Transcranial Color-Coded Sonography With Angle Correction As a Screening Tool for Raised Intracranial Pressure

Abstract

OBJECTIVES: Transcranial Doppler (TCD) has been evaluated as a noninvasive intracranial pressure (ICP) assessment tool. Correction for insonation angle, a potential source of error, with transcranial color-coded sonography (TCCS) has not previously been reported while evaluating ICP with TCD. Our objective was to study the accuracy of TCCS for detection of ICP elevation, with and without the use of angle correction. DESIGN: Prospective study of diagnostic accuracy. SETTING: Academic neurocritical care unit. PATIENTS: Consecutive adults with invasive ICP monitors. INTERVENTIONS: Ultrasound assessment with TCCS. MEASUREMENTS AND MAIN RESULTS: End-diastolic velocity (EDV), time-averaged peak velocity (TAPV), and pulsatility index (PI) were measured in the bilateral middle cerebral arteries with and without angle correction. Concomitant mean arterial pressure (MAP) and ICP were recorded. Estimated cerebral perfusion pressure (CPP) was calculated as estimated CPP (CPPe) = MAP × (EDV/TAPV) + 14, and estimated ICP (ICPe) = MAP–CPPe. Sixty patients were enrolled and 55 underwent TCCS. Receiver operating characteristic curve analysis of ICPe for detection of invasive ICP greater than 22 mm Hg revealed area under the curve (AUC) 0.51 (0.37–0.64) without angle correction and 0.73 (0.58–0.84) with angle correction. The optimal threshold without angle correction was ICPe greater than 18 mm Hg with sensitivity 71% (29–96%) and specificity 28% (16–43%). With angle correction, the optimal threshold was ICPe greater than 21 mm Hg with sensitivity 100% (54–100%) and specificity 30% (17–46%). The AUC for PI was 0.61 (0.47–0.74) without angle correction and 0.70 (0.55–0.92) with angle correction. CONCLUSIONS: Angle correction improved the accuracy of TCCS for detection of elevated ICP. Sensitivity was high, as appropriate for a screening tool, but specificity remained low.

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“…The results can exhibit significant inter-individual variability, as seen in measurements of the ONSD, making it challenging to establish universally applicable thresholds. Moreover, certain modalities such as TCD are operator-dependent [44][45][46], with outcomes that vary based on the practitioner's expertise. External factors, like changes in the carbon dioxide levels in TCD [47] or the intraocular pressure of the ONSD, can also influence interpretations.…”