Hydrocephalus. Red transillumination of the head of a baby suffering from hydrocephalus. The condition is also known as water on the brain". Illuminated yellow areas show fluid accumulation inside the skull which has caused enlargement of the baby's head. Hydrocephalus is a state of imbalance in production and absorption of cerebro- spinal fluid (CSF); an excessive amount of CSF accumulates under pressure within the cavities of the brain. It may be present at birth, or may be due to infection or injury. To prevent brain damage, the fluid must be drained by means of a tube (shunt) inserted through a hole in the skull. Surgery is usually successful."