On Oct. 9, 2024, scientists from Oregon Health & Science University (OHSU) released a study that used imaging of neurosurgery patients to definitively reveal the existence of waste-clearance pathways in the human brain known as the glymphatic system.

The new study examined five OHSU patients who underwent neurosurgery to remove tumors in their brains between 2020 and 2023. In each case, the patients consented to having a gadolinium-based inert contrasting agent injected through a lumbar drain used as part of the normal surgical procedure for tumor removal. The tracer would be carried with cerebrospinal fluid into the brain.

The findings were published in the Proceedings of the National Academy of Sciences.