| Popis: |
The mechanism driving flow through the glymphatic system is unclear. The pulsatile flow measured in the space surrounding the middle cerebral artery (MCA) suggests that peristalsis created by intravascular blood pressure pulses is a candidate. However, peristalsis is ineffective in driving significant mean flow when the amplitude of channel wall motion is small, as has been observed in the MCA paraarterial space. In this paper, peristalsis in combination with two additional mechanisms, a longitudinal pressure gradient and directional flow resistance, is evaluated to match the measured MCA paraarterial flow. Two analytical models are used that simplify the paraarterial branched network to a long continuous channel with a traveling wave in order to maximize the potential effect of peristalsis on the mean flow. For these models, the measured arterial wall motion is too large to cause the measured oscillatory velocity, indicating that the glial wall must also move. At a combined motion matching the measured oscillatory velocity, peristalsis is incapable of driving enough mean flow. Directional flow resistance elements augment the mean flow, but not enough to provide a match. With a steady longitudinal pressure gradient, both oscillatory and mean flows can be matched to the measurements. |
