Hydrocephalus

The old name for hydrocephalus, "water on the brain", is wrong twice over: there is no water in the head, and the brain does not float in it. What circulates inside the skull is cerebrospinal fluid, and its volume is normally held in a strict balance — as much is absorbed as is made. Hydrocephalus is that balance breaking down. Fluid keeps arriving, the outflow or the absorption fails, the cavities of the brain stretch and press on the tissue from inside. A baby's skull is pliable and gives way for a while; an adult's is not, which is why the picture looks entirely different at different ages. One thing is shared: untreated pressure damages the brain, and an operation in good time usually prevents the damage altogether.

Where the fluid comes from and where it gets stuck

Cerebrospinal fluid is made inside the ventricles of the brain — about half a glass a day — bathes the brain and spinal cord on the outside, and is absorbed back into the venous blood. It cushions the brain against knocks, carries away waste and brings what is needed. Its whole volume is renewed several times a day, so even a modest obstruction produces results quickly.

The obstruction comes in two kinds. Either the narrow channel between the ventricles is blocked, in which case fluid piles up above the blockage while the cavities beyond it stay normal — this is obstructive hydrocephalus. Or the path is clear but the fluid is poorly absorbed at the far end, for instance after a haemorrhage or meningitis has left the membranes around the brain scarred with adhesions. The distinction is not academic: which operation will suit follows directly from it.

Three different stories under one name

The word "hydrocephalus" gathers together conditions that share little beyond the mechanism.

• Congenital — the baby is born with excess fluid. The cause may be narrowing of the channel between the ventricles, spina bifida, a haemorrhage in a baby born prematurely, an infection the mother had in pregnancy (toxoplasmosis, cytomegalovirus, rubella), uncommon malformations or genetic faults. In many cases no cause is ever found.
• Acquired — it develops later, in a child or an adult, and always follows something: a serious head injury, a bleed beneath the coverings of the brain, meningitis, a tumour, a stroke. Sometimes a person is born with a narrow channel that copes for decades and then decompensates in adult life.
• Normal pressure hydrocephalus — a distinct form in older people, in which the ventricles are enlarged yet the pressure, when measured, stays within the normal range. The cause is usually unknown; occasionally it follows an injury, a bleed or meningitis.

How it shows, from newborn to adult

In a baby the skull bones have not yet fused, so the head simply grows faster than it should. That is why head circumference is measured at every check: a figure jumping across the lines on the chart says more than any symptom. Other warning signs are a tense, bulging fontanelle, a thin shiny scalp with veins showing through, eyes fixed downwards so that a strip of white shows above the iris, feeble feeding, vomiting, unusual sleepiness or, conversely, constant crying, and stiffness of the legs.

In an older child and in an adult the skull has nowhere to grow, so the whole of the pressure falls on the brain. The leading sign is headache, worst in the morning on waking and easing after sitting upright for a while: lying down, the fluid drains less well and builds up overnight. In time the headache stops letting go. Nausea and vomiting join it, more often in the morning, along with double or blurred vision, neck pain, growing drowsiness, slowness, confusion, unsteadiness on the feet and loss of bladder control.

Call an ambulance (in Europe, 112) if the headache worsens rapidly and comes with vomiting, if the person cannot be roused, if they stop recognising those around them, if there are seizures, or in a baby if the fontanelle becomes tight and bulging and the child turns floppy. A sharp rise in pressure inside the skull builds over hours and can only be treated urgently.

When the pressure is normal and the illness is there anyway

Normal pressure hydrocephalus deserves a section of its own, because it is the one dementia that can sometimes be reversed — which makes missing it particularly galling. It develops slowly in older people, over months and years, and is built from three parts.

Walking changes first and suffers most. The first step is hard to take, the feet seem glued to the floor; steps become short and shuffling, the stance widens, turning is difficult and often ends in a fall. From outside it resembles parkinsonism, but without the trembling hands.

The bladder starts to hurry things along: first frequent, sudden urges, later leaking.

Thinking slows down. It is not so much that memory goes as that the pauses lengthen: the person takes longer to find a word, longer to answer, longer to work things out. Initiative fades and interest in things drains away.

It is that third part that gets the condition mistaken for Alzheimer's disease, at which point everyone gives up. The difference matters: in Alzheimer's memory goes first and walking stays intact for a long time, whereas here it is the other way round — the legs go first. And unlike Alzheimer's, this one has an operation that often gives a person their independence back.

How the diagnosis is confirmed

Imaging is the foundation. CT and MRI show the enlarged ventricles, the signs of pressure on the tissue and often the cause itself: a tumour, adhesions, a malformation. In a baby, while the fontanelle is still open, an ultrasound through it is enough, and in a fetus enlarged ventricles are sometimes seen on a routine scan in pregnancy. The back of the eye is examined too: swollen optic discs confirm that the pressure really is raised.

Normal pressure hydrocephalus is harder: enlarged ventricles also appear with the ordinary loss of brain volume that comes with age, so the pictures alone will not settle it. Walking, memory and attention are assessed, the bladder is asked about, and then a test is done: some fluid is removed through a lumbar puncture and the walking is watched over the following hours and days. If the person moves noticeably better, a shunt will probably help. When the result is unconvincing, fluid is drained through a fine catheter over several days, or the way the body copes with an added volume is measured. These tests are not a formality: they filter out the people for whom an operation would offer nothing but risk.

Treatment: a tube or an opening

Hydrocephalus is not treated with tablets; only surgery helps, and there are essentially two options.

A shunt. A fine tube runs from a ventricle of the brain under the skin to the abdominal cavity, or less often to a vein near the heart, and the surplus fluid goes where it can be absorbed without trouble. A valve in the line stops it draining too fast; it can sometimes be felt under the skin as a small lump. The operation takes an hour to an hour and a half under general anaesthetic, with a few days in hospital. A shunt is generally in place for life, and in a child it has to be replaced as they grow.

Endoscopic third ventriculostomy. Through a small opening in the skull the surgeon passes an endoscope and makes a hole in the floor of the third ventricle so that the fluid bypasses the blockage and reaches a place where it is reabsorbed. No foreign body is left inside and the risk of infection is lower. But it does not suit everyone: it is designed for the obstructive form, where there is a specific blockage. The opening can also close over time, and then the symptoms return.

Any operation on the brain carries risks: bleeding, infection, seizures, temporary weakness down one side. They are discussed beforehand, and the decision is always weighed against what would happen without surgery.

Living with a shunt, and the signs not to miss

A shunt is a mechanical device and it can let you down. Two failures demand immediate action, and not only the patient but the whole family should know them.

Blockage. The fluid stops draining and the very symptoms of before the operation come back: headache, vomiting, drowsiness, double vision and, in a baby, a bulging fontanelle and a rapidly growing head. This is an emergency: surgery is needed at once and waiting is not an option.

Infection. It happens most often in the first months after insertion. It shows itself with fever, headache, vomiting, a stiff neck, redness and tenderness of the skin along the line of the tube, abdominal pain and, in infants, irritability or listlessness. It needs antibiotics and quite often replacement of the system.

The opposite happens too — too much fluid drains away. Then the head aches when upright and settles on lying down. This is dealt with by resetting the valve, in many modern models without an operation.

It is worth carrying a card with the shunt details: in an emergency it tells the doctors straight away what to look for. Otherwise there are few restrictions — most people with a shunt study, work and play sport without giving it much thought.

A word about children. Some children born with hydrocephalus grow and develop just like their classmates. Others are left with difficulties in learning, speech, memory, attention and organisation, and there may be a squint and reduced vision, problems with coordination, or epilepsy. All of it is better picked up early: school support, speech therapy and eye follow-up achieve more than hoping a child will grow out of it.

Online consultation

Remote care is useful at several points along this road. For the parents of a baby, a doctor will help make sense of the head circumference chart and decide whether the rate of growth is worrying. For an older person and their family, it helps to work out whether a changed walk and forgetfulness are more than age, and which specialist to see and which scan to ask for, so that a year is not lost to the wrong diagnosis. For those already living with a shunt, it is convenient to go through a headache online, weigh up changes in how they feel, discuss imaging results and understand what a line in a report means. The limit is worth remembering: with a headache worsening fast alongside vomiting, with confusion, with seizures, or with any suspicion that a shunt has failed, no consultation is waited for — call an ambulance.

This material is for information only and does not replace medical advice.