Whenever an older person starts having cognitive difficulties, trouble walking, or holding their urine, families immediately fear the diagnosis will be Alzheimer’s disease – a progressive neurologic condition that currently has no cure.
But in some cases, the cause is a lesser known – and potentially reversible – condition called normal pressure hydrocephalus (NPH). Characterized by an abnormal buildup of cerebrospinal fluid in the brain, NPH interferes with cognition, gait, and urinary continence.
Some NPH symptoms and features observed on brain scans overlap with other common neurodegenerative conditions, which is one reason many NPH cases may go unrecognized, untreated, or misdiagnosed. For example, some patients diagnosed with Alzheimer’s disease may actually have NPH.
Getting an accurate diagnosis for this uncommon cause of dementia (1.8 cases per 100,000 people) is crucial, but few health care centers have the depth of expertise to diagnose and treat NPH effectively.
At UT Southwestern’s Peter O’Donnell Jr. Brain Institute we have created a one-of-a-kind, patient-centered clinic that focuses on NPH, integrating care and research. The NPH clinic is staffed by a multidisciplinary team of experts from the departments of Neurosurgery, Neurology, Psychiatry, and Physical Medicine & Rehabilitation.
Together, we are delivering expert care for NPH and raising the standard for effective surgical and nonsurgical treatment options. We are also creating a database of knowledge to enhance clinicians’ understanding of NPH. By doing so, we hope that more patients will have access to care for one of the few forms of dementia that in some cases can be controlled or even reversed.
What causes NPH?
Cerebrospinal fluid surrounds and protects the brain in caverns called ventricles, but in some instances excess fluid accumulates, causing the ventricles to enlarge and leave less space for the brain.
“When we’re able to identify a patient with NPH, it’s often good news. Unlike many causes of dementia, NPH can be treated and symptoms can be relieved.”
In many cases of NPH we believe the problem is caused by a partial blockage of the outflow of cerebrospinal fluid. A specific cause for this cannot usually be determined, and it is referred to as primary, or idiopathic, NPH. In secondary NPH, also known as symptomatic, a cause can be identified, such as:
- Bleeding in or around the brain
- Traumatic head injury
- Complications from previous brain surgery
- Brain tumor
- Infections such as meningitis
Researchers have identified some characteristics that may make a person more likely to develop the condition. These include:
- Advanced age: NPH is most often seen in patients older than 70.
- Obstructive sleep apnea
- Mutated cilia: The brain’s ventricles contain tiny “hairs” that help keep cerebrospinal fluid flowing freely. In some patients with NPH, a genetic mutation impairs cilia function.
- Increased skull size: Some studies have shown that patients with NPH are more likely to have larger-than-average skulls, which may indicate congenital hydrocephalus that can become symptomatic later in life.
Having one of these associated conditions or risk factors does not mean neurological symptoms are automatically diagnosed as NPH. Specialized exams, imaging, and testing can provide a clear diagnosis.
How do we diagnose NPH?
There is not one specific test to identify NPH. Instead, we view the totality of the picture, from the history and exam through a series of tests. Getting an accurate diagnosis requires expertise in recognizing evidence for and against NPH, versus lookalike neurologic degenerations such as Alzheimer’s, Parkinson’s, or progressive supranuclear palsy. This is especially challenging in those patients who have both NPH and other potential neurodegenerative conditions.
Diagnosis typically starts with analyzing a patient’s symptoms in the context of their health history. Patients may have some or all these symptoms, which may be mild to severe:
- Gait disturbances, such as difficulty walking, are often among the first signs of NPH. Patients may walk slowly with a shuffling gait and heavy feet or have trouble turning, along with frequent falls.
- Cognitive decline, which can include short-term memory loss, difficulty making decisions, mood changes, and loss of interest in activities.
- Urinary incontinence, which causes patients to need to urinate often or urgently. In severe cases, NPH can cause total loss of urinary control due to malfunction of the nerves that control the detrusor muscle in the bladder wall.Advanced brain imaging is done to measure enlargement of cerebrospinal fluid spaces and to help differentiate between the normal aging brain, fluid buildup, and structural brain damage.
The neuropsychological assessment can reveal patterns that help specialists distinguish between NPH and other causes of dementia. It will also formally evaluate things like memory, attention, processing speed, language, visuospatial skills, and higher-level skills such as problem solving, divided attention, and abstract thinking. The assessment helps determine which areas of the brain are functioning better than others.
By means of a small drainage tube temporarily placed in the spine, we can remove cerebrospinal fluid over the course of three days. In some patients, this results in noticeable improvement in symptoms. We can also monitor variation in pressure and perform a stress test of the cerebrospinal fluid system using the same tube. This series of tests can be very helpful in diagnosing NPH.
When we can identify a patient with NPH, we start discussing treatment options immediately. Unlike many causes of dementia, it is possible for some cases of NPH to be significantly improved or even reversed with a surgical procedure.
Related reading: What genetic testing can reveal about your Alzheimer's disease risk
What are the treatment options for NPH?
The gold-standard treatment for NPH is a neurosurgical procedure to place a shunt in the brain that helps regulate its cerebrospinal fluid levels. The shunt consists of a valve and a flexible tube that drains excess cerebrospinal fluid into the abdomen.
There are some risks associated with the surgery, which can include complications from anesthesia, bleeding in the brain, infection, malfunction of the shunts, or seizures. Some people’s symptoms improve only partially, while others may improve only temporarily.
Complication rates in lower-volume neurosurgery centers hover between 8% and 9%. UT Southwestern is a high-volume center for NPH brain surgery, which means we see and treat more patients with the condition than most neurology centers. For many of our patients, the potential benefits of surgery outweigh the risks.
A 2022 study found that 91% of patients with NPH who were optimal candidates for surgery experienced symptom relief within a couple of months after their procedure. Among all candidates, shunting has been shown to improve symptoms in 50% to 84% of cases. The variation in outcome is due to factors such as concurrent health conditions and disease severity at the time of surgery.
Research has shown that long term, some patients' symptoms may return. However, patients often benefit from physical therapy to increase strength, which can help improve gait and balance after or in lieu of surgery. The implanted shunt can be adjusted to compensate for some of this worsening over time.
Our dedicated NPH clinic unites multidisciplinary specialists to provide well-rounded, thorough diagnoses, treatment options, and surgical assessments – all with a single clinic visit.
Leading innovations in NPH management
Early in the process, our patients learn about the condition with self-paced audiovisual education material developed in conjunction with patient advocates. At each stage of the care path, we have implemented a series of protocols to ensure consistent best practices for diagnosis and treatment measures. We are compiling a registry of data from our NPH patients that, over time, will enhance our understanding of NPH. We hope the data will lead to even better NPH clinical guidelines for more accurate diagnoses and better treatment protocols.
The database includes anonymized baseline and long-term data such as:
- Relevant health history
- Tests such as brain scans and pressure measures of cerebrospinal fluid
- Treatments and their complication rates
- Functional measurements such as gait, cognition, and bladder function
- Patient-reported quality of life and symptom improvement
To our knowledge, there are a limited number of centers in the U.S. running a dedicated interdisciplinary NPH clinic with systematic tracking of results for continuous quality improvement.
While NPH is not a new or rare condition, it is not yet widely understood in the medical community. If you or a loved one experience neurocognitive symptoms that affect gait, thinking, or bladder control, consider asking for a referral to our NPH clinic, where we can provide personalized treatment that might significantly reduce or reverse your symptoms.