Evaluation of the concordance between the pulsatility index measured by transcranial color flow imaging in the middle cerebral artery and in the internal carotid artery

Background/Objective Pulsatility Index (PI) measurements using transcranial color flow imaging via the temporal bone are clinical substitutes for invasive intracranial pressure (ICP) monitoring. Although the PI measurements obtained through this window are commonly used, they cannot be evaluated in up to 20% of patients. Given that PI in the internal carotid artery (ICA) can be easily measured through the submandibular window in all cases, this study aimed to investigate whether PI measurements through the submandibular window could be used as a substitute for PI measurements in the middle cerebral artery (MCA). Methods This single-center, retrospective, observational study included cases from our intensive care unit between May 2024 and September 2024, in which transcranial ultrasound was performed during the treatment of neurological disorders. The measurements of the PI from the temporal window (MCA-PI) and submandibular window (ICA-PI) were obtained at the same situation and the correlation between ICA-PI and MCA-PI was evaluated in patients with various types of brain damage. Results Data from 46 patients, totaling 116 measurements, were analyzed. The patients included 57 (49.1%) men, with an age of 67 (IQR, 49-74) years. The primary diagnoses were subarachnoid hemorrhage [n=52 (44.8%)], intracerebral hemorrhage [n=21 (18.1%)], cerebral infarction [n=9 (7.8%)], and traumatic brain injury [n=8 (6.9%)]. A significant correlation was found between the ICA-PI and MCA-PI, with a correlation coefficient of 0.894 (MCA-PI= 0.946 × ICA-PI + 0.057). The accuracy for detecting a PI > 1.3 at the temporal bone was: sensitivity= 88.6%, specificity= 91.4%. Conclusions Despite the inclusion of various neurocritical disorders, the ICA-PI through the submandibular window was strongly correlated with the conventional PI (i.e., MCA-PI through the temporal window). In neurocritical care, the ICA-PI can be used for the assessment of ICP and cerebral perfusion pressure monitoring when the view through the temporal window is unavailable.