Transcranial Doppler Ultrasonography for Noninvasive Intracranial Pressure Monitoring: A Systematic Review and Meta-Analysis

Abstract Background and objectives: Elevated intracranial pressure (ICP) is a critical secondary insult in acute brain injury. Invasive monitoring remains the reference standard but carries hemorrhagic and infectious risks. This systematic review and meta-analysis evaluates the diagnostic accuracy of transcranial Doppler (TCD)-derived indices for detecting intracranial hypertension compared with invasive ICP monitoring. Methods We searched PubMed, Embase, and Scopus to June 2026 for studies comparing TCD-derived indices (e.g., pulsatility index, estimated ICP [eICP]) with invasive intracranial monitoring in adults with acute brain injury. Methodological quality was assessed using QUADAS-2. Sensitivity and specificity were pooled using univariate random-effects models on the logit scale for studies providing sufficient 2×2 data. Results Nineteen studies evaluating heterogeneous acute brain injury populations met the inclusion criteria. Considerable methodological heterogeneity was observed across index tests and ICP thresholds. Four studies (925 paired observations) provided sufficient data to pool the performance of Czosnyka-derived eICP. Pooled specificity was relatively consistent at 74.1% (95% confidence interval [CI], 70.8–77.3%; I²=24.9%), whereas pooled sensitivity was highly variable and imprecise at 50.3% (95% CI, 1.5–98.5%; I²=81.7%). Other TCD parameters, including pulsatility index and venous flow velocity, demonstrated promising but inconsistent threshold-dependent diagnostic discrimination. Although several cohorts reported high negative predictive values, agreement between TCD-derived and invasive absolute ICP measurements was inconsistent, frequently exhibiting wide limits of agreement. Conclusions TCD-derived measures provide informative serial physiological assessments of cerebral hemodynamics but cannot interchangeably replace invasive ICP monitoring. Given its moderate specificity but heterogeneous sensitivity, TCD is most appropriately utilized as a complementary tool for noninvasive screening and multimodal monitoring rather than as a standalone absolute ICP estimator.