Normal pressure hydrocephalus (NPH)

Normal pressure hydrocephalus (NPH) happens when too much cerebrospinal fluid builds up inside the brain. Cerebrospinal fluid, or CSF, is the clear fluid that cushions the brain and spinal cord. In NPH, the fluid collects in open spaces deep in the brain called ventricles. The ventricles get bigger and press on the brain around them.^1,2

NPH matters because it is one of the few causes of dementia symptoms that can sometimes be treated. A small surgery called a shunt can help many people walk better.^3,7 But NPH is often mistaken for Alzheimer's, Parkinson's or "just getting older." If you or someone you love has trouble walking along with memory or bladder changes, it is worth asking a doctor about NPH.

What NPH is

Your brain makes CSF all the time, and your body normally absorbs it again. In NPH, the fluid is not absorbed the way it should be. It builds up and stretches the ventricles.⁴

The name sounds confusing. "Hydrocephalus" means water on the brain. "Normal pressure" means that when doctors measure the fluid pressure with a spinal tap, it often looks normal, even though too much fluid is there.³

There are two main kinds:^2,4

• Idiopathic NPH (iNPH). "Idiopathic" means no cause is found. This is the most common kind, and it mostly affects people over 60.
• Secondary NPH. This follows something that harmed the brain, such as bleeding in the brain, a head injury, brain surgery, a tumor or an infection like meningitis.

How common is it?

NPH is not rare in older adults. A careful Swedish study screened people 65 and older in one area. About 1 in 27 (3.7%) met the criteria for likely iNPH. The rate was about 2% in people aged 65 to 79, and close to 9% in people 80 and older.⁶

The Hydrocephalus Association estimates that about 800,000 older Americans may have NPH. It also says more than 80% of cases are never recognized or treated.⁴ That means fewer than 1 in 5 people with NPH get a diagnosis.^3,4

The three main signs

Walking is the key sign. People often walk with their legs wide apart and their body bent forward. Some say it feels like walking on a boat. Getting started or turning around can be hard.^3,4

Thinking changes are often mild at first. The person may seem slower, less interested in things, or have trouble with attention and decisions. Memory loss is usually milder than in Alzheimer's.^3,5

Bladder problems start as urgency (a sudden strong need to go). Later there may be leaks or accidents. Some people never have bladder problems.⁴ Our page on bladder and bowel problems has tips for daily care.

Not everyone has all three. In one Mayo Clinic study of 41 older adults thought to have NPH, all had walking problems. But only 12 had all three signs.³ Symptoms usually come on slowly, over months or years.²

How NPH differs from Alzheimer's and Parkinson's

The order of symptoms gives doctors a clue:⁵

On a brain scan, NPH shows large ventricles, often without the overall brain shrinking seen in Alzheimer's.³ A person can also have NPH and another condition at the same time. Learn more about Alzheimer's disease, Parkinson's disease dementia and mixed dementia.

How doctors check for NPH

There is no single test. Doctors put several pieces together, and they also rule out other causes.^1,4 Because NPH looks like other conditions, it is best to see a neurologist (brain doctor) or neurosurgeon who knows NPH.^3,4 See which specialist to see.

1. Exam and history. The doctor asks about symptoms and watches the person walk. A physical therapist may time a short walk.^2,4
2. Brain scan. An MRI (preferred) or CT scan looks for enlarged ventricles.^2,4 See brain scans.
3. Thinking tests. Memory and thinking tests show where the person is starting from.⁴ See memory and thinking tests.
4. Spinal tap ("tap test"). A doctor removes a larger amount of CSF through a thin needle in the lower back, often up to about 50 mL (about 3 tablespoons). Walking is tested before and after.^2,4 See spinal fluid tests.
5. Lumbar drain (sometimes). A thin tube stays in the lower back for a few days in the hospital to drain fluid slowly. This acts like a trial run of a shunt.^4,5

What the results mean. If walking clearly gets better after fluid is removed, a shunt is more likely to help.⁹ Many people first thought to have NPH do not improve on this test.³ But a test with no improvement does not fully rule out a good response to a shunt.^4,9 Your doctor will look at all the results together.

The longer drain carries a small risk of infection. A neurology guideline puts the risk of meningitis at about 2% to 4%.⁹

Treatment: the shunt

A shunt is the main treatment for NPH. No medicine has been shown to work, and water pills (diuretics) do not seem to help.³

What a shunt is. It is a thin, soft tube placed by a neurosurgeon. The most common type runs from a ventricle in the brain, under the skin of the neck and chest, to the belly. This is called a ventriculoperitoneal (VP) shunt. The body absorbs the drained fluid there.^2,10

A small valve under the skin, usually behind the ear, controls how much fluid drains.¹⁰ Many people get a programmable valve. A doctor can change its setting in the office with a magnetic tool, without more surgery.¹¹ The person is fully asleep (general anesthesia). The operation usually takes about an hour or a little more.^4,10

How well does a shunt work?

For many years, doctors were not sure how much shunts helped, because studies were small.^3,9 A major trial changed that.

The PENS trial, published in 2025, enrolled 99 people with iNPH who had improved after a spinal fluid drain. All got a shunt. For half, the valve was set to drain fluid. For the other half, it was set so almost no fluid drained, like a placebo. Neither the patients nor the testers knew which group they were in.⁷

After 3 months:^7,8

• Walking speed improved clearly in the draining group and barely changed in the other group. About 8 in 10 people with a draining shunt had a meaningful gain in walking speed, compared with about 1 in 4 in the placebo group.
• Balance improved more in the draining group.
• Falls happened less often: 24% in the draining group versus 46% in the placebo group.
• Memory and thinking scores and bladder symptoms did not improve by a clear amount in the first 3 months.

What this means in daily life. For people chosen carefully with the spinal fluid tests, a shunt can help them walk faster and more steadily, with fewer falls.⁷ Walking is the symptom most likely to get better. Thinking and bladder control are less likely to improve.^2,3 Longer-term results from this trial are still to come.⁸

Older studies found that more than 80% of carefully chosen patients improved after a shunt. Some studies found the benefit faded over time.⁹ Being older does not by itself lower the chance of a good response.⁹ Physical therapy for walking and balance after surgery is important.⁴ See strength and balance training.

Risks of shunt surgery

Shunt surgery is brain surgery, and it has real risks. A neurology guideline says the risks and benefits should be weighed carefully for each person.⁹

• Bleeding on the brain's surface (subdural hematoma). This can happen if too much fluid drains. In the PENS trial, it happened in 12% of the draining group and 2% of the placebo group.⁷
• Headaches when sitting or standing up. These were common in the PENS trial (59% versus 28%).⁷
• Infection of the shunt, brain or belly.^4,10
• Blockage or failure of the shunt, so fluid builds up again. More surgery may be needed.^4,10
• Seizures or bleeding inside the brain, which are less common.^7,10

Recent studies report complications in about 15% to 28% of people.⁹ With a programmable valve, the doctor can change the drainage setting without another operation.¹¹ Ask the surgical team how often they place shunts for NPH and how they will follow up.

Why early checking matters

NPH tends to get worse over time if it is not treated. In some people it can even be fatal.^1,2 Doctors cannot predict how fast it will change.⁴

Early diagnosis and treatment give the best chance of a good recovery.¹ People whose symptoms are still mild tend to do best after a shunt.² People who have had symptoms for a long time may still improve, so it is not too late to ask.⁴

Because walking problems raise the risk of falls, getting checked can also prevent injuries.² See preventing falls.

Living with a shunt

• Keep follow-up visits. Regular checkups help catch small signs that the shunt is not working well.¹
• Watch for returning symptoms. Walking, thinking or bladder problems that come back, new falls or mood changes can mean the shunt needs checking.⁴
• Watch the shunt site. Fever, redness or swelling along the tube can mean infection.⁴
• Be careful with magnets if the valve is programmable. Keep magnets away from the valve. Ask your doctor about other precautions, such as before an MRI.¹¹
• Carry a card that says the person has a shunt and what kind of valve it is. This helps in a hospital or emergency room. See hospital stays and emergency rooms.

The Hydrocephalus Association runs a helpline at 888-598-3789 (weekdays, 9 a.m. to 5 p.m. Eastern) and a directory to help find a neurosurgeon.⁴

Questions to ask the doctor

Could this be NPH?

• Do the brain scans show enlarged ventricles?
• Which came first, and does that pattern fit NPH?
• Could another condition, such as Alzheimer's or Parkinson's, also be present?
• Should we see a neurologist or neurosurgeon who treats NPH?

What tests do we need?

• Will we have a tap test or a lumbar drain? What are the risks?
• How will you measure walking before and after?
• If the test shows no change, what happens next?

Is a shunt right for us?

• How much improvement is likely in walking, thinking and bladder control?
• What are the main risks for this person, given their health and medicines?
• What kind of valve would you use? How often will we come back?
• Who do we call at night or on a weekend if something seems wrong?

When to get help

NPH is one of several conditions that can look like dementia but may be treatable. Read about others on our page treatable conditions that look like dementia, or see all types of dementia.

Education only. This page is general information written from the sources listed. It is not medical, legal or financial advice and does not replace a doctor, therapist or lawyer who knows your situation. How we write and check pages.