Effect of scanning pressure on intracranial hemodynamics during transfontanellar duplex US.

The purpose of this study was to determine the effect of transducer scanning pressure during duplex ultrasonographic evaluation of intracranial hemodynamics in newborns. Doppler spectra were obtained from the anterior cerebral artery with use of light and firm scanning pressure over the anterior fontanelle in 23 healthy infants and 20 infants with reduced cranial compliance due to ventricular dilatation, intracranial hemorrhage, diffuse cerebral edema, and extraaxial fluid. In healthy infants, the mean resistive index (RI) increased from 69.9 +/- 3 to 74.8 +/- 3 (P < .005), and mean time average velocity (TAV) decreased from 11.1 cm/sec +/- 1.3 to 8.6 cm/sec +/- 1.3 (P < .0001) with firm scanning pressure. In infants with decreased cranial compliance, mean RI increased from 67.8 +/- 4 to 85 +/- 5, and mean TAV decreased from 16.3 cm/sec +/- 2 to 10.7 cm/sec +/- 2 (P < .0001 for both comparisons). A significant alteration in RI with firm technique (> or = 20% increase in RI, or reversal of diastolic flow) was observed in 12 of 28 examinations in infants with decreased cranial compliance and in only one of 23 healthy infants (P < .005). These data show that scanning pressures during duplex ultrasonography can significantly affect intracranial hemodynamics, especially in infants with altered cranial compliance.