A guide for adults; normal pressure hydrocephalus, shunts, and living with one
Most people think of hydrocephalus ('water on the brain') as a condition of babies. But it occurs in adults too, and one adult form in particular deserves to be much better known, because it is sometimes mistaken for ordinary ageing or for dementia, and because, unlike those, it can sometimes be improved. This guide explains what hydrocephalus is in adults, focuses on that important condition called normal pressure hydrocephalus, and covers the shunts that are used to treat it (including what life with a shunt involves and what to watch for. If you or someone you care for has been getting slowly less steady on their feet, more forgetful, and less reliable with the bladder, this guide is worth reading carefully) that particular combination has a name, and sometimes a treatment.
The brain is bathed in a clear fluid (cerebrospinal fluid, or CSF) that is constantly produced inside the brain's chambers (the ventricles), circulates around the brain and spinal cord, and is then reabsorbed back into the bloodstream. Hydrocephalus develops when this cycle is disrupted, so that fluid accumulates and the ventricles enlarge.
In adults this happens in a few different ways. Sometimes the flow of fluid is physically blocked, by a tumour, a cyst, or a narrowing of one of the channels (this is called obstructive hydrocephalus). Sometimes hydrocephalus develops after another event, such as bleeding around the brain, meningitis, or a head injury. And sometimes it arises on its own, gradually, in older people, in the particular form described next.
Normal pressure hydrocephalus (NPH) is the form most often missed. The ventricles slowly enlarge, but when the pressure of the CSF is measured in the usual way it sits in the normal range; hence the name. Despite that 'normal' pressure, the enlarged ventricles interfere with how the brain works, producing a characteristic pattern of symptoms. NPH mostly affects people over 60, and because its symptoms overlap with several common conditions of later life, it is frequently put down to 'getting old', to Parkinson's, or to early dementia. That matters, because NPH is one of the few causes of this kind of decline that can sometimes be helped.
A separate group of adults living with hydrocephalus are those who have had it since childhood and have grown up with a shunt. For them, much of this guide (particularly the parts about shunts and what to watch for) applies directly.
The symptoms depend on which form of hydrocephalus is present. The first group is the classic, gradually developing picture of normal pressure hydrocephalus. The second and third groups are more urgent and are repeated in the 'when to seek help' section.
A brain scan (CT or MRI) is the starting point, and it shows the enlarged ventricles clearly. In normal pressure hydrocephalus, however, the scan alone cannot answer the most important question, which is not 'are the ventricles enlarged?' but 'will treating this person actually help them?'. Enlarged ventricles can also be a feature of normal brain ageing, so the scan has to be interpreted alongside the symptoms.
Because of this, the assessment for NPH usually includes a test of how the person responds to temporarily removing some fluid. This is done either by draining a larger-than-usual amount of CSF through a lumbar puncture (sometimes called a 'tap test'), or by a short hospital stay with a fine drain in the lower back removing fluid over a few days. Walking is carefully assessed before and after. A clear improvement strongly suggests that a shunt will help; the test is one of the most useful tools for selecting who will benefit.
For obstructive hydrocephalus, the scans are also looking for the cause of the blockage (a tumour, a cyst, or a narrowing) because treating the cause may be part of the answer.
The treatments aim to restore the balance of fluid, either by giving it a new drainage route or by relieving a blockage. The right one depends on the type of hydrocephalus.
Normal pressure hydrocephalus is sometimes described as a 'treatable' or 'reversible' cause of a dementia-like decline. That phrase needs care (it is treatable in some people, not all) but it captures why the diagnosis is worth pursuing rather than assuming that a slow decline in later life is simply ageing.
After a shunt is placed for NPH, improvement (especially in walking) often develops over the following weeks rather than overnight, and the valve may be adjusted once or twice to find the best setting for you. Most people then settle into ordinary life, with periodic follow-up to keep an eye on the shunt.
A shunt is designed to last, but it is sensible to know the signs of a problem (the return of your original symptoms, headache, nausea, drowsiness, or signs of infection along the shunt) and to seek help promptly if they appear. Many people live for decades with a well-functioning shunt and rarely think about it.
One genuinely important practical point for adjustable valves: some of them can have their setting changed by the strong magnet of an MRI scanner. If your valve is one of these, the setting is checked (and reset if necessary) after any MRI. So always tell any doctor or radiographer arranging a scan that you have a shunt, and make sure the setting is verified afterwards. Carry your shunt details with you if you can.
Low mood and frustration are understandable companions of any condition that affects walking, memory, or independence, and they are treatable. For families, watching a relative decline and then (sometimes) improve after treatment is its own emotional journey. Support is available, and the patient organisations below are a good place to start.
Gradual symptoms of normal pressure hydrocephalus should be assessed by your doctor in the usual way, without panic. But some situations need urgent attention; go to the emergency department or call the emergency services for any of the following, particularly if you have a shunt:
A shunt that stops working can allow pressure to build up, sometimes quickly, so the return of symptoms in someone with a shunt should never be ignored. This guide is general information, not personal medical advice, and cannot replace assessment by a clinician who knows your case.