Hydrocephalus

What is hydrocephalus?

Hydrocephalus is a build-up of fluid on the brain. This fluid, called cerebrospinal fluid, puts pressure on the brain and can damage it if the condition isn't treated.

What are the symptoms of hydrocephalus?

Symptoms depend on your age and how the condition developed. Babies born with hydrocephalus often have distinctive physical features, including:

• an unusually large head
• a thin, shiny scalp with visible veins
• a bulging or tense soft spot (fontanelle) on top of the head
• eyes that look downwards.

They may also feed poorly, vomit, seem unusually sleepy or irritable, and have stiffness or spasms in their lower limbs. In children and adults who develop hydrocephalus later (acquired hydrocephalus), the most common symptom is headache, often worse first thing in the morning and easing after sitting up for a while, though it can become continuous as the condition progresses.

Other symptoms can include:

• neck pain
• feeling or being sick, which may also be worse in the morning
• sleepiness, which can progress to loss of consciousness
• confusion or other changes in mental state
• blurred or double vision
• difficulty walking or poor coordination
• loss of bladder control, and sometimes bowel control too.

Normal pressure hydrocephalus (NPH), which mainly affects older people, causes three particular sets of symptoms:

• difficulty walking (often described as feeling frozen when trying to take the first step, or a shuffling gait)
• urinary symptoms such as a frequent or urgent need to pee
• slowed thinking that can resemble mild dementia. Unlike most causes of dementia, these symptoms can improve once NPH is treated.

What are the different types of hydrocephalus, and what causes them?

Hydrocephalus happens when the normal flow, drainage or reabsorption of cerebrospinal fluid is disrupted, so fluid builds up and puts pressure on the brain. There are three main types, grouped by when and how they develop. The likely cause differs for each.

Congenital hydrocephalus: present at birth

This can be linked to:

• spina bifida or other defects affecting the brain and spinal cord
• a narrowing of the small passage between two of the brain's fluid-filled ventricles
• complications of premature birth, such as bleeding within the ventricles
• infections during pregnancy, such as rubella.

In many cases of congenital hydrocephalus, no clear cause is found.

Acquired hydrocephalus: develops after birth, in a child or an adult

This is usually the result of:

• a head injury
• a stroke or bleeding inside the brain
• a brain or spinal cord tumour
• an infection such as meningitis.

Normal pressure hydrocephalus (NPH): usually develops slowly in older people, without necessarily raising the pressure inside the skull

This sometimes follows an injury, infection or bleeding in the brain, though often no clear cause is found.

Doctors also describe hydrocephalus by how the fluid becomes blocked. In communicating hydrocephalus, fluid can still flow between the brain's ventricles but is blocked once it leaves them. In non-communicating (obstructive) hydrocephalus, the blockage sits within the narrow passages connecting the ventricles themselves.

A related but separate condition, hydrocephalus ex-vacuo, can look similar on a scan: here, brain tissue shrinks after an injury or stroke, and the ventricles enlarge to fill the space, but pressure inside the skull usually stays normal.

How is hydrocephalus diagnosed?

Diagnosis starts with a neurological examination, checking things like muscle strength and reflexes, coordination and balance, vision and eye movement, and mental functioning.

Brain imaging is then used to confirm the diagnosis and look for a cause, which may include:

• an ultrasound scan, often the first test in babies, and one that can even detect hydrocephalus before birth
• an MRI scan, usually the main test in children and adults, showing the size of the ventricles and the fluid flow
• a CT scan, which can be used quickly in an emergency

In adults, further tests are sometimes used, including a lumbar puncture (spinal tap) to measure fluid pressure, a monitor temporarily inserted to measure pressure inside the skull, or an examination of the optic nerve at the back of the eye to check for signs of raised pressure. For suspected NPH, doctors also assess your walking, mental abilities and bladder control against a specific checklist, since correctly telling NPH apart from Alzheimer's disease matters: NPH can usually be treated.

How is hydrocephalus treated?

There's currently no cure for hydrocephalus, and no non-surgical treatment either: brain surgery is the only option, and there are two main types.

• Shunt surgery: a thin, flexible tube (shunt) is placed in the brain to drain excess fluid to another part of the body, usually the abdomen where it's absorbed into the blood. A valve inside the shunt controls the flow, and you can often feel it as a small lump under the scalp. The operation is performed under general anaesthetic and usually takes 1–2 hours, with a hospital stay of a few days to recover
• Endoscopic third ventriculostomy (ETV): instead of a shunt, a small hole is made in the floor of one of the brain's fluid chambers, creating a new pathway for fluid to drain and be absorbed naturally. This is generally used in children over the age of two, and long-term results are similar to shunt surgery

For normal pressure hydrocephalus, a shunt can help, but not everyone with NPH benefits from surgery, so doctors usually carry out tests beforehand, such as temporarily draining fluid, to see whether you're likely to respond well.

Shunts and ETVs both need long-term monitoring, as they can stop working or become infected, sometimes years after the original surgery, and may need to be repaired or replaced.

When should I see a doctor?

Contact a GP or call 111 if you think you or your child may have symptoms of hydrocephalus, such as the headaches, vision changes, sickness or walking difficulties described above.

If you or your child already has a shunt or has had an ETV, contact your surgical team immediately if you notice:

• redness or tenderness along the line of the shunt or the surgical wound
• a return of hydrocephalus symptoms, such as headache, vision changes, or nausea and vomiting
• neck or shoulder soreness
• seizures
• a high temperature

These can be signs that the shunt is blocked or infected, which can be serious and needs prompt attention.