Assessment of the Accuracy of Ultrasonographically Measured Optic Nerve Sheath Diameter as a Surrogate for the Detection of Intracranial Hypertension Compared to Optic Nerve Sheath Diameter Measured by MRI: A Prospective Observational Study.

Background:  Ultrasonographic measurement of optic nerve sheath diameter (ONSD) has been proposed as a non-invasive, bedside method to detect raised intracranial pressure (ICP) in various clinical settings. We aimed to correlate the ONSD obtained by ultrasonography (USG) with the ONSD obtained by magnetic resonance imaging (MRI) and to find its measurement accuracy.

Methods:  A prospective double-blind study was carried out by performing ocular ultrasounds on 32 patients with clinical features of intracranial hypertension. ONSD was measured by both USG and MRI. Three ultrasonographic scans were performed in both the eyes and the average value of the same was correlated with ONSD obtained from MRI. The three ultrasonographic ONSD scans were also compared among each other for reproducibility and intra-observer variability.

Results:  There was a significant correlation between the ONSD measured by MRI and USG (r = 0.954, p = 0.0000, mean difference <5%). A notable degree of agreement between the two measurement modalities was found by the Bland-Altman test (coefficient = -0.116, p = 0.050).

Conclusions:  ONSD measured by USG has a significant degree of agreement with that of MRI and hence can serve as an effective, fast, and reliable evaluation technique in patients with intracranial hypertension.