Billy Joel has excess fluid in his brain – a neurologist explains what happens when this protective liquid gets out of balance

Billy Joel was diagnosed with normal pressure hydrocephalus. Ethan Miller/Getty Images

Cerebrospinal fluid, or CSF, is a clear, colorless liquid that plays a crucial role in maintaining the health and function of your central nervous system. It cushions the brain and spinal cord, provides nutrients and removes waste products.

Despite its importance, problems related to CSF often go unnoticed until something goes wrong.