Optic Nerve Sheath Diameter on Brain Magnetic Resonance Imaging: A Single Center Study

Abstract

Objective: To find correlations between diameters of the optic nerve sheath (ONSD), the eyeball, and the optic canal that might be important for intracranial pressure monitoring. Methods: In a prospective cohort study, the CT data of consecutive 400 adults (18+) with healthy eyes and optic nerves and absence of neurological diseases were collected and analyzed. When the CT scans were obtained, the diameters of the optic nerve sheath, the eyeball, and the optic canal were measured and statistically analyzed. The data obtained from the left and from the right eyeballs and optic nerves were compared. The correlation analysis was performed within these variables, with the gender, and the age.Results: In healthy persons, the ONSD varies from 3.65 mm to 5.17 mm in different locations within the intraorbital space with no significant difference between sexes and age groups. There is a strong correlation between the eyeball transverse diameter (ETD) and ONSD that can be presented as ONSD/ETD index. In healthy subjects, the ONSD/ETD index equals 0.19. Conclusion: The calculation of an index when ONSD is divided by the ETD of the eyeball presents precise normative database for ONSD intracranial pressure measurement technique. When the ONSD is measured for intracranial pressure monitoring, the most stable results can be obtained if the diameter is measured 10 mm from the globe. These data might serve as a normative database at emergency departments and in general neurological practice.

Measurement of the Optic Nerve Sheath Diameter with Magnetic Resonance Imaging and Its Association with Eyeball Diameter in Healthy Adults

“…In the present study, the ONSD was measured using TOF-MRA source images with a 1-mm slice thickness and sufficient anatomical contrast. Ko 19 measured the ONSD using the same MRI protocol in 301 Korean adults, and found a mean value of 4.37 mm, although they were patients with neurological disorders. Alternatively, variations in ONSD may be influenced by race, but this needs to be investigated further due to inconsistencies in the previous results.…”

Optic nerve sheath diameter threshold by ocular ultrasonography for detection of increased intracranial pressure in Korean adult patients with brain lesions

“…Lee et al [ 13 ] showed a mean ONSD of 4.1 mm ranging from 2.9 to 5.3 mm in Korean population using CT scan. Ko [ 14 ] also reported that the mean ONSD on MRI was 4.37 mm in patients with normal ICP. In their study, ONSD was not significantly different according to age, sex, and underlying diseases.…”