Pulsatility Index Reflects Intracranial Pressure Better Than Resistive Index in Patients with Clinical Features of Intracranial Hypertension

 The intracranial pressure (ICP) is measured through various noninvasive methods to overcome complications of invasive ICP monitoring. In this study, transcranial Doppler was used to measure pulsatility index (PI) and resistive index (RI) that were correlated with opening intraventricular ICP. The opening intraventricular ICP was measured with the placement of intraventricular catheter in lateral ventricle without loss of cerebrospinal fluid.  The prospective, observational study was conducted on 40 patients with clinical and radiological features of raised ICP who underwent either endoscopic third ventriculostomy or ventriculoperitoneal shunt surgery. The PI and RI were measured simultaneously with opening ICP measurements under general anesthesia. Both PI and RI were correlated with ICP by using Pearson correlation coefficient. The receiver operating characteristic (ROC) curve was used to get the optimal values of PI ad RI for corresponding ICP values.  The mean PI was 1.01 ± 0.41 and mean RI was 0.59 ± 0.32. The mean opening ICP value was 21.81 ± 8.68 mm Hg. The correlation between PI and RI with ICP was a statistically significant with correlation coefficient of 0.697 and 0.503, respectively. The ROC curve shown statistically significant association between PI and ICP from 15 to 40 mm Hg, whereas the association between RI and ICP was from 15 to 25 mm Hg, with various sensitivity and specificity.  The opening intraventricular ICP correlated better with PI than RI in patients with features of raised ICP.