video: This movie illustrates the basic findings of the article. The upper left image is an example of the imaging that was employed in this study. Using an imaging technique called 2-photon microscopy, the authors imaged CSF flow into the brain of live mice. The brain vasculature was visualized with one fluorescent tracer that was injected intravenously (red), while the CSF surrounding the brain was visualized with a second fluorescent tracer (green). They found that CSF moves first along the arteries at the surface of the brain, then moves into the brain along the outside of arteries that penetrate straight into the tissue. From the spaces surrounding penetrating arteries, the CSF moves into and through the brain tissue via specialized water channels, called aquaporin-4, then drains from the brain along large draining veins. The continuous flushing of CSF inward along arteries, through the brain tissue, and out along veins sweeps waste from the brain tissue and out of the brain. In the study, they authors demonstrate that amyloid β, a peptide that accumulates in the brain during Alzheimer's disease, is cleared from the brain in this manner. These findings suggest that the failure of this clearance pathway may contribute to the onset of neurodegenerative disease such as Alzheimer's, which are characterized by the mis-accumulation of toxic proteins. This video relates to a paper that appeared in the Aug. 15, 2012 issue of Science Translational Medicine, published by AAAS. The paper, by Dr. J.J. Iliff at the University of Rochester Medical Center in Rochester, N.Y., and colleagues, was titled, "A Paravascular Pathway Facilitates CSF Flow Through the Brain Parenchyma and the Clearance of Interstitial Solutes, Including Amyloid Beta." view more
Credit: Movie from J. Iliff and M. Nedergaard