Objective: The optic nerve sheath diameter (ONSD) excluding the dura mater (ONSDE; i.e., the subarachnoid diameter) and the ONSD including the dura mater (ONSDI) have been used differently in studies, but the predictive ability of these two different measurements of the ONSD as measured by invasive intracranial pressure (ICP) monitoring has never been compared. Additionally, studies on the prediction of ICP using central retinal artery (CRA) Doppler ultrasonography are scarce. The authors aimed to determine how the two different ONSD measurements, the ONSD/eyeball transverse diameter (ETD) ratio, and transorbital Doppler ultrasonography parameters are associated with ICP via external ventricular drainage (EVD).
Methods: This prospective observational study included 50 patients with brain injury who underwent EVD between August 2019 and September 2020. The mean of three repeated measurements of the ONSDI and ONSDE was calculated to reduce artifact and off-axis measurements. ETD, an immutable value, was measured from the initial brain CT with a clear outline of the eyeball. Simultaneously, flow velocities in the CRA and posterior ciliary artery (PCA) were compared with the ICP.
Results: The ONSDE, ONSDI, and ONSD/ETD ratio were significantly associated with ICP (p = 0.005, p < 0.001, and p < 0.001, respectively). The ONSD/ETD ratio showed the highest predictive power of increased ICP (area under the curve [AUC] 0.897). The ONSDI was correlated more with the ICP than was the ONSDE (AUC 0.855 vs 0.783). None of the Doppler ultrasonography parameters in the CRA and PCA were associated with ICP.
Conclusions: The ONSD/ETD ratio is a better predictor of increased ICP compared with the ONSDI or ONSDE in brain-injured patients with nonsevere ICP. The ONSDI may be more available for predicting the ICP than the ONSDE.
Keywords: intracranial pressure; optic nerve sheath diameter; retinal vessels; traumatic brain injury; ultrasonography.