Transvaginal Doppler assessment of fetal intracranial venous flow

To investigate physiologic blood-flow-velocity waveform patterns of the fetal cerebral venous system during normal pregnancies by transvaginal Doppler studies and to evaluate cases with abnormal venous-flow patterns.

Internal cerebral veins and the three dural sinuses, those of the superior sagittal sinus, vein of Galen, and straight sinus, were examined in normal cephalic-presenting fetuses of 20-40 weeks' gestation. For analysis, the venous index was defined as maximum minus minimum velocity divided by maximum velocity. Different cases with intracranial abnormalities were evaluated with emphasis on abnormal venous blood-flow patterns.

Internal cerebral veins had pulsatile patterns with a venous index of 0.22 in 47.6% of fetuses, whereas all fetuses had pulsations in the dural sinuses. The vein of Galen had a significantly lower venous index (0.31) than the superior sagittal sinus (0.39) and the straight sinus (0.36), indicating that the amplitude of the intracranial venous pulsation might increase as the flow runs from the periphery toward the proximal portion. Significant regression lines of venous index were obtained, indicating the stability of the pulsation during pregnancy. A flat pattern of superior sagittal sinus flow was found in three cases of hydrocephalus and one of craniosynostosis.

We showed the normal patterns of fetal cerebral venous blood-flow velocity and the abnormal patterns which might be associated with increased intracranial pressure. Doppler assessment of the intracranial venous system enabled us to evaluate intracranial abnormalities accompanied by increased intracranial pressure that might have prognostic clinical importance.