ABSTRACT Background and Purpose The optic nerve sheath diameter (ONSD) measured by sonography is a well‐known noninvasive technique for estimation of intracranial pressure (ICP). Still, test‐retest reliability and the minimal detectable change (MDC) for ONSD sonography remains unexplored in the setting of acute brain injury (ABI), which this study aimed to evaluate. Methods This was a post‐hoc study based on data extracted from two previous studies of ONSD measured with a 10 MHz linear probe in ABI patients with invasive ICP monitoring. We included repeated measurements of ONSD in short time intervals with invasively measured ICP fluctuating ≤2 mmHg between observations. Intraclass correlation coefficient (ICC) with absolute agreement, standard error of measurement (SEM), MDC and limits of agreement (LOA) were calculated for right, left and mean ONSD. Results 31 patients were included. Test–retest reliability was considered good to excellent, with intraclass correlation coefficients values ranging from 0.80 (95%CI:0.63–0.90) to 0.91 (95%CI:0.82–0.95). Measurement errors were small, with SEM values ranging from 0.31 mm to 0.17 mm and MDC values ranging from 0.87 mm to 0.47 mm. The best SEM and MDC were achieved using a bilateral mean of ONSD measured internal of the dura mater (ONSD int ). Conclusions According to our results, a bilateral mean ONSD int is recommended for noninvasive estimation of ICP in an ABI population. Using this technique, a change ≥0.5 mm may be safely assumed to represent underlying physiological or anatomical changes, most likely changes in the ICP.
Pansell et al. (Thu,) studied this question.