About Normal Pressure Hydrocephalus
What is Normal Pressure Hydrocephalus (NPH)?
Normal pressure hydrocephalus (NPH) is an accumulation of cerebrospinal fluid (CSF) that causes the ventricles in the brain to become enlarged, sometimes with little or no increase in intracranial pressure (ICP). In most cases of NPH, the cause of blockage to the CSF absorptive pathways is unclear.
The name for this condition, normal pressure hydrocephalus, originates from Dr. Salomon Hakim’s 1964 paper describing certain cases of hydrocephalus in which a triad (a group of three) of neurologic symptoms occurred in the presence of ’normal‘ CSF pressure – gait disturbances (which is usually the first sign), dementia, and impaired bladder control. These findings were observed before continuous pressure-recording techniques were available.
The phrase ‘normal pressure’ is misleading as many patients experience fluctuations in CSF pressure that range from high to low and are variable within those parameters. However, normal pressure hydrocephalus (NPH) continues to be the common name for the condition.
Who develops NPH?
NPH is most commonly seen in older adults.
- It is estimated that more than 700,000 Americans have NPH, but less than 20% receive an appropriate diagnosis.
- Without appropriate diagnostic testing, NPH is often misdiagnosed as Alzheimer’s disease or Parkinson’s disease, stroke, or other neurodegenerative conditions. Sometimes the symptoms are mistakenly attributed to “normal aging”.
- NPH is one of the few causes of dementia that can be improved through direct treatment.
What Causes NPH?
The majority of cases of NPH are idiopathic, meaning of unknown cause (also known as primary NPH).
NPH can also develop as the result of a known cause, in which case it is referred to as secondary NPH. Some of these causes are head injury, cranial surgery, subarachnoid hemorrhage, tumor or cysts, as well as subdural hematomas, bleeding during surgery, meningitis, and other brain infections. It is also appreciated that some people can be born with hydrocephalus but not develop symptoms until late in life. Such persons may be completely unimpaired only to have their hydrocephalus identified on CT or MRI scans performed for unrelated reasons (for example, because of head injury). It is presently unclear what percentage of asymptomatic congenital hydrocephalus patients will eventually develop symptoms of NPH.
What are the Symptoms of NPH?
NPH is typically characterized by a triad of symptoms: gait disturbance (difficulty walking), cognitive impairment, and impaired bladder control. These symptoms may not all occur simultaneously and can emerge at different stages of the disease with varying levels of severity.
- Gait disturbances (difficulty walking) range in severity from mild imbalance to the inability to stand or walk at all. The gait disorder is typically slow, short-stepped, often wide-based, and shuffling in character. Falls can occur with increasing frequency and persons develop trouble descending stairs or downsloping surfaces. Turns are often made with a series of choppy short steps and many will describe hesitancy when approaching objects in their path, trouble maintaining a uniform walking pace, or sometimes a tendency to accelerate unintentionally. A delayed or absent protective response to balance loss contributes to an increase in falls as well as the need to reach out to walls or furniture while walking to stabilize is common. Individuals can also describe a feeling of heavy feet, as though they are magnetically attracted to the floor – “magnetic” gait, or find themselves stuck and unable to initiate a normal stride – “freezing of gait”. A gait disturbance is often the most troubling symptom and can be the first to become apparent.
- Mild dementia (cognitive impairments) is described as a loss of interest in daily activities, forgetfulness, mood changes, difficulty dealing with routine tasks, difficulty making decisions or multi-tasking, and short-term memory loss. NPH is one of the few treatable forms of dementia.
- Urinary Incontinence (Impairment in bladder control) in mild cases is typically characterized by urinary frequency and urgency, and in severe cases is a complete loss of bladder control or urinary incontinence. Some people with NPH never display signs of bladder problems.
Learn more, watch: NPH From Symptoms to Diagnosis to Treatment.
How is NPH Diagnosed?
What makes the diagnosis of NPH difficult is the fact that symptoms of NPH occur in other conditions that are common in an aging population, such as Parkinson’s disease (PD), osteoarthritis, perpherial neuropathy, and Alzheimer’s disease (AD). NPH-like symptoms can occur in Alzheimer’s, vascular dementia, and Parkinson’s disease, or NPH may be a comorbidity with (accompany) AD or PD. In NPH, not all of the symptoms arise at the same time. The combination of dementia-like symptoms, walking problems, and urinary problems (the “classic” Hakim triad – named after Salomon Hakim, MD, PhD, the clinician who first defined NPH over 50 years ago) alert health care providers to the possibility of NPH. However, it may take years for all three symptoms to present (if at all). The triad is neither necessary nor sufficient to make the diagnosis. One may present with just gait impairment and have NPH. On the other hand, even if the full triad is present, one cannot be assured of the diagnosis without further ancillary testing, detailed below.
When healthcare professionals suspect possible NPH, they can help by offering a prompt referral to a neurologist or neurosurgeon. One or more of the following tests are usually performed to confirm the diagnosis and to assess the person’s candidacy for surgical treatment:
Brain imaging exams identify enlarged ventricles.
Computed tomography (CT scans) is a reliable procedure for diagnosing and assisting in the management of hydrocephalus. It is a sophisticated technique in which x-ray beams are passed through a patient’s body and pictures of the internal structures, in this case, the brain, are made by the computer.
Magnetic Resonance Imaging (MRI), like the CT scan, is a diagnostic technique that produces images of the brain—but unlike CT scanning, MRI does not use x-rays/radiation. Instead, MRI uses radio signals and a very powerful magnet to scan the patient’s body, and the signals are then formed into pictures by a computer. MRI is a painless procedure and has no known side effects. There are two types of MRI scans:
- The Single Shot Fast Spin Echo (also called a “quick brain MRI”), which takes about three minutes and rarely requires sedation, is used to assess ventricular size.
- The full MRI, which takes 30 to 60 minutes and may require sedation, shows more minute details.
Some physicians believe that high CSF flow through the aqueduct predicts improvement with the treatment of NPH. The MRI provides more information than the CT, and is, therefore, the test of choice in most cases, but people with cardiac pacemakers or certain other metallic implants may not be able to have MRI scans because of potential interference with these devices.
Cisternography, more involved than CT scan or MRI, is not widely used. Using the injection of tracers, it highlights the absorption of the CSF. It involves having a radioactive isotope injected into the lower back through a spinal tap, in order to monitor the absorption of CSF over a period of several days. This test is done in the hospital.
Neuropsychological testing is the most accurate means of determining and documenting cognitive strengths and problems and can help provide a more accurate diagnosis of the range of neuropsychological and cognitive issues. The testing involves answering questions and performing tasks.
- An individual’s appearance, mood, anxiety level, and experience of delusions or hallucinations are evaluated.
- Cognitive abilities such as memory, orientation to time and place, attention, use of language, and abilities to carry out a range of tasks and follow instructions are assessed.
- Reasoning, abstract thinking, and problem-solving are analyzed.
Gait assessment performed by a licensed physical therapist is often very useful in determining the degree of impairment of an individual. It is also useful for following patients after shunt surgery or endoscopic third ventriculostomy to evaluate the success of the surgical treatment.
Lumbar CSF removal predicts the response to shunting. When a large volume of CSF, typically 30-40 cc, is removed from the lower back region, one or more of the NPH symptoms may lessen or reverse. Such symptomatic improvement with a lumbar puncture is interpreted as meaning that a surgical shunt would be clinically beneficial. It is important to note that the reversal of symptoms from the lumbar puncture is temporary but indicates that shunt implantation may be beneficial.
- Lumbar puncture (spinal tap) allows an estimation of CSF pressure and analysis of the fluid. Under local anesthetic, a thin needle is passed into the spinal fluid space of the lower back. Up to 50 cc of CSF is removed to see if symptoms are temporarily relieved by this CSF volume reduction. If removal of some CSF dramatically improves symptoms, even temporarily, then surgical treatment is likely to be successful. A limitation of lumbar puncture and removal of a small volume of CSF as a screening test for NPH is that some people may have little or no improvement after the test, and yet may still improve with a shunt. When the response to a lumbar puncture is “negative” or uncertain, further evaluation may be helpful.
- External lumbar drainage, also called lumbar catheter insertion or continuous lumbar drainage, is a variation of the lumbar puncture where a thin, flexible tube, called a catheter, is left in place to drain CSF. The procedure, which is performed in the hospital, allows for either intermittent or continuous removal of spinal fluid over several days to imitate the effect that a shunt would have. It also allows for a more accurate recording of CSF pressure. With an intermittent drainage protocol, the person is free to move around when the fluid is not being drained. Spinal fluid drainage over time can be thought of as a “test drive” of a shunt without actually undergoing shunt surgery. However, because it requires hospitalization and has associated risks, it may not be recommended for all patients. People who respond dramatically to such spinal fluid drainage are likely to respond to shunt surgery, which will be necessary for long-term treatment of NPH. Some physicians advocate using the pressure results for selecting the type of shunt or initial shunt setting for programmable and adjustable shunts.
- The measurement of CSF outflow resistance is a more involved test that requires a specialized clinical setting. This test begins with a lumbar tap and assesses the degree of blockage of CSF absorption back into the bloodstream. It requires the simultaneous infusion of artificial spinal fluid and the measurement of CSF pressure. If the calculated resistance value is abnormally high, then there is a very good chance that the patient will improve with shunt surgery, since the shunt mimics the function of the body’s normal CSF drainage pathways.
- For ICP monitoring or spinal pressure monitoring, a small pressure monitor is surgically inserted through the skull into the brain or ventricles or in the lumbar region to measure the ICP. Pressure monitoring, either by the lumbar catheter or the intracranial method, requires admission to a hospital. It can detect an abnormal pattern of pressure waves as well as low or high pressure. It is possible for NPH to occur even when CSF pressure is not measurably high. The results of this test can also be used to select initial shunt pressure if a shunt is being implanted.
These diagnostic tests assist medical professionals in determining the existence and severity of NPH in a patient, as well as the potential treatment options. As previously mentioned, it is recognized that many patients with suspected NPH may also be suffering from other age-related neurologic disorders that can produce similar symptoms. The presence of such potentially co-morbid diseases like Alzheimer’s and Parkinson’s can now be estimated through specialized brain scans and spinal fluid analysis. The use of these techniques can help clinicians decide if NPH should continue to be pursued, particularly if the response following a lumbar puncture or external lumbar drainage is minimal or equivocal.
How is NPH Treated?
The most common, and typically the only available treatment for NPH is the surgical implantation of a shunt. In the past five to ten years, new diagnostic techniques, better shunt design and recognition of prognostic factors have improved patient selection and outcomes for NPH treatment. Although the insertion of a shunt is a relatively simple neurosurgical procedure that is typically completed in less than one hour, the decision to undergo shunt surgery is complex.
A shunt is a flexible tube placed into the ventricular system of the brain that diverts the flow of CSF into another region of the body, most often the abdominal cavity, where it can be absorbed. A valve within the shunt maintains CSF at normal levels and pressure within the ventricles.
Endoscopic Third Ventriculostomy (ETV)
A surgical procedure called endoscopic third ventriculostomy (ETV) may be considered as an alternative to a shunt for people diagnosed with aqueductal stenosis, a narrowing of the aqueduct of Sylvius located in the brain. In this procedure, the neurosurgeon uses a special endoscope to create an alternative CSF passageway that bypasses the obstruction at the cerebral aqueduct.
Determination of aqueductal stenosis can be made by MRI, and the success of ETV in adults is variable, and some people who undergo the procedure later require shunt surgery to treat their symptoms. Clinical trials are currently exploring ETV as a treatment for NPH.
To find an adult neurosurgeon, visit our Physician Directory.
Management of NPH
NPH can be treated with a shunt system. However, this surgical procedure can result in complications days after the surgery or years later. The most common shunt complications are malfunction and infection as well as a subdural hematoma.
Signs and Symptoms of a Malfunction
Symptoms of shunt malfunction can vary from person to person. It’s important to be aware of what your symptoms were prior to shunt implantation so that you or your caregiver are able to alert your physician if symptoms return after shunt implantation. Returning symptoms may be a sign of an obstructed or malfunctioning shunt. Symptoms of shunt failure in NPH:
- Difficulty walking/gait disturbances
- Cognitive challenges/mild dementia
- Urinary urgency or incontinence
- Swelling along shunt track
- Fever (a sign of shunt failure or infection)
- Redness along the shunt tract (a sign of shunt failure or infection)
What is the Prognosis After Surgery?
Symptom improvement after shunt surgery to treat NPH is impacted by a number of variables. It’s estimated that more than 80% of those properly diagnosed with NPH and screened for shunt responsiveness will experience rapid improvement in their condition, although it may take weeks or months to see the full benefits of the procedure. Physical therapy to address gait and balance impairments is important to assist with return to a safe and independent gait as well as progress to independent functioning in the community.
Early diagnosis is typically an indicator of successful treatment, but even those patients who have had symptoms for years may improve with treatment.
You’re not alone. The journey with NPH can be frustrating and unpredictable. For those living with NPH and their caregivers, staying informed about the condition is essential to managing care. The challenges of living with a chronic illness or caring for a chronically ill parent or spouse are stressful for all involved. Adults with hydrocephalus may resent their dependence on a spouse, child, or another family member. Acknowledging emotional responses to this chronic and potentially disabling condition can help all those involved.
We provide essential tools and resources that enable you to have more control of your life. There is a large community across the country that is engaged and connected through the Hydrocephalus Association ready to support you and your family.
There is currently a great deal of interest in the diagnosis and management of NPH, with the expectation that the reported incidence of this condition will increase dramatically as baby boomers reach retirement age and beyond. Physicians, medical device manufacturers, and patient advocates are cooperating on a variety of levels to improve methods of diagnosis, techniques and devices for treatment, and public awareness of NPH. It is anticipated that these efforts will result in years of a better quality of life for people affected by this condition.
NPH Left Untreated
NPH is typically characterized by progressive symptoms that require intervention on some level. Without treatment, symptoms may worsen and cause death. No one is able to predict how fast the symptoms will progress, and the seriousness of symptoms may vary day-to-day.
For patients whose symptoms are very mild, their doctor may advocate for close monitoring of the clinical condition without proceeding immediately to treatment with a shunt. This proposition is often scary to the individual and family as they see their loved one struggling in ways they hadn’t before. However, monitoring allows the doctor to be assured of the diagnosis as well as determine if the NPH is the primary medical condition or if there are other medical conditions occurring with the NPH. This determination will impact the treatment plan.
Some individuals with NPH may not be a candidate for treatment, despite a definitive diagnosis of NPH. Many patients that face this seek a second or third opinion from a neurosurgeon experienced in NPH. Some reasons an individual may not be a candidate include evidence from testing to remove fluid, the presence of other medical conditions, and poor health. In this case, the doctor will continue to follow the patient closely and assist the individual and their loved ones in preparation for the progression of symptoms. This may include referrals to social work or elder care management services as well as physical therapy to assess their current functional status and adaptive equipment to assist with mobility needs and decrease the risk of falls.
2019 Ask the Expert Video Series on NPH.
Dr. Mark Luciano, neurosurgeon, and Dr. Abhay Moghekar, neurologist, answer commonly asked questions from our community focused on adults living with hydrocephalus. This Ask the Expert NPH Video Series was made possible through the generosity of our industry partner Codman, a part of Integra Lifesciences who we thank for supporting this important program!
Research and Hydrocephalus
As the leading private funder of hydrocephalus research in the country, we are investing in research to improve outcomes, prevent the development of hydrocephalus and, ultimately, find a cure. The Adult Hydrocephalus Clinical Research Network (AHCRN) is a network of hospitals that conduct clinical research on hydrocephalus to improve treatment for the adult forms of hydrocephalus, including transitional patients who were diagnosed as children, those who acquire hydrocephalus as adults, and patients with NPH.
You can be a part of research. Enroll in HAPPIER, the only hydrocephalus patient-powered registry in the country, and help our doctors and scientists better serve you!
The Hydrocephalus Association regularly supports our scientists and doctors by assisting in gathering data through surveys as well as through helping enroll patients in current research studies.
Information you can trust! This article was produced by the Hydrocephalus Association, copyright 2021. We would like to thank the following individuals for their valuable contributions and expert input: James B. Golomb, MD, and Sharon Hayden, PT.