Determination of the difference between normal and pathological findings of optic nerve sheath diameter measured by computerized tomography of patients applying to the emergency room

Introduction: Measurement of the optic nerve sheath diameter (ONSD) via computed tomography of the brain(CT) is a useful diagnostic tool in the emergency room to demonstrate patient prognosis due to its non-invasiveness, no additional procedures, no cost and ease of use. The reference values used in local study populations are different in studies conducted with ONSD. For this reason, in our study, it was aimed to find the normal range of ONSD according to age and gender of the Turkish people, and to show the increase in ONSD in the brain CTs, which is predicted to have increased intracranial pressure. Material & Method: All patients who applied to Dokuz Eylul University Emergency Room within one year and who underwent CT of the brain were included in our study. The distribution of normal ONSD values with respect to age and gender as well as the difference between the normal CTs and the CTs of the brain with widespread brain edema were studied by the research team. Results The median and the interquartile range values of the ONSD for Turkish people are 5.50mm (5.00-6.00mm) when measured from 3mm from the end of the eyeball, 4.90mm (4.43-5.30mm) when measured from 5mm from the end of the eyeball and 4.30mm (4.00- 4.60mm) when measured from 10mm from the end of the eyeball. In pathological cases, this values are 6.85mm (6.20-7.40mm) for 3mm, 6.20mm (5.60-6.83mm) for 5mm and 5.65mm (4.98-6.10mm) for 10mm measurements of the end of the eyeball. A statistically significant difference was found between the normal and pathological cases in ONSD (p <0.001). In all cases, we found that the median value of the ONSD measurement decreased as the measurement point progressed distally (p <0.001). We found that the median value of ONSD in normal cases increased significantly as the age progressed and it gave meaningful results for all measurement points (p <0.05). When we look at the change of the median value of the ONSD in normal cases with respect to gender, we found that the median value of the ONSD was higher in all measurement points in men than women (p <0.001). In pathological cases, we did not find a significant difference by gender (p> 0.05). Discussion: In pathological cases, we found that the median value of the ONSD was significantly higher at all ONSD measurement points compared to normal cases (p <0.001). Both normal and pathological cases ONSD values decreases as move away from the eyeball. In male gender and advanced ages ONSD values increases. Key Words: Optic nerve sheath diameter, computed brain tomography, emergency room, turkish people