continues to rise, it can lead to papilledema, blurred vision, and seizures. Further exacerbation may result in consciousness disorders and cerebral herniation. All of the children in the increased ICP group had one or more symptoms of increased ICP, while only 20% of the normal ICP group had headaches, 13.3% had vomiting, and 33.3% had convulsions. Based on clinical experience, we believe that the above symptoms in the normal ICP group may be related to the pathogenicity of infection with the virus, such as rotavirus easily causing vomiting and convulsions caused by electrolyte disturbance in gastroenteritis. In addition, fever can also lead to headaches and high fever convulsions. It can be seen from this that even though some children with viral encephalitis may have individual symptoms of increased ICP, the actual ICP has not truly increased. The measurement and evaluation of ICP at this time is of great significance for subsequent medication and efficacy evaluation.

This study had some limitations. In accordance with treatment guidelines and ethical requirements for viral encephalitis in children, invasive dynamic monitoring of intracranial pressure after treatment was not performed in this study. Thus, the most intuitive intracranial pressure data were lacking. In addition, it is not clear whether direct inflammatory stimulation of the optic nerve by encephalitis virus has an effect on the ONSD measurement data.

ONSD/ETD ratio measured by ultrasound is an accessible tool to identify increased ICP in children with viral encephalitis. It is also an innovative and convenient way to dynamically monitor ICP changes during treatment. Further studies are required to reveal the benefits of ONSD/ETD ratio measurements by ultrasound in the course of increased ICP caused by viral encephalitis.

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

The studies involving humans were approved by Medical Ethics Committee of Yuyao People's Hospital. The studies were conducted in accordance with the local legislation and institutional requirements. Written informed consent for participation in this study was provided by the participants' legal guardians/next of kin.

CZ: Conceptualization, Data curation, Funding acquisition, Investigation, Methodology, Project administration, Writing – original draft, Writing – review & editing. P-CS: Data curation, Formal Analysis, Investigation, Methodology, Writing – review & editing. K-JF: Data curation, Investigation, Methodology, Writing – review & editing. H-HF: Data curation, Formal Analysis, Investigation, Writing – review & editing. L-FW: Conceptualization, Supervision, Writing – review & editing. Y-YM: Data curation, Writing – review & editing. X-XG: Data curation, Writing – review & editing. X-LW: Data curation, Writing – review & editing.

The author(s) declare financial support was received for the research, authorship, and/or publication of this article. This work was supported by the Yuyao Health Technology Plan Project (2023YPT04).

We would like to acknowledge all medical staffs, patients and their families for their contribution toward the advancement of scientific study.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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