The tunnels produce immune system cells and funnel them to the brain in case of inflammation or damage:
It seems that our brains are specially protected by “highly localized and specific” systems, not just general ones. The researchers hope that this knowledge could help fight autoimmune disorders such as multiple sclerosis.
News, “Confirmed: “Secret” tunnels connect our skulls and brains” at Mind Matters News (March 18, 2022)
Takehome: Formerly, neuroscientists believed that materials to repair the brain would be ferried up from big leg bones but the brain gets special delivery close to home.