Surface periarterial spaces of the mouse brain are open, not porous

Fatima Min Rivas, Jia Liu, Benjamin C. Martell, Ting Du, Humberto Mestre, Maiken Nedergaard, Jeffrey Tithof, John H. Thomas, Douglas H. Kelley

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


Fluid-dynamic models of the flow of cerebrospinal fluid in the brain have treated the perivascular spaces either as open (without internal solid obstacles) or as porous. Here, we present experimental evidence that pial (surface) periarterial spaces in mice are essentially open. (1) Paths of particles in the perivascular spaces are smooth, as expected for viscous flow in an open vessel, not diffusive, as expected for flow in a porous medium. (2) Time-averaged velocity profiles in periarterial spaces agree closely with theoretical profiles for viscous flow in realistic models, but not with the nearly uniform profiles expected for porous medium. Because these spaces are open, they have much lower hydraulic resistance than if they were porous. To demonstrate, we compute hydraulic resistance for realistic periarterial spaces, both open and porous, and show that the resistance of the porous spaces are greater, typically by a factor of a hundred or more. The open nature of these periarterial spaces allows significantly greater flow rates and more efficient removal of metabolic waste products.

Original languageEnglish (US)
Pages (from-to)20200593
Number of pages1
JournalJournal of the Royal Society, Interface
Issue number172
StatePublished - Nov 1 2020


  • brain clearance system
  • cerebrospinal fluid
  • fluid dynamics
  • glymphatic system
  • hydraulic network models
  • perivascular spaces

PubMed: MeSH publication types

  • Journal Article
  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, Non-U.S. Gov't


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