Normal pressure hydrocephalus is a brain condition that mainly affects older adults, causing walking difficulties, memory problems, and bladder control issues that can sometimes be reversed with proper treatment.
Understanding Normal Pressure Hydrocephalus
Normal pressure hydrocephalus, often shortened to NPH, is a condition where too much cerebrospinal fluid (the clear liquid that cushions and nourishes the brain) builds up inside the skull. Despite its name calling it “normal pressure,” this fluid buildup gradually compresses the brain, disrupting its normal function and causing symptoms that can look very similar to dementia or Parkinson’s disease. What makes this condition particularly important is that unlike many other causes of dementia in older adults, NPH can sometimes be treated and even reversed if caught early enough.[1]
Your brain and spinal cord are constantly bathed in cerebrospinal fluid. Adults typically have only about 5 fluid ounces of this fluid—less than half the amount in a standard beverage can. Even though this seems like a small amount, it plays a huge role. Your brain actually floats in this fluid, which cushions it from injury and helps remove waste products while delivering nutrients. Your body continuously creates new fluid and absorbs the old fluid to maintain a constant balance. When something disrupts this balance and the fluid cannot be properly absorbed back into the bloodstream, it begins to accumulate in hollow spaces inside the brain called ventricles.[1]
The name “normal pressure” refers to the fact that when doctors measure the pressure of this fluid through a spinal tap, it often appears to be within the normal range or only slightly elevated. However, research suggests that people with NPH can experience periods of increased pressure inside their skulls, even if it doesn’t always show up in testing. As the fluid continues to build up, the ventricles enlarge and begin pressing on nearby brain tissue. This compression and the resulting damage to brain cells cause the symptoms that affect movement, thinking, and bladder control.[4]
Who Gets Normal Pressure Hydrocephalus
Normal pressure hydrocephalus is primarily a disease of older adults. The condition is most common in people over the age of 65, and it becomes increasingly frequent as people age. The average age when symptoms begin is around 70 years old. In fact, studies show that while only about 0.2% of people between ages 70 and 80 are affected, the rate jumps to 5.9% in people over 80. This means that globally, approximately 8.4 million people over age 80 live with this condition.[1]
Among people under 65, NPH is very rare, affecting only about 0.003% of this age group. Increasing age is the only factor that makes this condition more likely to occur. Unlike many other diseases, the chances of developing NPH do not change based on a person’s ethnicity, race, or biological sex. Men and women are affected equally.[1][4]
Despite being relatively well-known in medical circles, NPH remains an uncommon condition compared to other causes of dementia and movement problems in elderly people. Research from Norway found an incidence of about 5.5 cases per 100,000 people, with prevalence ranging from just 3.3 per 100,000 in people ages 50 to 59, up to 181.7 per 100,000 for those between 70 and 79 years old. It’s estimated that over 700,000 people in the United States have NPH, though fewer than 20% have been properly diagnosed. This suggests that many cases go unrecognized, often because symptoms are mistaken for other age-related conditions like Alzheimer’s disease or Parkinson’s disease.[4][8][11]
What Causes Normal Pressure Hydrocephalus
Doctors recognize two main forms of normal pressure hydrocephalus based on what causes them. The first type, called idiopathic NPH or primary NPH, occurs when there is no identifiable cause for the fluid buildup. This is the most common form and typically affects people aged 60 and older. Despite extensive research, scientists still don’t fully understand why the brain suddenly stops absorbing cerebrospinal fluid properly in these cases. The exact mechanism that triggers the condition remains unclear, though it appears to involve problems with how the fluid drains from the brain’s ventricles.[7][8]
The second type is called secondary NPH, which develops as a result of another medical problem. Secondary NPH can occur at any age, not just in older adults. Known causes include head injuries, brain surgery, bleeding in the brain (particularly subarachnoid hemorrhage, which is bleeding around the surface of the brain from a ruptured blood vessel or aneurysm), infections of the brain or its surrounding membranes such as meningitis, and tumors or cysts that block fluid drainage pathways.[7][8]
While the causes differ between idiopathic and secondary NPH, both types share the same underlying problem: cerebrospinal fluid is not circulating or being absorbed properly. This leads to fluid accumulation in the brain’s ventricles, causing them to enlarge and compress surrounding brain tissue. Over time, if left untreated, this compression can cause permanent damage to brain cells. The exact reason why the body’s normal fluid absorption process fails in idiopathic NPH remains one of the mysteries that researchers continue to investigate.[1]
Risk Factors for Developing the Condition
For idiopathic normal pressure hydrocephalus, advanced age is the primary risk factor. As mentioned earlier, the condition becomes progressively more common after age 65, with the highest rates seen in people over 80. Beyond aging, researchers have identified several other health conditions that appear more frequently in people with NPH, though it’s not always clear whether these are true risk factors or simply conditions that commonly occur together in older adults.[1]
Studies have found associations between idiopathic NPH and several chronic conditions. These include high blood pressure (hypertension), diabetes mellitus, elevated cholesterol levels (hyperlipidemia), and even Alzheimer’s disease. However, the relationship between these conditions and NPH is complex and not fully understood. It’s possible that some of these conditions might contribute to the development of NPH, or they might simply be common age-related diseases that happen to occur in the same patient population.[6]
For secondary NPH, the risk factors are more clearly defined since they represent the actual causes of the condition. Anyone who has experienced a traumatic brain injury, had brain surgery, suffered bleeding in or around the brain, or developed a brain infection like meningitis faces an increased risk of developing secondary NPH. The key difference is that secondary NPH can affect people of all ages, not just the elderly, because it results from these specific medical events rather than age-related changes.[6][8]
Recognizing the Symptoms
The symptoms of normal pressure hydrocephalus typically begin gradually and worsen over a period of three to six months. The condition is characterized by a classic combination of three main symptom types, known as Hakim’s triad, named after the Colombian neurosurgeon Salomón Hakim who first described NPH along with Raymond Adams in 1965. Between 50% and 75% of people with NPH experience all three symptoms at the same time, though not everyone has the complete triad. Having problems with walking plus one additional symptom is generally enough for doctors to consider NPH as a possible diagnosis.[1][6]
Walking and balance problems are the most common and often the earliest symptoms of NPH, appearing in nearly all patients. The typical walking pattern is described as broad-based, slow, and shuffling, with short steps. Many people describe feeling as if their feet are stuck to the floor or that there are magnets holding them down, making it difficult to lift their feet. This is sometimes called a “magnetic gait.” People with NPH often have particular trouble when first starting to walk or when trying to turn. As the condition progresses, the walking difficulty worsens. Initially, someone might just feel slightly off-balance, but over time they may need a cane or walker, and they may experience frequent falls or near-falls. Because the lateral ventricles enlarge and press on nerve fibers that control movement, these walking problems are directly related to the physical compression of brain tissue. Some people with NPH may also develop trembling or shaking of the hands, legs, or feet, which occurs in up to 40% of patients.[1][6]
Cognitive problems and memory difficulties represent the second component of Hakim’s triad. These symptoms are present in about 60% of patients at the time of diagnosis. The mental changes caused by NPH primarily affect what doctors call frontal-subcortical functions—abilities controlled by the front part of the brain and the structures beneath it. People might have trouble planning activities, organizing their thoughts, paying attention, or concentrating on tasks. They may forget recent events or conversations, experience mental “fogginess,” and find it difficult to complete routine tasks that used to be easy. Difficulty managing finances, remembering to take medications, keeping track of appointments, and making decisions are common complaints. As the condition advances, people may become apathetic (showing little interest in activities they once enjoyed), experience slowed thinking and speech, and have reduced drive or motivation. While these symptoms closely resemble other forms of dementia, the cognitive problems in NPH are different because they can potentially improve with treatment.[4][6]
Bladder control problems are the third symptom in Hakim’s triad. These urinary symptoms typically appear later in the course of the illness and are present in about 50% of patients when they seek treatment. The bladder problems usually begin with urinary frequency—needing to urinate more often than normal—and a sense of urgency, where the person feels a sudden, strong need to urinate immediately. This can progress to actual urinary incontinence, where the person loses control and cannot make it to the bathroom in time. The bladder symptoms occur because the enlarging ventricles press on areas of the brain that control bladder function, causing what’s called detrusor overactivity, where the bladder muscle contracts involuntarily. Less commonly, some people may also experience bowel incontinence.[6][11]
It’s important to understand that symptoms develop gradually, and the slowness of onset can make it difficult to recognize that something is wrong. Family members might notice changes before the affected person does. Because each of the three main symptoms can also be caused by many other conditions common in older adults, proper diagnosis requires careful evaluation by healthcare professionals who are familiar with NPH.[1]
Preventing Normal Pressure Hydrocephalus
Unfortunately, there are no known ways to prevent idiopathic normal pressure hydrocephalus. Because the exact cause remains unclear, doctors cannot offer specific prevention strategies for the primary form of the disease. Since advanced age is the only clear risk factor for idiopathic NPH, and aging cannot be prevented, there are currently no lifestyle changes, dietary modifications, or medications that have been proven to reduce the risk of developing this condition.[1]
For secondary NPH, prevention focuses on avoiding or properly treating the underlying conditions that can lead to the disorder. This means taking appropriate safety precautions to prevent head injuries, such as wearing seatbelts in vehicles, using helmets when riding bicycles or motorcycles, and taking steps to prevent falls, especially in older adults. Prompt and proper treatment of brain infections like meningitis is essential. Managing conditions that can cause bleeding in the brain, including controlling blood pressure to reduce the risk of ruptured blood vessels, may also help prevent secondary NPH. However, even with these precautions, it’s not possible to eliminate all risk of secondary NPH since many of its causes, such as sudden bleeding or accidents, cannot be fully prevented.[7]
The most important aspect of managing NPH is early recognition and diagnosis. While the condition itself may not be preventable, seeking medical attention when symptoms first appear can lead to earlier treatment, which generally results in better outcomes. Regular health checkups, especially for older adults, and being aware of the characteristic symptom combination of walking difficulties, cognitive changes, and bladder problems can help ensure that NPH is identified before permanent brain damage occurs.[1]
How the Disease Affects the Body
To understand how normal pressure hydrocephalus affects the body, it helps to know how cerebrospinal fluid normally functions. This clear fluid is continuously produced in specialized structures inside the brain’s ventricles at a rate of about 500 milliliters per day. The fluid circulates through the ventricular system, flows around the brain and spinal cord, and is eventually absorbed back into the bloodstream through specialized tissues. In healthy adults, the amount of fluid remains constant at about 150 milliliters because production and absorption stay in perfect balance.[1]
In NPH, something disrupts the normal circulation or absorption of cerebrospinal fluid. While the exact mechanism isn’t fully understood, the result is that fluid begins to accumulate faster than it can be absorbed. This excess fluid collects in the brain’s ventricles, causing them to gradually enlarge. The term doctors use for this enlargement is ventriculomegaly. As the ventricles expand, they take up more space inside the skull, which is a fixed, rigid structure that cannot expand to accommodate the extra fluid.[6]
Because the skull cannot grow, the expanding ventricles begin to compress the surrounding brain tissue. The pressure builds gradually enough that it often remains within the technically “normal” range when measured, but it still causes significant problems. The compression particularly affects specific regions of the brain. When the lateral ventricles enlarge, they press on nerve fiber pathways called the corticospinal tracts that control leg movement, explaining why walking difficulties are usually the first symptom. The pressure on the frontal regions of the brain and subcortical structures beneath the cortex accounts for the cognitive symptoms, affecting planning, memory, and executive function. The compression of areas controlling bladder function leads to urinary urgency and incontinence.[6][11]
Over time, if the condition remains untreated, the sustained compression can cause permanent damage to brain cells. Brain tissue that is compressed for too long may die or become irreversibly damaged. This is why early treatment is so important—catching NPH before permanent damage occurs gives patients the best chance of symptom reversal. The good news is that if treatment is started before extensive permanent damage happens, the brain tissue can often recover its function once the excess fluid is drained and the pressure is relieved.[1]
Research has shown that while NPH is called “normal pressure,” some studies suggest that people with this condition may experience intermittent periods when the pressure inside their skull actually increases beyond normal levels, even though it appears normal during testing. This fluctuation in pressure, combined with the mechanical compression from enlarged ventricles, contributes to the progressive nature of symptoms and the damage to brain tissue over time.[4]
