Normal pressure hydrocephalus is one of the only forms of dementia that can actually be reversed. Unlike Alzheimer’s disease or vascular dementia, which progressively destroy brain tissue with no way to undo the damage, NPH is caused by a buildup of cerebrospinal fluid in the brain’s ventricles — and draining that fluid through a surgically implanted shunt can restore cognitive function, walking ability, and bladder control. According to research published in the Journal of Clinical Medicine, 91.2% of patients who received shunt surgery showed overall improvement at 12 months. When Billy Joel announced his NPH diagnosis in May 2025 and canceled his tour dates, millions of people heard the term for the first time — but for the estimated 700,000 American adults living with the condition, the stakes have always been personal and urgent.
The tragedy of NPH is not that it lacks a treatment. It is that roughly 80% of people who have it are never properly diagnosed, according to the Hydrocephalus Association. They are told they have Alzheimer’s or Parkinson’s, and they receive care plans for diseases they do not have while a treatable condition goes unaddressed. This article covers what NPH actually is, how it differs from other dementias, what the shunt surgery involves and how well it works, the landmark 2025 PENS Trial that validated the procedure, emerging alternatives like the eShunt system, and what Billy Joel’s public diagnosis has meant for awareness.
Table of Contents
- What Is Normal Pressure Hydrocephalus and Why Is It Called Reversible Dementia?
- How Often Is NPH Misdiagnosed — and What Gets Missed?
- Shunt Surgery — What the Procedure Involves and How Well It Works
- How Do Doctors Determine If a Patient Will Respond to Shunt Surgery?
- The PENS Trial — Why a 2025 Study Changed the Conversation
- The eShunt System — A Less Invasive Alternative on the Horizon
- Billy Joel, Public Awareness, and What Comes Next for NPH
- Conclusion
- Frequently Asked Questions
What Is Normal Pressure Hydrocephalus and Why Is It Called Reversible Dementia?
The brain constantly produces cerebrospinal fluid, which cushions the brain and spinal cord, delivers nutrients, and removes waste. In a healthy system, CSF is produced, circulates through the ventricles, and is reabsorbed at roughly the same rate. In NPH, that reabsorption slows or fails. Fluid accumulates, the ventricles enlarge, and the expanded ventricles press against surrounding brain tissue. The word “normal pressure” in the name refers to the fact that, unlike other forms of hydrocephalus, the pressure readings during a lumbar puncture often fall within the normal range — which is part of why the condition is so frequently missed. NPH is defined by a characteristic set of symptoms known as the Hakim triad: cognitive decline, gait instability, and urinary incontinence. The complete triad shows up in 50–75% of patients, but gait and cognitive problems appear in 80–95% of cases, making walking difficulty and mental slowing the most reliable early signals.
Urinary incontinence is present in 50–75% of patients and often develops later. The reason NPH qualifies as “reversible” is that the cognitive and physical symptoms are caused by mechanical pressure, not by the death of neurons. Remove the pressure by draining the fluid, and the brain tissue can recover — at least partially, and sometimes substantially. Compared to Alzheimer’s disease, where amyloid plaques and tau tangles cause irreversible neuronal loss, NPH’s mechanism is fundamentally different. An Alzheimer’s patient who receives a shunt will not improve, because their symptoms are not caused by fluid pressure. An NPH patient who receives Alzheimer’s medications will not improve either, because cholinesterase inhibitors do nothing to address a plumbing problem. This distinction matters enormously, and getting the diagnosis right is the difference between decline and recovery.
How Often Is NPH Misdiagnosed — and What Gets Missed?
The Hydrocephalus Association estimates that nearly 700,000 adults in the United States have NPH, but fewer than 20% receive a correct diagnosis. That means more than half a million Americans may be living with a treatable condition while being managed for the wrong disease. NPH accounts for an estimated 1–6% of all dementia cases, according to the Alzheimer’s Association. While that percentage sounds small against the broader dementia population, the absolute numbers are significant — and every misdiagnosed case represents a person who could have been helped. The overlap in symptoms is the core problem. NPH’s gait instability looks similar to Parkinson’s disease. The cognitive slowing mimics early Alzheimer’s. The urinary incontinence can be attributed to aging or prostate issues in men.
A busy primary care physician who sees a 75-year-old patient with memory problems and shuffling steps has every reason to suspect Alzheimer’s or Parkinson’s before considering NPH. However, if a patient presents with gait problems that appeared before or alongside cognitive decline — rather than after it — NPH should be on the differential. In Alzheimer’s, memory loss typically comes first, with motor problems developing much later. In NPH, the walking difficulty is often the earliest and most prominent symptom. The incidence of NPH rises steeply with age. In the general population, the annual incidence is approximately 1.8 per 100,000. But a large Swedish population study found prevalence rates of 0.2% among people aged 70–79 and 5.9% among those 80 and older. That sharp increase means NPH becomes far more common precisely in the age group where Alzheimer’s and Parkinson’s are also prevalent, making misdiagnosis even more likely. Families and clinicians should be especially alert when an older adult develops the combination of walking problems, cognitive changes, and bladder issues in relatively close succession.
Shunt Surgery — What the Procedure Involves and How Well It Works
There is no medication that treats NPH. The standard treatment is a ventriculoperitoneal shunt, a device surgically implanted to divert excess cerebrospinal fluid from the brain’s ventricles to the abdominal cavity, where the body can reabsorb it naturally. The shunt consists of a catheter placed in one of the brain’s ventricles, a valve mechanism that regulates flow, and tubing that runs under the skin down to the peritoneal cavity in the abdomen. The surgery typically takes one to two hours and is performed under general anesthesia. The outcomes are genuinely encouraging. Between 50% and 80% of shunted patients show symptom improvement in the first two to three years. In one multicenter study, 91.2% showed overall improvement at 12 months. Cognitive gains are substantial: 74% of patients demonstrated significant cognitive improvement — defined as at least one standard deviation gain on memory tests — after shunt surgery.
Walking improvement tends to be the most durable benefit. Research shows that 83% of patients maintained gait improvement at three years, and 87% still showed improvement at a seven-year follow-up. Median survival after shunt surgery is 7.7 years. However, shunting is not without risks or limitations. The complication rate is approximately 8.8%, and the reoperation rate is 9.4%. Complications can include shunt infection, over-drainage or under-drainage of fluid, subdural hematomas, and mechanical failure of the shunt itself. Older patients and those with significant comorbidities face higher surgical risk. Timing also matters: patients who receive a shunt earlier in the course of the disease tend to have better outcomes than those diagnosed late, when the prolonged pressure may have caused some degree of permanent damage. A shunt cannot reverse damage that has already become irreversible — which is another reason why early and accurate diagnosis is so critical.
How Do Doctors Determine If a Patient Will Respond to Shunt Surgery?
Not every patient suspected of having NPH will benefit equally from a shunt, and one of the most important clinical questions is predicting who will respond well. The standard diagnostic workup starts with brain imaging — typically an MRI — which can reveal the enlarged ventricles characteristic of hydrocephalus. But enlarged ventricles alone are not enough, because brain atrophy from Alzheimer’s or other conditions can also cause ventricular enlargement. The key distinction is whether the ventricles are disproportionately large relative to the degree of cortical atrophy. The most widely used predictive test is the large-volume lumbar puncture, sometimes called a tap test. A physician removes 30 to 50 milliliters of cerebrospinal fluid through a spinal needle, then evaluates the patient’s gait and cognition before and after the procedure.
If symptoms improve noticeably in the hours or days following the tap, the patient is considered a strong shunt candidate. Some centers also use extended lumbar drainage over several days for patients whose tap tests are equivocal. The tradeoff is straightforward: the tap test is quick and lower-risk but less sensitive, while extended drainage is more invasive but provides a longer observation window and higher predictive accuracy. A positive tap test is a strong predictor of shunt success, but a negative result does not definitively rule out benefit from surgery. Some patients who do not respond to a single lumbar puncture still improve after shunt placement, which is why clinical judgment, imaging findings, and symptom history all factor into the decision. Families navigating this process should understand that the workup is designed to balance the real benefits of shunt surgery against the real risks of an unnecessary procedure.
The PENS Trial — Why a 2025 Study Changed the Conversation
For decades, neurosurgeons operated on NPH patients based on observational studies and clinical experience. No randomized controlled trial had ever definitively validated shunt surgery for idiopathic NPH — until the PENS Trial. Published on September 16, 2025, in the New England Journal of Medicine, the Placebo-Controlled Effectiveness in iNPH Shunting trial was the first study of its kind. Its design was rigorous: patients received either an active shunt or a sham procedure, and neither patients nor evaluators knew which group was which. The results showed significant improvements at three months in gait velocity and gait-and-balance measures among the shunt group compared to the sham group.
Cognition and incontinence did not reach statistical significance at the three-month mark, though this may reflect the short evaluation window rather than a true absence of benefit. As Johns Hopkins Medicine noted in its coverage of the trial, the study “restores walking and independence in older adults with iNPH.” The PENS Trial matters because it shifts the evidence base from “this probably works based on decades of clinical practice” to “this definitively works based on a gold-standard randomized trial.” For clinicians who were hesitant to refer patients for surgery without RCT-level evidence, the PENS Trial removes that barrier. One important limitation: the trial’s three-month endpoint is relatively short. The long-term studies showing gait improvement at seven years and cognitive improvement after shunting predate the PENS Trial and relied on different study designs. Future follow-up data from the PENS cohort will be valuable in confirming whether the early improvements observed in the trial hold up over years.
The eShunt System — A Less Invasive Alternative on the Horizon
A clinical trial called the STRIDE Pivotal Study, led by CereVasc Inc., is currently testing a device called the eShunt System. Unlike a traditional ventriculoperitoneal shunt, which routes fluid from the brain to the abdomen, the eShunt is implanted between a vein in the neck and a CSF-containing space at the base of the skull. The design mimics the body’s natural CSF drainage pathways. The procedure is minimally invasive compared to traditional shunt surgery, which requires tunneling tubing from the head down through the neck and chest to the abdomen.
The STRIDE trial is enrolling patients at multiple sites, including Tampa General Hospital, Rhode Island Hospital, and VCU Health. Yale Medicine has described the eShunt as a potential step forward in NPH treatment because it avoids the abdominal component of traditional shunts, which is responsible for many of the complications associated with current devices. Results from the trial are not yet available, and the device is not approved for general use. But for patients and families watching the field, the eShunt represents the possibility that the next generation of NPH treatment may be both more effective and less invasive.
Billy Joel, Public Awareness, and What Comes Next for NPH
When Billy Joel announced his NPH diagnosis on May 23, 2025, and canceled all tour dates through July 2026, the condition entered the public conversation in a way it never had before. Joel, then 76, cited trouble with hearing, vision, and balance. In a July 2025 podcast interview, he was candid about the ongoing nature of his treatment: “It’s not fixed… it’s still being worked on.” Then, on January 2, 2026, Joel performed publicly for the first time since the diagnosis — a two-song set of “We Didn’t Start the Fire” and “Big Shot” in Wellington, Florida. The Hydrocephalus Association published a dedicated response to his announcement, recognizing the moment as a significant opportunity to educate the public.
Celebrity diagnoses are a blunt instrument for public health awareness, but they work. The conversation Joel’s announcement started — about a treatable form of dementia that most people have never heard of — reaches people who might otherwise dismiss their own symptoms or those of a family member as “just aging.” The research pipeline is more promising now than at any point in NPH’s history. The PENS Trial has provided gold-standard evidence. The eShunt offers a glimpse at less invasive options. And every clinician who reads about Joel’s diagnosis and thinks twice before labeling a shuffling, forgetful patient as “probable Alzheimer’s” is a clinician who might catch what was being missed.
Conclusion
Normal pressure hydrocephalus occupies a unique and frustrating position in medicine: it is one of the few dementias that can be meaningfully treated, yet the vast majority of people who have it never receive the correct diagnosis. The numbers tell a clear story — nearly 700,000 affected adults in the U.S., fewer than 20% diagnosed, and strong evidence that shunt surgery can restore walking ability in over 80% of patients and improve cognition in nearly three-quarters. The 2025 PENS Trial put the final piece of evidence into place, confirming through a randomized controlled trial what neurosurgeons had observed for decades.
For families watching a loved one decline with walking difficulty, cognitive changes, and bladder problems, the most important step is asking the question: could this be NPH? A brain MRI and a lumbar puncture tap test are the starting points. Not every case will be NPH, and not every NPH patient will have a dramatic recovery from shunt surgery. But the possibility of meaningful improvement — of reversing what looked like irreversible decline — makes it a question worth asking every single time.
Frequently Asked Questions
What is the difference between NPH and Alzheimer’s disease?
NPH is caused by excess cerebrospinal fluid pressing on the brain, and it can be treated with shunt surgery. Alzheimer’s is caused by the progressive death of neurons due to amyloid plaques and tau tangles, and it cannot be reversed. In NPH, gait problems typically appear early and prominently, while in Alzheimer’s, memory loss is usually the first symptom and motor problems develop much later.
How is NPH diagnosed?
Diagnosis typically involves brain imaging (MRI) to check for enlarged ventricles, followed by a large-volume lumbar puncture (tap test) in which 30–50 milliliters of cerebrospinal fluid are removed. If symptoms improve after the tap, the patient is considered a strong candidate for shunt surgery.
Is shunt surgery safe for elderly patients?
The overall complication rate is approximately 8.8%, and the reoperation rate is 9.4%. While any surgery carries risk for older patients, the PENS Trial and long-term studies have shown that the benefits of shunting — particularly for gait — tend to outweigh the risks for appropriately selected patients. The decision should be made on a case-by-case basis with a neurosurgeon experienced in NPH.
Can NPH be treated with medication?
No. There is currently no medication that effectively treats NPH. The standard treatment is surgical placement of a ventriculoperitoneal shunt. The eShunt System is being studied as a less invasive surgical alternative, but it is not yet approved.
How quickly do symptoms improve after shunt surgery?
Gait improvement is often the first and most noticeable change, sometimes within days to weeks. Cognitive improvement may take longer to become apparent. The PENS Trial documented significant gait improvements at three months, and longer-term studies show improvements sustained at three and seven years.
Does Billy Joel have dementia?
Billy Joel was diagnosed with normal pressure hydrocephalus, which can cause dementia-like cognitive symptoms. Unlike Alzheimer’s, NPH-related cognitive decline can potentially be improved with treatment. Joel has described his condition as ongoing and “still being worked on” as of mid-2025, and he performed publicly again in January 2026.
