A new discovery in medicine shows an anatomical structure of the brain never described before. It plays a very important role in the human body.
The layer of tissue, called the subarachnoid lymphatic membrane (SLYM), plays an important role in both the removal of waste products from the brain and the immune system by acting as a protective barrier and protecting immune cells.
The newly discovered membrane was first characterized in mice but has since been observed in the adult human brain. It is only a few cells thick and is one of four of its kind membranes between the skull and the brain.
The other three are the dura, arachnoid and pia mater membranes which together make up the meningeal layer. The most recent addition divides the space under the arachnoid layer, the subarachnoid space, which contains cerebrospinal fluid (CSF).
In doing so, it joins the other meningeal membranes creating a barrier between the brain and the rest of the body. SLYM, in particular, appears to separate freshly made, “clean” CSF from “dirty” CSF containing cellular waste. Therefore, it is likely involved in the glymphatic system, a network responsible for removing waste from the brain.
“The discovery of a new anatomical structure that segregates and helps control the flow of cerebrospinal fluid (CSF) in and around the brain now gives us a much greater appreciation of the sophisticated role CSF plays in more than just waste transport and removal from the brain, but also in supporting its immune defences,” said Maiken Nedergaard, one of the authors of a study describing the discovery, in a communicated.
Medical breakthrough showing a new area of the human brain
SLYM is a type of mesothelium membrane, examples of which can be found around other organs in the body, including the lungs and heart. These membranes typically protect organs and house immune cells, and SLYM is no different.
It was found to be full of immune cells, suggesting its importance for brain defense. These cells can use SLYM to monitor the CSF for signs of infection or inflammation. The new discovery could have implications for the study of brain injuries and diseases like multiple sclerosis and Alzheimer’s.
The researchers observed that the number and diversity of immune cells in SLYM increased in response to inflammation and aging. They also suggest that: “Physical disruption of SLYM could, by altering CSF flow patterns, explain the prolonged suppression of glymphatic flow after traumatic brain injury, as well as the increased posttraumatic risk of developing Alzheimer’s disease” .
SLYM, they add, could allow immune cells in the skull to gain access to the brain, perhaps explaining the sustained inflammation after injury. In short, this new structure could influence a range of brain conditions and, the researchers hope, its discovery should help us better understand them. The study is published in the journal Science.
