Hydrocephalus is a condition caused by excessive accumulation of fluid in the brain. Once known as “water on the brain,” the fluid actually is cerebrospinal fluid, a clear fluid surrounding the brain and spinal cord. An excessive accumulation causes potentially harmful pressure on the tissues of the brain. Hydrocephalus can be present at birth or caused by traumatic injury or diseases such as meningitis and cancer. Symptoms in infants include an unusually large head size, vomiting, sleepiness and seizures. Older children and adults may experience headaches, vomiting, nausea, vision problems, balance and coordination disturbances, urinary incontinence, and personality or cognitive changes. Magnetic resonance imaging (MRI) may help diagnose the condition. Hydrocephalus can be treated with the surgical placement of a shunt system, which diverts the flow of fluid to another part of the body where it can be absorbed as part of the normal circulatory process.