Abstract
The optic nerve sheath diameter (ONSD) is considered as an indirect marker for intracranial pressure (ICP). However, the optimal cut-off value for an abnormal ONSD indicating elevated ICP and its associated factors have been unclear. Thus, we investigated normative values for the ONSD using ultrasonography and investigate the potential factors affecting it. We prospectively recruited healthy volunteers between September 2016 and March 2017. A total of 585 individuals were included, in which the mean ONSD was 4.11 mm [95% confidence interval (CI), 4.09–4.14 mm]. Although ONSD was correlated with sex (p = 0.015), height (p = 0.003), and eyeball transverse diameter (ETD) (p < 0.001) in simple linear regression analyses, multiple linear regression analysis revealed that only ETD was independently associated with ONSD (p < 0.001). Accordingly, we further established a normative value for the ONSD/ETD ratio and its associated factors. The mean ONSD/ETD ratio was 0.18 (95% CI, 0.18–0.18), but the ONSD/ETD ratio was not correlated with sex, height, weight, body mass index, and head circumference. Our findings suggest that the ONSD had a strong correlation with ETD, and ONSD/ETD ratio might provide more reliable data than ONSD itself as a marker of ICP.
Highlights
Elevated intracranial pressure (ICP) is a potentially devastating condition resulting from various neurological and non-neurological disorders[1]
The mean [95% confidence interval (CI)] values for optic nerve sheath diameter (ONSD), eyeball transverse diameter (ETD), and the ONSD/ ETD ratio were 4.11 ± 0.35 mm (4.09–4.14 mm), 22.91 ± 0.93 mm (22.83–22.98 mm), and 0.18 ± 0.02 (0.18–0.18), respectively, and ONSD was associated with ETD, but not with sex, height, weight, body mass index (BMI), and head circumference
The present study included the largest number of healthy volunteers among all studies evaluating ONSD using ultrasonography
Summary
Elevated intracranial pressure (ICP) is a potentially devastating condition resulting from various neurological and non-neurological disorders[1]. The golden standard for estimating ICP includes invasive methods such as intraventricular catheterization and intraparenchymal probes[4]. Such procedures are not routinely performed because of the absence of neurosurgeons or intensive care units and the risk of complications including hemorrhage and infection. They are contraindicated in patients with thrombocythemia or coagulopathy[5,6]. Despite its usefulness and popularity, the optimal cut-off value for an abnormal ONSD indicating elevated ICP has been unclear, because most studies on ONSD measurement included only a small number of healthy individuals. The main aims of the current study were to establish normative values for ONSD using ultrasonography in a large number of healthy Korean adults and investigate potential factors affecting this parameter
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