Hydrocephalus is an abnormal increase of cerebrospinal fluid in the fluid-filled cavities of the brain. It occurs when there is an imbalance between the amount of cerebrospinal fluid that is produced and the rate at which the body absorbs it. It used to be known colloquially as “water on the brain”. The symptoms vary with age, the progression of the disease and the individual’s tolerance to cerebrospinal fluid but may include a rapid increase in head size, vomiting, sleepiness, irritability, seizures, headache, nausea, papilledema, blurred vision, double vision, sunsetting of the eyes, poor balance or coordination, gait disturbance, and urinary incontinence. Treatment options are usually surgical and involve inserting a shunt or removing obstructions, but medication is another option in mild cases.