The human brain does not have a system like the lymphatic system in the rest of the body to remove waste. Naessens: 'Despite much research, we do not yet fully understand how the brain keeps itself clean and balanced. The 'glymphatic system' now seems to be a possible route to clean up waste products.’ This system works through the so-called perivascular spaces. These are cerebrospinal fluid-filled spaces surrounding blood vessels in the brain. 'If we understand this system better, it could help treat diseases related to the accumulation of waste products in the brain, such as Alzheimer's and Parkinson's disease.'