Comparison of B-Scan Ultrasound and MRI-Based Optic Nerve Sheath Diameter (ONSD) Measurements in Children.

Background: Qualitative, noninvasive assessment of intracranial pressure is of eminent importance in pediatric patients in many clinical situations and can reliably be performed using transorbital ultrasonographic measurement of the optic nerve sheath diameter (ONSD). MRI-based determination of ONSD can serve as an alternative if ultrasound (US) is not possible or available for various reasons, for example, in small, incompliant children. This study investigates repeatability and observer reliability of US ONSD and correlation and bias of US- versus MRI-based ONSD assessment in pediatric patients.

Methods: One hundred fifty children diagnosed with tumor (n = 40), hydrocephalus (n = 42), and other cranial pathologies (n = 68) were included. Bilateral ONSD was quantified by US using a 12-MHz linear array transducer. This was compared with ONSD measured in simultaneously acquired (≤24 h) T2-weighted MRI scans of the orbit.

Results: Repeatability of individual US values and intraobserver ONSD was outstanding (Cronbach's α = 0.984 and 0.996, respectively). Overall mean values for ONSD were 5.8 ± 0.88 mm and 5.7 ± 0.89 mm for US and MRI, respectively. Correlation between US and MRI-based ONSD was strong (r = 0.976, P < 0.01). Bland and Altman analysis showed a mean bias of 0.078 mm. A repeated-measures correlation (r) in 9 patients showed an excellent value (r = 0.94, P < 0.01).

Conclusions: Repeatability and reliability of US ONSD determination is excellent. In case US ONSD assessment is not possible or available, MRI scans can serve as an excellent alternative. The difference of US and MRI ONSD is minimal and insignificant, and thus, both techniques can complement each other.