Brain drain is real

Friday, October 6th, 2017

Brain Drain via Lymphatic SystemIn 1816, an Italian anatomist reported finding lymphatic vessels on the surface of the brain, but for two centuries the dogma has remained that the brain is an exceptional organ, with no way to remove waste:

Then in 2015, two studies of mice found evidence of the brain’s lymphatic system in the dura. Coincidentally, that year, Dr. Reich saw a presentation by Jonathan Kipnis, Ph.D., a professor at the University of Virginia and an author of one the mouse studies.

“I was completely surprised. In medical school, we were taught that the brain has no lymphatic system,” said Dr. Reich. “After Dr. Kipnis’ talk, I thought, maybe we could find it in human brains?”

To look for the vessels, Dr. Reich’s team used MRI to scan the brains of five healthy volunteers who had been injected with gadobutrol, a magnetic dye typically used to visualize brain blood vessels damaged by diseases, such as multiple sclerosis or cancer. The dye molecules are small enough to leak out of blood vessels in the dura but too big to pass through the blood-brain barrier and enter other parts of the brain.

At first, when the researchers set the MRI to see blood vessels, the dura lit up brightly, and they could not see any signs of the lymphatic system. But, when they tuned the scanner differently, the blood vessels disappeared, and the researchers saw that dura also contained smaller but almost equally bright spots and lines which they suspected were lymph vessels. The results suggested that the dye leaked out of the blood vessels, flowed through the dura and into neighboring lymphatic vessels.

To test this idea, the researchers performed another round of scans on two subjects after first injecting them with a second dye made up of larger molecules that leak much less out of blood vessels. In contrast with the first round of scans, the researchers saw blood vessels in the dura but no lymph vessels regardless of how they tuned the scanner, confirming their suspicions.

They also found evidence for blood and lymph vessels in the dura of autopsied human brain tissue. Moreover, their brain scans and autopsy studies of brains from nonhuman primates confirmed the results seen in humans, suggesting the lymphatic system is a common feature of mammalian brains.

“These results could fundamentally change the way we think about how the brain and immune system inter-relate,” said Walter J. Koroshetz, M.D., NINDS director.

Dr. Reich’s team plans to investigate whether the lymphatic system works differently in patients who have multiple sclerosis or other neuroinflammatory disorders.


  1. Lucklucky says:

    “In 1816, an Italian anatomist reported finding lymphatic vessels on the surface of the brain, but for two centuries, it was forgotten. ”

    I find this difficult to believe.

    Any idea of who was the anatomist?

  2. Isegoria says:

    The Italian anatomist was Paolo Mascagni:

    Mascagni, P., and G.B. Bellini. 1816. Istoria Completa Dei Vasi Linfatici. Vol. II. Presso Eusebio Pacini e Figlio, Florence. 195 pp.

  3. Lucklucky says:

    Thanks, Isegoria.

  4. Lucklucky says:

    By “I find this difficult to believe,” I meant that I find this difficult to believe that it was forgotten, not that it was discovered by an Italian anatomist.

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