Congenital hydrocephalus: causes, signs, shunts and outlook

The brain is surrounded and protected by a clear fluid called cerebrospinal fluid, or CSF. The NHS explains that this fluid protects the brain from damage, removes waste products and supplies nutrients, and that the brain constantly makes new CSF, about a pint a day, while old fluid is absorbed into the blood vessels. In hydrocephalus that process is interrupted and the fluid builds up and presses on the brain.

In the past hydrocephalus was called water on the brain, although the NHS notes the brain is not surrounded by water but by CSF. Congenital hydrocephalus is the form that is present at birth. The NHS lists it as one of three main types, alongside acquired hydrocephalus, which develops after birth, and normal pressure hydrocephalus, which usually develops in older people.

The NHS says the causes of hydrocephalus are poorly understood. Congenital hydrocephalus may be the result of a brain defect that restricts the flow of CSF. It can be caused by conditions such as spina bifida, and can develop in babies born prematurely, before 37 weeks, when bleeding in the brain blocks the flow of CSF.

Other possible causes listed by the NHS include a mutation of the X chromosome (X-linked hydrocephalus), rare genetic disorders such as Dandy-Walker malformation, and arachnoid cysts. The NHS overview also mentions infections the mother develops during pregnancy, such as mumps or rubella. In many cases of congenital hydrocephalus the cause is unknown, .

The NHS says babies born with hydrocephalus often have distinctive physical features and may show other signs of pressure in the head.

• An unusually large head.

• A thin and shiny scalp with easily visible veins.

• A bulging or tense fontanelle (the soft spot on top of the head).

• Downward-looking eyes.

• Poor feeding, irritability, vomiting or sleepiness.

• Muscle stiffness and spasms in the lower limbs.

The NHS says to call a GP or use NHS 111 if you think you or your child may have symptoms of hydrocephalus. The NHS says untreated hydrocephalus can damage the brain, and lists sleepiness, vomiting and a bulging fontanelle among the signs in babies. It also says a shunt blockage can be very serious and needs emergency surgery, and that people with a shunt who develop redness along the shunt line, a high temperature, headache, vomiting, neck stiffness or irritability should contact their care team immediately.

The NHS says congenital hydrocephalus is sometimes found before birth during a pregnancy ultrasound scan, but is usually diagnosed soon after birth at the newborn physical examination, when a baby's head may be noticed to be larger than normal. CT and MRI scans are often used together to confirm the diagnosis. They show the build-up of fluid and the pressure, and can highlight any structural defect that may be causing the problem.

The NHS says hydrocephalus is treated with surgery, and babies born with hydrocephalus usually need prompt treatment to reduce pressure on the brain. There are two main operations.

In shunt surgery a neurosurgeon implants a thin tube in the brain so that excess CSF drains to another part of the body, usually the tummy, where it is absorbed into the blood. A valve in the shunt controls the flow. The operation is done under general anaesthetic, usually takes 1 to 2 hours and may need a few days in hospital.

Endoscopic third ventriculostomy (ETV) is an alternative in which the surgeon makes a small hole in the floor of the brain so trapped fluid can escape to the surface. The NHS says it is not suitable for everyone but may be an option when the build-up is caused by a blockage, takes around 1 hour, and carries less risk of infection than a shunt. Long-term results are similar to shunt surgery, with a risk of blockage months or years later.

The NHS says a shunt is a delicate piece of equipment that can malfunction, usually by becoming blocked or infected. Infection is a relatively common complication and is more likely in the first few months after surgery. A shunt may also become too small as a child grows and need replacing, and as most people need a shunt for life, more than one replacement may be needed.

Shine produces shunt alert cards for children and adults, which help emergency staff recognise a possible blockage or infection. Possible complications of ETV include the hole closing, infection, minor bleeding and, rarely, nerve problems or epilepsy; if the hole fails, the procedure may be repeated or a shunt fitted.

The NHS says many babies born with hydrocephalus have permanent brain damage, which can lead to long-term difficulties. These can include learning disabilities, speech, memory and attention problems, problems with organisational skills, vision problems such as squint or vision loss, problems with physical coordination and epilepsy. Each child is different, and treatment aims to limit damage from pressure.

The NHS notes that if a child has learning disabilities they will need extra support from their nursery or school. Families can contact Shine, the charity for spina bifida and hydrocephalus, for details of local support groups and carer support.