Abnormal accumulation of cerebrospinal fluid within the ventricles of the brain. It is sometimes known as “water on the brain.” Within the center of our brains each of us has two fluid-filled areas called cerebral ventricles. Cerebrospinal fluid is made within these ventricles and distributed over the surface of the brain and spinal cord. When the normal circulation of cerebrospinal fluid is interrupted, fluid can accumulate within the ventricles. This fluid puts pressure on the brain, forcing it against the skull and enlarging the ventricles. In infants, this fluid accumulation often results in bulging of the fontanelle (soft spot) and abnormally rapid head growth. The head enlarges because the bony plates making up the skull have not yet fused together. In preemies the most common cause of hydrocephalus is intraventricular hemorrhage.
