What exactly is hydrocephalus?

Hydrocephalus is a condition where an excessive amount of fluid collects in the brain. The "water" is cerebrospinal fluid, which flows through passageways in the brain. If these get blocked, the liquid accumulates, widens spaces within the brain, and causes pressure on brain tissue. In babies, this can cause the head to enlarge. In adults, it can result in a variety of symptoms.

The most common triggers for hydrocephalus in children are infections, such as meningitis; premature birth, or head injuries. Genetic causes are rarer. Some experts estimate that hydrocephalus affects roughly one in 500 children. In adults, it can result from meningitis, a brain tumour or brain trauma.

Symptoms vary with age, the stage of the disease, and an individual's tolerance of the condition. An infant's skull can expand in response to the pressure of fluid, while an adult's cannot. Adults and older children may suffer from headaches, vomiting, nausea, blurred or double vision, poor coordination or lack of balance. Hydrocephalus can also result in incontinence, memory loss, irritability, lethargy, and lack of reasoning ability. Many born with the condition will lead full, normal lives.

The symptoms can overlap with other diseases – such as Alzheimer's and Parkinson's – and are often misdiagnosed. Doctors sometimes need to conduct multiple tests, such as brain scans and spinal taps, to ensure accuracy. In infants, a rapid increase in head circumference is an obvious sign. An ultrasound can usually detect signs of hydrocephalus before birth.

There is no real cure, but the disease is usually treated with a shunt system – a plastic tube, a catheter and a valve. This is inserted to divert fluid from the brain to another part of the body, such as the abdominal cavity, where it can be absorbed without harm. Shunts usually stay in place for life, but can get infected; they may also need to be adjusted if a patient grows, rendering the tube too short. Hydrocephalus can also be treated by inserting a small fibre-optic camera into your body, allowing doctors to make a small hole in a brain ventricle.