Objective: To evaluate the accuracy of ultrasonography to assess the increase of intracranial pressure by assessing optic nerve sheath diameter (ONSD) and transcranial Doppler (TCD), consisting of the black box (BB) model, arterial diastolic flow velocity (FVd), critical closing pressure (CrCp), and pulsatility index (PI) as parameters, in adult traumatic brain injury (TBI) patients.
Methods: A systematic search through the electronic databases including Medline through PubMed and Embase for studies evaluating the use of optic nerve and TCD USG to evaluate increased intracranial pressure (ICP) compared with the invasive method. Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool was used to assess the risk of bias.
Results: Ten studies consisting of 727 patients were included in this study. The overall pooled sensitivity and specificity for the prediction of elevated ICP by measuring ONSD were 94% (95% CI: 89%-97%) and 88% (95% CI: 81%-95%), respectively. Positive and negative likelihood ratios were 12.7 (95% CI: 6.6-25.3; Cochran Q-statistic =14.6; p=0.04) and 0.06 (95% CI: 0.03-0.10; Cochran Q-statistic =14.1; p=0.05), respectively. All I2 values were >0.50. The area under the receiver operating characteristic (ROC) curve was 0.92 (95% CI: 0.81-0.98) as shown in the summary ROC (sROC) plot. A meta-analysis could not be performed for the TCD subgroup due to several incomplete sensitivity and specificity data and differences in the evaluated parameters. Four studies evaluated the role of TCD with mixed results. In one study, averaging the parameters of TCD displayed favorable results.
Conclusion: ONSD can be used as a parameter to evaluate the increase of ICP in TBI patients. BB model, FVd, and CrCp are potential promising parameters of TCD ultrasonography for noninvasive ICP estimation as opposed to PI. However, more studies with complete accuracy results are required in the future.