Massaging the neck and face may help flush waste out of the brain

A device that massages the face and neck boosts the brain’s waste disposal system, suggesting it could reduce the severity of conditions like Alzheimer’s disease.

Cerebrospinal fluid (CSF) bathes our brain, pumped into it before leaving through a network of thin tubes called glymphatic vessels. Studies in mice have shown that this fluid flushes out waste products made by brain cells, including beta-amyloid, a protein linked to conditions such as Alzheimer’s and Parkinson’s disease.

This has spurred scientists to wonder whether enhancing the flow of CSF could boost brain health. But glymphatic vessels have previously only been identified deep in the neck, making them hard to manipulate, says Gou Young Koh at the Korea Advanced Institute of Science and Technology in South Korea.

Now, Koh and his colleagues have found a network of glymphatic vessels around 5 millimetres below the skin on the face and neck of mice and monkeys. They made the discovery by injecting the animals with a fluorescent dye that labels CSF and imaging them under anaesthesia. “We used a different type of anaesthesia than used in prior studies – the anaesthesia other studies used blocked the detection of the vessels nearer the skin,” says Koh.

To see whether massaging these vessels could boost CSF flow, the researchers built a device with a small rod attached to a 1-centimetre-wide cotton ball. They used it to stroke downwards along the face and neck of older mice, aged around 2 years, and younger mice that were a few months old, for a minute. “Gently massaging down the face and upper neck can push the fluid down, enhancing the CSF flow,” says Koh.

Up to half an hour later, the CSF flowed around three times faster through the mice’s brains, on average, compared with before the animals were massaged. The procedure also seemed to reverse age-related declines in CSF flow. “After stimulation, the older mice’s CSF flow was similar to that of younger mice [that hadn’t yet been massaged],” says Koh.

In unpublished work, the team found similar results in monkeys. What’s more, they have pinpointed glymphatic vessels under the skin of human cadavers, suggesting massaging could also boost CSF flow in people, says Koh.

But mice and monkeys have some anatomical differences to humans so further work is needed to establish this, says Vesa Kiviniemi at the University of Oulu in Finland. “It’s somewhat a different ball game.”

What’s more, it is still unclear whether enhancing CSF flow really can slow brain ageing or protect against neurodegenerative diseases such as Alzheimer’s disease, says Steven Proulx at the University of Bern in Switzerland. Koh says his team is planning to explore this in mice bred to have features of Alzheimer’s disease.