Normal Pressure Hydrocephalus

Normal pressure hydrocephalus is a brain condition that happens when fluid builds up inside your skull, causing walking problems, memory difficulties, and loss of bladder control. While these symptoms can look like dementia or Parkinson’s disease, this condition is sometimes treatable and even reversible with surgery.

Table of contents

• What is normal pressure hydrocephalus?
• Who is affected?
• Symptoms
• Causes
• Diagnosis
• Treatment
• Outlook and prognosis

What is normal pressure hydrocephalus?

Normal pressure hydrocephalus is a brain disorder in which excess cerebrospinal fluid (a clear liquid that surrounds and cushions the brain and spinal cord) accumulates in the brain’s ventricles, which are fluid-filled spaces inside the brain^[1][3]. This buildup of fluid causes the ventricles to enlarge and puts pressure on nearby brain tissue, which can damage it and lead to problems with walking, thinking, and bladder control^[3].

The condition is called “normal pressure” because despite the excess fluid, the pressure of the cerebrospinal fluid as measured during a spinal tap is often within the normal range or only slightly elevated^[3][6]. However, there is evidence that people with this condition can have periods of increased pressure inside the skull^[4].

Adults typically only have about 5 fluid ounces (150 milliliters) of cerebrospinal fluid, less than half the volume of liquid in a standard beverage can. Your body constantly creates, circulates, and reabsorbs this fluid to keep that amount constant^[1]. When your body can’t circulate or reabsorb the fluid correctly, too much of it accumulates inside your skull. With normal pressure hydrocephalus, this fluid buildup usually happens gradually over three to six months^[1][6].

There are two forms of normal pressure hydrocephalus. Idiopathic (also called primary) normal pressure hydrocephalus has no identifiable cause^[8]. Secondary (also called symptomatic) normal pressure hydrocephalus occurs when earlier trauma, bleeding in the brain, infection, brain surgery, tumors, or cysts contribute to the condition^[6][7][8]. Secondary normal pressure hydrocephalus can affect people of any age, while idiopathic normal pressure hydrocephalus mainly affects older adults^[8].

Who is affected?

Normal pressure hydrocephalus is most common in people over 65, becoming more and more common the older a person gets. The average age for this condition to start is around age 70^[1]. It affects about 0.2% of people between the ages 70 and 79, and about 5.9% of people over 80^[1][8]. This means it affects about 8.4 million people over the age 80 worldwide^[1].

The condition is very rare in people under 65, affecting only about 0.003% of people in that age group^[1]. It’s estimated that over 700,000 people in the United States have normal pressure hydrocephalus, though under 20% of them have been diagnosed with the condition^[4]. Men and women are affected in equal numbers^[8].

Normal pressure hydrocephalus may cause up to 5% of dementia cases in the United States^[4]. However, it is often misdiagnosed as other conditions including Alzheimer’s disease (due to memory and thinking problems), Parkinson’s disease (due to walking difficulties), or Meniere’s disease (due to balance problems)^[6].

Symptoms

The symptoms of normal pressure hydrocephalus usually start gradually, developing and worsening over three to six months^[1][6]. The three main symptoms are known as Hakim’s triad or Adams triad, named after the doctors who first described the condition in 1965^[6][8]. Between 50% and 75% of people with normal pressure hydrocephalus show all three symptoms at the same time^[1]. The triad consists of walking difficulty, cognitive impairment, and urinary problems^[6].

Walking and balance problems are present in nearly all patients and are typically the first symptom to appear^[6]. This is caused by enlargement of the ventricles, which can press on the nerve fibers that control movement^[6]. People with normal pressure hydrocephalus might experience anything from feeling a little off balance to not being able to walk^[4]. Common problems include trouble taking first steps, difficulty with turns, taking short steps, shuffling, or a “magnetic gait,” which feels as if there are magnets on the floor making it difficult to lift up the feet^[4][7]. The gait abnormality is typically broad-based, slow, and short-stepped^[6]. As problems with walking worsen, the person may need a cane or walker and might fall or almost fall more often^[4]. A tremor of the hands, legs, or feet can be seen in up to 40% of patients^[6].

Cognitive impairment or memory problems are present as progressive decline in mental function, affecting 60% of patients at the time of treatment^[6]. This is caused by distortions predominantly at the front part of the brain^[6]. People with normal pressure hydrocephalus might lose interest in activities, have trouble remembering things that happened recently, feel “foggy,” forget things, and have trouble doing routine tasks^[4]. Initial problems involve planning, organization, attention, and concentration^[6]. Further difficulties include managing finances, taking medications, driving, keeping track of appointments, daytime sleeping, short-term memory problems, and slowed thinking and movement^[6]. It’s common for someone with normal pressure hydrocephalus to be disorganized when trying to complete tasks^[4]. Late-stage features include lack of interest (apathy), reduced drive, slowed thinking, and reduced speech^[6].

Urinary incontinence appears late in the illness and is present in 50% of patients at time of treatment^[6]. Bladder problems begin as increased frequency of urination, often progressing to urgency and then incontinence (loss of bladder control)^[6][7]. Some people may also have problems controlling their bowels^[7].

Causes

In about half of patients with idiopathic normal pressure hydrocephalus, doctors don’t know what causes the condition^[4][7]. The exact process that leads to the disorder remains unclear^[8]. However, the condition has been associated with various other health problems including high blood pressure, diabetes, Alzheimer’s disease, and high cholesterol^[6].

In other patients, the condition can be caused by a head injury, brain surgery, tumors and cysts, certain types of bleeding in the brain (such as bleeding from a blood vessel or aneurysm), and infections in the brain such as meningitis^[4][6][7]. When normal pressure hydrocephalus is caused by one of these underlying causes, it is known as secondary normal pressure hydrocephalus^[4].

The condition happens because the body can’t properly circulate or reabsorb cerebrospinal fluid. When cerebrospinal fluid keeps accumulating with nowhere else to go, the brain starts to compress and give way, causing symptoms. If the compression of the brain lasts too long, the pressure can permanently damage or destroy brain tissue^[1].

Diagnosis

Diagnosis of normal pressure hydrocephalus typically involves a combination of clinical evaluation, brain imaging, and specialized testing^[3][4]. Normal pressure hydrocephalus should be considered as a diagnosis for patients with unexplained walking difficulty, a pattern of thinking problems affecting planning and organization, and urinary urgency or incontinence^[14].

Your healthcare provider will perform a physical examination and ask about your symptoms^[7]. They will likely find that your walking pattern is not normal and you may also have memory problems^[7].

Brain imaging tests such as MRI (magnetic resonance imaging) or CT (computed tomography) scans are essential for diagnosis^[3][4][7]. These scans can show the characteristic enlarged ventricles and help rule out other conditions^[3][4].

Lumbar puncture (also called a spinal tap or tap test) involves careful testing of walking before and right after removing a large volume of cerebrospinal fluid through a needle inserted into the lower back^[7][8][14]. If symptoms improve after fluid removal, this suggests the person may respond well to surgical treatment^[14].

External lumbar drainage is another test where a temporary spinal catheter is inserted for several days to continuously drain cerebrospinal fluid, with walking and thinking tests performed before and after^[8][14].

Cerebrospinal fluid infusion testing measures how well the body can absorb cerebrospinal fluid by measuring the resistance to fluid outflow^[8][14].

Properly selected patients using these diagnostic tests have an 80% to 90% chance of responding to surgical treatment^[14].

Treatment

The usual treatment for normal pressure hydrocephalus is surgery to place a thin tube called a shunt to drain excess cerebrospinal fluid^[1][3][4]. Surgery can sometimes reverse the symptoms, especially if treatment is started early^[1][4].

During shunt surgery (also called ventriculoperitoneal shunting), a surgical team inserts the shunt into a ventricle in your brain. Then they gently move it under your skin from your head through your neck and chest to your abdomen (stomach)^[3][7]. The extra cerebrospinal fluid in your brain flows through the shunt into your abdomen, where your body absorbs it^[3]. Inside the shunt there’s a valve that controls the flow of fluid so it doesn’t drain too quickly^[1]. The shunt stays in place as long as there is too much cerebrospinal fluid in the brain. The operation is done under general anesthesia (you are asleep) and usually takes 1 to 2 hours^[12]. You may need to stay in the hospital for a few days after the operation to recover^[12].

An alternative procedure is endoscopic third ventriculostomy, where instead of inserting a shunt, the surgeon makes a small hole in the floor of the brain to allow the trapped cerebrospinal fluid to escape to the brain’s surface, where it can be absorbed^[12]. This procedure is not suitable for everyone, but it could be an option if the buildup of fluid is caused by a blockage^[12]. The surgeon makes a small hole in the skull and brain, and uses an endoscope (a long, thin tube with a light and camera at one end) to look inside the chambers of the brain and make the opening^[12].

A newer, minimally invasive approach called the eShunt System is being studied in clinical trials. With this approach, the device is implanted between a vein in the neck and a cerebrospinal fluid pocket at the base of the skull through a needle puncture in the groin, without the need for drilling holes in the skull^[10]. This reduces the risk for complications and infection compared with traditional surgery^[10].

Implanting a shunt does not work for everyone. However, when patients are properly selected using diagnostic tests, many people benefit from the surgery^[3]. Getting a prompt diagnosis and treatment improves the chances of a good outcome^[4]. Walking problems are the symptoms most likely to improve after surgery^[3][7][11], while thinking changes and loss of bladder control are less likely to improve^[3]. All symptoms can improve following shunt surgery when patients are properly selected^[14].

Outlook and prognosis

Without treatment, symptoms often get worse and could lead to death^[7]. However, when normal pressure hydrocephalus is caught early, its effects may be reversed by surgical treatment^[4]. If the condition is diagnosed later, once significant brain damage has occurred, those symptoms cannot be reversed^[4].

Surgery improves symptoms in some people, and those with mild symptoms have the best outcome^[7]. Properly selected patients have an 80% to 90% chance of responding to shunt surgery^[14]. With contemporary diagnostic tests and treatment with programmable shunts, the benefit-to-risk ratio of shunt surgery is highly favorable^[14].

Possible complications that may result from normal pressure hydrocephalus or its treatment include problems from surgery (infection, bleeding, shunt that doesn’t work well), worsening loss of brain function, injury from falls, and shortened lifespan^[7]. There’s also a risk that a blockage can happen months or years after surgery, which will cause symptoms to return^[12].

It’s important to contact your healthcare provider if you or a loved one is having increasing problems with memory, walking, or bladder control. You should go to the emergency room or call emergency services if there is a sudden change in mental status, which may mean that another disorder has developed^[7].