Measurement of Optic Nerve Sheath Diameter by Trans-Orbital Ultrasound to Detect Raised Intracranial Pressure in Children

ABSTRACT

Aims Raised Intracranial Pressure (ICP) is frequently encountered condition amongst children due to neurological and non-neurological etiologies. It contributes towards 20% of the admissions in our PICU at tertiary care institute of North India. Timely diagnosis of raised intracranial pressure is critical for appropriate management. Ultrasonographic measurement of optic nerve sheath diameter (ONSD) is non-invasive point of care tool to recognize raised intracranial pressure however there are very limited studies in pediatric population on this. Aim of this study was to measure the ONSD of children admitted in pediatric intensive care unit (PICU) to identify the difference in ONSD among the pediatric patients with normal and raised ICP and to achieve the cut-off value for diagnosing raised ICP. Methods A Hospital based observational comparative study conducted at PICU of a tertiary care institute of national importance in North India. ONSD measurement of all the patients aged 2-14 years admitted in pediatrics department for >48 hours was done in two phases due to COVID-19 related restrictions in routine admissions for some months. First phase was from 1st January 2020 to 31st March 2021 and second phase started from 15th January 2022. Complete enumeration technique was used for the study. Children receiving treatment for raised ICP based on clinical features (Muir's criteria) and neuroimaging were included in raised ICP group and they were compared with the patients without any signs of raised ICP. Optic nerve sheath diameter was measured in both the groups on Day 1 (i.e. within 24 hours of admission) and Day 2 of admission. Third and last ONSD measurement was done on any day between day 4 and day 7 of admission. On each day, 3 readings were taken from each eye and average of 3 readings was used for final statistical analysis for that particular day. Treating team was unaware of the USG findings throughout the stay of the patient in the department. Results Total 101 patients recruited, among them 16 patients had raised ICP and 85 patients had normal ICP. The mean optic nerve sheath diameter on day 1 was found to be higher in the patients with raised ICP (Mean ONSD = 4.955 +/- 0.80) as compared to those with normal ICP (Mean ONSD = 4.05 +/- 0.43). Their mean difference was 0.90 mm (95% CI 0.07-1.48 p value <0.01). Mean ONSD on day 2 also was higher in raised ICP patients (Mean ONSD = 4.82 +/- 0.73) in comparison to normal ICP patients (Mean ONSD = 4.06 +/- 0.47) which was statistically significant (p value = 0.001). The cut-off ONSD value for detecting the raised ICP was estimated to be 4.35 mm on ROC curve with area under the curve 0.862 (95% CI, 0.721-0.943), sensitivity of 75% and specificity of 76.5%. Conclusion Raised ICP is one of the important neurological entities in children contributing towards significant morbidity. Measurement of ONSD by trans-orbital ultrasound was able to detect raised ICP with excellent discriminatory performance.