Glymphatic system discovered

That's not a typo.  It's a new anatomical system.

Kari Alitalo had studied lymphatic vessels for more than two decades. So he knew that this network, which carries immune cells throughout the body and removes waste and toxins, didn’t extend into the brain: This had been accepted wisdom for more than 300 years. “Nobody questioned that it stopped at the brain,” says Alitalo, a scientist at the University of Helsinki in Finland...

But when Alitalo and Aspelund repeated the experiment, they got the same result. It seemed that the lymphatic vessels extended to the brain after all. This was surprising, to say the least: In the 21st century, major findings involving basic human anatomy are rare...

Researchers have identified two networks: the vessels that lead into and surround the brain, and those within the brain itself. The first is known as the lymphatic system for the brain, while the latter is called the glymphatic system. The “g” added to “lymphatic” refers to glia, the kind of neuron that makes up the lymphatic vessels in the brain. The glymphatic vessels carry cerebrospinal fluid and immune cells into the brain and remove cellular trash from it. Alitalo, Nedergaard, Kipnis and others have found evidence that when the systems malfunction, the brain can become clogged with toxins and suffused with inflammatory immune cells.

Over decades, this process may play a key role in Alzheimer’s disease, Huntington’s disease, Parkinson’s disease and other neurodegenerative illnesses, research suggests. “This is a revolutionary finding,” Nedergaard says. “This system plays a huge role in the health of the brain.”..

One key to glymphatic performance seems to be sleep. Nedergaard has shown that at least in mice, the system processes twice as much fluid during sleep as it does during wakefulness. She and her colleagues focused on amyloid beta; they found that the lymphatic system removed much more of the protein when the animals were asleep than when they were awake. She suggests that over time, sleep dysfunction may contribute to Alzheimer’s and perhaps other brain illnesses. “You only clean your brain when you’re sleeping,” she says. “This is probably an important reason that we sleep. You need time off from consciousness to do the housekeeping.” 

Further details at The Washington Post.  Absolutely fascinating.