Variability of optic nerve sheath diameter measurement on computed tomography; need for standardization
DOI:
https://doi.org/10.61386/imj.v17i3.491Keywords:
Optic nerve sheath diameter, computed tomography, window setting, variations, standardizationAbstract
Context: Computed tomography measurement of optic nerve sheath diameter (ONSD) is established for the indirect evaluation of intracranial pressure in traumatic brain injury (TBI). There is however a significant difference in the reported values across different techniques with no clear-cut range of values agreed upon.
Objective: To measure the ONSD of patients with TBI and those with normal brains using different window settings and locations and compare with published values.
Methodology: Comparative evaluation of 300 ONSD measurements obtained from cranial CT examinations at the Radiology department of a tertiary institution. Seventy-five patients had radiologic signs of TBI while 75 had normal findings (controls). For each subset, ONSD was measured at 3mm and 8mm retrobulbar regions using spine window (ww/wl 250/50). ONSD was measured using additional settings (mediastinal ww/wl 450/60 and soft tissue 380/40) for controls. Correlation between age, gender, and side of the ONS complex at different lengths and contrast settings were also evaluated.
Results: The age range of the patients was 1-78 years, mean age of 40.4 years ± 21.7 with male: female ratio of 3:1. The mean ONSD was statistically different (p<0.0001) using the different window settings with the highest value obtained with the mediastinal window. There was also a significant difference(p <0.0001) between the ONSD of TBI and control patients at 8mm and 3mm retrobulbar regions but no correlation with gender, age, and side.
Conclusion: Significant variations in the CT measurements of ONSD with regards to retrobulbar locations and window settings highlight the need for standardization of protocols. Measurement taken at 3mm retrobulbar using a spine window setting shows greater distensibility and details of the optic nerve and allows for more reliable measurements.
Published
Issue
Section
Categories
License
Copyright (c) 2024 Itanyi UD, Aiyekomogbon JO, Atim TT, Ambali-Belgore A
![Creative Commons License](http://i.creativecommons.org/l/by/4.0/88x31.png)
This work is licensed under a Creative Commons Attribution 4.0 International License.