The central nervous system has no conventional lymphatic vessels.

The lymphatic system is a network of vessels that drains excess fluid from tissues and helps move immune cells and other material toward lymph nodes. For generations, standard anatomy taught that the central nervous system lacked conventional lymphatic vessels.

That claim was too broad.

The vessels are not spread densely through brain tissue in the same way lymphatics run through many other organs. Instead, they lie in the meninges—the membranes surrounding the brain—and connect drainage around the brain with lymph nodes in the neck.

Earlier anatomists had occasionally described structures that might have been meningeal lymphatics, but the finding did not become part of mainstream modern anatomy.

In 2015, two research groups independently used high-resolution imaging and tracer experiments to show functional lymphatic vessels in the dura, one of the outer meningeal layers. Tracers placed around the brain could move through these vessels toward cervical lymph nodes.

The discovery did not mean that the brain itself contains an ordinary peripheral-style lymphatic network. It showed that the central nervous system is connected to conventional lymphatic drainage through vessels in its surrounding membranes.