WHY CURRENT DOPPLER ULTRASOUND METHODOLOGY IS INACCURATE IN ASSESSING CEREBRAL VENOUS RETURN. THE ALTERNATIVE OF THE ULTRASONIC JUGULAR VENOUS PULSE
Paolo Zamboni, MD

WHY CURRENT DOPPLER ULTRASOUND METHODOLOGY IS INACCURATE IN ASSESSING CEREBRAL VENOUS RETURN. THE ALTERNATIVE OF THE ULTRASONIC JUGULAR VENOUS PULSE
Paolo Zamboni, MD

AbstractThe research on the physiological modality of cerebral venous return is a topic with growing interest also for potential application in several neurovascular and in neurodegenerative diseases. The non-invasiveness of the wide spread Doppler ultrasound (DUS) is very attractive to propose it as a screening tool. However, both current qualitative and quantitative flow assessment of the main extracranial outflow route are affected by low reproducibility and significant differences in results by comparing studies in literature. Meta-analysis of qualitative DUS protocol, initially proposed to detect a condition named chronic cerebrospinal venous insufficiency (CCSVI) demonstrates a big heterogeneity among studies. In an attempt to improve accuracy, several Authors alternatively proposed the flow rate quantification, based on the automated calculation of the product of the time average velocity with the cross sectional area (CSA). However, also the quantification protocols show significant differences among studies and currently does not permit to measure the outflow with the necessary accuracy. The reason of the inaccuracy of DUS assessment of the venous flow are: a) automated CSA measurement of the elliptical jugular vein by assimilating it to a circle; b) use of just a single CSA value whereas the jugular vein is a pulsatile vessel with significant changes of the CSA along the cardiac cycle; c) time average velocity assessment accurate only when the flow regimen is laminar. Finally, the tutorial describes alternative ultrasound calculation of flow based on the Womersley method, which takes into account the variation of CSA overtime through the ultrasound assessment of the jugular venous pulse. In the near future, it will be possible to synchronize the electrocardiogram with the brain inflow (carotid distension wave) and with the outflow (jugular venous pulse) in order to nicely have a non-invasive ultrasound picture of the brain heart axis. This novel assessment may have potential use in neurovascular, neuro-cognitive, neuro-sensorial, and neurodegenerative disorders.

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